Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Mike_J on August 24, 2014, 09:51:35 am
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The power transformer I had made for the Plexi/800 sluckey inspired amp has two sets of taps for the B+ voltage. The lower voltage is in the neighborhood of 400 volts and the higher tap is around 480 volts.
There were two reasons I had the PT made this way. First, I did some research on some Marshall sites where some people liked lower voltage in the 400 volt range and others liked the voltage around 480 volts and sometimes even higher. The second reason is they didn't charge me any more money to make it this way so I figured why not.
Now for my questions. Is it possible to lower the B+ to the power section yet keep the preamp section voltages constant? If so, how would I go about it? I guess I should also ask the question does it matter whether or not the preamp voltages are changed along with the HT voltage?
Thanks
Mike
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Is it possible to lower the B+ to the power section yet keep the preamp section voltages constant? If so, how would I go about it?
Yes. Use larger value dropping resistors on the B+ rail if you use the higher voltage windings. This ain't something I would ever consider making user switchable.
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Is it possible to lower the B+ to the power section yet keep the preamp section voltages constant? If so, how would I go about it?
Yes. Use larger value dropping resistors on the B+ rail if you use the higher voltage windings. This ain't something I would ever consider making user switchable.
Sluckey
It does complicate matters when making it user switchable. Especially with the voltage doubler needed for the PT I have. I would think if one of the two taps had adequate voltage you might be able to Y off to the preamp with one of the two HT lines and send the other side of the Y to the switch. Don't know if it is feasible but it would make for a more versatile amp if it worked.
Any thoughts on whether the above ramblings would be feasible? If so I might make a separate amp that is just Marshall with no overdrive but maybe with an active effects unit that can be switched in or out. All I have to do is have them build the transformer I need for the job.
Thanks
Mike
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Your voltage doubler is really just a full wave bridge. Nothing complicated about that. What you're talking about sounds like two separate rectifier/filter rails, one for the power stages, and another for the preamp stages. I've never seen anyone do that with bridge rectifiers. Not gonna say it can't be done, but if you will draw a schematic (not a layout) of your proposal and study it, then you could say yes this will work, or no, I see some sneak path that will wreck it. But if you still don't know for sure, one way or the other, maybe you would consider dropping the idea?
I think it's just another whistle to throw at your "be everything amp". That amp is already overly complicated. :think1: You need a reality check! And I mean that in a positive way.
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Your voltage doubler is really just a full wave bridge. Nothing complicated about that. What you're talking about sounds like two separate rectifier/filter rails, one for the power stages, and another for the preamp stages. I've never seen anyone do that with bridge rectifiers. Not gonna say it can't be done, but if you will draw a schematic (not a layout) of your proposal and study it, then you could say yes this will work, or no, I see some sneak path that will wreck it. But if you still don't know for sure, one way or the other, maybe you would consider dropping the idea?
I think it's just another whistle to throw at your "be everything amp". That amp is already overly complicated. :think1: You need a reality check! And I mean that in a positive way.
Sluckey
Thanks for the good comments. There is no doubt that this amp is somewhat complex and I am just looking to find a way to further complicate it. As the layout is currently structured the Plexi normal channel plate voltage would be 150 volts at 480 volts B+. If I switched the B+ to 400 volts the normal channel plate voltage would drop down to 125 volts. I don't think that is a practical voltage. Your suggestion to drop the switch is the right one.
I can't figure out how to show a bridge rectifier on a schematic. I will have to do some research on splitting the preamp and power amp power strings on my next Plexi/800 build and probably will not use a PT that requires the use of a bridge rectifier because I think I may be able to solve that riddle. For the meantime I guess I am going to have to change my faceplate and go with the 480 volt tap because I have enough to do already.
Thanks
Mike
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Your voltage doubler is really just a full wave bridge. Nothing complicated about that. What you're talking about sounds like two separate rectifier/filter rails, one for the power stages, and another for the preamp stages. I've never seen anyone do that with bridge rectifiers. Not gonna say it can't be done, but if you will draw a schematic (not a layout) of your proposal and study it, then you could say yes this will work, or no, I see some sneak path that will wreck it. But if you still don't know for sure, one way or the other, maybe you would consider dropping the idea?
I think it's just another whistle to throw at your "be everything amp". That amp is already overly complicated. :think1: You need a reality check! And I mean that in a positive way.
Sluckey
I prepared a hybrid schematic of the separate power supply rails. On the preamp side I need 368 volts to operate the effects circuit. Therefore, I must have the full wave bridge in order to be able to achieve that voltage. Is the fact that the CT is tied to the power caps okay for the preamp side? Disregard the 245 volt comment. Do you think this will work the way I have it drawn?
Thanks
Mike
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Your voltage doubler is really just a full wave bridge. Nothing complicated about that. What you're talking about sounds like two separate rectifier/filter rails, one for the power stages, and another for the preamp stages. I've never seen anyone do that with bridge rectifiers. Not gonna say it can't be done, but if you will draw a schematic (not a layout) of your proposal and study it, then you could say yes this will work, or no, I see some sneak path that will wreck it. But if you still don't know for sure, one way or the other, maybe you would consider dropping the idea?
I think it's just another whistle to throw at your "be everything amp". That amp is already overly complicated. :think1: You need a reality check! And I mean that in a positive way.
Sluckey
Here is my latest attempt at a schematic for a Dual HT Power Supply. It should be the same as the last one I sent you but I found some schematic elements for the switches. Hopefully it will make sense to you.
Thanks
Mike
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Look at the complexity of the switching. Do you really want to do that? And why???
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Look at the complexity of the switching. Do you really want to do that? And why???
Sluckey
The only reason I wanted to do it is because I read somewhere that some people prefer the amps at 400 volts versus the higher voltages. Most of them are EVH fanatics. They go to great lengths with Variacs and other means that have the potential of starving the heaters and lowering the voltages to the preamp tubes well below their circuit specifications. I believe my method is a more correct way of accomplishing the objective of lowering the B+.
I have very little experience playing Marshall amps. I know a lot of the music I enjoy was recorded and performed using the amplifiers. I am just trying to get as much versatility out of the amp as possible. I have no idea if the difference in tone makes the additional effort worthwhile but I just see it as an additional 4pdt toggle switch and a 1000 volt bridge rectifier which is not that big of deal. About $5 worth of parts.
If your objection to this is that the difference in tone would not be enough to warrant any additional effort being made then your point is very valid because why should I do anything that would make little or no tonal difference. However, if the only concern is a little added complexity then I don't mind the added complexity as long as the way I drew the circuit will work.
I guess to answer your question I like some of EVHs work too. I just want to know whether the circuit I drew will work properly to accomplish the objective of lowering the voltage to the power tubes while leaving the preamp tube voltages intact.
Thanks
Mike
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Look at the complexity of the switching. Do you really want to do that? And why???
If your objection to this is that the difference in tone would not be enough
His objection is about safety: Most of those multi-pole switches are small and have closely-spaced lugs. If your wiring is less than perfect, you will create short-circuits and probably a burned transformer. Good wiring would involve careful soldering and probably heatshrink covering every exposed lug (which then requires a decent heat gun or some careful use of a very hot hair dryer).
How about bringing the PT secondary wires out to a terminal strip (be sure it's a VERY good one)? You could bolt down the wires running from PT to terminal strip, and have a 2nd set of wires to be bolted at the terminal strip running to the rectifier. This would not be "user changeable" but it could be changed if you wanted to test each mode, and would be safer wiring than using a switch.
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Hey Mike,
I've been reading some of your posts and just figured I'd throw my 2 cents out there...
If it's the EVH trick you're after,, then why separate the power tube voltages from the preamp tube voltages?
Using a variac to lower voltages at the input would cause all of those B+ voltages to be affected proportionately, and that would have something to do with the magic....right?... :dontknow:
Respectfully,
SG
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Look at the complexity of the switching. Do you really want to do that? And why???
If your objection to this is that the difference in tone would not be enough
His objection is about safety: Most of those multi-pole switches are small and have closely-spaced lugs. If your wiring is less than perfect, you will create short-circuits and probably a burned transformer. Good wiring would involve careful soldering and probably heatshrink covering every exposed lug (which then requires a decent heat gun or some careful use of a very hot hair dryer).
How about bringing the PT secondary wires out to a terminal strip (be sure it's a VERY good one)? You could bolt down the wires running from PT to terminal strip, and have a 2nd set of wires to be bolted at the terminal strip running to the rectifier. This would not be "user changeable" but it could be changed if you wanted to test each mode, and would be safer wiring than using a switch.
VAC,
HotBluePlates
Thank you for your comments. The 4PDT switch I am considering is rated at 16A 125, 10A 250 VAC, DC 500 100M ohm min, AC 1500 V 1 minute. The only negative is that it has screw terminals instead of solder terminals. If this is not safe then I agree with you 100% that I need to pick one of the voltages or the other and stick with it. Do you think that switch would be adequate for the job I need it to do? The switch body is about 1-1/2" X 1-1/2" so it is pretty hefty.
I failed to mentioned I will make a separate circuit board for the rectifiers with turrets or eyelets to tie into. I think it will also help in placement to reduce the chances of AC noise entering the inputs.
Thanks
Mike
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Hey Mike,
I've been reading some of your posts and just figured I'd throw my 2 cents out there...
If it's the EVH trick you're after,, then why separate the power tube voltages from the preamp tube voltages?
Using a variac to lower voltages at the input would cause all of those B+ voltages to be affected proportionately, and that would have something to do with the magic....right?... :dontknow:
Respectfully,
SG
SG
I have a very nice Variac that would do the trick but I am concerned about starving the heaters. HBPs opinion regarding the safety of the available 4pdt switch will be the determining factor in which direction I will go. If he doesn't think it is safe then I will definitely choose the higher voltage tap and move on from there.
Thanks
Mike
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Hey Mike,
I've been reading some of your posts and just figured I'd throw my 2 cents out there...
If it's the EVH trick you're after,, then why separate the power tube voltages from the preamp tube voltages?
Using a variac to lower voltages at the input would cause all of those B+ voltages to be affected proportionately, and that would have something to do with the magic....right?... :dontknow:
Respectfully,
SG
SG
I have a very nice Variac that would do the trick but I am concerned about starving the heaters. HBPs opinion regarding the safety of the available 4pdt switch will be the determining factor in which direction I will go. If he doesn't think it is safe then I will definitely choose the higher voltage tap and move on from there.
Thanks
Mike
Since you're only switching the HT winding(s), your design wouldn't affect the heater winding
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Your dual HT tap PT is a great platform for doing just what you are thinking of.....without the side affect of starving the heaters
If I was doing what you're doing and going after the VH thing,,,,I wouldn't hesitate to do just that...a basic low/high B+ switch that only switches between the 2 HT taps is ideal.
:thumbsup:
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Your dual HT tap PT is a great platform for doing just what you are thinking of.....without the side affect of starving the heaters
If I was doing what you're doing and going after the VH thing,,,,I wouldn't hesitate to do just that...a basic low/high B+ switch that only switches between the 2 HT taps is ideal.
:thumbsup:
SG
Thank you for your support concerning this matter. The key is as to whether it can be done safely. That is a determination someone like HBP is qualified to make. I think the switch is more than adequate for the job but I would like confirmation from HBP because I would trust his judgment concerning the safety of the switch.
Thanks
Mike
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Just for the record, here's what I'm suggesting for you...
It does not take the bias winding into consideration, and that will be unaffected as well, so it will result in a "colder" bias condition (when switched to the 'low voltage' setting), because the bias voltage will stay the same as the B+ is lowered........
That will contribute to an overall more overdriven output stage......could be cool.
***I'm going off of memory that you do have a separate bias winding***
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The 4PDT switch I am considering is rated at 16A 125, 10A 250 VAC, DC 500 100M ohm min, AC 1500 V 1 minute. The only negative is that it has screw terminals instead of solder terminals. If this is not safe then I agree with you 100% that I need to pick one of the voltages or the other and stick with it. Do you think that switch would be adequate for the job I need it to do? The switch body is about 1-1/2" X 1-1/2" so it is pretty hefty.
Well, you seem determined to give it a go. Your switch also sounds bigger than I envisioned. It is likely workable, then.
Since you have screw terminals (a blessing in this case), you won't need to worry about solder blobs on the switch (solder bridges and stray wire strands were the big issues I was concerned about). Do yourself a huge favor and find ring terminals which fit the screws on the switch. Strip the PT wires, crimp & solder the ring terminals, with heatshrink over the "non-ring" part of the terminals. Now they're ready to be bolted in place on your switch. It probably doesn't include a locking mechanism for the screws, so add your own lock washers (you don't want these to loosen, ever, without you putting some effort into removing them).
I'd encourage you to have the amp at least in standby (preferably off) when switching the high voltage levels. Also ensure you have enough rectifier and filter cap voltage rating reserve for unexpected high wall voltage.
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Would a VVR on the power tubes achieve what you are wanting. Replace the 1M with fixed resistors on a switch. :think1:
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The 4PDT switch I am considering is rated at 16A 125, 10A 250 VAC, DC 500 100M ohm min, AC 1500 V 1 minute. The only negative is that it has screw terminals instead of solder terminals. If this is not safe then I agree with you 100% that I need to pick one of the voltages or the other and stick with it. Do you think that switch would be adequate for the job I need it to do? The switch body is about 1-1/2" X 1-1/2" so it is pretty hefty.
Well, you seem determined to give it a go. Your switch also sounds bigger than I envisioned. It is likely workable, then.
Since you have screw terminals (a blessing in this case), you won't need to worry about solder blobs on the switch (solder bridges and stray wire strands were the big issues I was concerned about). Do yourself a huge favor and find ring terminals which fit the screws on the switch. Strip the PT wires, crimp & solder the ring terminals, with heatshrink over the "non-ring" part of the terminals. Now they're ready to be bolted in place on your switch. It probably doesn't include a locking mechanism for the screws, so add your own lock washers (you don't want these to loosen, ever, without you putting some effort into removing them).
I'd encourage you to have the amp at least in standby (preferably off) when switching the high voltage levels. Also ensure you have enough rectifier and filter cap voltage rating reserve for unexpected high wall voltage.
HBP
Great advice. I am going to make a check list of your recommendations and incorporate every one of them into my build. Thanks again for your input.
Mike
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Would a VVR on the power tubes achieve what you are wanting. Replace the 1M with fixed resistors on a switch. :think1:
Timbo
Thank you for your reply. The amp already has three master volumes. If I put another one on it I believe I would be in agreement with everyone that is telling me the amp is over complicated. Maybe on another amp. I have never installed a VVR in any of my amps. Given most of them are 100 watt amps I should probably study it. Just not right now.
Thanks
Mike
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Just for the record, here's what I'm suggesting for you...
It does not take the bias winding into consideration, and that will be unaffected as well, so it will result in a "colder" bias condition (when switched to the 'low voltage' setting), because the bias voltage will stay the same as the B+ is lowered........
That will contribute to an overall more overdriven output stage......could be cool.
***I'm going off of memory that you do have a separate bias winding***
SG
Yes, I have a dedicated bias winding. When I was working on the power supply schematic I went back and forth as to whether I should treat the PI as part of the power section and therefore have it increase and decrease with the HT voltage. Decided having it on the preamp side would be easier. I hope the lower voltage setting will give the amp a different and pleasing tone.
Thank you for your input.
Mike
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Yes, I have a dedicated bias winding. When I was working on the power supply schematic I went back and forth as to whether I should treat the PI as part of the power section and therefore have it increase and decrease with the HT voltage. Decided having it on the preamp side would be easier. I hope the lower voltage setting will give the amp a different and pleasing tone.
The lowered voltage to the PI will result in a reduction in headroom in that stage, and will contribute to the PI clipping...with the amount of gain you have in your preamp plan, you should wind up with one seriously square wave.
Funny you mention it because I just suggested using a 12AT7 in the PI on your other thread right before I read this post. I believe it lends itself well to the circuit when you've got that much preamp gain on hand.
I'm totally benind you and look forward to the end result....my only fear for you is the fear of the unknown.
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Here is my latest attempt at a schematic for a Dual HT Power Supply.
I believe that will work. You'll probably need more filtering in the upper B+ rail.
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Here is my latest attempt at a schematic for a Dual HT Power Supply.
I believe that will work. You'll probably need more filtering in the upper B+ rail.
Sluckey
Thanks for your reply. Do you have a suggestion as to values? Maybe 220uF @ 450 or 500 volts? Do I also need to boost the caps for the screen supply? Do I need the 1A fuse on the preamp side?
Looking back at my ODS - HRM build I used two 200uF @450V in series on the HT and two 47 uF @ 350V in series for the screen supply. Probably good choices for this amp too don't you think?
Thanks
Mike
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Yes, I have a dedicated bias winding. When I was working on the power supply schematic I went back and forth as to whether I should treat the PI as part of the power section and therefore have it increase and decrease with the HT voltage. Decided having it on the preamp side would be easier. I hope the lower voltage setting will give the amp a different and pleasing tone.
The lowered voltage to the PI will result in a reduction in headroom in that stage, and will contribute to the PI clipping...with the amount of gain you have in your preamp plan, you should wind up with one seriously square wave.
Funny you mention it because I just suggested using a 12AT7 in the PI on your other thread right before I read this post. I believe it lends itself well to the circuit when you've got that much preamp gain on hand.
I'm totally benind you and look forward to the end result....my only fear for you is the fear of the unknown.
SG
Thanks for the 12AT7 suggestion it is a good one. Also, thanks for your support. I am fairly confident in the Marshall side of this build as I can ground the potential problem area, OD & FX out of the signal path. However, the excitement is in adding the OD & FX to the amp. It could be one high gain monster or it could be unusable only time will tell.
What I am confident in is there are people on this forum that can help increase the odds that the overall build will be a success. This amp may stretch the boundaries a little bit but I think that is a good thing.
Thanks
Mike
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I would ditch the idea of a toggle switch in favor of using an octal tube socket and two different octal plugs (with covers, of course). One is labeled 480V, the other is labeled 400V. With an octal plug, you can connect 1,2 to be the 480V PT leads, 3,4 to be the 400V PT leads, 5,6 to be the circuit to your rectifier, and 7,8 would be a series interconnect of one of the PT's primary (i.e. MAINS, in series between the power switch and the PT ).
On the 480V plug: connections are 1-5, 2-6, 7-8, (3,4 NC)
On the 400V plug: connections are 3-5, 4-6, 7-8, (1,2, NC)
The advantage of doing it this way: (1) when going between the two voltage selections, the amp is effectively OFF because of the mains lead in series and (2) the plug and sockets are rated for 500+VDC, (3) you get a 1-2 second delay in the time it would physically take you to swap plugs.
If you want to be super snazzy, use 5,6 instead of 7,8 for the mains interconnect. Make pin 6 be the connection from the power switch so if someone doesn't read the socket label and inserts an EL34, then the main voltage is on pin-6, a pin not used by the tube.
also, you may already be planning it this way...: I would design the entire power supply (all electrolytics for everything from the power tubes to the preamps) to operate at acceptable voltages with your 400V power tube voltage. Do so such that the preamps are at some acceptable voltage. When you switch to 480V, those preamp voltages will increase, but they should still be acceptable.
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I would ditch the idea of a toggle switch in favor of using an octal tube socket and two different octal plugs (with covers, of course). One is labeled 480V, the other is labeled 400V. With an octal plug, you can connect 1,2 to be the 480V PT leads, 3,4 to be the 400V PT leads, 5,6 to be the circuit to your rectifier, and 7,8 would be a series interconnect of one of the PT's primary (i.e. MAINS, in series between the power switch and the PT ).
On the 480V plug: connections are 1-5, 2-6, 7-8, (3,4 NC)
On the 400V plug: connections are 3-5, 4-6, 7-8, (1,2, NC)
The advantage of doing it this way: (1) when going between the two voltage selections, the amp is effectively OFF because of the mains lead in series and (2) the plug and sockets are rated for 500+VDC, (3) you get a 1-2 second delay in the time it would physically take you to swap plugs.
If you want to be super snazzy, use 5,6 instead of 7,8 for the mains interconnect. Make pin 6 be the connection from the power switch so if someone doesn't read the socket label and inserts an EL34, then the main voltage is on pin-6, a pin not used by the tube.
also, you may already be planning it this way...: I would design the entire power supply (all electrolytics for everything from the power tubes to the preamps) to operate at acceptable voltages with your 400V power tube voltage. Do so such that the preamps are at some acceptable voltage. When you switch to 480V, those preamp voltages will increase, but they should still be acceptable.
Terminalgs
Unfortunately I am not familiar with the use of plugs. I would need a schematic and part numbers to follow what you are saying. It is way over my head.
The advantage to the way I have wired it with the switch is the preamp voltages will be consistent whether the B+ is 400 volts or 480 volts. Only the HT and the screen voltages will change. There is a 17% difference between the two voltages. To me that seemed like too much of a swing in the preamp section which is what led to my decision wire the supply the way I did.
I am always open to new ideas but it seems like turning the standby switch to off and changing the HT voltage using two switches is as easy as this can be done.
Thanks
Mike
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Hi Mike,
this is what I'm talking about.
(http://i.imgur.com/GvCCeZ1.jpg)
If the procedure to switch between voltage involves two different independent switches (voltage switch, and a stand-by switch), someday, someone (you, or someone else) will throw the switches the wrong way, at the wrong time. If the amp is likely to blow up in that event, it is a very bad design decision.
I drew the plugs as a straight line, but you can use an octal tube socket. the plugs are $2ea (you need two for this), the socket is $2-$20ea, depending on your quality tastes.
See "9 Pin Tube Base" on Doug's "tube Sockets' page in the store.
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Here is my latest attempt at a schematic for a Dual HT Power Supply.
I believe that will work. You'll probably need more filtering in the upper B+ rail.
Sluckey
The F&T electrolytics that are available are only 220uF at 300 volts. That means running two of them in series would give me 110uF at 600 volts. Do you think that is enough voltage for a 480 volt B+ amp? There are no name caps that are 220uF at 350 volts. They claim to be high quality and low leakage. Any suggestions?
Thanks
Mike
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I wasn't referring to increase the size of the caps. I meant you need to put a CLC pi filter following the fuse. You lost all that filtering when you split the B+ rail. Your original CLC filter is still on the power amp rail but it does not benefit the preamp rail.
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Mike J.,,,,just for the record.
IMHO, just dropping the B+ on the power tubes is going to give you the audible equivalent of turning the amp's PPIMV down from 8 to 6.5
Lowering all of the voltages however, will produce a more noticeable effect and probably get you closer to your tone goal......if the VH1 tone is truly what you're after and not just a more complicated or unique B+ rail. :wink:
I'll shut up now. :icon_biggrin:
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Mike J.,,,,just for the record.
IMHO, just dropping the B+ on the power tubes is going to give you the audible equivalent of turning the amp's PPIMV down from 8 to 6.5
Lowering all of the voltages however, will produce a more noticeable effect and probably get you closer to your tone goal......if the VH1 tone is truly what you're after and not just a more complicated or unique B+ rail. :wink:
I'll shut up now. :icon_biggrin:
If I can accomplish the same thing by just reducing the PPIMV then it would not make much sense to go to the effort of doing the dual HT taps with split rectifiers. I have very little experience with these things but as sluckey just mentioned in his last post the circuitry to split the rectifiers is getting more complicated by the moment. With more caps required I start to get into space issues.
By lowering all of the voltages I just need a second 2pdt switch the way I wired it in the original layout, correct? In other words, a switch that will send one of the HT secondary voltages (i.e. 400 volts) or the other.
Thanks
Mike
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I wasn't referring to increase the size of the caps. I meant you need to put a CLC pi filter following the fuse. You lost all that filtering when you split the B+ rail. Your original CLC filter is still on the power amp rail but it does not benefit the preamp rail.
Sluckey
I am coming around to your original way of thinking. This gets into a space issue with more power caps at which point I suppose I need to do the center tap thing again. It is becoming a mess that is not worth the effort. I thank you for bringing this to my attention as it adds a considerable amount of additional complexity to the design. With the additional caps I have to start thinking about where to put them and it does not seem as feasible.
I am also wondering whether the existing power supply will provide adequate filtering for the overdrive channel. If I increase the uF rating on the B+ tap then I lose the originality of the Marshall amp. This is something that I won't know for sure until the amp is finished. My chassis man thinks he will have my chassis ready during the next few days. In the meantime I will start the circuit boards.
Thanks
Mike
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Hi Mike,
this is what I'm talking about.
(http://i.imgur.com/GvCCeZ1.jpg)
If the procedure to switch between voltage involves two different independent switches (voltage switch, and a stand-by switch), someday, someone (you, or someone else) will throw the switches the wrong way, at the wrong time. If the amp is likely to blow up in that event, it is a very bad design decision.
I drew the plugs as a straight line, but you can use an octal tube socket. the plugs are $2ea (you need two for this), the socket is $2-$20ea, depending on your quality tastes.
See "9 Pin Tube Base" on Doug's "tube Sockets' page in the store.
Thank you for the explanation. I think it is getting too complex for my first build that is not completely paint by numbers. I think I am going to back away from the dual HT idea.
Thanks
Mike
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Mike J.,,,,just for the record.
IMHO, just dropping the B+ on the power tubes is going to give you the audible equivalent of turning the amp's PPIMV down from 8 to 6.5
Lowering all of the voltages however, will produce a more noticeable effect and probably get you closer to your tone goal......if the VH1 tone is truly what you're after and not just a more complicated or unique B+ rail. :wink:
I'll shut up now. :icon_biggrin:
If I can accomplish the same thing by just reducing the PPIMV then it would not make much sense to go to the effort of doing the dual HT taps with split rectifiers. I have very little experience with these things but as sluckey just mentioned in his last post the circuitry to split the rectifiers is getting more complicated by the moment. With more caps required I start to get into space issues.
By lowering all of the voltages I just need a second 2pdt switch the way I wired it in the original layout, correct? In other words, a switch that will send one of the HT secondary voltages (i.e. 400 volts) or the other.
Thanks
Mike
One switch will do it....
Yup Mike...it's just that simple...see my schematic in reply #16
I have tried both methods on my breadboard and sincerely believe that you will be going in the right direction if you drop the entire rail.
It's not exactly like lowering the PPIMV, but I gave you that example to try to demonstrate the little 'audible' difference that it would make to just do the power tubes by 17%...
In my mind, the extra circuitry needed doesn't justify the outcome.......i.e. a lot of work for a little change in tone
But on the other hand, the small amount of work needed to drop the entire rail will yield a greater change in tone, and more closely mimic the use of a variac.
I wouldn't steer you wrong. :icon_biggrin:
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Mike J.,,,,just for the record.
IMHO, just dropping the B+ on the power tubes is going to give you the audible equivalent of turning the amp's PPIMV down from 8 to 6.5
Lowering all of the voltages however, will produce a more noticeable effect and probably get you closer to your tone goal......if the VH1 tone is truly what you're after and not just a more complicated or unique B+ rail. :wink:
I'll shut up now. :icon_biggrin:
If I can accomplish the same thing by just reducing the PPIMV then it would not make much sense to go to the effort of doing the dual HT taps with split rectifiers. I have very little experience with these things but as sluckey just mentioned in his last post the circuitry to split the rectifiers is getting more complicated by the moment. With more caps required I start to get into space issues.
By lowering all of the voltages I just need a second 2pdt switch the way I wired it in the original layout, correct? In other words, a switch that will send one of the HT secondary voltages (i.e. 400 volts) or the other.
Thanks
Mike
One switch will do it....
Yup Mike...it's just that simple...see my schematic in reply #16
I have tried both methods on my breadboard and sincerely believe that you will be going in the right direction if you drop the entire rail.
It's not exactly like lowering the PPIMV, but I gave you that example to try to demonstrate the little 'audible' difference that it would make to just do the power tubes by 17%...
In my mind, the extra circuitry needed doesn't justify the outcome.......i.e. a lot of work for a little change in tone
But on the other hand, the small amount of work needed to drop the entire rail will yield a greater change in tone, and more closely mimic the use of a variac.
I wouldn't steer you wrong. :icon_biggrin:
SG
I came across an on-off-on switch with the same high voltage capabilities of the other on-none-on switch. Seems like that would be safer than two Carling 2p2t switches. Would you agree? I could place the HT taps on the ends and run the middle of the switch to the rectifier. When the switch is placed in the middle it is in standby. Go one direction it is 400 volts the other is 480.
Hopefully HBP is looking in and can comment on the safety of doing it this way.
Thanks
Mike
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Hi Mike,
this is what I'm talking about.
(http://i.imgur.com/GvCCeZ1.jpg)
If the procedure to switch between voltage involves two different independent switches (voltage switch, and a stand-by switch), someday, someone (you, or someone else) will throw the switches the wrong way, at the wrong time. If the amp is likely to blow up in that event, it is a very bad design decision.
I drew the plugs as a straight line, but you can use an octal tube socket. the plugs are $2ea (you need two for this), the socket is $2-$20ea, depending on your quality tastes.
See "9 Pin Tube Base" on Doug's "tube Sockets' page in the store.
What is your opinion concerning the use of one beefy on-off-on switch with the 400 volt tap tied to one side and the 480 to the other and the middle lugs go to the rectifier? That way the standby switch (middle position) is in the same switch. I would only use one rectifier in the power supply string.
How can you throw the switch the wrong way? One switch has both HT voltages on it and the other is a fairly common standby switch. I don't see how I could get in trouble as long as the switches are adequate to handle the voltages.
I hate to admit it but I am still stuck in the weeds with my 1948 Western Electric circuitry. The drawing is still over my head. I appreciate your efforts in that regard but I think it will take me some time to graduate to your level as far as the wiring you refer to is concerned.
Thanks
Mike
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SG,
I came across an on-off-on switch with the same high voltage capabilities of the other on-none-on switch. Seems like that would be safer than two Carling 2p2t switches. Would you agree? I could place the HT taps on the ends and run the middle of the switch to the rectifier. When the switch is placed in the middle it is in standby. Go one direction it is 400 volts the other is 480.
Hopefully HBP is looking in and can comment on the safety of doing it this way.
Thanks
Mike
Mike,
That would work, but I personally would be hesitant to combine the voltage selector switch with the standby switch (even though it does seem convenient)
I just don't want to be cycling that switch that often, and the standby is the most often cycled power switch on the amp.
Just my opinion,,,but your idea is fine and would work as you intended
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I could place the HT taps on the ends and run the middle of the switch to the rectifier. When the switch is placed in the middle it is in standby. Go one direction it is 400 volts the other is 480.
That's a nice simple solution for switching the B+. And the standby switch in many Marshall amps actually switches the PT HT leads on/off.
You still need to consider what you will do with the bias voltage. Maybe use a 3PDT ON-OFF-ON switch to change B+ and bias with one toggle.
That said, I'd still just pick one voltage winding and keep the whole thing simple.
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What is your opinion concerning the use of one beefy on-off-on switch with the 400 volt tap tied to one side and the 480 to the other and the middle lugs go to the rectifier? That way the standby switch (middle position) is in the same switch. I would only use one rectifier in the power supply string.
That would work.
How can you throw the switch the wrong way?
I mistakingly got the impression that two independent switches were in the works. a DPDT for the voltage, and separate stand-by switch.
The plug type of voltage selector was very common on european tube gear in the 50's/60's, only on the primary side of the PT for 230,220,115,110 voltages etc..
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What is your opinion concerning the use of one beefy on-off-on switch with the 400 volt tap tied to one side and the 480 to the other and the middle lugs go to the rectifier? That way the standby switch (middle position) is in the same switch. I would only use one rectifier in the power supply string.
That would work.
How can you throw the switch the wrong way?
I mistakingly got the impression that two independent switches were in the works. a DPDT for the voltage, and separate stand-by switch.
The plug type of voltage selector was very common on european tube gear in the 50's/60's, only on the primary side of the PT for 230,220,115,110 voltages etc..
Terminalgs
You weren't mistaken at all. One of the choices is using two on-none-on DPDT switches. The first switch would have the 400 volt tap attached to one end of the switch and the 480 volt tap attached to the other end. The common connections would go to one of the ends of the second switch which is the standby switch. The common side of the standby switch would feed the full wave bridge rectifier.
The switches are Carling's with 125 volt at 6A and 250 volt at 3A ratings. Whether this is adequate for the job I do not know but it is the same rating Fender used in their SPST switches I have used for years without any problems whatsoever and they were carrying almost double the AC voltage.
I have attached a layout of what I was discussing above.
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I could place the HT taps on the ends and run the middle of the switch to the rectifier. When the switch is placed in the middle it is in standby. Go one direction it is 400 volts the other is 480.
That's a nice simple solution for switching the B+. And the standby switch in many Marshall amps actually switches the PT HT leads on/off.
You still need to consider what you will do with the bias voltage. Maybe use a 3PDT ON-OFF-ON switch to change B+ and bias with one toggle.
That said, I'd still just pick one voltage winding and keep the whole thing simple.
Sluckey
The on-off-on switch I would use is a 4pdt so there is room for what you are talking about although I am not sure what you are talking about where the bias voltage is concerned. Could you please explain what I would need to do in more detail?
Another option is to set the bias on whichever voltage gives me the most conservative bias setting when the other voltage is selected.
I may end up taking the simple method after I have tried the more difficult method. Just want to see if I can get any sounds I like out of having the both choices.
Thanks
Mikes
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I am not a proponent of 400-off-480 volt switch, where the off is standby.
Remember you have capacitors charged, and a quick switch from 480-0-400 can introduce some funny spikes.
Drgonzonm
Are you, like HBP, in favor of turning off the amp to change voltages instead of just switching the standby switch off? Is there a way to curb the funny spikes?
Thanks
Mike
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There will be no more "funny spikes" than you would normally have by switching any standby switch.
Here's my idea of simultaneously switching the bias. You could make it more elaborate by switching another pot so you would have an adjustment for either voltage setting.
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There will be no more "funny spikes" than you would normally have by switching any standby switch.
Here's my idea of simultaneously switching the bias. You could make it more elaborate by switching another pot so you would have an adjustment for either voltage setting.
Sluckey
Thanks. I think I can make room for another pot and 47K resistor on the board. Good thing I am asking these questions before I finish my boards. I am going to make a layout and post it to make sure I have it right.
Thought of another question. If we put the bias on an on-off-on switch and we flip the switch to the middle position which is off or standby are we getting any bias to our power tubes? If not, are they going to redplate? May require a separate switch for the standby and a 4pdt on-none-on for the 400V - 480V - 400 volt bias - 480 volt bias. But in standby we are removing the voltage from the power supply so why would there be redplating? Just thinking out loud.
Thanks
Mike
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Yes, I have a dedicated bias winding.
Would bias problems go away if you abandoned the dedicate bias tap, and used the 400v or 480v tap instead?
Would the bias change be proportional in such a way that it results in the correct bias (or close enough?)
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There will be no more "funny spikes" than you would normally have by switching any standby switch.
Here's my idea of simultaneously switching the bias. You could make it more elaborate by switching another pot so you would have an adjustment for either voltage setting.
Sluckey
I am getting enthused by this. Certainly with voltages of 400 and 480 and separate bias adjustments for each you could completely adjust each voltage to taste and get two unique sounds. Much better than average in my opinion.
Thanks
Mike
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Yes, I have a dedicated bias winding.
Would bias problems go away if you abandoned the dedicate bias tap, and used the 400v or 480v tap instead?
Would the bias change be proportional in such a way that it results in the correct bias (or close enough?)
Terminalgs
Thank you for your reply. I think what is so good about Sluckey's approach is the ability to adjust the bias for each voltage. You wouldn't then just be stuck with what was left over but you could adjust bias for each voltage to taste. I like that idea a lot.
Thanks
Mike
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If we put the bias on an on-off-on switch and we flip the switch to the middle position which is off or standby are we getting any bias to our power tubes?
Yes. The bias voltage will actually increase to some larger negative value when the switch is in the middle position. So it's a safe condition for the tubes. But so what. Even if you did kill the bias voltage, you also killed the B+, so the tubes are double safe.
Would bias problems go away if you abandoned the dedicate bias tap, and used the 400v or 480v tap instead?
That's very possible.
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If we put the bias on an on-off-on switch and we flip the switch to the middle position which is off or standby are we getting any bias to our power tubes?
Yes. The bias voltage will actually increase to some larger negative value when the switch is in the middle position. So it's a safe condition for the tubes. But so what. Even if you did kill the bias voltage, you also killed the B+, so the tubes are double safe.
Would bias problems go away if you abandoned the dedicate bias tap, and used the 400v or 480v tap instead?
That's very possible.
Sluckey
If we abandoned the dedicated bias tap then we lose the ability to adjust the bias for each voltage level. I like that feature, don't you?
Thanks
Mike
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There will be no more "funny spikes" than you would normally have by switching any standby switch.
Here's my idea of simultaneously switching the bias. You could make it more elaborate by switching another pot so you would have an adjustment for either voltage setting.
Sluckey
Attached is the layout for the dual bias control schematic you drew. This subject has been solved to my satisfaction unless someone has any comments they would like to make.
Thanks
Mike
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If we abandoned the dedicated bias tap then we lose the ability to adjust the bias for each voltage level. I like that feature, don't you?
The idea is that the bias circuit, being a constant function of the input voltage, would produce a bias voltage proportional to the input voltage (400V or 480V).
If your target bias is -43V for the 480V circuit, the same bias circuit, if provided 400V instead, would (I think) produce -36V.
You could put a trim pot in that bias circuit. If you have 480V selected, and you trim your bias to -38V, when you switched to 400V, the bias would be -32.
Did you find a 4 pole ON-OFF-ON switch?
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If we abandoned the dedicated bias tap then we lose the ability to adjust the bias for each voltage level. I like that feature, don't you?
The idea is that the bias circuit, being a constant function of the input voltage, would produce a bias voltage proportional to the input voltage (400V or 480V).
If your target bias is -43V for the 480V circuit, the same bias circuit, if provided 400V instead, would (I think) produce -36V.
You could put a trim pot in that bias circuit. If you have 480V selected, and you trim your bias to -38V, when you switched to 400V, the bias would be -32.
Did you find a 4 pole ON-OFF-ON switch?
Terminalgs
Thank you for your response. It seems to me it would be easier to set the bias for each setting to my liking and then it is done. It is probably because I am familiar with adjusting bias voltage but not familiar with what you are saying. It is not that I don't believe your way will work, it is just that I am familiar with the method Sluckey recommended and still don't quite understand your method.
I bought the 4 pole ON-OFF-ON switch at Del City. It is part no. 7920008 and is quite beefy. Lists a dielectric strength of 1500V AC for one minute. I bought five of them and five of the ON-NONE-ON switches which is part no. 7920007. Should last me a while and have more than enough beef for any guitar amp I will ever make.
Thanks
Mike
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I know I said I was done with this subject but the thought of the preamp plate voltages dropping 17% when the switch was changed from 480 volts to 400 volts bothers me.
The new dual adjustable bias adjustments for the amp that Sluckey proposed gives tonal flexibility to the amp through the ability to adjust the 400 and 480 volt bias supplies individually. I really am enthusiastic about this feature. However, the preamp plate voltage drop of 17% leaves the adjustable B+ as less than perfect.
We still have one switch left on our 4pdt switch. Could we use that for a resistor in the power string to make the plate voltages the same, or different if that is what was wanted, when the B+ was switched from 400 to 480 volts or vice versa. As it is now the plate voltages will drop 17% when the 400 volt setting is selected.
If we could set the preamp voltages so that they are correct to Marshall or Dumble specifications at 400 volts then it would only be necessary to add another dropping resistor to the 480 volt side to get the voltage the same or different if that is what you were looking for. The only issue I see is how to run the wire from the switch to avoid adding noise to the amp. Does anyone know if that will work or have any suggestions?
I have attached the power string for the amp. I think the dropping resistor would need to be between node B and anything downstream of it.
Thanks
Mike
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ARRRGGGH!
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I know I said I was done with this subject but the thought of the preamp plate voltages dropping 17% when the switch was changed from 480 volts to 400 volts bothers me.
Be aware that in the original EVH variac backed Super Lead Plexi scenario, when Edward cranked the 480V down to 400V, the preamp voltages dropped as well..
so.... don't over think the mojo.
If you are looking for alternate uses of the extra switch pole... consider some LED or incandescent bulbs to indicate "EVM mode" or "Angus mode"...
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ARRRGGGH!
That's funny.
Thanks
Mike
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I know I said I was done with this subject but the thought of the preamp plate voltages dropping 17% when the switch was changed from 480 volts to 400 volts bothers me.
Be aware that in the original EVH variac backed Super Lead Plexi scenario, when Edward cranked the 480V down to 400V, the preamp voltages dropped as well..
so.... don't over think the mojo.
If you are looking for alternate uses of the extra switch pole... consider some LED or incandescent bulbs to indicate "EVM mode" or "Angus mode"...
Terminalgs
Compromise position would be to place an extra turret between the B mode on the power string and the downstream supply. For the time being I could just put a solid wire there. If I decided to experiment then I could use the extra spot on the switch and a three conductor shielded wire to make the changes I was considering above.
Thanks for your input, it will probably turn out for the best.
Mike
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My experience with stuff like this is that I very quickly figure out a preferred position for the tone I want and then never really use that feature anymore. Once that happens, I often remove the switching feature in favor of a fixed position. Simple example of that for me was pentode/triode switches. It got left in pentode 98% of the time & I removed the pentode/triode switch.
Maybe your experience will be different and the feature will be worth while to you? Your amp already has so many tonal options to it, I am skeptical whether you will use this very much? My guess is that there are quite a few other features that you will switch or adjust before getting around to using this feature?
With respect, Tubenit
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My experience with stuff like this is that I very quickly figure out a preferred position for the tone I want and then never really use that feature anymore. Once that happens, I often remove the switching feature in favor of a fixed position. Simple example of that for me was pentode/triode switches. It got left in pentode 98% of the time & I removed the pentode/triode switch.
Maybe your experience will be different and the feature will be worth while to you? Your amp already has so many tonal options to it, I am skeptical whether you will use this very much? My guess is that there are quite a few other features that you will switch or adjust before getting around to using this feature?
With respect, Tubenit
Tubenit
Thank you for the reply and your support.
That is why I told my metal man to make me two chassis. I will see what works and doesn't and remove what doesn't from the first amp. I think the chassis that is left over will be a good trial chassis because it will certainly have enough holes for tubes and controls to breadboard almost any amp. If I am happy with everything the way it is, or will be, then I have a chassis for my next project on the shelf.
I am going to start making the boards today. My metal man says my chassis will be completed this week. Of course he also said that last week so we will see.
Thanks
Mike
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My "ARRRGGGH!" was not out of disgust. It was because I knew you could not stand the idea of having an unused pole on that switch. :icon_biggrin:
What you proposed will work. The resistor needs to be shorted by the switch when in the lower B+ position. (See attached.) You can likely use a 3 watt MF resistor but you'll have to determine the value experimentally. You don't need shielded wire. B+ wires are not noisy, nor are they subject to picking up noise from other wires. Filter caps will take care of that. And surely this switch will be located in the power end of the chassis.
Now that you have it all figured out I want you to at least think about it from a safety standpoint before you pull the trigger. Do you really want your very critical negative bias voltage on the same switch with 4 PT HT wires and 2 B+ wires? Is your switch up to the task, and I don't just mean current rating? Will the switch provide satisfactory isolation between the poles? If I was considering doing this, I would be using a high quality mil spec switch. Otherwise I'd probably want to use my safety gloves to operate the switch. :wink:
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Now that you have it all figured out I want you to at least think about it from a safety standpoint before you pull the trigger. Do you really want your very critical negative bias voltage on the same switch with 4 PT HT wires and 2 B+ wires? Is your switch up to the task, and I don't just mean current rating? Will the switch provide satisfactory isolation between the poles? If I was considering doing this, I would be using a high quality mil spec switch. Otherwise I'd probably want to use my safety gloves to operate the switch. :wink:
This is a very important point! (I would not do this in an amp.)
But if I did I would also get a switch like Sluckey said with a plastic handle bat.
Brad :w2:
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My "ARRRGGGH!" was not out of disgust. It was because I knew you could not stand the idea of having an unused pole on that switch. :icon_biggrin:
What you proposed will work. The resistor needs to be shorted by the switch when in the lower B+ position. (See attached.) You can likely use a 3 watt MF resistor but you'll have to determine the value experimentally. You don't need shielded wire. B+ wires are not noisy, nor are they subject to picking up noise from other wires. Filter caps will take care of that. And surely this switch will be located in the power end of the chassis.
Now that you have it all figured out I want you to at least think about it from a safety standpoint before you pull the trigger. Do you really want your very critical negative bias voltage on the same switch with 4 PT HT wires and 2 B+ wires? Is your switch up to the task, and I don't just mean current rating? Will the switch provide satisfactory isolation between the poles? If I was considering doing this, I would be using a high quality mil spec switch. Otherwise I'd probably want to use my safety gloves to operate the switch. :wink:
Sluckey
You are correct. An unused pole on a switch or an unused triode will drive me up a wall. It feels like I didn't get my $3 worth out of the switch.
As for the safety factor, I have attached the data sheet for the switches. The ON-OFF-ON and the ON-NONE-ON are rated the same. Seems pretty hefty to me. Willabe sent a post suggesting a plastic handle bat. Something like a rubber boot to go over it would be a good idea. Getting electrocuted by my amp sounds like a bad day to me. Need to make sure I avoid that.
Good news from my chassis guy. My chassis are ready and I am headed over there to get them. I will be getting this project off the ground today.
Thank you for the schematic. Presuming the switch with a rubber boot on it is deemed safe enough, I may be adding it. Going to try the amp with the lower voltage on the preamp plates first to see if I like it. If not I will experiment to see if I can find some setting that makes having a high and low voltage capability worthwhile.
Thanks
Mike
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If the switch is up to the task I would not be concerned about an insulated toggle. Those Chinese symbols on the drawing do raise my eyebrows though.
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If the switch is up to the task I would not be concerned about an insulated toggle. Those Chinese symbols on the drawing do raise my eyebrows though.
Sluckey
Do you think it would be a good idea for me to send you one in the mail. You may be able to tell if it is any good or not. As far as the Chinese characters, while I don't disagree with you that they are not ideal but what isn't made in that part of the world today. Don't know where Carling is making their switches now but I would be surprised if it wasn't somewhere in Asia. I know that the CTS pots are being made over there and based on my recent experience with the 12A jack, I would expect they are now being made over there as well.
I do know that everything that is made in China is not junk. However, if the Chinese are told to make something cheaply they will do that and it will be junk. If they are told to make quality components they seem to be able to do that too. I am buying them from Del City Electronics out of Wisconsin. I will call them and see if they have a tech that can enlighten me further regarding the switches. Will let you know what I find out. In the meantime if you want one of the switches let me know and we can make arrangements to send one to you.
Thanks
Mike
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If the switch is up to the task I would not be concerned about an insulated toggle. Those Chinese symbols on the drawing do raise my eyebrows though.
The tech that I spoke with at Del City Electronics says he has been with the company for two years. They have been selling the switches for the entire time he has been there and he hasn't heard one complaint or had any returns where the switches are concerned. I think they are probably as safe as anything available today. Certainly in our litigious society if someone was electrocuted by one of their switches he would know.
Thanks
Mike
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I'll bet you're the first person to use one of those switches in a configuration to control high voltage AC and high voltage DC.
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I'll bet you're the first person to use one of those switches in a configuration to control high voltage AC and high voltage DC.
Is there a way to throw 1500 VAC and 500 DC at the switch and test it? Maybe even higher DC to be safe.
What would we test for. I guess you wouldn't want the power in one switch to transfer into another switch. They would need to be isolated from each other. Tops on my list is you wouldn't want the power to jump to the toggle switch. That would not be good.
Question: Is it the high volt AC and high volt DC combined in the same switch what you are most concerned about?
Thanks
Mike
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I'll bet you're the first person to use one of those switches in a configuration to control high voltage AC and high voltage DC.
Sluckey
I had another thought. If I am adjusting the voltages from the screen node I will be at around 480 VDC and probably more at start up. If it is only rated for 500 VDC then it is not beefy enough I wouldn't think. Might be a good idea to keep DC off the switch if it is at or near the stated limit of the switch for safety sake.
Thanks
Mike
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I would be using a high quality mil spec switch. Otherwise I'd probably want to use my safety gloves to operate the switch. :wink:
It feels like I didn't get my $3 worth out of the switch.
A new $3 switch (as apposed to NOS surplus switch) is not a high quality mil spec switch with 500dcv+ specs. It's not so much about where it's made it's the spec it's made to (and IF what they claim is real world reliable in at those claims/spec in use) and I really doubt that a new $3 with that many contacts, what 4P2T(?) is built to high voltage mil. spec.
For an example, Doug sells a carling SPST (big body) switch for $4.50 and I don't know if that's mil. spec, I don't think so. We know that that switch works for a standby switch for many years at 450+dcv but it's only make/break 1 wire connection in the B+ rail, there's nothing right next to the contacts to arc-over too.
The carling short bat SPDT, 3 position, center off (big body) switch he sells is $5.30. (Don't forget there's not more only external contacts, there's more internal contacts too, so more $$.)
Brad :icon_biggrin:
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Question: Is it the high volt AC and high volt DC combined in the same switch what you are most concerned about?
Bingo!
But also the bias voltage is in very close proximity. You got a lot of expensive stuff riding on the bias voltage pony. Maybe I'm being over cautious. But if you only paid $3 for that switch I would not call it a quality switch.
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But also the bias voltage is in very close proximity. You got a lot of expensive stuff riding on the bias voltage pony. Maybe I'm being over cautious. But if you only paid $3 for that switch I would not call it a quality switch.
No your not, for the reason's you have stated.
Bias voltage goes so do the output tubes and maybe the OT. Or the B+ could arc over to the bias voltage and you now have put 450+dcv's on the power tube grids? That's not good.
I've been here now ~4 years? I don't remember anyone trying this, I'm not saying it can't be done but your dealing with the highest voltages and the most current (plus the -bias) in the amp. (Maybe someone did and they will post their results with the switch brand they used?)
Brad :w2:
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But also the bias voltage is in very close proximity. You got a lot of expensive stuff riding on the bias voltage pony. Maybe I'm being over cautious. But if you only paid $3 for that switch I would not call it a quality switch.
No your not, for the reason's you have stated.
Bias voltage goes so do the output tubes and maybe the OT. Or the B+ could arc over to the bias voltage and you now have put 450+dcv's on the power tube grids? That's not good.
I've been here now ~4 years? I don't remember anyone trying this, I'm not saying it can't be done but your dealing with the highest voltages and the most current (plus the -bias) in the amp. (Maybe someone did and they will post their results with the switch brand they used?)
Brad :w2:
If anyone can or knows someone who can test one of these switches I would be glad to send one or more to them to test. It is probably no secret by now that I like to poke at the edges of what can be done. However, I will not do it at the expense of safety. I am somewhat stubborn but I strive to not be stupid. My goal is to make amps that will last in excess of fifty years and operate safely.
The switches supposedly were $16 switches marked down to $3. However, if you can buy them for $3 they are $3 switches. I mentioned how much I paid for the switches because I thought it was relevant and it most likely is. Generally, you get what you pay for but 20 years ago you could get a nice leather bombers jacket in China for $18. Not all of the product pricing coming out of Asia makes economic sense. Much of it is government supported to promote job growth.
The reason I am babbling on about this is the only true way to know whether the switches are any good would be to test them under stress loads. If nobody on the forum considers it a hobby to test switches I guess I am out of luck. To do it properly I suppose it would have to be cycled thousands of times while under stress load which I am thinking might not make for a very enjoyable Friday night. I don't think I could get my wife to spend Friday night flipping a switch back and forth over and over again when the purpose of the test is to make sure it won't electrocute anyone. I know for sure I am not volunteering for the job.
I suppose I should take the conservative approach and pull out a Carling DPDT switch and test each voltage individually to see if it even makes enough of a difference to justify the fuss.
Thanks
Mike
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Mike,
We all want you to be successful and enjoy the amp (safely). Please note the "caution" that has been conveyed by some very experienced builders regarding this idea.
Anything that Sluckey was hesitant about from a safety standpoint, I would not even remotely consider.
Respectfully and with best regards, Tubenit
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Mike,
We all want you to be successful and enjoy the amp (safely). Please note the "caution" that has been conveyed by some very experienced builders regarding this idea.
Anything that Sluckey was hesitant about from a safety standpoint, I would not even remotely consider.
Respectfully and with best regards, Tubenit
Tubenit
I agree 100%. If a component is unsafe or may result in premature failure of the amplifier then the appropriate thing to do is to not use that component. I know you have been encouraging me to take a more conservative approach because of the experience you have. Part of what I like to do is explore possibilities. It is how I learn.
In this instance after exploring the options it is only appropriate to accept the recommendations of wise counsel. I appreciate everyone's participation in trying to find a solution to what I was trying to accomplish. I think it comes down to the fact that we do not have sufficient confidence in any toggle switches larger than the Carling DPDT switch.
The Carling switches have been used successfully for many years. It would be very nice if a 4PDT toggle switch existed that was known to be reliably able to do what I wanted to be able to accomplish as has been discussed in this post. Unfortunately, I don't know of any that fit that category. Our other option was to split the rectifiers but that is impractical because too many electrolytics would be required and limited space precludes the use of same.
Thanks to all that have participated in this post. I have learned a lot from this exercise.
On a side note, I got my chassis today and they look great. Will get to work building the amp and figure out what works and doesn't work. What is worthwhile and what isn't worthwhile. I think having the separate tone stacks will in the long run be a good thing. The active effects loop that can be switched out of the signal path should be worthwhile. The overdrive circuitry is up in the air and is a we will have to see type of thing. The different voltages and appropriate bias and plate voltage settings is an experiment I am looking forward to. Only time will tell whether that experiment is fruitful.
In the end if I end up with a Plexi/800 amp with individual tone stacks that can each be used with an A/B/Y switch the project will be a success. I look forward to your future help and wise counsel and again much appreciation for the help and support you have given me.
Thanks
Mike
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Mike, We all want you to be successful and enjoy the amp (safely).
Yes, absolutely, what Tubenit said. :icon_biggrin:
It is probably no secret by now that I like to poke at the edges of what can be done.
That's fine, it can be very good to poke/push things and experiment to get new results, new boundary's. The guys here and on other fourms do that all the time. :icon_biggrin:
But........ some things are much easer to 'poke' than others. Like high dcv and current. :w2:
Again I'm not saying and I don't see anyone else saying it can't be done, it's just this 1 needs to be thought out from a stress and safety point with the right parts to get'er done.
Brad :icon_biggrin:
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Mike,
I love to see innovative ideas and amp designs! Your amp easily qualifies as a unique "one of a kind" approach. I am anticipating your amp sounding great! I think once it's built and you have tweaked it, it will a remarkable and superb creation.
:thumbsup: :thumbsup:
I look forward to your project coming together. I think you have taken a very thoughtful and reasonable approach to this & all your efforts will pay off for you, IMO.
A bunch of us are rooting for your success and will cheer you on (and help when and if you need some input).
With respect, Tubenit
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Yeah, what he said! Now quit talking 'bout it and get busy! :icon_biggrin:
We're all eager to see this amp fired up.
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Mike, We all want you to be successful and enjoy the amp (safely).
Yes, absolutely, what Tubenit said. :icon_biggrin:
It is probably no secret by now that I like to poke at the edges of what can be done.
That's fine, it can be very good to poke/push things and experiment to get new results, new boundary's. The guys here and on other fourms do that all the time. :icon_biggrin:
But........ some things are much easer to 'poke' than others. Like high dcv and current. :w2:
Again I'm not saying and I don't see anyone else saying it can't be done, it's just this 1 needs to be thought out from a stress and safety point with the right parts to get'er done.
Brad :icon_biggrin:
Brad
You and others provided very sound advice. I appreciate your input.
Thanks
Mike
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Mike,
I love to see innovative ideas and amp designs! Your amp easily qualifies as a unique "one of a kind" approach. I am anticipating your amp sounding great! I think once it's built and you have tweaked it, it will a remarkable and superb creation.
:thumbsup: :thumbsup:
I look forward to your project coming together. I think you have taken a very thoughtful and reasonable approach to this & all your efforts will pay off for you, IMO.
A bunch of us are rooting for your success and will cheer you on (and help when and if you need some input).
With respect, Tubenit
Tubenit
Thanks as always for your kind words and inspiration.
Mike
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Yeah, what he said! Now quit talking 'bout it and get busy! :icon_biggrin:
We're all eager to see this amp fired up.
Sluckey
Got both of my chassis and the faceplate and back plate came in today. I drilled the holes for the tubes today and drilled and tapped the holes for the bias circuit that will be place one the inside of the front of the amp. Tomorrow I will put the faceplate and back plates on and get started on the boards. I think I have all my parts here or they are on there way over the next few days. After the faceplate and back plates have had a day to set I will drill the holes for the jacks, pots, switches, etc. Then it is a matter of installing the transformers and hope for the best.
I will try to get my daughters to take some pictures for me. My camera proudly proclaims "Sponsor of the 1980 Olympics" on it so needless to say it won't be of much help but my daughters are able to take pictures so I will try to post some tomorrow.
Thanks for all your help.
Mike