lego's spin on Sluckey's AC15

[sluckey]

Ed, I did some checking this morning.

1. I don't have any squeals with the cut control at any position, even with both volume controls set to max.

2. I had just the opposite results concerning jumping channels and input jacks. My input jacks had dirty switch contacts. Bet yours do too. I just used some sandpaper and contact cleaner to fix mine. Once the jacks are cleaned and switching properly you will need an open plug (not shorted) inserted in the unused input jack to get any sound when jumping the channels.

Lego, to lower the B+ just insert a 250Ω resistor between V8-3 and the STBY switch. I have an idea that will be easy to implement. It basically replaces the SPST STBY/OP switch with a three position DP switch that would provide STBY/SAG/OPERATE functions. The dropping resistor would mount directly to the switch. Doug has the switch.

BTW, I've updated my web page to include a better gut shot that also shows the Brilliance Switch mod. And the original PDF has been updated to show all the changes we've talked about throughout this thread.

[Ed_Chambley]

Awesome Ed, I feel better knowing another amp has fired up. I thnk I'll be the only one with the two board version tho. Details on your tweaks for lowering the voltage, it's not that I can't look it up but I'd rather see it from you guys. I should order my cabinet so it's here when I'm done. I think I want a combo now , but how would I do that with the way the chassis is built

With a combo you can mount the amp to the back panel just as you would mount it to the botton of a headbox.  This is one method and works well if your back panel is thick, like 1/2 inch plywood.


Another method, which I prefer is to drill holes at the end of the faceplates and matching holes in the tip of the main cabinet like a tweed and many other amplifiers from the late 50's and earlier.  The huge benefit in this method is when you remove the back panel the entire amp is right there.  Makes it easy to change tubes and check bias and do some repairs.  Some of the newer amps are this way again, but doesn't make them much easier.  Like the Hot Rod Deluxe, bit it is easier to change tubes and set the bias than in a Blackface Deluxe.


If I hang the chassis like I mentioned, i usually use large fender washers and acorn nuts to finish it off.  It will need a vent in the top behind the handle for a heat vent for the tubes.  I put one in my head box and at the rear also.


The only difference in the 2 boards is the filter caps are together.  Gotta remember all those loved Fender amps were done that way and did not hurt the tone of the BlackFace amps.  If anyone has an old BlackFace amp they do not like, PM me and I will take it off your hands.

[Ed_Chambley]

Ed, I did some checking this morning.

1. I don't have any squeals with the cut control at any position, even with both volume controls set to max.

2. I had just the opposite results concerning jumping channels and input jacks. My input jacks had dirty switch contacts. Bet yours do too. I just used some sandpaper and contact cleaner to fix mine. Once the jacks are cleaned and switching properly you will need an open plug (not shorted) inserted in the unused input jack to get any sound when jumping the channels.

Lego, to lower the B+ just insert a 250Ω resistor between V8-3 and the STBY switch. I have an idea that will be easy to implement. It basically replaces the SPST STBY/OP switch with a three position DP switch that would provide STBY/SAG/OPERATE functions. The dropping resistor would mount directly to the switch. Doug has the switch.

BTW, I've updated my web page to include a better gut shot that also shows the Brilliance Switch mod. And the original PDF has been updated to show all the changes we've talked about throughout this thread.

I bet I do as well.  I also bet that is where the squeal is coming from.  Lease I have had open inputs cause noises.  Anyway, thanks for checking.  The squeal is not very bad and I am sure it will be simple to find.  I am not concerned at all.  At least now I know it is something that can be fixed.  I was so excited last night playing it, I did not care as it has to be almost wide open to squeal anyway.


The switch idea sounds good, but I would never use the sag and I did not notice any additional sag that was not present from the tube.  I promise I was running it WIDE OPEN


Why do you propose the sag switch?  Heat?


I do not trust that JJ rectifier tube so much that I installed 3 series diodes exiting pin 3.   Did you have the Mullard already?  Do you ever buy NOS tubes?  From where?  I am looking for one now.  I have 2 pulls, but I sure would like to find an old new one.   Then I could just forget about it forever.

[Ed_Chambley]

Another thing.  I built another rail for the back of the chassis similar to the front.  I really like working with the metal wire over the copper I used to use.  You are correct about the floor noise.  I cannot even hear the amp.

[sluckey]

Why do you propose the sag switch?  Heat?

Just thought I'd throw that idea out there. I'm not fond of using a resistor to drop the main B+ voltage. I believe that was your idea. I thought it might be handy to switch back and forth between 350VDC and 304VDC. Then you would know if there is really much difference in the tone.

I do not trust that JJ rectifier tube so much that I installed 3 series diodes exiting pin 3.

What does that do for you?

Did you have the Mullard already?

I don't have a Mullard. It's a Telefunken. It came in one of the Hammond AO-44s that I have. I also have a couple of JJs.  One is in my Marshall 18W and the other is in my AC15 Lite. I can't tell any difference except that the JJs are prettier. 

[sluckey]

Ed, about the Celestion Blue, what power rating and impedance do you recommend for this amp?

[lego4040]

So as for dropping the B+ voltage and you not being fond of the 250ohm resistor, what options are there? Changing the rectifier would work wouldn't it, I haven't  looked into which would work as a replacement. What about adding a bias pot? If yours worked out then I dont see why I should worry Thanks for the tip on the combo, I thought about putting it in a tweed cab, Which one

[Ed_Chambley]

Ed, about the Celestion Blue, what power rating and impedance do you recommend for this amp?

They only come in 1 power rating and that is 15 watts.  In reality the wattage is more.  I am using 16 ohms, but you do not have a 16 tap do you.  I prefer to use the largest tap I have available when possible.  Something about using all the windings in the transformer has stuck in my mind ever since a pedal builder said it to me at a NAMM show.


I tried a JBL and a Altec and they both sounded very nice.  All the Jensen types, Weber etc sound good, but do tend to be a tad sharp and sound better with 6v6 to me.


These speakers and amp go together like pecan pie and ice cream.


I skipped lunch today.

[sluckey]

So as for dropping the B+ voltage and you not being fond of the 250ohm resistor, what options are there?

Honestly, I'm happy with the voltages I have. I believe you will be too. You won't be disappointed.

The resistor is the dead nuts easiest/cheapest way to go from 340V to 300V. New PT is the most expensive and that's a gamble. You may not get the voltage reduction you expected.

Why not put this on the back burner until you have some actual measured voltages and an idea of the sound with those voltages?

[Ed_Chambley]

Why do you propose the sag switch?  Heat?

Just thought I'd throw that idea out there. I'm not fond of using a resistor to drop the main B+ voltage. I believe that was your idea. I thought it might be handy to switch back and forth between 350VDC and 304VDC. Then you would know if there is really much difference in the tone.

I do not trust that JJ rectifier tube so much that I installed 3 series diodes exiting pin 3.

What does that do for you?

I read in the Trainwreck papers where it protects the rectifier and transformer.  Probably not the case, right?  See the last page of this PDF.  Except I stated whet I did wrongly.  I have them between the Transformer and the tube on both HT's.


http://www.blueguitar.org/new/schem/trainwreck/the_trainwreck_pages.pdf
This shows tube protection.  Not a bad idea in any build since diodes are so cheap.  I use them often.  May not do much, but I feel better.


BTW, I just ordered a Mullard Rectifier, but the JJ power tubes get good reviews.

[Ed_Chambley]

So as for dropping the B+ voltage and you not being fond of the 250ohm resistor, what options are there?

Honestly, I'm happy with the voltages I have. I believe you will be too. You won't be disappointed.

The resistor is the dead nuts easiest/cheapest way to go from 340V to 300V. New PT is the most expensive and that's a gamble. You may not get the voltage reduction you expected.

Why not put this on the back burner until you have some actual measured voltages and an idea of the sound with those voltages?

+1, the amp sounds great with the voltages at 330 to 340.  You will love it.  I am just weird.

[lego4040]

$260 for a 12" 8ohm celestion blue

[Ed_Chambley]

$260 for a 12" 8ohm celestion blue

Sorry Buddy, they are expensive.  I would go with a Greenback 25 watt next if that were to pricy or a Blue Dog Weber in low watts.


Keep an eye on Craigslist.  That is where I get the majority of mine, ebay gets too expensive but sometimes I find a good deal there as well.

[lego4040]

I had two 10" greenbacks in crate vintage club 30 when they just came out with that amp. I'll look at those blue webers and maybe sell a cigar box guitar for some cash

[lego4040]

Ed, on that TrainWreck schem they are using a 6v6 type tube and pin3 with diodes to ground. The el84 would be pin 7, so by adding those diodes onto to pin 7 then to ground is what you did? I'm all for safety and saving components. That mod is like $1.00

[lego4040]

Like thishttp://ampgarage.com/forum/files/tw_express_layout_rlw_18_635.pdf

[lego4040]

Sluckey on your power tubes you just used the 1 ohm power resistor from board to pin 3! Genius , I think I'll mark that change

[Ed_Chambley]

Ed, on that TrainWreck schem they are using a 6v6 type tube and pin3 with diodes to ground. The el84 would be pin 7, so by adding those diodes onto to pin 7 then to ground is what you did? I'm all for safety and saving components. That mod is like $1.00

I referred to the wrong thing.  No need to do this.  I put diodes on the HT wires from the PT.  No need to do this, but you can.

[lego4040]

  less work. I am ready to wire up the 6 pole tone switch. The pins don't exactly line up with your pic Sluckey but is it safe to say that I should count 6 tabs that make contact with tab as one side and the other is for other tab

[sluckey]

Without seeing the switch I'd say that's probably safe. However, it only takes a couple minutes with an ohm meter to remove all doubt.

[lego4040]

It's the switch that you posted from antique supply. 2 pole/ 6 pos, MBB.  I could do that with the meter. I get ahead of my self. I'm working on trying to figure out how scaffold company is gonna work. They need 150amps to run 5 rigs down my building in midtown. We are maxed out

[lego4040]

I dont have a .0015uf for the switch, can I sub with a .001uf

[Ed_Chambley]

I dont have a .0015uf for the switch, can I sub with a .001uf

Sure it will.  Just looking for some variety in tones.  I have found I like the larger caps.


I meant to mention it.  I tried the amp with Greenbacks and it sounds really close to the Blue.  Not the Vintage 30 tho.  Highs are sharp.  I also ran it with a single Celestion Gold 10" and it was very nice.  I am thinking about making a single 10 cab.

[lego4040]

Got a few more leads soldered today, not much tho. I did the rotary switch( thanks for the help Sluckey), one input and the standby here v8-3 to one side of standby, the other side has lead from cap board +one leg of choke. The other leg of choke is B capped to other hot lead from cap board

[jojokeo]

I dont have a .0015uf for the switch, can I sub with a .001uf

Sure it will.  Just looking for some variety in tones.  I have found I like the larger caps.


I meant to mention it.  I tried the amp with Greenbacks and it sounds really close to the Blue.  Not the Vintage 30 tho.  Highs are sharp.  I also ran it with a single Celestion Gold 10" and it was very nice.  I am thinking about making a single 10 cab.

Wow Ed, you and SG both getting your amps up and running within a few days of each other!? Congrats! I love the golden 10 also. If I had two that were needed I'd probably match it to a Weber Blue pup. Not sure if you had one of those or not? But the Blues are nice too. Another thing with a 10 that I have in a EF86 and EL84 that I think you'd really love is...don't laugh...an Eminence Ram Rod. I don't know what it is exactly about that speaker but it's up there with any of them. When you start playing and something just sounds right and makes you want to keep playing and playing...? I highly recommend this one if you can give it a try. I'd love to hear your thoughts too.

[Ed_Chambley]

I dont have a .0015uf for the switch, can I sub with a .001uf

Sure it will.  Just looking for some variety in tones.  I have found I like the larger caps.


I meant to mention it.  I tried the amp with Greenbacks and it sounds really close to the Blue.  Not the Vintage 30 tho.  Highs are sharp.  I also ran it with a single Celestion Gold 10" and it was very nice.  I am thinking about making a single 10 cab.

I assume you mean a 10" Ram Rod.  Let me know and I will "find" one.  I know you are speaker crazy, just like me so I really respect your opinion.


June 11th, I will be gone for  while as I am having disk replacement.  I wish you a complete spededy recovery.
Wow Ed, you and SG both getting your amps up and running within a few days of each other!? Congrats! I love the golden 10 also. If I had two that were needed I'd probably match it to a Weber Blue pup. Not sure if you had one of those or not? But the Blues are nice too. Another thing with a 10 that I have in a EF86 and EL84 that I think you'd really love is...don't laugh...an Eminence Ram Rod. I don't know what it is exactly about that speaker but it's up there with any of them. When you start playing and something just sounds right and makes you want to keep playing and playing...? I highly recommend this one if you can give it a try. I'd love to hear your thoughts too.

[jojokeo]

Yes Ed they only make the Ramrod in a 10" size. It is doped w/ large magnet for it's size & rated higher than most 10's @ 100dB efficiency. Good luck with your disk too. The recovery period still sucks but it's the end result that counts and at least knowing that things will get better eventually. The nerve block works wonders initially and only needed pain meds for a few days, hope yours is similar. Maybe neodymium speakers are in our future? Probably not but it makes the 10's seem more attractive now don't it? 

Give a listen specifically to Tomo Fujita's demos as they are most representative of how it sounds in person: http://www.eminence.com/support/tone-guide/?model=Ramrod

[lego4040]

got the buss up and soldered to pots and the speed switch done.

[SILVERGUN]

Looks GREAT lego!

 

[sluckey]

We need bigger pics.

[lego4040]

Out of respect I am keeping pics small if someone wants a picture larger I would gladly email. I already see where I'm going to fix some solder joints. Of coarse I pulled out the surf rod for some weekend stripe bass/ blue fish fishing

[sluckey]

I understand that but you went from one extreme to another.

[lego4040]

Ok next one will be bigger

[sluckey]

Ed, here's a channel jump switch that will positively work. Be good if you could squeeze the switch in between the input jacks.

[lego4040]

Gotta use a subminiature for that one, is that on/on/on

[sluckey]

Gotta use a subminiature for that one, is that on/on/on

It's a mini DPDT two position.  on/on

This is my preferred jumper...

[Ed_Chambley]

Gotta use a subminiature for that one, is that on/on/on

It's a mini DPDT two position.  on/on

This is my preferred jumper...

OI have a few of these types.  The switch is easy and a good mod, I think I like it.  I will use a mini long bat.  Got a few of them around.


I have overworked myself and I am having to take it easy.  I absolutely love this amp.  Last night I was playing Tom Petty with a Gretsch 6120 (a friends) through it and it really sounds great.  I am going to take a break since all I have left is these little things like the switch you proposed and also I am just about finished with a footswitch.


I have been rolling tubes and I found a few nice ones I did not know I had.  Thanks for the switch idea.

[sluckey]

Speaking of switches, I can't believe you haven't noticed the switch next to my footswitch jack. 

[lego4040]

Hey guys, the Hammond 270fx has two choices for main hook up. Grey/white for 115v and black/white for 125volts. I'm reading 120 volts at my outlets, should I use the 125v hookup

[g-man]

Deleted

[sluckey]

I'm reading 120 volts at my outlets, should I use the 125v hookup

Yes.

[sluckey]

Fast/Slow switch?

 

[lego4040]

Thanks Sluckey, got more done and will post pics. Of coarse I soldered up 115v like a dummy. That's a 2 second change

[lego4040]

trying to keep it neat, I ran the secondary 6.3 to lamp first then to heaters. I had more room on those tabs first

[Ed_Chambley]

Speaking of switches, I can't believe you haven't noticed the switch next to my footswitch jack. 

Still cannot see it in your build page.  Did you post another photo?  I don't see it on the schematic.


Spill the beans, what you been doing?  I have a couple of things I am going th have to change on the wiggle channel.  Maybe I need to know this as well.

[sluckey]

It's just a fast/slow switch. If you don't see it maybe you need to refresh/reload the page.

[lego4040]

Almost there. I'll post some updated pics later. Have a great Memorial Day Weekend

[sluckey]

Another minor mod...

IMO, the AC-15 Vib/Trem has a design flaw. The footswitch operation has a delayed turn on. IOW, step on the footswitch for that sweet Vib sound and it may be a second or longer before you actually get the effect.

This is because the footswitch in the original circuit disables the oscillator. When you turn it on with the footswitch, it takes time for the oscillator to build up. That's just the way it is.

But if you're like me, when you stomp the footswitch, you want the Vib now, not later. There's a simple solution that I've used in the Revibe and other trem circuits... Just leave the oscillator running all the time and kill the LFO signal farther downstream. This can easily be done with a simple mod.

Move the existing wire on the tip of the footswitch jack to the sleeve (ground) lug. This enables the oscillator all the time. Now connect a wire from the tip of the footswitch jack to the top side of the Depth control (or Depth Preset if you have an original). That's all!

Now you have instant VIB when you step on the switch.

[lego4040]

  That's easy enough, top side? Leg 1or 3.  For people who have bought empty combo cabs, I've looked at Mojo, Mather, sour mash and weber. I might keep it simple and go with mojo cause I can get speaker at the same time. Any preferences out there

[sluckey]

That's easy enough, top side? Leg 1or 3.

Top when looking at the schematic. Right lug when looking at the layout. But regardless of your viewpoint, it's the outside lug that ain't grounded. I recommend trying it as is first. You may be happy just the way it is.

I've been kinda drooling for this cab with Blue lately. I really like the blonde pic...

     http://www.avatarspeakers.com/vintage%20g112.htm