Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tubenit on June 26, 2013, 08:20:04 am
-
I love the overdrive and FAT tone of the HoSo56 with it's slight chime. And while I could get a beautiful clean tone out of my HoSo56, it had to be done by lowering the guitar volume or volume pot on amp volume.
I love the clean channel of my D'Mars ODS better than any clean tone I've gotten out of an amp.
So I was pondering this am about "how could I maybe get both in one amp?" A nice clean tone that I could switch for a FAT slightly overdriven tone. Note the 1MA for the clean volume and the 500ka for the OD volume.
I was thinking two relay switching one between the clean 12AY7 V1a and the 5879 pentode. And the other relay for the mid boost since I have a strong preference for that on my amps.
Any thoughts? Think this could be switched on the fly without popping noises?
With respect, Tubenit
-
I was pondering having both the D'mars and the HoSo56 initial preamp sections in my current build. Was going to look at switching or mixing into the grid of current D'Mars V1b and using the FET cathode(Source) follower instead of HoSo cathode follower. The bias on that valve is a bit different between the two amps so I was wondering about a compromise bias between the two. Wanted to use an EF86 coz the D'Mars already has the 5879 sound.
The relay solenoid switching low level guitar signal may induce hum/ripple/crackle, if so a suitable snubber circuit on the relay solenoid may need to be devised. Just my inexperienced two bobs worth.
Won't know if you don't give it a go.
-
Glenn,
Thanks for the thoughts! They are appreciated.
The bias thought is interesting. One could change the bias on V1-3 to match whichever of the first gain stage and have dual switching simultaneously (if needed)?
Geezer and I experimented with 6AU6 and 5654 (thanks to Sluckey supplying one) in the V1 position on HoSo56's. I thought those sounded good also as an alternative to 5879's. It's been a while but I seem to remember really liking the 5654 tone in the first gain stage. I think the max voltage on 5654 plates needed to be watched.
Don't know about the EF86? I think that's gonna give ALOT of overdrive and little headroom in the clean channel.
With respect, Tubenit
-
Hi Jeff your brain is an erupting volcano
every few days you've a new good idea :thumbsup:
K
-
Hi Jeff!!!
It's really amazing your willing to share one-of-a-kind amps!!!! Keep them coming!! :worthy1:
I relocated the switch so that you can smack the pentode harder. Don't know if this is what you are after??? I kept both pots, there is, before and after the pentode stage so that you can dial how much drive you want.
Hope this helps.
With Respect,
Best regards,
R.
-
Jeff I have always found its best to run your input to both tubes at the same time and switch after the fact before tonestack or maybe 2 tonestacks and switch a volume after the tonestack for the clean channel like you did in the old TOS just a thought.
Thanks for thinking outside the box again Bill
-
My goal is to recreate the original HoSo56 sound .............. AND the original D'Mars clean channel sound as best as possible with the fewest tubes used. I love both those amps would love that tone in one amp.
Rzenc, Your idea is a great idea! And using the 5879 sort of as a Hoffman "hot switch" is good thinking. I've done that before but it will not allow me to reproduce the original HoSo56 tone which is essential to the effort on this amp design.
Bill, Not sure what you are saying there?? Got a schematic that you could show, please? Is this idea going to accomplish the goal that I have stated in this reply. I'm trying to envision what you are suggesting.
With respect, Tubenit
-
Jeff were you have the switch now just run into the 2 tubes just like you have it, and between the 2, 100k resisters and V1b put the switch, that way its exactly the same just a better switching spot. That way you can put the non used channel to ground which in past experiance makes it quieter.
But the volume after the clean channel and possibly 2 tone stacks were just ideas to throw around.
If you remember your first version of the TOS you had a volume that would switch in just for the clean channel so you had a better chance of matching the two volumes togther.
Im thinking because one channel is clean and one has a little more gain that would be helpful in this one to.
Just thoughts to throw around you think outside the box alot, I was just joining in the fun.
Thanks Bill
-
Yes Sorry for getting this side tract you had a great idea and I kind of got it going sideways . I was interested because i always wanted to try the hoso56. but i think this idea here that you have is way better. blending a unique lead channel with an exellent clean channel. I must be getting old but I need a good clean channel in every amp I play (LOL).
So thanks for coming up with the idea.
Bill
-
Who's going to be first up to give it a try.
Bill
-
Bill, thanks for the help with this. I do think your idea of switching prior to V2b is a good idea.
I am going to seek some input from Geezer on this idea especially since the HoSo56 is his design and is such a great amp.
I "think" this will get the HoSo56 tone reasonably well but not totally certain. Geezer can probably make a better guess about that.
I've tweaked the schematic already and have drawn up a layout now that I will post later. I am considering building this for myself.
with respect, Tubenit
-
Tubenit, something you've probably already thought about... but IIRC lower voltage for the 5879 was pretty important. Maybe use a voltage divider at the end of the power rail, so you could lower the voltage to the 5879? That is if the standard dropping resistor didn't do it for you.
As with all your excellent ideas, I'm watching closely! :smiley:
-
I'm sure that circuit was there, or am I hallucinating schematics.
-
OK, looking at parts I have on hand and then costs of ordering more ................ I can build this amp reasonably inexpensively. So I've just finished ordering parts that I need.
I don't really need a 3rd amp but intuitively I am thinking this might be a winner and very versatile.
So, I will start on it probably next wkend (7/4 wkend) by building the board and punching out a blank chassis.
Anyone else interested in a collaborative effort over this forum and trading notes and observations and tweaks?? Meaning you're interested in starting this build in the next few weeks? I've enjoyed doing that with Geezer in the past and found trading information to be quite useful.
I am going to build if first with toggle switching from the clean/5879 OD & midboost and then come back later for relay switching after tweaks are done.
With respect, Tubenit
-
Will splice the front end onto my D'Mars EL84 during that time frame and tweak as best I can.
Have a spare 5879 and unused socket in place.
Have not put in FX section yet and I think the EL84 version needs that as an essential part of the gain structure.
Notice you've changed bias on V1b, easy to accommodate with some parallel R's and a switch.
All the best.
-
Im a few cap and resister boxes and some more of my breadboard items away from testing sadly 2 to 3 weeks out .
Bill
-
Well, I went ahead and punched out the chassis today. Turned out nice!
IF anyone is interested in doing this build along with me and trading notes and tweaks ........... this is the chassis I am using. It's an inexpensive blank off ebay. Since Hoffman doesn't carry chassis blanks, I thought I'd share how I am approaching this. With the chassis being 17" x 8" x 2", it should have plenty of room to install the relays.
Using a 275-0-275 100ma PT to use either 6K6's with 5Y3GT or 6V6's with GZ34 or 5V4. Hoffman's 18w PT & OT should work fine also.
http://www.ebay.com/itm/Tube-Amp-Chassis-17x8x2-12-gauge-/181111392458?pt=LH_DefaultDomain_0&hash=item2a2b1488ca (http://www.ebay.com/itm/Tube-Amp-Chassis-17x8x2-12-gauge-/181111392458?pt=LH_DefaultDomain_0&hash=item2a2b1488ca)
Getting pretty enthused about this build!
With respect, Tubenit
-
This looks like just the thing for that gutted out Judybox I bought a while ago. Just need to order up some caps and a 12 AY 7 (would a 5751 be OK?) Oh man, how am I going to fit this with all the other projects I have lined up?
-
I think a 5751 could sound good. I've used one in that position before and liked it. The 12AY7 would simply give a cleaner tone and offer more contrast with the 12AY7.
With respect, Tubenit
-
Jeff, what differences other than micro-phonic issues in the 5879 as opposed to the ef86? I really like the idea of this build, but was just wondering about your tube choice. I know you like the tube. They seem cheap as far as I can tell. What brand do you prefer as I plan to bet a couple. I have everything else onhand.
-
5879 does not have as much gain as an EF86. I have 5 RCA's, 1 Sylvania and 2 JAN Phillips. I can't tell a brand that is better. It's just that some individual tubes sound better than others to me.
With respect, Tubenit
-
5879 does not have as much gain as an EF86. I have 5 RCA's, 1 Sylvania and 2 JAN Phillips. I can't tell a brand that is better. It's just that some individual tubes sound better than others to me.
With respect, Tubenit
Let me rephrase. I really like the transparent sustain in your clips. Very similar to studio quality compression. Does the lower gain of the tube lend itself more to that liquid tone as opposed to a distorted tone you get when pushing EF86 or does the gain better complement the 12AY7?
-
Ed,
Excellent question regarding the 5879 "liquid tone" vs EF86 "distorted" tone.
I am honestly not familiar enough with the EF86 to give a really valid answer. My best guess is that the 5879 "softer" gain and tone may play a positive factor in sort of a smooth or liquid tone which I prefer.
With respect, Tubenit
-
Tubenit --
I have the same unused chassis as you mention and suitable PT/OTs for this build. I had considered building both of these but if I can just build ONE ... I'm in!!! However I really doubt I can keep up with you :laugh:, but I am game to try. I would like to also add the "second" boost pentode option for the 5879 side (like Geezers).
Could you possibly publish your chassis punching plan?
That would help me alot. Are you building a combo amp or a head? I think I would rather do a head (ala marshall where the chassis sits on the bottom of the cab). Even if you are doing a combo - a pattern for the knobs/tubes would help me out. I am dog slow with that kinda stuff. Do you think the 17x8x2 is big enough for a head?
Is there room for your famous 1 tube reverb you think? Thanks for doing this for all of us.
-
Ed,
Excellent question regarding the 5879 "liquid tone" vs EF86 "distorted" tone.
I am honestly not familiar enough with the EF86 to give a really valid answer. My best guess is that the 5879 "softer" gain and tone may play a positive factor in sort of a smooth or liquid tone which I prefer.
With respect, Tubenit
Thanks for the honest answer. I ordered a few 5879's this morning to play with. Sometimes the only way to know is melt some solder.
-
Could you possibly publish your chassis punching plan?
Don't have a drawn plan really. BUT, I will post a couple of chassis photos on Thurs July 4th prior to noon with some comments about spacing etc.
Gonna try and get the layout board done this wkend and the pots, sockets and trannies installed.
Initially, I am thinking it will be just a head. However, I punched it out and laid it out so I can flip it upside down into a combo if I want.
I think you could scratch the active FX and do the one tube reverb real easily and a PPIMV instead.
With respect, Tubenit
-
I will post a couple of chassis photos on Thurs July 4th prior to noon with some comments about spacing etc.
Much appreciated I will start rounding up a list of waht I need to order. thx!
-
OK, here is a D'MoSo56 with one tube reverb and PPIMV. The power rail is on the SCH version.
The reason for the PPIMV is that the active FX acted like a master volume, so the PPIMV is my other favorite master volume for this type of amp.
I did the 56T which had reverb and was Geezer's HoSo56 with one tube reverb. It was a nice amp and the reverb worked just fine, IMO.
With respect, Tubenit
-
Just built and debugged the 5879 front end.
Highly likely I'm wrong but we may be short 1 triode.
Mine sounds pretty similar with channels running at same volume. Very useful DRIVE N BOOST with a relay I should imagine.
Maybe the HoSo is getting it's overdrive from the pentode saturating the following triode stage.
Maybe include HoSo's V1b after the pentode, change this V1b back to D'Mars spec and follow the first triode with it, as per D'Mars, mix them into a triode, either a cathode follower or a gain stage with a MOSFET follower. OR could the 2 V1b's be mixed into a MOSFET follower directly, leaving us with a spare triode. OR have both V1b's followed by their own MOSFET followers (2 MOSFETS) and then mix.
OR somehow use relay switching to change the gain after the MOSFET with passive R divider. When using triode clean there is no attenuation after the MOSFET but when using pentode driving V1b harder for overdrive, reduce the gain after the MOSFET to get a more balanced volume setup.
I don't know, I'm a NEWBIE.
This amp, D'Mars EL84, has had a funny little intermittent fizzy bug since I fired it up and have not been able to find it until now, a weird brand new 1 Meg pot of all things.
-
Results of valve swapping for D'HoSo front end in D'Mars EL84
12AY7 sounds much more open or transparent than 5751's or 12AX7's, fuller bottom and more scooped in low mids.
Got a HiFi sort of vibe to it. (NICE IMHO)
Using 12AY7 V1(a&b) the 5759 won't really go to lots of overdrive (pre gain max, master vol down).Guess that depends on your definition.
There is a nice contrast in tone between 5879 and 12AY7. Not much difference in sound between 5879 and 5751/12AX7 with D'Mars biasing on V1b.
If I really want to get loads of overdrive with 5879 then need to plug a 12AX7 in the first slot. So if using separate 2nd stage triode for 12AY7/5879 first stage I'd want a 12AX7 backing up the pentode and a 12AY7 backing up the 12AY7.
Got any use for a spare side to a 12AX7 - reverb ?
Maybe!
12AY7 is nice foundation for front end, just won't go the whole way with OD.
(12AT7 not enough GO, and lacking the tonal twinkly bits of the 12AY7, 12AU7 is plain dull to my ears)
Just thinking out loud folks.
-
Mine sounds pretty similar with channels running at same volume
Yikes! That is NOT good news! If that is truly the case using 6V6's, then it sort of defeats the original idea behind the amp design.
Just to make sure that I am understanding you. Your saying that at the same volume ............. the 12AY7 triode sounds like the 5879 pentode? *See schematic comparison below.
Given the significant gain difference between the 12AY7 and the 5879, I was anticipating a significant difference in tone at the same volume?
My thinking is that you'd have the "clean" clean of the D'Mars vs. the "FAT chimey" slightly overdriven/clean of the HoSo56??
I wasn't expecting a giant difference but at least a clearly significant difference in tone.
So now I am wondering IF maybe your EL84's are being so easily overdriven that the overdriven tone from the power section (meaning EL84's) is coloring the tone so much that it masks a difference between the 12AY7 triode vs. 5879 pentode?
:think1: :dontknow:
Glenn, can you PLEASE confirm that I am understanding you correctly & that essentially the 12AY7 triode and the 5879 pentode sound pretty similar in your amp? Thanks!
With respect, Tubenit
-
There is a nice contrast in tone between 5879 and 12AY7. Not much difference in sound between 5879 and 5751/12AX7 with D'Mars biasing on V1b
OK, that helps explain it. Thank you! That is what I was anticipating.
I am understanding that there is indeed a nice contrast between the 5879 and the 12AY7.
However, using a 5751 or 12AX7 (which have higher gain than 12AY7) lessens the contrast in the tone between the 5879 and the 5751?
Am I now understanding this correctly?
and THANK YOU for the information, it is a great help! It's this very kind of trading observations and tweaks that makes this forum a really fun and innovative place to be
With respect, Tubenit
-
Don't take my word for anything special, I'm a bit thick when it comes to subtleties.
There is a difference between the 5879 and the 12AY7, not there if using 12AX7/5751.
The 5879 is a little brighter in the upper mids / lower treble and has less low bass.
I'm not driving the output tubes hard, master volume way down, like 5 watts.
Once again, just giving you my perception, I think you folks have much more experienced ears when it comes to the subtleties of guitar sounds, plus I'm running through speakers designed for a completely different application( I'll have my Loarantz Greenback clone in a few days).
-
OK, thanks for the clarity! Definitely helpful and useful info. And thanks for ruling out that it was EL84's being overdriven.
One change in the design that may help with even more contrast is to use a 2.2uf instead of 4.7uf on the V1-3 cathode and have the V1-3b
cathode cap be simulataneously switched. * schematic below
I'll plunge on into the fog and report back after I get the amp built. :icon_biggrin: :l2:
Guys, maybe you want to proceed with caution and a back up plan in mind in case this doesn't work out like I am hoping?
I'm not shooting for a clean to OD change where you would not need or use an OD pedal. Just attempting to go from clean clean to FAT chimey overdriven/clean. AND then use a pedal for additional OD when needed.
With respect, Tubenit
-
Also,
The 5879 and 12AY7 could be tweaked by changing the value of volume pots and coupling caps to "select" the character that one likes in the valves.
I have both tubes loaded with 250K pots running off .01uF caps INTENTIONALLY so I can hear the difference in the tubes. Your original schem has the 12AY7 running into 1Meg and the pentode running into 500K so that will make the pentode a bit brighter methinks, and its got the extra gain, so it could all even out nicely.
-
I have had an ultra-fun day tweaking with these two valves.
Did not sleep last night, lying in bed thinking about what sort of ideas could be tried with this setup.
I am mixing the two channels together now, not switching them.
With selection of bypass and coupling components into the valve bias and feedback networks I have got a really interesting input section.
Using the strength of the 12AX7, Nice clean fat bottom and bright transparent tops, I scooped out the frequency response between about 200Hz and 800Hz, big mid cut sound.
Using the strengths of the 5879, punchy low mid to high treble, I rolled off the bass and bright /presence part of the frequency response.
Now the two input gain controls can be adjusted to give a really wide range of tonal effects. Gain and tone stack in one two knob unit.
I'll get a sound clip up to demonstrate this within the next couple of hours.
Next I'm going to extend this idea with a 3 pos rotary switch on each channel switching bias and bypass reactances. Maybe I could get rid of pots altogether and just have lots of rotary switches on my amp. :happy2:
-
Very cool!! Nice idea with blend pot approach.
With respect, Tubenit
-
Here is the soundclip.
Anderson Hollow Drop Top with Neck and Centre single coil in parallel. Vol dimed, Tone dimed.
I touched nothing except the two gain controls for input valves, V1a (12AY7) and V2 (5879).
http://soundcloud.com/glennjeff/testing-the-scoopers (http://soundcloud.com/glennjeff/testing-the-scoopers)
-
Wow! That is quite a variation of tone! Cool tone. Thanks for sharing it.
Amp sounds like it is reasonably touch sensitive and articulates well.
With respect, Tubenit
-
Moonbird,
Here are some photos and dimensions for punching out a chassis.
And for doing a layout board which is 12" in length.
With respect, Tubenit
-
Here is the soundclip.
Anderson Hollow Drop Top with Neck and Centre single coil in parallel. Vol dimed, Tone dimed.
I touched nothing except the two gain controls for input valves, V1a (12AY7) and V2 (5879).
http://soundcloud.com/glennjeff/testing-the-scoopers (http://soundcloud.com/glennjeff/testing-the-scoopers)
I just listened on computer speakers and 0:56 sounds really very nice, I can imagine that would work well in a song / band context.
tony
-
Keeping in mind, that I presume this amp will need some tweaking (since I've never not tweaked one) .......... I tried to lay this out using turrets in a way that would be the easiest to remove a part and replace it with something else.
Note the direction of the Orange Drop caps installation. A couple of these may seem headed the wrong direction, but if you study the layout 7 schematic, I think you'll see that they are correct.
Since I am trying to make this an inexpensive amp, many of the parts are "used" meaning were perhaps in another build for some months and then removed. About 66% of the caps are used and I even had to use two used 1M resistors (ugh).
As I populated this board, I realized that adding a couple more turrets between rows of outer turrets made sense. And I will update the schematic and layout after I do some initially tweaking to reflect that.
I narrowed the board from 3" to 2.5" to make sure that there will be plenty of room to install relays for footswitching the clean/5879 & midboost. I cut one of Doug's boards down using a hacksaw. It took about 20-30 seconds to cut the 12" strip. And I kept the strip to install turrets on for mounting other components.
IF all goes well, I may finish this up next wkend!
With respect, Tubenit
-
Tubenit --
Thanks most kindly for posting the punch info. Should really help me!!! :icon_biggrin:
GJ --
What an interesting preamp layout. It would be a perfect match for an idea I have had for some time. I have been collecting old organ swell pedals for a while now. Some of the Lowrey pedals are really cool in that they have 3 pots connected to one pedal. My idea was to use these pedals as part of an amp. If they were applied to your amp, you could have fulltime access to these tone changes. This got me thinking about organs -- the rotary switches you are considering would almost be like the pull "stops" giving you a different "base" tone if you will.
I think your *all nighter* really produced something new and interesting. :thumbsup: Thanks for sharing!!
-
moonbird,
PLEASE, don't get me started, I need sleep. Had that foot pedal, multi-pot thing floating round in the dark recesses of consciousness for a few days, thinking it may be a bit susceptible to noise however.
At some point I will need to reconcile Utility with Complexity. Not all guitarists have engineering degrees and astronaut licences.
Dr Frankenstein's monster and it's actually very noise / hum free ???
All the best.
-
Tubenit -
Messy? Messy?!? Weren't exactly the thoughts that went though my mind. :l2:
On the contrary - thanks much for the look at the master's work. Looking forward to the final gut shot. I am very intersted in how you will route the power across the board. This is VERY helpful for me. Thanks MOST kindly for posting this!! :icon_biggrin:
-
That looks great. Can see a few ways to do things better just from looking at your pictures.
Looking forward to hearing it.
-
Looks good Jeff , cant wait to hear it.
Thanks Bill :guitar1 :headbang: :occasion14:
-
OK, I got it wired up. Not sure about the layout design? :dontknow:
Wiring is sort of odd color coded, but it's actually very easy to follow what goes where.
Since I am expecting to be tweaking this, I wanted it reasonably easy to follow and access parts.
Hopefully, I will get to fire it up Sat am and see how it sounds. IF the layout is not problematic, then I think it will be a very nice sounding amp and friendly to pedals also.
With respect, Tubenit
-
Looks great....I like the layout
-
Yep, looks great Jeff!
Brad :icon_biggrin:
-
OK, it's done and it sounds GREAT!! Very very touch sensitive!!
It is very very quiet at idle. Just a whisper. No hum at all. If you heard the whisper and then I hit a chord, you might be startled at how loud it is with such quiet at idle.
The clean does not sound as clean as the D'Mars clean ............ but I am using 6V6's instead of 5881's and the voltages overall are somewhat lower. Does it sound like a clean channel? Oh, yeah .......... definitely. Not quite black face Deluxe non-reverb clean but headed that direction.
The V1 5879 pentode really surprised me in this amp. This amp sounds a lot better than the 56T I used to have. But it has some smoothing caps, a different tone stack, an active FX and an enhance cap going into the LTPI. The overdriven tone of the 5879 is quite a bit smoother than the 56T was and there is NO top end hash. So I am very pleased with it.
The 5879 will sustain like crazy. It is very touch sensitive and expressive. Somewhat chimey and has very nice harmonics. It is not as smooth as the D'Mars or Tweed BluezMeister. It sounds more cranked then a buttery smooth overdrive. Kind of hard to describe the difference but you could hear the difference in person.
Is there a significant contrast between the 12A_7 triode and the 5879? Absolutely when using a 12AY7 or 12AV7 in V2. You could easily pick out which one is which with your eyes closed. It is certainly very noticeably different when chording. I think the contrast is very useful and sure gives a different flavored tone. I did try a 12AX7 in V1 and it does narrow the gap between clean and 5879 cranked. 12AY7 or 12AV7 is a better choice for contrast between clean and cranked.
I would NOT describe the 12AV7 to 5879 as clean to OD. Not a good description. It's more like clean to cranked at the same volumes. The contrast is significant but not as dramatic as the D'Mars or the Tweed BluezMeister which actually have an OD channel.
If you're considering building this, I would recommend highly the on board active FX. It's a really nice feature! You can dial it to accent cleans or a little more OD cranked tone. It works as a great master volume. I use a delay in mine, but it works like a boost even without the delay in it. And it works like a master volume also.
I have a NFB switch. I like the NFB the most. Disengaging the NFB gives some more tweed tone to the amp. I think the NFB switch could be left out and have the NFB in all the time. However, some people might prefer the tweed accent?
I was surprised that the midboost did not prove to be that useful. I think it could be left out?
Did I have oscillation problems with my layout? Well, I'm not sure??? With a 5Y3GT rectifier I played an hour with the amp really cranked to the point of my ears ringing. No oscillation issues at all playing at volumes that exceed what I normally play at.
Then I put a 5V4 rectifier in. The chassis was inside facing up about 15 inches from the speaker & I was sitting in front of the chassis within 3 feet with my guitar volume on "10". I could crank everything pretty much up to "10" except the FX send and level with no oscillation.
However, with everything cranked ............. I can not dial the FX send and FX level both above "7" without oscillation setting in. In other words, send at 5 and level at 8 or 9 was fine. Both at 6-7 was fine. One at 7 and the other higher than 7 would give oscillation. A fix to that might be to use a 100k pot on the FX send or parallel a resistor from wiper to non-grounded side which is probably what I'll do.
The truth is that I can't imagine playing the amp that loud though?
The 5879 was pretty microphonic, so I'll have to try another one. And the 12AV7 was slightly microphonic too. So, the tubes and proximity may be the culprit regarding oscillation at cranked volumes? I'll try different tubes and such and report back.
But honestly, with this amp waaaayyyyy louder than I'll ever normally play it, ............ I had NO oscillation problems at all. And the amp can get really loud. It's like Deluxe Reverb loud, IMO. I'm thinking this is maybe because of the active FX loop which definitely added some gain.
The amp can sound beautiful clean and very cranked (vs. smooth overdrive). It's a nice amp.
I'll update the schematic and post voltages sometime later this weekend. I'll try to get some soundclips up also within the week.
With respect, Tubenit
-
OK, here is the current schematic and I indicated the changes from the original. There may be some more tweaks down the line & if so I will up date this in a wk or two.
with respect, Tubenit
EDIT: I've added a picture to show how I would "better" reposition the board to be somewhat easier to wire up and work on.
I should've stated in the previous post, that (at least with the mini-toggle DPDT) that there is NO popping switching from clean (12AY7) to cranked (5879).
-
excellent work guys....I love the stuff you do with your love of amps and your willingness to expand the platform...
your quest reminds me of my favorite Tom Petty quote "If you're not trying new things with your music, you're not going to live where the magic happens" (paraphrased)
some famous dude said "Get 'er done" but you dudes say "tweak 'er 'till she squeals and then back her off half a frog hair"
:icon_biggrin:
-
OK, I think I am actually done with the amp! To borrow an expression from HotBluePlates ............. it sounds "crazy good"!
I think I should have done a better job with the layout as illustrated in my previous post. My guess is that I'll eventually move the board out a little bit as it should just take me less than an hour (I think).
Yet, I can play it waaayyy past volumes that I would play it at normally & with NO oscillation issues. I can dime everything ....... except the FX send on "7.5" with no oscillation problems. Above 7.5 on the FX send with everything else dimed, I will get oscillation.
Now having said that. I like both volumes on 4.5 & the FX send at around 5-6 and the FX level at 7. That is around the most volume that I like. And the amp just sounds wonderful to me at those settings.
I tried both and decided I like the 12AV7 somewhat better than the 12AY7 in this amp but both sounded good.
There is a significant difference in clean to cranked between the 12AV7 triode and 5879 pentode at similar volumes. The 5879 really has a chimey cranked harmonically rich tone, IMO.
IF I have anything that I wished would've turned out different, it would be the volume level. The amp is much louder than I was expecting for some reason? I actually prefer the 6K6 power tubes with the 5Y3GT rectifier the best & it's still pretty loud & that is what I am currently leaving in the amp.
I don't anticipate any significant tweaks beyond this schematic here. I'll get around to putting the SCH schematic and layout in the SCH Library of schematics later. And I'll post some soundclips within a wk or two.
With respect, Tubenit
-
Tubnit could you take voltage readings for us .
Thanks Bill
I'm especially curious about your readings at the mosfet cathode follower and 5879 tube.
-
Forgot to take the 6V6 screen readings, but here is the rest of them. The mosfet "plate" connects to node D.
Played this amp until I had blisters underneath my callouses and could barely touch the strings. I like the amp!
With respect, Tubenit
-
My fingers look they've been hit by a meteor storm working on this D'Mars tubenit, Zero Sympathy Buddy. Really need to hear some soundclips to get the ears calibrated. Currently Max'd out on tube satisfaction, get back to you when it's sane.
-
> I can dime everything ....... except the FX send on "7.5" with no oscillation problems. Above 7.5 on the FX send with everything else dimed, I will get oscillation.
Counting on thumbs: you have four gain stages; a guitar amp needs two gain stages, three with tone-stack loss.
That's a testment to your skill, that you can have so much gain and not have a humm/hisss machine.
A more detailed calc says you have up-to at-least 4V at "FX Send", which is more than studio gear needs, far more than pedal-gear can tolerate well.
I think I'd try some fixed loss at "FX Send" pot. Like replace 100K pot with 100K fixed plus 20K pot to ground. Then "10" on Send knob is like "5" now. You could run the Send and the Return at "10" and have around the same gain as you have with your S=6 R=7 settings, and a sane level to any FX devices.
OTOH, you could buy earplugs, book bigger venues, and do heavier metal.
-
That's a testment to your skill, that you can have so much gain and not have a humm/hisss machine.
Well, .............. no hum or hiss problem at volumes that exceed what I normally play. With pushing everything towards dimed, yeah it's reasonably noisy with hiss. However, my statement about no oscillation with everything dimed but the FX send holds true.
I will look at the send pot idea and probably give it a try & report back if I go that route. Thank you for the idea!
With respect, Tubenit
My fingers look they've been hit by a meteor storm working
Glennjeff, yeah ............. it gets pretty bad when the finger is painful to even look at. :l2:
-
PRR could you draw a diagram of how you would run that 100k resister with the 20k pot to ground. I would find this helpful but I can't quite rap my tired little brain around it.
Thanks Bill
-
replace 100K pot with 100K fixed plus 20K pot to ground
Bill, you asked a good question. I don't know if "plus" means parallel or in series?
Having said that, checking the resistance from wiper to ground on the pot ................ I think a 25ka pot with 22k to ground (in series) might be the most useful solution? (That is based on experimenting with different setting on send and level FX pots) Or maybe a 50ka pot with 10k to ground?
Turns out that dialing the send pot higher and lowering the level pot .............. VS............. lowering the send pot and having the level pot higher both give useable tone variations. The higher send pot setting with a lower level pot setting gives sort of a compressed tone.
I can verify now that the amp takes OD pedals really well. I used my TimZee and the Zenith Drive and both sounded great to me thru the amp.
I found the midboost on chording is not that useful to me because the chord loses some articulation and note distinction. However, the midboost on playing lead and single notes or double stops sounds pretty cool, IMO. There might be more useful uses for that switch though than midboost for other people.
This is truly a fun amp and very expressive, IMO.
You can get the amp cranked using the pentode and get notes to sustain for a reasonably long time (the FX needs to be dialed up also to do this). However, as I mentioned before ........... it is a cranked chimey tone far more than a smooth tone. Very distinctly different than the Tweed BluezMeister of D'Mars ODS.
With respect, Tubenit
-
I plan to start on the amp cab this weekend. This may prove to be the prettiest cabinet I've built.
I have a really nice piece of flamed maple for the cab top and the front chassis panel cover. The sides and bottom will be ribbon mahoganey. The grill cloth might be oxblood with gold or maybe cane weave? I think the contrast between the flame maple and the other woods will give a nice visual appeal using the half blind dovetails.
I'll hopefully get around to posting some sound clips this weekend also.
With respect, Tubenit
-
Tubenit --
Well that settles it. I am gonna build this one fer sure. Kinda humg back waiting to see what you thought. Good enough for me. I think I will go with the 6K6s as well. I wonder if this would be a good amp for 6AQ5s? Might tame the loudness a bit.
I did notice that the diagram you made for the PRR suggestion had a 12AU7 instead of 12AV7. Was that intentional? Are you planning to use a 12AU7 for the active FX? :w2:
Thanks SOOO much for the gut shots. Only someone with your skills would have the "guts" to put one up :laugh:. It is really great to see how you do stuff.
-
I think 6AQ5's would sound superb!! I didn't have anymore of them though.
Yeah, I settled on 12AU7 for the active FX but the 12AV7 sounds really good also.
I hope you pay attention to how I would've done the layout board differently. While the amp is very quiet even at volumes way above what I normally play ............... my guess is that with the layout board further away from the tube & slightly more towards the pots that it would've been even quieter.
I really like this amp! IF the cab turns out like I hope, it should be quite beautiful. :thumbsup:
With respect, Tubenit
-
Tubenit --
Yessir I am watching your layout "redo" closely. Thanks for the reminder tho ... never hurts!!
I have many 6aq5s - would be happy to send you a couple. Maybe I will do a 6aq5 version just for grins. The plate voltages seem ok but would I need to change any other components aside from a lower impedence OT? What would you recommend?
-
Yeah, I'd love to hear what you think of a 6AQ5 version. I built a 6AQ5 amp years ago and really liked it. And I know Geezer is quite fond of 6AQ5 tone.
Thanks on the offer for the 6AQ5. Since the amp is already built, I'll pass on the generous offer. Right now I can plug in 6K6 or 6V6 with no rebiasing. And I can use a 5Y3, 5V4 or GZ34.
I don't know about the OT and impedence issue? I used an OT with an 8ohm speaker. Maybe take a look at the Gibson Scout?
http://www.el34world.com/charts/Schematics/files/gibson/GA-17RVT_SCOUT.pdf (http://www.el34world.com/charts/Schematics/files/gibson/GA-17RVT_SCOUT.pdf)
With respect, Tubenit
-
Hey T, Is the FX level still working well as a master volume? Thanks
-
FX level works great as a master volume. I tend to set the "volume/gain" pot & then increase or decrease the volume with the FX level.
With respect, Tubenit
-
Tubenit -
That 305V on the PA plates rang a bell in my mind - so I went to check and sure enough. It is the SAME plate voltage on the 6V6s in the Fender Harvard 5F10 - which many believe had the best clean tone of any amp ever.
Goodness sakes Tubenit - I guess great minds end up at the same places. Pretty doggone impressive if you ask me!! :worthy1: :icon_biggrin:
-
I got a couple of mediocre soundbits done for the amp. Honestly, the recording does not do justice to the contrast between the 12Av7 triode versus the 5879 pentode.
The 12AV7 sounds cleaner. The 5879 has some chime and fullness to it and sounds a little more aggressive while maintaining a reasonably clean tone under "5" on volume pot.
Nothing is changed on the amp or guitar other than simple switching the 12Av7 to the 5879.
The volume knobs were around 4 to 4.5. At around 6-7, you get some really nice sustain particularly if the FX is cranked. FX send was 5 and the FX level was 6.
On the soundbit with chording. Everything is done first with the 12AV7 and then the 5879. The last chording group has the 12AV7, the 5879 and then the 5879 with midboost and the NFB turned off.
http://www.soundclick.com/player/single_player.cfm?songid=12428140&q=hi&newref=1 (http://www.soundclick.com/player/single_player.cfm?songid=12428140&q=hi&newref=1)
With respect, Tubenit
-
I apologize for yet another worn out blues tune. I didn't have much time today and wanted something that I could demo with one take which this was.
http://www.soundclick.com/player/single_player.cfm?songid=12428144&q=hi&newref=1 (http://www.soundclick.com/player/single_player.cfm?songid=12428144&q=hi&newref=1)
12AV7 first ................ at 58 sec, then the 5879 ...................at 1:14, then the 5879 with midboost and no NFB. (All of this was the neck pickup)
At 2:27 (bridge pickup), the 5879 with midboost and NFB ................... at 4:47, back to the 12AV7 with no midboost and NFB engaged.
With respect, Tubenit
* When I have time, I'll try to do something that sounds better than this & is maybe more interesting. :think1:
-
Really beds in well in a blues mix hey.
Your ears are a lot more refined than mine. When I tried out that front end there was less contrast between the AY and the 5879. Notice you're now using an AV, I have one, cost like $6 and it's a General Electric, looks like it might have had some use. Might try again.
Thanks for all your support here. :thumbsup:
-
Well, I think I'm gonna try something ...................
I think I'll take the first triode of the 12AV7 and make it into a "hot switch" & see what that sounds like. I'll lose the extra clean tone on the amp, but the 5879 still sounds reasonably clean at around 4.5 on vol.
Will report back and see what unfolds from this.
Tubenit
-
OK, this is cool! And it's staying in!!
I am renaming it "the 56 PLUS." Geezer's HoSo56 ........... plus a hot switch gain stage ............. plus active FX on board. The D'MoSo56 no longer fits since it no longer has the D'Mars front end on it.
I can dial the clean-chime (5879) or the 5879 with 12AV7 gain stage so that you can switch them at the same volume level and there is a pretty dramatic contrast between the two.
Kind of hard to describe but the 5879 alone is somewhat clean/FAT/chimey .............. and when you switch in the 12AV7 you get an increase in sustain and harmonics and it's somewhat brighter. This is a really nice contrast to my ears and should be pretty versatile. The 5879 alone sounds kind of "organic" and is pretty touch sensitive to my ears. You lose a little of that organic feel when switching in the hot switch but it increases the harmonics significantly.
I'll post a picture of the cab later today, hopefully. And then a new soundclip when I can showing the harmonics and sustain of the extra gain stage.
BTW, I can not hear any increase in floor noise at all. Amp is very quiet at idle.
With respect, Tubenit
-
Needs a brown leather handle and some long screws so I can actually mount the chassis in it. Chassis is just sitting inside it in the photos not bolted down.
Kind of hard to take a picture of the flamed maple. Camera flash typically washes everything out. It's fairly iridescent looking in person.
Sides are ribbon mahogany. And ironically, the piece of mahogany was quite lightweight for some reason.
with respect, Tubenit
-
Drool.
How did you join the wood?
-
Half blind dove tail joints. Made some errors but overall it turned out pretty nice, I think.
This "hotswitch" gain stage sure worked out great. I didn't know whether I could adjust the 5879 volume to balance with the 5879 & 12AV7 triode, but it does that really well. I'm sure a pot before and after the stage helps considerably with that.
Tubenit
-
Tubenit, that is gorgeous
-
Very nice my friend. :m8
Bill
-
WOW! Absolutely Stunning!
Brad :icon_biggrin:
-
Beautiful inside and out!
-
Guys, thanks for the nice remarks!
I did some speaker testing with this amp. I tried an Emminence Red, White and Blues (that I use for the D'Mars) & a Texas Heat (that I use for the Tweed BluezMeister) and a Cannabis Rex that is in the 56 PLUS cabinet.
I like all of them with this amp.
Texas Heat was my favorite and it had a slightly more compressed sound that made it a little smoother when pushed. It has a nice top end and the bass is very good also.
However, .......... IF .......... I was a really good player (which I'm not) & wanted to hear all the subtle aspects of playing, I think the Cannabis Rex would be the best. And my best guess is that the Cannabis Rex would cut thru a mix the best of all of them with the Texas Heat being 2nd. It seems to express all the articulation of the amp the best to my ears.
To summarize, if you like smooth and compressed ....... the Texas Heat. If you like chimey with more harmonics, go the Cannabis Rex.
IF I had another Texas Heat, I'd probably put it in the cab. But, I'll be very happy with the Cannabis Rex as is.
I made just a few minor changes. The 5879 cathode cap was lowered from 4.7uf to 2.2uf. It made the 5879 a little brighter and perhaps a little smoother removing a tiny dash of grit. Worth changing this out.
The 12AV7 hotswitch triode cathode resistor got lowered from 2.7k to 1k. BIG improvement. Very smooth sounding now and greater sustain and some sweeter musical harmonics. I also added a .002 Orange Drop cap in parallel with the .01 off the plate of that triode.
Amp sounds great and looks really decent, IMO. Very very very fun amp to play!!!
The mid boost switch could be removed with no loss, IMO. I'll experiment and find another use for that.
With respect, Tubenit
-
Very very nice tubenit. I like the way you have the speaker baffle tilted back and have the front panel vertical. I will have to try that next time around. Where do you get all this nice wood? Punky
-
Where do you get all this nice wood?
Usually at the WoodCraft store here locally.
The ribbon mahoganey sides/bottom for the amp was about $45 total. I'm thinking the flame/quilty maple was maybe around $35? I bought it some time ago. I don't have a good picture of it, but the ribbon mahoganey is just about as irridescent as the maple.
When you consider buying plywood and then tolex and glue and chrome corners, the wood cabs are not much more expensive if at all?
With respect, Tubenit
-
Great job Tubenit :icon_biggrin: You are the master of tweaks :worthy1: and this one again you have hit the mark and are happy with the final result but I can't help but think that there can be more to add :BangHead: as I have found in the short time I have been on this forum that there is an endless array of circuits that can be added to refine the final sound.
Looking over your schem, the thing I like about it is it is simple and gets the job done.
Just one thought, would adding a CF (mosfet)to the AY7 boost/fatten your sound as I have found this in other builds.Thanks
-
would adding a CF (mosfet)to the AY7 boost/fatten your sound as I have found this in other builds.
I am wondering the same thing? :think1: :icon_biggrin:
However, I don't have much chassis real estate to work with so it's probably not gonna happen?
:dontknow:
With respect, Tubenit
-
Order to Hoffman Monday am for a leather handle. Got it today Tuesday. Man, he fills orders fast!
-
That maple top looks so nice, exquisite (there I can spell that word :icon_biggrin:).
It appears to be two pieces joined, did you do that? If so How?
My wood working is not anywhere near to that standard but, LEVEL UP, it has to be done. Off to the craft shop.
-
Yes, it is two pieces of maple from a left over project. Just glued together, no biscuit joint or anything. Similar to a two piece guitar body.
Remember the cab is half blind dovetail, so it's pretty strong and held together well. I didn't have enough maple to do an entire cab but I am glad I didn't. I really like the contrast between the maple top and the ribbon mahogany sides/bottom.
The ironic thing is the piece of maple looked very plain and little to no flame really showing. I would've rated it a AA maple at the most (vs. AAAA maple being the best).
However, I "popped" the flame on it 3 times. With a "natural" look, I do this by applying amber analine dye 3 times sanding it off each time back into the natural wood color the best I can. However, the dye does color the softer part of the wood when this is done and adds contrast.
(As a tip, the only thing that I have found that removes water based analine dye off my skin is Windex cleaner. I'm thinking maybe it's the ammonia in it? )
Then I apply Minwax "natural" oil stain on the wood. Result is a fairly iridescent look under lighting. I used Minwax semi-gloss polyurethane for the finish simply because I can put a hot coffee mug or cold drink on the cab with no problems. Something like gloss Deft Clear Wood Finish allows an even more intense flame to show up but won't hold up with a hot coffee mug as well.
With respect, Tubenit
-
I am really enjoying this amp.
I wanted to do a sound clip showing how this 56T Plus takes pedals. I am using a homemade overdrive pedal.
http://www.soundclick.com/player/single_player.cfm?songid=12464167&q=hi&newref=1 (http://www.soundclick.com/player/single_player.cfm?songid=12464167&q=hi&newref=1)
With respect, Tubenit
-
Thanks for posting Tubenit. You have got some great tone with that setup, and your playing was really enjoyable, especially around the 2:15-2:25 mark