Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Tubes and Hybrids => Topic started by: skynyrd on March 17, 2010, 06:25:51 PM

Title: Peavey Mace Question ?
Post by: skynyrd on March 17, 2010, 06:25:51 PM
I have a vintage peavey mace vt series from the late 70`s, the amp that lynyrd skynyrd used and it is a hybrid with 6 6L6 power tubes and a SS pre amp. I would like to mod the pre amp so it packs a little more distortion, would love to have a cross between skynyrds sound and blackfoots sound. Naturally I play southern rock so hence the 2 sounds. I am going to get a shematic on the amp from peavey and would GREATLY appreciate any and all help that you can offer. I know throwing in a pedal is the easiest option but I would really like to stay on a straight plug and play basis if possible.
Title: Re: Peavey Mace Question ?
Post by: EddieTavares on March 24, 2010, 09:52:46 AM
Hi, I'm brasiliam forgive my poor english

I bought years ago a cousin of your amp, a PV Classic VT that its circuit is almost the same of mace/deuce. My amp has just one tonestack and just 2 6l6 in the power section.

When I bougth the amp I tested it in the shop, the amp shows a lot of punch and bass frequences but not nuck mids and treebles enough and the tonestack seems didn't work at all... but it was

too cheap!!! Aproximately U$ 200.

I bought!

So I replaced all electrolitic caps, the smaller values I decided to use a bipolar electrolitic. This changes was not enough to becomes the amp brighter to my taste but becomes perfect to play jazz.

Some months reading manuals and schematics of Classic and deuce/mace in addiction other amps that have two tubes in the power section like bassmann and Hiwatt and schematics of solid states preamps, Too many hours trying different values of resisistors in different places... But just few and not complex mods made all difference, follow:

- I Added a presence control in phase splitter/power section. I made this With a 2x2 circuit board, 1 resistor, 1 trimpot and one cap, follow:


         22K    680N
   |---\/\/\/\/\--||--|
   | |   /\               |
   | |____|             |
   |                       |
   |     5k1             |
   |--/\/\/\/\/------|
   |                      |
   |                      |
  ---             fd back
   -

  This circuit must replace the IR24 (1k).

- I replaced the IR14 (1k) with 5k1 resistor.

- In the preamp section I replace R42 (33k) to 47k and R51 (33k) to 22k, this change makes the tonestack more effective.

All this changes make the amp more louder with mids and highs, Increased the distortion of power section, tonestack more effective ... perfect to rock'n'roll!!!
Title: Re: Peavey Mace Question ?
Post by: EddieTavares on March 24, 2010, 03:09:12 PM
Sorry, the schematics:

http://music-electronics-forum.com/attachments/7192d1260305788-pv_classic_vt.pdf
http://music-electronics-forum.com/attachments/6852-pv-mace-series.pdf
Title: Re: Peavey Mace Question ?
Post by: J M Fahey on March 24, 2010, 07:06:35 PM
Hi skynyrd (I loved them too).
Really the best and shortest path to what you need *is* adding a clean boost ahead of the amp.
If you have the soldering iron itch, on which I agree, build it yourself.
On the Peavey, modding it has more possibilities to mess the fine sound it has now, than to improve it.
Oi Tavares, todo bem amigo? Bem-vindo no Fórum.
Title: Re: Peavey Mace Question ?
Post by: EddieTavares on March 25, 2010, 01:33:19 PM
Thank you J M Fahey, tudo na paz!


So if you use a cleam bosst it will increase the preamp distortion... remember it's a ss preamp... It'll distort in the second stage opamp (u5a), maybe some diodes in paralel to r42 will give you something like tubescreamer...

Something that I think now is increase the r100, it will increse the amount o signal to power amp!



Sorry one more time... this is the correct version of peavey mace:

http://www.abeltronics.co.uk/download.php?manu=peavey&file=peavey-mace-deuce-vt.pdf
Title: Re: Peavey Mace Question ?
Post by: skynyrd on March 25, 2010, 06:27:45 PM
Thanks for the replies, I have talked with a couple of techs ;ocally and none of them really seem to know much about the electronics of the hybrid which I found hard to believe with them being techs. Now the resistors you mentioned to change Eddie?  Have you had any problems out of the amp since you changed them? I do fine with simple cap and diode and resistor changes but building circuit boards I have zero luck with and as much as I would like to build the presence control I best leave that alone,,lol.
Title: Re: Peavey Mace Question ?
Post by: EddieTavares on May 07, 2010, 09:57:07 AM
skynyrd

         I bought this amp in 2006, in the beginning I intended to replace the old ss preamp to all tube, but the solid state phase splitter make the amp much more louder tham a tube long tail pair specialy with that mods becouse became brighter. I compared with a Jcm800 side by side and my amp seems to be louder with more top-end and less mids.

        No problems with eletronics, heating, the power supply is ok, I ask a friend to mesure the bias and its all ok.
Title: Re: Peavey Mace Question ?
Post by: Enzo on May 08, 2010, 02:53:51 AM
I guess a good question is what do you want the techs to know.  The fact it is hybrid doesn;t really matter.  The amp is a solid state amp with a very basic tube power amp on the back.  That same preamp could just as easily have fed a solid state powr amp, and in fact PV made a few that way.  SO your techs should know how a PV SS preamp works, because it works like any other PV SS preamp.  HAving specific part number knowledge would be ther only if they had occasion to study the particular amp circuit.

I am not sure about that R100 reference,  in the VT version R100 is the feed resistor to the reverb drive.

The diode trick would be simple to try, and easy to remove if not pleased.  R42 is in the Normal channel.  The same position resistor in the effects channel is R11.
Title: Re: Peavey Mace Question ?
Post by: skynyrd on May 09, 2010, 07:13:05 AM
Thanks for the replies, Enzo I didn`t mean to sound like I was putting down the local guys. I had talked with them about Eddies mods he listed and they were very apprehensive in even talking about it, all they would say is they know nothing about the hybrid amps ? I pretty much took it they weren`t into doing mods to adds and left the subject alone out of respect for their feelings. I will give Eddies mods a try, I found a duece vt that has the same board as the mace vt and may be able to get it ultra cheap and use it for a tester. I appreciate the help and the info.
Title: Re: Peavey Mace Question ?
Post by: skynyrd on May 14, 2010, 03:47:08 PM
- I replaced the IR14 (1k) with 5k1 resistor.

- In the preamp section I replace R42 (33k) to 47k and R51 (33k) to 22k, this change makes the tonestack more effective.

All this changes make the amp more louder with mids and highs, Increased the distortion of power section, tonestack more effective ... perfect to rock'n'roll!!!
[/quote]

There must be some difference between the 2 amps, I checked over the schematic I have and found that R42 is a 22k and R51 is a 4.7k ?  not sure if I need to find the resistors in that area that match your numbers or what?
Title: Re: Peavey Mace Question ?
Post by: skynyrd on May 15, 2010, 09:10:20 PM
To do the 2 diode clipper trick I would basically lift 1 end of R42 and R11, put 2 diodes side by side and solder the resistor leg to the 2 legs of 1 end of the diode and run the other 2 legs to the hole where the end of the resistor came out? Assuming the cathode end of the diodes would go to the board connection and not the resistor?
Title: Re: Peavey Mace Question ?
Post by: skynyrd on May 17, 2010, 03:43:05 PM
Well done some homework, it looks like I remove the resistor and put the 2 diodes in its place. Going to pick up some 1n4007`s and give it a shot on 1 channel to see how it sounds.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on May 18, 2010, 02:23:30 PM
you can try the diode clipping circuit , the peavey Triumph used it , I removed it from mine , but you may like it. I personnally like my overdrive to realy be overdrive not clipping from diodes lol lol lol
Title: Re: Peavey Mace Question ?
Post by: Enzo on May 18, 2010, 07:39:58 PM
The Triumph is all tube, the Mace is solid state but for the power tubes.

The diodes in the Triumph are not clipping diodes, they are noise reduction diodes. They never did any clipping.  Totally different function from those in the Mace.
Title: Re: Peavey Mace Question ?
Post by: skynyrd on May 19, 2010, 03:25:11 AM
One of these days when I learn much much more about amp electronics I want to set this amp up like its first version where I can run both channels in series rather than paralell.  I wish Hartley hadn`t of changed that aspect of the origonal Mace, maybe I will get lucky and find an old 320T Mace that isn`t completely trashed and set it up as a spare head to have both.
Title: Re: Peavey Mace Question ?
Post by: skynyrd on May 23, 2010, 07:53:09 PM
Well I tried the diode clipper, first with the resistor then without and it didn`t change anything. I had talked with Kevin Silva he does alot of work for some of the big names, Charlie Daniels, Ted Nugent, Dokken, and a bunch of others, he said the answer to my muddyness problem  and over bassyness that the Deuce and Mace were famous for was actually a easy fix, just place a .001uf cap across the outer legs of the Post Volume controls and call it done. I did that and WOW, opened that amp up in a hurry. I can actually run the bass on 6 and the mids on 4 and highs on 7-8 and it has a solid rock tone with a sweet little touch of growl to her. My buddy came over and he was shocked,,said it didn`t even sound like the same amp. I do appreciate everyones input as well as their patience with my questions, I still wish I had a touch more drive to it but the tone is so much livelier now I am not going to worry about messing with it. Once again many thanks to all that posted.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on May 26, 2010, 02:57:31 PM
The Triumph is all tube, the Mace is solid state but for the power tubes.

The diodes in the Triumph are not clipping diodes, they are noise reduction diodes. They never did any clipping.  Totally different function from those in the Mace.

Yea they are brother follow the circuit , I do amps all day everyday and have done a number of peavey triumph's , yes the mace is a solid state pre-amp and power tube output typically 6L6GC as a matter of fact.
Title: Re: Peavey Mace Question ?
Post by: Enzo on May 26, 2010, 07:56:29 PM
I am following the circuit, are we looking at CR1, CR2 in the Triumph?   This is the same noise reduction circuit Peavey has been putting in many of their high gain amps the last 20 years.

The two diodes are in series with the signal, hard to clip in series.  Clipping diodes are generally across the signal path, not in series.  Or in the case of op amp related circuits, in the feedback circuit.  COnsidering the fairly strong signal at that point consider what the diodes do.  The need to have about half a volt across them before they conduct.  Noise in the signal tends to be a lot smaller than the signal itself.  SO until the signal waveform gets over that half-volt threshold - and in either direction since ther are two diodes cross wired - the signal doesn't pass.  Once the waveforn exceeds that junction potential, then things flow as normal.

That is not clipping.  What that is is slicing out a little bit of signal at the zero crossing.  It introduces a slight crossover distortion that is almost impossible to hear in the distorted overdriven signal.  But in so doing, it also slices out the majority of noise.

Look at the circuit for the PV JSX.  The same two diodes are there as D1, D2.  But in that amp they added a 1 meg pot in parallel with them to dial in the amount of effect they have.  That control is named "Noise Gate."


And at the risk of tooting my own horn, I have worked on a few of these myself in the last 24 years of running a Peavey authorized repair shop.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on May 30, 2010, 04:13:47 PM
put a O-scope on it brother , that's what the circuit does , I'm not saying you don't know what your doing , and I'm also Peavey authorized (for 30 years) . however , take those 2 diodes out of the circuit and bridge the circuit and you tell me what they do lol lol lol I charge $65 for that mod lol lol lol

                                                    Rock On
Title: Re: Peavey Mace Question ?
Post by: J M Fahey on May 31, 2010, 12:13:53 AM
Well, I'm not Peavey authorized, never was, never will be, so I can look at that pair of diodes with fresh eyes.
What do I see?
1) They are in series with signal, not shunting it to ground
2) They are silicon, 1N4148, so they have a threshold below which they do not pass any voltage, be it signal or DC
3) If you have signal on V2B's plate, it must go through those diodes to follow its path. Whatever's below 600 mV peak gets heavily attenuated or dies.
Diodes have some capacitance , which in parallel with them and in series with a load of 1M7 (R27+R28+R29) will certainly allow some noise feedthrough; this is effectively shunted to ground thanks to C17.
4) I agree that if you place a scope probe to the left side of the diodes, you may see some clipping.
5)  I agree that if you place a scope probe across the diodes, say hot clip on the left, ground clip on the right, you will see a clipped signal.
6) If you place your hot scope clip to the right, you will see a signal which shows crossover distortion, and most noise gone.
7) From all 3 signals described (4/5/6) , the one that goes on and is eventually heard through the speakers, is signal #6. Re-read its description and that's what Peavey intended to get.
8) Personal opinion: I hate crossover distortion and even more farting sputtering noise gates, and would prefer to live with some extra noise, yet others may discord. Maybe some or most of Jack's clients think the same and willingly part with $65 to get rid of it, good for them and for Jack, yet I think that the above description of the circuit's action is accurate. Those diodes are not there to clip the signal per se nor to increase sustain , quite the contrary.
9) I may see some usefulness for them in the Ultra gain setting, but definitely not on the Crunch setting. (Personal opinion)
Love and peace, brothers.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on June 01, 2010, 02:26:08 PM
Well J M the customers alway's right when they have cash lol lol lol
Title: Re: Peavey Mace Question ?
Post by: J M Fahey on June 02, 2010, 01:13:00 AM
Sure they do .... but guess who keeps the money at the end of the game ;)
Title: Re: Peavey Mace Question ?
Post by: mensur on June 02, 2010, 05:09:32 AM
I agree with Fahey that diodes are not there to clip, they are to prevent noise to come out.
When there is no signal present at the first triode, ordinary noise is from the mains-50Hz.On the first triode is very small 0.000001 volts or so(this is an example), multiplication on the third stage is already enormous(couple thousands of times), so our noise is multiplied too, and it jumped from 0.000001 to 0.15V.The fourth gain stage has mu of 50 times, and PA has the mu of around 30, so 0.15V*1500= 225V of noise(IN REAL LIFE THIS IS IMPOSSIBLE THIS IS JUST AN EXAMPLE!!!).The diodes are preventing that voltage on the third stage, cause their threshold voltage is around 0.6V, until the guitar signal passes (cause he is a lot larger).The 1M pot is letting the signal and the hum (if there is any) to pass unaffected, something like the mix pot.The same goes for the hiss,which comes from parasitic capacitive, high freq. oscillations which comes from uncontrollable gain...
470K resistor after cc cap is there to reduce the gain, and 1nF is forming low pass filter with 1M pot or resistor (JSX/XXX) of 159Hz, so that basically means that freq under 159Hz are unaffected, only the freq's above are(-3dB's). I think this works like this, on the crunch ch. 1nF  cap is not shunting, cause that ch. has a lot less gain than the ultra.When the ultra is engaged cap is shunting.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on June 02, 2010, 07:13:21 AM
Yes according to Peavey they are in the circuit for noise reduction , but they do clip the signal. That's all I said folks ;D

                                     
                                          Rock On
Title: Re: Peavey Mace Question ?
Post by: teemuk on June 02, 2010, 09:00:39 AM
I guess it's just a matter of semantics. If removing signal information that exceeds a certain threshold counts as "clipping" then why not removing signal information that's below a certain threshold as well (even if the removed parts are nothing but noise).

The way I view it, both circuits "clip" but the process is different and applies to different portions of the signal. Either way, the diodes are erasing parts of the signal.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on June 02, 2010, 12:34:54 PM
I guess it's just a matter of semantics. If removing signal information that exceeds a certain threshold counts as "clipping" then why not removing signal information that's below a certain threshold as well (even if the removed parts are nothing but noise).

The way I view it, both circuits "clip" but the process is different and applies to different portions of the signal. Either way, the diodes are erasing parts of the signal.

yes both circuits do , I removed  the diodes in my own Triumph and I like it better without them , however , I will say this , when you remove this diodes , if you use the gain channel on the amp it is a bit more noisy(yea I know , but I did say peavey say's it's a noise reduction circuitg lol lol lol)

                                                        Rock On
Title: Re: Peavey Mace Question ?
Post by: bry melvin on June 02, 2010, 01:54:37 PM
I did that mod on my triumph head. It makes the crunch channel quite useful with vintage single coils (~4.7ohm) for a blues tone at low pre settings which it couldn't do before. I use a boss NS2 with that amp for the increased noise.


I also did a jumper cut mod that allows the tone stack to work in the crunch and ultra channels.
There are some on the peavey forums that say not to do this as a capacitor failure might wipe out the tone stack.
I never tried to analyze if that is true or not


link to peavey forum comment: http://forums.peavey.com/viewtopic.php?f=19&t=5232&sid=1ef08c4335d3c863fc2de985ce5febd3&start=15

I am taking my chances as the amp didn't work out for me before the mods and was a closet ornament.

I've also considered putting 5751s in V2 and V3 but haven't tried that yet
Title: Re: Peavey Mace Question ?
Post by: Enzo on June 02, 2010, 07:43:35 PM
Semantics?  Well yes, if we are not all using the same definition of clipping then it will be difficult to agree.   In my world clipping is a classic term meaning the removal of the waveform beyond some certain amplitube away from zero.  In other words lopping off the tops of the waveform.

I don't consider slicing out part of the waveform at zero crossing but leaving the larger amplitude portions of the waveform to be clipping.  Distortion, yes, removal of part of the waveform, yes, but not "clipping."

If someone else uses the term clipping to refer to the removal of ANY part of a waveform, well there is our disagreement right there.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on June 03, 2010, 09:01:36 AM
Enzo , call it what you want brother , it really makes no difference.  bry melvin  there is a post on Hoffman's amp forum about mods on this amp , that are very good I have done all but one of them , check it out , after modding this amp it is one great little amp.

                                             Rock On
Title: Re: Peavey Mace Question ?
Post by: Enzo on June 03, 2010, 10:03:25 PM
I am not stressed out by this, Jack, I am merely trying to determine if we are calling things by different names.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on June 04, 2010, 11:02:51 AM
I call it a clipping circuit because it actually does clip , peavey calls it a noise reduction circuit, and it does reduce noise , I suppose it really depends on who your talking to and in what context what this circuit would be called. however if you call Peavey or a authorized service center and ask about this circuit , they refer to it as a noise reduction circuit. To make a long story short , I have bridged this circuit many times for customers as well as on my own Triumph the amp in my opinion sounds better without it.


                                                     Rock On
Title: Re: Peavey Mace Question ?
Post by: skynyrd on July 03, 2010, 08:25:06 AM
Well here is is after the mods I did, I like the sound alot better, am going to do the bias mod as well shortly. My bridge tone pot is going bad and need to get a CTS for it.
http://www.youtube.com/watch?v=rOieBJplBIE
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on July 07, 2010, 09:28:12 AM
Sounds good  :tu:

                                 Rock On
Title: Re: Peavey Mace Question ?
Post by: skynyrd on July 07, 2010, 07:30:17 PM
Thanks Jack, I got the tone pot replaced and that lends much more to the variety of tones possible. I have been comparing several different amp schematics with my mace schematic and found a few things that I thought may lend to the elder Peavey mud tone. There is a resistor in the mace that is a 10K it goes between the bass pot and the treble pot, I noticed on a few marshall models they have 100K resistors. Makes me wonder if switching the 10K to maybe a 50K  would also help with the mud tone and give the bass and treble more independant tonal characters.
Title: Re: Peavey Mace Question ?
Post by: phatt on July 08, 2010, 08:37:18 AM
Hi Skynyrd,
               Re the tone tweaking;
Think long and hard before changing much in the circuit because by the time you find the magic R and C for that tone circuit the tracks will have been destroyed from so much reheating.
No matter how you tweak it that tone circuit is rather mundane no matter how much you wish to change the surrounding values.

What is often missed in the pursuit of greater tone is that the only part that *Cannot be replaced* is the PCB itself.
(parts are easy to find,,Boards are NOT) :'(

You would be far better served by using an outboard circuit for tone.
Tweak a new circuit on a bread board until you are happy, That way no harm comes to the Amp.
A quick simulation tells me what I already knew, that being about 10~14 Db of difference at any freq of interest. (i.e. from 100hZ to 4kHz,,, guitar response worth boosting or cutting)

Read my post for a simple off board tone control that can deliver a 35Db cut at 400hZ.
You will be pleasantly supprised.
http://www.ssguitar.com/index.php?topic=1136.0

I've added my findings of your circuit at full boost and full cut.
My *PhAbbTone* (at full boost) is added for ref.

Mace Trace1 B=0, M=10, T=0  (Green)
Mace trace2 B=10, M=0, T=10  (Yellow)
PhAbbTone   B=10, M=0, T=10  (violet)

Note,
       Passive Tone circuits like these can only actually cut
(no real boosting)
So the only way to make them effective is create the biggest possible cut/difference, especially in the mid bands.

Big shallow dips tend to pull too much out and hence you are always fighting against something,,Tone/verses Signal loss.

You will find that pulling a deep notch in the mid band delivers the best possible result.
Delivers a more defined tone alteration with minumal signal loss. 

Having played with gear for many years it eventually dawns on you that you are far better to work *outside of amps,, not in them*.

Unless there is something major wrong it's easier to work with external circuits.
you can still use the onboard Tone to do some extra tweaking. :tu:
Have fun,,, Phil.






Title: Re: Peavey Mace Question ?
Post by: Jack1962 on July 08, 2010, 12:40:29 PM
I have do disagree with Phatt , the tone tank in this amp as with most peavey's is just a variation of the FMV tone tank the most common tone tank in the indusrty, with may variations to give each amp a different flavor , I would advise you to go to http://www.schematicheaven and check out the different tone tanks and there configurations, you can greatly alter your tone thru the tone tank.

                                                  Rock On
Title: Re: Peavey Mace Question ?
Post by: skynyrd on August 15, 2010, 07:16:57 PM
Here she is, I got her where I want her now.
http://www.youtube.com/watch?v=7WXwWwl6-Qw
Title: Re: Peavey Mace Question ?
Post by: phatt on August 17, 2010, 09:52:27 AM
If you are happy then it matters little but I heard a lot of blocking type distortion happening in your clip.
Of course it's hard to tell with clips.

Having also peeked at the schematic then I doubt if the tone controls are doing much.
For me personally I would be wanting more clarity from my chords but again some folks may want all the muddyness.
All just my observations.
Cheers Phil.

Title: Re: Peavey Mace Question ?
Post by: skynyrd on August 26, 2010, 06:24:37 PM
I found out that my volume pot has issues, and the noise was getting worse and the distortion started sounding like it was compressed badly, changed out the volume pot to a new CTS and it cleared it up alot, plus I found that the 1/4 jack plug on the cable going from the amp to the cab was crackling when I wiggled it, replaced it with a new heavy duty audio cable ( the old 1 was a elcheapo) and she is much much better. I wouldn`t have thought the cable would make the difference it did but that brought the biggest change in the sound, it doesn`t sound like the amp is forcing the sound through the cab anymore.
Title: Re: Peavey Mace Question ?
Post by: Steve Dalllman on December 12, 2010, 12:29:29 PM
I recently obtained a Peavey Bravo 112. I put a switch across the diodes and listened to it carefully for a while. (BTW, I am an amp tech, authorized by many companies like Line 6, Fender, etc.)

The diodes only work when the gain boost is on, and they do work well. I can hear no discernable difference with the diodes working or shorted in the guitar tone, but the noise is unbearable with the diodes shorted. The decay is as smooth with or without the diodes. I hear no gating action.

I'm quite happy with this simple circuit.
Title: Re: Peavey Mace Question ?
Post by: Jack1962 on April 11, 2011, 12:33:05 PM
Steve a lot of people like these amps just like they are
(BTW I am a Authorized tech also by Fender, Peavey, Mesa , Korg(that's Marshall and Vox) and a few others  )