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Author Topic: Peavey Mace Question ?  (Read 33396 times)

skynyrd

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Re: Peavey Mace Question ?
« Reply #15 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.

Jack1962

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Re: Peavey Mace Question ?
« Reply #16 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.

Enzo

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Re: Peavey Mace Question ?
« Reply #17 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.

Jack1962

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Re: Peavey Mace Question ?
« Reply #18 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

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J M Fahey

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Re: Peavey Mace Question ?
« Reply #19 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.

Jack1962

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Re: Peavey Mace Question ?
« Reply #20 on: June 01, 2010, 02:26:08 PM »
Well J M the customers alway's right when they have cash lol lol lol

J M Fahey

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Re: Peavey Mace Question ?
« Reply #21 on: June 02, 2010, 01:13:00 AM »
Sure they do .... but guess who keeps the money at the end of the game ;)

mensur

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Re: Peavey Mace Question ?
« Reply #22 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.

Jack1962

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Re: Peavey Mace Question ?
« Reply #23 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

                                     
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teemuk

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Re: Peavey Mace Question ?
« Reply #24 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.
« Last Edit: June 02, 2010, 09:03:41 AM by teemuk »

Jack1962

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Re: Peavey Mace Question ?
« Reply #25 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)

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bry melvin

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Re: Peavey Mace Question ?
« Reply #26 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

Enzo

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Re: Peavey Mace Question ?
« Reply #27 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.

Jack1962

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Re: Peavey Mace Question ?
« Reply #28 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.

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Enzo

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Re: Peavey Mace Question ?
« Reply #29 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.