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Peavey Classic 30-More Gain

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  • Peavey Classic 30-More Gain

    I have read alot of threads but nothing for more gain. The guy who owns the amp likes the normal channel but wants more "shit" in the OD channel. His words. So I have V2A and V2B to work with. I changed R11 to 1M, not too big of a change. I raised C4 to .0022 and I got more low end which kind of took away from the higher gain sound. I changed the TS treble to 470p for more marshallesqe sound. I dont want to keep trying different values everywhere because I already raised one trace and I hate working on this pcb, getting it in and out of the chassis sucks. How would changing the slope resistor to 100k sound? I also lowered the boost cap and R12 to 2.2M. So give me your ideas on boosting the two middle stages please.

  • #2
    Change both plate resistors (R2, R3) to 220k. While you're at it change R16 (cathode resistor on second stage) to something like 3.3k-4.7k. That should pretty much be a guaranteed set of changes for "more shit" and a higher gain.

    You may also want to change R5 from 470k down to 220k or even 100k to drive the 3rd stage even harder (if the amp can handle it). That will work well with your R11 change to 1M. You should notice an appreciable difference if you go down to 100K. You might actually just want to start with this mod since you can just parallel resistors to what is already there and see if it is doing what your customer wants.

    I don't know how important C7 is to the stability of the amp but cutting that out would definitely open up the higher harmonics. Rolling off that much treble early on can just kill the higher harmonics in the distortion. You may have to re-distribute smaller amounts of capacitance around the other two stages to keep the amp from squealing when dimed.

    If you do all of the changes I suggested it will probably sound like a ratty nest of horse shit. Your customer should be pleased. (Maybe just try them in stages until it is enough).

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    • #3
      On the question of the OD 'channel in this amp, after a lengthy discussion with Amp Kat last year, I came up with a couple of variations on an SLO100 mod for my C30, which I quite like as a compromise in terms of OD and as a clean sound . The SLO100 has a similar pre-amp topology (if you hold the schematic at arms length and squint). You have to alter just about everything in the first three stages. There is a description and schematic of my latest variation on this thread:

      http://music-electronics-forum.com/s...ead.php?t=9416

      The voicing on the amp has changed but not in a bad way. It is more lead gueetary sounding even on clean (It has less lows/more mids). It sounds good with a humbucker or single coil.

      With these 2-in-1 clean/dirty channel amps, you can either tend towards bassman style cap and resistor values in the first stage, and get a super lovely fendery very clean sound, or go marshallesque values throughout and get a really good overdrive with attentuated lows and accentuated mids.

      I cannot find a simple way of getting both without complicating everything with extra leads wires switches and pots (and I have been there and back several times). However I am finding I like my latest SLO configuration - it keeps all the stock pots and does not require any new wires or switches, and only breaks one trace (by the V2A grid pin) to insert a 470k grid stopper, and the rest of the parts solder into existing holes (C4 becomes .002uF and is piggybacked with 470k), or onto existing pots (.001uF across the input to wiper of VR2 tacked straight onto the pot terminals), or on the back of existing boards (.001uF across R3 to the plate pin of V2B). (remember to swap C5 and R7 around when changing their values)

      I should add that I also have kept Steve Ahola's tone stack mod, which works well with this SLO mod. For the record, I used .047uF for the Bass cap, and 330pF for the treble and 390pF for the boost. I also did the 120k on the plate of V3A (to compensate for the slight loss of gain from the change in the tone stack slope resistor to 56k. Oh and I changed the resonance resistor (R56) to 330k (or rather it was left that way after I undid the presence mod)

      What's left of everything else is pretty much stock now except for the speaker
      Last edited by tubeswell; 11-05-2008, 06:13 PM. Reason: Forgot some stuff
      Building a better world (one tube amp at a time)

      "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

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      • #4
        Changes so far

        Alright, I changed C4 to .0022 and paralleled it with a 470k. I read somewhere it will give a heavier distortion.
        R5-220k
        R11-1M
        C11-250p
        Boost Cap-250p
        R12-2.2M
        R19-100k
        Changed mid and bass cap to 715p's(.022)
        I am not really getting any more gain that I can hear. I like the boost being on which would actually be 2 250pf's in parallel which is 500pf, standard marshall eq.
        tubeswell: do you have a clean and od clip of your amp that I could hear?

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        • #5
          here ya go

          Me twiddling on Strat. X'cuse the occassional missed note - no time to rehearse this. Mic'd the speaker in the combo (alnico Bulldog) - would sound fuller with the extn cab hooked up. I'm not really pushing the amp either - clean was on 4, the pre was on fullish and the post was on 5.5 - would get some nice feedback going if the vols were a bit higher - Dry sound with SM57 through crappy mixing desk into Garageband, then iTunes (but you get an idea)
          Attached Files
          Building a better world (one tube amp at a time)

          "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

          Comment


          • #6
            That's a pretty sweet tone when the lead comes in. I dig it.

            I've done high gain mods to my Fender DRRI and, while I like its sound with humbuckers, it doesn't sound nearly as good with single coils. I find single coils (at least my single coils) really hard to work with. Kudos to you!

            Chip

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