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Fender Performer 1000 (Roc Pro 1000) gain channel mod

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  • Fender Performer 1000 (Roc Pro 1000) gain channel mod

    I have a Performer 1000 (same amp as Roc Pro 1000). I really like the clean channel. I really dislike the gain channel. I cannot for the life of me figure out why they would want to design this as a high gain amp, with blackface aesthetics no less. The amp is "hybrid" in a sense that there is a tube in the gain channel, but it is only used as a clipping diode. I have tried different types of tubes (12AT7, AY7, AU7), IIRC the AY7 made the distortion a little less harsh, . I also reduced the gain in the op amp circuit that drives the tube diode. I cut the gain by about 3x, and now at least with drive at minimum you are on the edge of breakup rather than already into metal territory. The distortion is a little nasal and boxy. Looking for suggestions on other mod ideas to get more of a bluesy or classic rock sort of distortion. It looks like they change the cathode voltage for the two different drive levels, the yellow "lower gain" mode has a lower cathode DC voltage, if I were to drop that lower would I get even less clipping? I haven't found a good detailed explanation of the "tube as diode" thing. Maybe some treble bleeding would be good as well.

    Thanks,
    Greg

    Performer 1000.pdf

    Performer 1000.zip

  • #2
    Itīs a scam

    Itīs exactly same circuit as all other modern SS Fender, same gain, EQ, etc. , harsh, buzzy, *just* it has a diode strapped (grid to plate) 12AX7 instead of a couple Red Leds.

    So no "real tube" there, at least itīs not a gain stage, it has no +B feed, nothing.

    "Nobody" uses Fender Distortion channel, much preferring a good pedal ahead of it.

    Meaning donīt waste time polishing a turd.

    I strongly suspect it was a way for Fender to use the huge amount of unusable/microphonic/gassy/you-name-it defective 12AXy they must have stockpiled by now.

    The ones I saw had the 12AX7 wrapped in shrink wrap, go figure.

    Best part is that user manual boasts: "look inside other amplifiers (mainly Marshall Valvestate ), youīll see a couple Red Leds shining in rhythm with the Music, thatīs cheating, we have a real tube" .... REALLY?

    As of "blackface looks", I remember one Kustom ampifier which came in 2 versions: a Tweed looking one, suggested for Blues, with fake Tweed Tolex and matching control panel graphics, and a Modern Metal one, flashy, robotic looking ... *Ļ*exact same circuit inside**
    Funny thing is that Musicians argued about them in some of the Guitar Forums and found them very different , praising one and shooing the other according to personal preference

    EDIT: the real clipper is 100k R36 in series with signal, and back to back diodes V1a and V1b clipping to ground.
    You get about 2V peak there, not too different from 1.9V found with Red Leds.

    Slightly more rounded than plain duiodes, but not a game changer by any means.

    Itīs followed by the infamous mid killing buzzy "Contour" control , here called "body", should have been called "scoop" because thatīs what it does.

    To hide buzzyness, they lobotomize Treble control, instead of the 250k pot Fender EQ requires, they use 50k R60 pot in series with fixed 220k R166 so 0>10 knob sweep now is really 0>2 ... very cheesy.

    Again, leave as is and use a good pedal, the alternative being full dirty channel uprooting and building something better there ... clearly not worth it.
    Last edited by J M Fahey; 12-30-2018, 01:21 PM.
    Juan Manuel Fahey

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    • #3
      Originally posted by J M Fahey View Post

      Again, leave as is and use a good pedal, the alternative being full dirty channel uprooting and building something better there ... clearly not worth it.
      This amp is one that I loan to a nonprofit that has a music hall and open mic, if I put a pedal out with it it would probably be quickly stolen.

      I think this would benefit from more mids, what about bypassing the body control, or minimimizing it?

      Comment


      • #4
        OK, thereīs more than one mid killing network on the Dirt channel:

        1) disable the first one by removing C14 and C15 and shorting across C13

        2) you may double C27 and halve C30 ... this diminishes scooping effect, let your ear be the judge.
        In principle, with pot set to "5" or "12 o clock" effect is minimized .

        3) I would short across R166 so Treble control behaves like a normal one; then increase C33 to 2200 or 2700 or 3300 pF , each increase allowing more mids and making sound less harsh/brittle.

        Donīt just apply all of them at once, but one by one and test them.

        If too messy/long pulling the board out each time, Iīd add a small post (piece of wire) at each capacitor position so they can be replaced/soldered "from above" without constant disassembly.
        Juan Manuel Fahey

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        • #5
          Great suggestions, thank you! Will have to see when I can steal this back from the music hall to work on it.

          Comment


          • #6
            Replying to my own necrothread for anyone looking for info on this amp that reducing R48 to ~100k really makes the clipping and volume on the drive channel of this much more useable. This is in addition to lowering R35 to lower the gain of that op amp stage. These are easy changes to make by looping a resistor in parallel to the existing so you don't even need to remove the board. I can now get a passable if not great crunch tone at the expense of some of the fizzy highest gain stuff.

            Also, a speaker swap might also help. I tried a similar amp with a donor speaker from a Crate amp and it is actually much smoother sounding than the stock Fender speaker.

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