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Peavey 6505+ 112 mod for channel balance

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  • Peavey 6505+ 112 mod for channel balance

    The difference in the response of the lead and rhythm volume (post) controls on this amp really bugs me. The rhythm channel is as loud at 5 as the lead channel is on 8. Looking at the schematic I see a ~3:1 voltage divider following the final gain stage before the tone stack and I assume this is partly responsible. It is shown in the schematic bit here, formed by R32 and R46:

    Click image for larger version

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    I am considering a few ways of changing this:

    Bypass R32 with another resistor to divide the voltage by less
    Jumper R32 to eliminate voltage divider entirely
    Remove R46 to eliminate voltage divider entirely
    Jumper R32 and replace R46 with 1M to eliminate voltage divider

    Which option is the right one?

  • #2
    Why focus on that point? The lead channel has similar voltage dividers going into one side of V3 and both sides of V4. The clean channel has a voltage divider between its two triodes, have you thought about increasing it to tame the clean channel as an alternative?

    Any of your options would reduce the signal attenuation at that node, I don't know that any of them is "right". And I am not implying any is wrong. My personal opinion is that I don't follow the control numbers so much. I turn the knobs until I get tone, drive, and volume that suits me. If the knobs point different ways, so be it.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Thanks, I just needed to do it for my sanity I guess, and to make volume adjustments a bit easier during gigs. I soldered a 22k resistor in parallel with R32 and set all the knobs on both channels at noon. The relative volume level is exactly where I want it to be now. I think the lead channel might be a bit meaner now too, maybe because there is more signal going into the tone stack, but it's probably just my imagination. I think I'm going to pop this pair of Winged C tubes in before rehearsal tonight and see how that goes.

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      • #4
        you've roughly doubled the voltage going to the tone stack, so yes it should get meaner!

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