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Fender Hot Rod DeVille & Deluxe Drive/More Drive mod

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  • #31
    OK, for what it's worth, the owner preferred the 12AX7 in V2 with the drive down lower than the master volume. Both tubes sounded killer, but the 12AX7 suited his tastes. He was astounded at the gain reduction though and says that mod is a keeper.

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    • #32
      Originally posted by Tone Meister View Post
      OK, for what it's worth, the owner preferred the 12AX7 in V2 with the drive down lower than the master volume. Both tubes sounded killer, but the 12AX7 suited his tastes. He was astounded at the gain reduction though and says that mod is a keeper.
      With the 12AX7 in V2, it DOES have a bit more gain....like 8 or 9dB over the Drive mode, but still doesn't rip your head off like the stock circuit. Every so often, one of our HRD amps or a client's HRD amps that I've made the mods on shows up with a 12AX7 in V2. Such a simple change for nice results....thanks!
      Logic is an organized way of going wrong with confidence

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      • #33
        Personally, I've decided to do something different with the drive channel of a HRD. Stock, yellow and red modes were way too hissy whatever were the tubes and switchable cathode caps used, so here is what I've done:

        -C8: replaced with a 1.8k resistor, giving 820 Ohm when put in parallel with the stock 1.5k cathode resistor.

        -C9: swapped for > a 1k resistor in series with [a 1µ cap parallel with (a 1k resistor in series with a 100nF cap)]<. It’s a “stepped” cathode cap giving a stepped boost… and mimics more or less the effect of the bright switch, on the clean channel.

        -R21: lowered to 820 Ohm (1.5k, stock value for the V2b cathode resistor, was making it too grainy sounding in the amp as I’ve modified it).

        -R19 value halved for less overall gain in drive modes.

        I've also clipped the 390pF to ground on the master volume pot (I don't remember its number on the schematic, sorry).

        Red channel distorts hardly more than the yellow one now. When cranked, Both deliver a decent emulation of “classic Fender amp @ full tilt” with comparable volumes and two different voicings.

        When their gain pot is lowered, these yellow and red channel deliver a slightly crunchy clean tone that I find usable...

        NOTE that I've done 17 other mods elsewhere in the amp so I don't know how my tweaks on the drive channels would sound in a bone stock HRD.

        At least, I'll have shared something. Maybe it will be useful for someone, some day. :-)

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        • #34
          Out of curiosity and in a shameless crisis of "what if...", I've tested the drive circuit paired to... a single yellow LED diode, before C20, in parallel with R19.

          Associated to my former mods, it sounds nice to my ears. :-)

          But I've put back the 390pF cap to ground on the master volume: clipping it wasn't a good idea when it comes to use the amp with bright loudspeakers.

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