Home Forums GuitarPCB Build Support Animal Buffer Bypass Consideration

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  • #11945
    Cybercow
    Moderator

    I’m finally getting around to completing a combo pedal using two “Tone TwEQ”s, a “RotoTone”, an “Animal” and a “Super Sonic 02”. (No order switching as the SS-02 will be driving the Animal.) The focus of my inquiry is on the Animal. I want to be able to incorporate the Animal’s buffer section, but also be able to completely toggle switch the buffer in and out of circuit. So far, the only configuration I can derive calls for using a 4P2T toggle switch. Am I making it too complicated or is another switching option available that I’ve overlooked?

    The 4P2T toggle I’m considering will be doing this using the buffered wiring pattern in the build doc:

    Pole 1: Switch the input jack between the PCB “In T” and stompswitch “S2”

    Pole 2: Break the connection between the PCB “S2” and the stompswitch “S2”

    Pole 3: Break the connection between the PCB “S8” and the stompswitch “S8”

    Pole 4: Switch the output jack between the PCB “Out T” and stompswitch “S8”

    Screenshot of buffered wiring for your viewing reference . . . .

    Your time and consideration is appreciated.

    #11946
    wilkie1
    Moderator

    How about using a DPDT switch connected as follows?

    SIgnal IN > Lug 2

    Lug 1 > IN pad

    Lug 3 > Lug 4

    Lug 6 > S2

    Lug 5 > S1

    Your thoughts?

    #11990
    Cybercow
    Moderator

    Thanks Wilkie!  With your suggestion, the components that come after S8 (R38 & R39) remain in the circuit. Will that have any bearing on the output? With R38 at just 91Ω, I can surmise there is no issue. But with R39 at 50K Ω going to ground, will that not effect the behavior (taper) of P3 (the Volume pot)?

    #11996
    wilkie1
    Moderator

    I used a voltage divider calculator to determine that the voltage at the out jack will be 99.8% of the voltage at S8 when using the stated values for R38 and R39.  However, when adding the consideration of the resistance of P3 in parallel with R37 (39K), that would add more resistance to the upper half of the voltage divider.  The result would be a voltage even lower than the S8 voltage.  If this would affect the taper of the P3 vol pot, I assume it would be very minor.  I would think you could bypass R38 and R39 and take your output directly from S8.  I have no idea what function is provided by the R38/R39 voltage divider.  Most of the circuits I have seen do not use this at the end of the circuit.  Do you have any ideas?

    #12032
    Cybercow
    Moderator

    Wilkie – my best guess, (and that’s all I have is a guess), is that those are artifacts of Peter Cornish’s foundational buffer circuit used in almost all of his designs. I did a bit more poking around in some of Peter’s schematic designs (reverse engineered traces mostly) and that “R38 & R39”, (R29 & R30 – 91 Ω and 51K Ω respectively in Peter’s schematic found here: Cornish Soft Sustain Schematic [SS-3]) seem to be part of his schtick.

    Aion, which does a number of traced Cornish-style circuits (for comparative exploration) and also demonstrates the same final resistor elements at the end of their “Cygnus” (a traced P.C. G-2 distortion\sustainer) and “Oceanid” (a traced P.C. OC-1 compressor) builds.

    I can only surmise that the final resistor arrangement acts as a sort of ‘bleed’ cushion or path in order to, (at switch time), to minimize any switching noise or popping from either the circuit itself or any potential that may exist in to what it is connected.

    So I concur that the impact of the 91 Ω and 50K Ω resistors at the output would & do indeed have minimal impact on the performance and behavior.

    #12036
    wilkie1
    Moderator

    Interesting.  I have seem many circuits that use a “bleed” resistor to ground at the output of circuits just as they are used at the inputs.  Usually these are large values from 100K up to 1 or 2M.

    I suppose you could switch the output between S8 and the OUT jack to see if you can hear any difference or notice any difference in the taper of the VOL pot.

    #12079
    Cybercow
    Moderator

    Again, as a “best guess”, the lower values may keep the output at a lower impedance also. Will have to do some testing before combining this Animal with the SS-02 and Tone TwEQ PCBs. Thanks Wilkie.

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