M15MK1 : Big POP when I switch the channel or the FAT switch

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    • M15MK1 : Big POP when I switch the channel or the FAT switch

      Hi ,
      I have just finished to build the M15MK1 amp without the footswitch option.
      Everything seems to work fine but I have a big POP when I use the FAT switch or when I change the channel with the switch.
      Do you have an idea how to kill this POP please or maybe I have made a mistake on wiring?
    • Hi and welcome to the forum,
      there should be no loud pop when switching (presuming we have the same understanding of "loud"). Did you measure all voltages and are they OK? Do you measure any DC at the center taps of VR7 or VR2? There should be not much more than 0.9V DC at pin 8 of V1a.
      Regards,
      Martin
      ========== MAD = Martin Adams / Digital ist nicht alles / madamp.de ==========
      ========= Meine Alben: musikding.rocks/index.php/AlbumList/6475/ ========
    • Hi, thank you.
      yes I have 0.9V on pin 8 of V1a.
      I have read some threads on this kind of problem and it seems to occur when a capacitor has one pin with no voltage when the switch is triggered.
      So I wonder if I can add a resistor with high value (1MOhm) at the pin connected to the switch of C14 ? Will it change the sound or have a impact on VR7 or VR2 ? More oven I wonder if I could connect a resistor (1Mohm) between the ground and the pin not connected of C2 ?
    • Well. I've never had that issue with any of my prototypes, but you're right, the reason might be a voltage difference between both sides of the switch (at least for C2). So you can try a high value resistor (say 1M) across SW1 so the the capacitor is always grounded. SW2 is another story - all sides of the switch are grounded through VR2 and VR7 (which also means that both sides of C14 are grounded) so I don't see a chance to get rid of that noise with an additional resistor.
      ========== MAD = Martin Adams / Digital ist nicht alles / madamp.de ==========
      ========= Meine Alben: musikding.rocks/index.php/AlbumList/6475/ ========