Today, I installed the Push-Pull Tone control to the Valve Jr. This mod, which I bought from BitMo, uses a DPDT attached to a potentiometer, a resistor and a few capacitors. The potentiometer is wired up similar to the volume knob potentiometer, with the left-most terminal being power, middle being the wiper (variable), and the right being ground. The tone of the amp is affected by the bottom two terminals of the DPDT when the pot is in the "down" position. This is just one small capacitor (once again, I'm not supposed to disclose values. I think). When the pot is in the "up" position, the upper terminals of the DPDT is used, which is using three capacitors and a resistor. The external wires for the pot were soldered to two resistors already on the Valve Jr board, R6 and R8. Capacitor C4 was cut off of the board, to be overridden by the new pot components.
The result: This tone knob adds a great more tone options (of course) to the amp. When turned all the way left, or counter clockwise, the bass is super high. The resulting sound is mellow and jazzy. Towards the right, the treble is picked up, and it sounds incredible paired with a distortion pedal. Using the push-pull option gives you even more diversity with the tonal range. There are so many different styles of sounds I can get from the amp now, especially paired with my pedal board. I don't know what else I can want from an amp. Pictures below!
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| Starting soldering caps to the DPDT. |
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| Soldering pot across two resistors on top of the board. |
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| Current inside of amp. |
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| All mods visible. |
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| Rear of recent mods. |
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| Trio mod (far left), volume pot (left), tone pot (right), and bright switch (below, with green wires). |
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