I've been searching through guitar amp schematics to see if there is a simple technique for channel switching by footswitch.
For opamp based amps, there is a simple method of ungrounding the feedback network of a stage to silence that same opamp stage. This lends to a very easy to implement footswitch requiring only one contact and no relays or other devices.
I was looking through commercial tube guitar amp schematics but could find no equivalent trick, all I could find were relay based channel switching by footswitches. Any ideas?
For opamp based amps, there is a simple method of ungrounding the feedback network of a stage to silence that same opamp stage. This lends to a very easy to implement footswitch requiring only one contact and no relays or other devices.
I was looking through commercial tube guitar amp schematics but could find no equivalent trick, all I could find were relay based channel switching by footswitches. Any ideas?
Anybody? Bueller...Bueller...
How about ungrounding the cathode bias network? Is this OK if the grid and anode remain terminated?
How about ungrounding the cathode bias network? Is this OK if the grid and anode remain terminated?
There are several issues to contend with: tube impedance, how much signal is bled through, and sending audio through the cable to the switch.
Relays solve a lot of problems and allow channel switching without "tricks", which is why they are used.
The Super Twin Reverb did use a foot switch to change the bias point of a preamp tube to move it into distortion. Unfortunately, most people did not like the tone.
Relays solve a lot of problems and allow channel switching without "tricks", which is why they are used.
The Super Twin Reverb did use a foot switch to change the bias point of a preamp tube to move it into distortion. Unfortunately, most people did not like the tone.
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