Is a cap needed between MV - SE with bias?

[PRNDL]

I'm designing a single-ended amp with tremolo and variable bias. It's based on the princeton reverb circuit.

I've added a master volume pot before the grid (pin 5) of the 6V6, which also has a 220K connected to the intensity pot and bias board. This would have -35 volts.

I'm wondering if a coupling cap is needed to stop that DC (-35) from going onto the Master volume pot (via the wiper).

Thanks!!

[tubeswell]

Yep anywhere you've got DC that would otherwise connect to a pot - its a good idea to put a blocking cap in between the DC source and the pot

[PRNDL]

Easy enough to add it. -- thanks

[PRNDL]

I'm wondering if adding a master volume before the output tube is a good idea in a single-ended amp.

Also, whether I it's advisable to switch to cathode bias.

Any advice is welcome!!

[mooreamps]

Originally Posted by PRNDL

I'm designing a single-ended amp with tremolo and variable bias. It's based on the princeton reverb circuit.

I've added a master volume pot before the grid (pin 5) of the 6V6, which also has a 220K connected to the intensity pot and bias board. This would have -35 volts.

I'm wondering if a coupling cap is needed to stop that DC (-35) from going onto the Master volume pot (via the wiper).

Thanks!!

Without seeing the print, I'm thinking yes it does. Not that the voltage is going to harm the volume pot, but more so if the -35 volts is attached to the wiper of the pot, and then you turn the pot to zero, it could short out the bias voltage. Also, the bias voltage across the pot would make it very scratchy. Because of the low input input impedance to the grid of the power tube, I would start with a 0.1uF cap





-g