Dukane 1A385

[sluckey]

Still ain't right. Why are you even mucking around with the phase inverter? What's your goal?

[angelodp]

I want to insert a master volume on this amp as simply as possible. I saw on various posts that it was possible between the gain stage and the concertina.

A

[Ten Over]

Try this

DuKane MV.JPG

[angelodp]

Thanks, how does this version keep the DC off of the Pot?

Best A

[Ten Over]

Thanks, how does this version keep the DC off of the Pot?

There is no DC path, so there is no DC across the pot.

[sluckey]

Thanks, how does this version keep the DC off of the Pot?

There will be dc on the pot but since there is no path to ground there will be no current flowing through the pot, therefore no static when you turn the knob. However, you must remember that the pot is "hot" and will bite you if you touch the terminals!

You posted a good mv circuit a while back. Just need to convert from dc coupled input to ac coupled input and use bootstrap bias. This circuit has been successfully used in Princeton Reverb amps. This MV will not completely kill the sound when set to zero, but it's still very useful.

[Ten Over]

However, you must remember that the pot is "hot" and will bite you if you touch the terminals!

It should be noted that the 500KA pot in your diagram is also "hot", just in case someone might develop an inexplicable desire to touch something in a live amplifier.

[angelodp]

Ok I'll try this.

[angelodp]

Yes, it work quite well as you suggested. Once again thanks for assisting with your knowledge. I put in the 500k pot and its fine.
Time to play this amp now. I am keen to build a Princeton reverb at some point. The Hoffman layout looks very clean.

Best Ange

[angelodp]

Would a cap at the lower leg of the pot be advisable in eliminating the 90v on the pot?

[sluckey]

Would a cap at the lower leg of the pot be advisable in eliminating the 90v on the pot?

No! That would also eliminate the bias voltage on the grid. Let it be.

[angelodp]

Does the Princeton Reverb have voltage on the pot (Hot pot)?

wait PR has no master...

Ok done.


Ange

[angelodp]

Just added a 390pf bright cap to the #2 Volume and its a nice addition. With the Radial ABY the amp has a bit more Fendery sparkle now.

[sluckey]

Does the Princeton Reverb have voltage on the pot (Hot pot)?

The PR has no MV. But if you mod a PR to use that MV circuit, there will be dc on the pot. Any amp that uses that MV circuit will have dc on the pot.

Do you really notice any benefit to using that MV in your Dukane, or is it just another knob to play with?

[angelodp]

Yes the MV does allow me to dial in a bit of dirt at lower volume. I think that is the desired attribute. Right now with the dual input through the radial ABY, I have a reverb unit and going through two 12" speakers, its pretty cool.
If you have any suggestions on the tone knob to render it more dynamic? Right now it needs to be dimed to get the higher frequencies to emerge.