Hello,
I am in the process of building the original Zen amp, and I would like to have a volume control on it. How can this be added to the circuit?
Thanks
I am in the process of building the original Zen amp, and I would like to have a volume control on it. How can this be added to the circuit?
Thanks
I’m looking for a way to incorporate the volume control in the existing circuit., not to add an additional circuit...
Could the R9 be replaced with a potentiometer of same value and the negative of C6 be connected to the 2nd pin of the potentiometer?
Could the R9 be replaced with a potentiometer of same value and the negative of C6 be connected to the 2nd pin of the potentiometer?
Here you go.
Remove R9. Replace with this (see attached image).
Wiper of 25k Potentiometer (middle pin) is connected to C6
There is one possible draw back from doing this, that is the input capacitance of Q1 is a little high and the output impedance of the pot creates an RC filter at input, so bandwidth will be reduced a little bit. Maybe not significant, too lazy to do the calculation.
That is why we use the buffer on an amp like this, since input capacitance of a small signal jfet is much lower, so is not affected by the output impedance of the volume pot, and the jfet provides a lower output impedance than the pot alone does, so can drive any amp without affecting bandwidth too much.
Just to be sure we are talking about the same amp, I have attached link.
http://www.firstwatt.com/pdf/art_zen_amp.pdf
Remove R9. Replace with this (see attached image).
Wiper of 25k Potentiometer (middle pin) is connected to C6
There is one possible draw back from doing this, that is the input capacitance of Q1 is a little high and the output impedance of the pot creates an RC filter at input, so bandwidth will be reduced a little bit. Maybe not significant, too lazy to do the calculation.
That is why we use the buffer on an amp like this, since input capacitance of a small signal jfet is much lower, so is not affected by the output impedance of the volume pot, and the jfet provides a lower output impedance than the pot alone does, so can drive any amp without affecting bandwidth too much.
Just to be sure we are talking about the same amp, I have attached link.
http://www.firstwatt.com/pdf/art_zen_amp.pdf
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