I've seen other questions and answers here on choosing resistance values for potentiometers in audio circuits (headphones, speakers, amps, etc.) and have heard of a "4 to 10 x's the target load" rule, but continually hear people suggest values between 50 and 100K ohms, and have become confused because the impedances and location of the pot in the circuit vary so much.
I'm hoping for a fairly straight ahead answer: I have an amp that delivers 30W to each of the two (2) channels. Each channel contains a crossover composed of a 6 ohm and a 4 ohm speaker in parallel with each other. I can draw this full circuit out, or provide more amp specs if necessary.
To add a simple volume knob between the source (a phone or ipod) and the input jack of the amp, what is the logical process for determining a resistance value, and type (Lin/Log)?
Best Answer
That's all irrelevant other than you have a stereo power-amplifer. The potentiometer will be going to the input. The output power doesn't matter.
simulate this circuit – Schematic created using CircuitLab
Figure 1. Your setup.
A 1 kΩ to 10 kΩ pot should be fine.
If you use too high a value for the potentiometer the amplifier input impedance will load it excessively and distort the volume curve. See Electrically loaded resistive Potentiometer! for more on the subject.