Yes you can. Why? The best way to use a pot for volume control is to use it as a pot. That should minimise distortion if the track is slightly nonlinear or the wiper contact is less than perfect.
Input impedance will vary with control setting. Minimum input impedance = shunt resistor R.
If you intend to use this as a line level input circuit, then I recommend R = 47K. You can go lower, but if you go too low you'll introduce problems.
This circuit would work best with a buffer driving it.
If you intend to use this as a line level input circuit, then I recommend R = 47K. You can go lower, but if you go too low you'll introduce problems.
This circuit would work best with a buffer driving it.
Why do you want to do it this way? It could be a suitable method if you want to attenuate the signal even at maximum volume and control it over a limited range. The potentiometer is the shunt element not the fixed resistor
Thank a lot, brothers!
I want to take advantage of shunt volume control type.
But I'm afraid of trouble when the pot is broken. It will cause a rustle (Or something more dangerous??)
I want to take advantage of shunt volume control type.
But I'm afraid of trouble when the pot is broken. It will cause a rustle (Or something more dangerous??)
What advantage does this circuit have? I can't think of any. You have been warned about disadvantages.
Volume will go to maximum.
What advantage does this offer? The potentiomenter still affects the sound. I've read claims that it doesn't in this configuration, but it does. And it's still subject to acting like a low pass filter from stray capacitance.
It still has all the disadvantages of a conventional potentiometer attenuator.
Yes. Some people claim that the pot is 'not in the signal path' and so cannot affect the sound. The opposite is true: the pot is still in the signal path, and in this configuration any imperfections in the pot affect the sound more than for the usual configuration.Fast Eddie D said:
That's exactly what I heard. And I know it's wrong too, just by looking at the circuit diagram.
I measure parts before I put them in my builds. Volume control pots ("audio taper") are designed to work correctly in the conventional configuration, and every single pot I measured had closer tracking tolerance than it did matching of resistance between the channels. In other words, a volume control might have one channel measure 97K, and the other channel measure 107 K (typical measurements). But they still track together very closely.
This typical pot I described would work offer very poor tracking in the OP's circuit.
Want a good, cheap volume control for your builds? Here you go. PDB182-K430K-104A Bourns Inc. | Potentiometers, Variable Resistors | DigiKey
Want a fancy pants volume control? Here you go. https://www.parts-express.com/alps-...taper-stereo-potentiometer-6mm-shaft--023-206
I've used both of these and both are fine. The Alps offers much closer tolerance and has a lot of cool factor.
I would like to point out that proper circuit layout gets the most performance out of a volume control potentiometer. This means placing the pot right on the board if possible, with a buffering op amp as close as possible to the pot. This buffer should have a high impedance input.
The buffer can do dual duty like provide voltage gain, etc.
Doing this will mitigate the worst effects of any potentiometer and also kick the precision up a notch.
The buffer can do dual duty like provide voltage gain, etc.
Doing this will mitigate the worst effects of any potentiometer and also kick the precision up a notch.
Thanks you.
I see some schematics with buffered circuits, and there are no input capacitors for that buffer, but only input capacitors in front of potentiometers. Is that okay?
It's OK if you use low input bias current op amps like jfet input devices. Add an auxiliary input bias resistor in parallel with the wiper to ground. Make its value about 5-10 times pot resistance value.
Any appreciable DC current flowing through the pot will make it noisy. So sometimes you do need to use a cap between the pot and chip, like typically when you use a 5532 chip.
As a designer, it is up to you to decide which configuration to use.
- Status
- Not open for further replies.