Digital Volume Control

Analog Devices makes some nice digital pots. I worked on a project many years ago where a digital pot was an option for replaced resistive pots. It was a short lived idea. The digital pots all had problems with "zipper noise" Each time a signal was sent to attenuate, or boost a signal, the pot made a "clicking" sound. If someone held down the up or down button for volume, these clicks were all strung together, and sounded almost like a zipper.

An option might be to use a digital pot, and a voltage controlled amplifier. You won't get zipper noise this way, but will get a noticeable attenuation or boost step. Unless you pick a digital pot with a high number of steps. The this step end up being very small, and not as noticeable.

Another problem, memory. The digital pot has to start somewhere. You'll need to find a way to set it up so the volume is blaringly loud. You may also not want your device to always start with no signal. Or, you may want it to always remember where you last left the volume set.

In any case, it's a fun project.

The DS1802 has a zero crossing detector to prevent "zipper" noise.

My project ended up not using a digital pot at all. The cost of adding a VCA into the design was too great. For my own circuit, I'd go with a VCA.

I can't ever use a Maxim or Dallas Semiconductor part ever again. They bit me hard while working in the audio industry, and failed to deliver a million piece order. For a onesy twosy hobby project, they may be fine.

If you ask nicely, Maxim might send you a Sample.
 

Quote:

Originally Posted by jtavrisov 

DS 1802 is quite expensive but seems to be what I'm looking for. I don't quite understand what a VCA is and doesnt seem like a simple drop in circuit.

 

Any other (cheaper) alternatives. That digi pot is more than half of the cost of the entire amp section of my project.

You can use a level shifter like in the data sheet or you

can try a dual rail power supply like this:

You could add a tacky "70's VU meter while your at it if you like...

So the noises people complain about with the worst digital volume controls are only from when you adjust the volume, right?  This is not a present problem when the volume is left alone?

I can't speak for all digital volume controls, but for DS1802, there should be no noise

even when changing the volume.