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[on:]

So a while back I wanted to automate a guitar pedal with 5 pots. I was told that an actual digital pot chip is too noisy for an audio circuit. Also using optoisolation was really difficult, I never got it working right. I ended up giving up.

Has anyone done this? Is there a well documented way of doing it?

Thanks.

[Reply #1 on:]

http://datasheets.maximintegrated.com/en/ds/MAX5407.pdf

Do you have a link to the previous discussion?

[Reply #2 on:]

http://arduino.cc/forum/index.php/topic,74465.msg
This one is about the optoisolator. I never managed to find one with two outputs.

As for that chip, I know it says "audio" but I think that refers to the log taper. I actually want a linear taper. Does the word "audio" refer to the taper, or to it's ability to be used in audio applications? I mean I know it's a log taper but does that necessarily mean it is suited for audio applications?

Oh sorry, also the first issue I ran into was that my circuit uses 9v. So the digipot would need to be suited for that.

[Reply #3 on:]

it's got a built-in zero crossing detector and my guess is that's why they called it for audio use.

Personally, I haven't found a worthy digital pot for use in audio apps.... if you're making a one-off device, sure they'll be fine.

But if you'll be mass-producing gear that uses them, or creating a matched pair, good luck!  Check out the datasheet:

End to End resistance... for a 20K spec part, it varies from 15K to 25K.
That's a 25% tolerance!

[Reply #4 on:]

Reliable digital Pot for audio

Not sure if they are "reliable", but PGA23xx would be the gold standard for audio digital pots.

[Reply #5 on:]

The PGA23xx say they are for volume control but I actually need a pot, they don't mention resistance or anything. I need to control an effect pedal.

[Reply #6 on:]

MAX5394 and MAX5395 are linear pots.

[Reply #7 on:]

MAX5394 is 6v max, MAX5395 5.5v max.

[Reply #8 on:]

OK, how about a AD5293?

[Reply #9 on:]

Pretty expensive for just one channel. It's got the higher voltage but totally overkill on the resolution. Plus is doesn't seem to be suited for audio circuits which was one of my first issues above.

I'm afraid I might just have to figure out how to get the optoisolators working the way I need.

[Reply #10 on:]

OK, how about a AD5293?

Nice!  $5.48 in quantities of 10.  Reasonable, just a bit more expensive than a Bourns potentiometer.