[sdiy] Using DG-series analog switches for PWM VCA

[Tom Wiltshire]

I’ve been working on and off on a “stutter pedal” design. This is basically a severe volume-chopping tremolo effect. I’ve experimented with using FETs to do the signal muting, but wasn’t happy with it. So I thought I’d try a PWM VCA, since I’m controlling the mute signals from a micro controller anyway - unlike the FET mute, I’d actually get some control of the volume level.

The chip I decided upon was the DSG413LE:

http://www.farnell.com/datasheets/2311996.pdf

Since the PWM needs to be at a reasonable frequency, I’m unlikely to have massive control over the gain (9-bit PWM at 62.5KHz would give me -54dB attenuation before ‘Off”). But since the alternative was a FET that was basically “on” or “off” this still represents an improvement!

Has anyone else done anything like this? Do you have any experience to share or gotchas that I should avoid? How do the DG-series chips compare with the old 4066 circuits that I’ve seen this technique used with?

Thanks,
Tom