Tap timing, hideously complex?

[Vsat]

Yup, this thread was getting sidetracked into a "Generic Interface Module" thread. Certainly a good idea to build up a application library for your favorite uC, and pick and choose as req'd. If someone was offering a pre-programmed PIC  as a general-purpose tap tempo controller/LFO then it would make sense to include several  output and interface options, otherwise, program specifically for the intended usage.

A "two-transistor autowah" circuit hooked up to a uC might seem like going overboard, but completely new functions could be incorporated  (and selected/modified/added)  quite easily, as long as you have the programming tools, without adding a lot of circuitry... just a few extra switches on the panel.
Cheers, Mike

[Transmogrifox]

Transmogrifox,

If you use an opamp "polarity reverser" like

http://www.geofex.com/Article_Folders/polarity_reverser/polarity_reverser.htm

(I think there's a similar circuit in one of the Craig Anderton's books)

You can control the switch with a PWM for a range of -1 .. +1.

Doh!  Thanks GFR!  I'm doing this in a much more complicated way than necessary.  I'm using 2 opamps with one inverting the signal then arranging the CMOS switches in a "Pot" like configuration.  It works well, but I may be able to decrease the number of op-amps by using this simple technique.  Due to the op-amp's slewing capability, it may be necessary to do all the 100kHz PWM carrier filtering before the opamp's + terminal to make sure the slewing isn't causing distortion.  This is just as easy as using a few passives all the same.

[A.S.P.]

here`s another nice "reverser", continuously controllable by a single variable resistor to ground... :
http://www.pat2pdf.org/patents/pat3633005.pdf