[sdiy] basic CV source question

[john mahoney]

I posted something to Analogue Heaven that I'm not quite sure about. :-/
Someone asked about a CV pedal, like a volume pedal that sends a variable
control voltage. I basically suggested that a DC wall wart and a pot could
be used as a CV source. Was I correct to say that?

Ya' see, Larry Hendry (thanks, JLH!) once gave me a schemo for a CV source
that used an op amp. I've posted it here:
    http://www.bitshifted.com/images/cv_source.gif
(R1 thru R4 have not been specified -- that was left as an exercise for
yours truly, with generous hints provided by Larry.)

I would say that an op amp-based circuit is better because it is buffered,
so it should be more stable.

My questions are (a) is it necessary to use an op amp, and (b) will an AC/DC
adapter work as I suggested above? It seems almost too simple -- probably
needs at least a current limiting resistor, too, and what else?
--
john