changing the sweep direction of an envelope follower??

[loss1234]

i have been messing around with envelope followers for awhile now and i would love to be able to make a mod where you could flip a switch and it would reverse the direction of the sweep (so you could have up to down or down to up)

anyone know how to do this?

the basic circuit i have been building off of is contained in this link

http://www.digisound80.co.uk/digisound/modules/80-13/construction/80-13_ETI.pdf

but it doesnt have to be for this specific follower. if anyone knows of a different circuit with this already built in, that would be helpful too.

thanks so much!!

[slacker]

With that envelope follower you should just be able to put an inverting opamp stage after it to invert the signal. Just connect the output to the inverting input of an opamp with a 1k resistor between the output and the inverting input and connect the non-inverting input to ground. The output of the new opamp should give you a reverse sweep.
I've got something very similar on the breadboard at the moment and it works pretty well.

[loss1234]

hey thanks a ton

so i will just wire up a switch to switch between the inverted out and the regular out.

great!

by the way, i have added a few mods, one a pot instead of a resistor to control the range, and then on the output i have added a 100k pot after the 1k out resistor and then a 22uf cap to ground (this adds attack lag)

its a nice small circuit!