Dr quack envelope follower

[birt]

http://www.muzique.com/schem/quack.gif

in that schematic the circuit around Q1 is buffer right? so the part at the bottom of the schematic is the envelope follower with Q2 as a variable resistance to ground?

what are the red leds for? because i want to know if i can use the envelope follower to light a led. and is it possible to inverse the envelope?

tnx
birt

[Mark Hammer]

http://www.muzique.com/schem/quack.gif

in that schematic the circuit around Q1 is buffer right? YES  so the part at the bottom of the schematic is the envelope follower with Q2 as a variable resistance to ground?  YES AGAIN

what are the red leds for? THEY ARE FOR BIASING THE OPAMP AND THEN SUBTRACTING THE BIAS VOLTAGE  because i want to know if i can use the envelope follower to light a led. I USED THE IDENTICAL CRCUIT TO LIGHT UP LEDS IN THE NOSE OF A HALLOWEEN MASK I MADE FOR MY SON.  WORKS FINE.  KEEP IN MIND ONLY THE SECOND LED FLASHES.and is it possible to inverse the envelope?  YES, SEE SOME OF THE CIRCUITS TIM ESCOBEDO HAS LIKE THE GARGLER.

tnx
birt

[birt]

so to have an inverse envelope he uses a JFET as variable resistance in the gargler because that acts the opposite way of an NPN in such a circuit i suppose?

oh except for the JFET part there are other differences between the gargler and the Dr Quack envelope. do they have an important reason or doesn't it change a lot?

[Mark Hammer]

There is where you have to ask someone a lot smarter than me.