SICK DUCK...quack quack... :)

[deadastronaut]

okey dokey....

[phector2004]

What about a 2N5088 + LM386?

Like in the coloursound inductorless wah?

[deadastronaut]

ok, i put the envelope  and wah on seperate breadboards, with seperate 9v supplies, but the wah still distorts when i add the envelope follower....hmmm...

using 2 x lm358n's.....

[Gurner]

Ok, so now we know that the distortion (oops there's that word again) isn't getting into the signal via some PSU nasty.

You also say that the wah is fine with the envelope circuit, disconnected.... so the problem is now more likely to relate to the envelope detect part of the circuit loading the input signal.

Towards getting to the bottom of the problem, after you "T" off the signal to the envelope detector, temporarily put in a 'voltage follower' opamp circuit inline with the envelope detect feed (like this http://evilturtlestudios.webs.com/photos/Schematics/Buffer.JPG - ignore the speaker it was the first google image I found! Its +ve pin will need biasing to 1/2 your supply)....this will completely isolate the signal from being loaded down by the envelope detector.

[phector2004]

Could running a buffered effect in bypass before the breadboard be a simpler solution to test this?

[Gurner]

Could running a buffered effect in bypass before the breadboard be a simpler solution to test this?

Yes, quite possibly....that said it only takes a minute or two to knock up a voltage follower on a breadboard ....which will completely isolate the 'envelope detect' aspect from the pure signal path aspect..

[deadastronaut]

ok,cheers guys,  so it will be..

wah > voltage follower > envelope follower dooby...

voltage follower at 4.5v....not totally sure how to wire it up, but i'll give it a go..

[Gurner]

voltage follower at 4.5v....not totally sure how to wire it up, but i'll give it a go..

to bias it up to 4.5V...

DC blocking cap in series with the envelope detector 'T' off fleg (say a 4.7uF), two 1M resistors connected just like in your TL072 shown in you schematic (one to 9V the other to gnd - the junction to the +ve pin). The output of the opamp is shorted to the opamp -ve pin,so ...

                                                   9V
                                                    |
                                            1M Resistor
Envelope detect feed -->4.7uf ------|----------------------opamp +ve pin                             Opamp 'output' is shorted to opamp -ve pin + also feeds onwards to the envelope detect circuit.
                                            1M Resistor
                                                    |
                                                  Gnd

[deadastronaut]

cheers gurner, i think ive got it. thanks ...i'll try it later, gotta go do stuff today....

[deadastronaut]

@gurner:  like this?...

[Gurner]

No, relocate what you've got going to pin 8 over to pin 3.

Put 9V as normal on pin 8.

As an aside, I think the whole peak detect cct needs a rejig, but whether to bother or not depends on the results you get here.

[deadastronaut]

ok, yeah probably needs a bit of a radical rethink really....shame....i thought it would be ok as is...but hey..nothings simple is it..

i'll try it now though ok...cheers!..

[deadastronaut]

nope, still distorts like f....   the sensitivity of the pluck to light seems more reactive though...hmmm....

radical re-think it i then!....


it cleans up a bit if i change the 22k on the follower to a 47k...

[Gurner]

nope, still distorts like f....   the sensitivity of the pluck to light seems more reactive though...hmmm....

radical re-think it i then!....

Ok, now you've buffered the incoming signal, rather than have the main part of the circuit fed from where you have it now (ie unbuffered IN->R10), try feeding the main part from the output of the opamp (voltage follower) you've just put in, therefore connect the ouput of the opamp to the left hand side of R10 (but remember to disconnect what was originally feeding into R10 too)

it cleans up a bit if i change the 22k on the follower to a 47k...

You've lost me on that one - there is no 22k on the voltage follower (what's the component on your schematic that you're referring to?)

[deadastronaut]

sorry i meant 22k on the envelope follower....

hmmmm  .....i think i'm going to have to have a major re-think on this....it just don't like it.....thanks a lot for your help though man!..appreciate it!.. .

[Gurner]

sorry i meant 22k on the envelope follower....

hmmmm  .....i think i'm going to have to have a major re-think on this....it just don't like it.....thanks a lot for your help though man!..appreciate it!.. .

Hey, no worries...but as it goes there wasn't much left to eliminate!

[deadastronaut]

yeah, shame though, it could've been a cool one!....

i'll take a look at other envelope follower circuits and see what happens.....

phungnosis/nurse quacky/dr q etc....