Developer AutoWah

[Kipper4]

This is a project that came out of my grey paper on Optical enveloping.
Simple but effective Autowah on a budget.
More details when I get the paper ready.
I'd stick a A100k output pot in too.
Thanks for the idea Eric.

[Kipper4]

[Kipper4]

https://youtu.be/6XbnA2W0FGU

[Kipper4]

Anyone done this?
I havent tried it yet in the MFB filter.

[Mark Hammer]

Not that I am unappreciative of your effort and diligence, but we gotta get some 2-pole lowpass filters in here.  Bass  players need some love too, you know.  All youneed to do s drive two LDRs from one or two LEDs.

[Kipper4]

You mean like the bottom figure here Mark?

http://www.radio-electronics.com/info/circuits/opamp_low_pass_filter/op_amp_lowpassfilter.php

But swap R2 for an ldr?

[Mark Hammer]

Yes, although there are other configurations, as well as single transistor versions, and also the matter of setting Q.

One would insert LDRs, and series resistors (for setting maximum points on sweep), in place of both R1 and R2 in that diagram.  Depending on the LDRs, placing a fixed resistor in parallel with the LDR, in addition to sticking something like a 1k or 2k2 in series with each LDR, might be a good idea.

As a sidenote, one of the nice things about higher-Q lowpass filters is that the resonance of the corner frequency can sound like a bandpass, but without losing the low end.  I have to get ready for Scotland, so I'll leave the math to you, good sir.

[Kipper4]

Thanks Mark.
Enjoy Scotland.
I have a spare op amp so I can mess with the lp filter while it's on the breadboard.
I'll post some other ideas too.

[EBK]

As a sidenote, one of the nice things about higher-Q lowpass filters is that the resonance of the corner frequency can sound like a bandpass, but without losing the low end.  I have to get ready for Scotland, so I'll leave the math to you, good sir.

The Crybaby was based off of one of those (I believe-- haven't actually looked at that schematic in a long time).

[bluebunny]

. . . we gotta get some 2-pole lowpass filters in here.  Bass  players need some love too, you know.

Now you're talking!   

Enjoy Scotland.  Send my love to the midges...   

[Mark Hammer]

. . . we gotta get some 2-pole lowpass filters in here.  Bass  players need some love too, you know.

Now you're talking!   

Enjoy Scotland.  Send my love to the midges...   

I'll give each one a hearty slap on the back. 

[Kipper4]

I just can't stop playing with this thing.
All this is not getting the paper done.

Another ghetto lab demo

https://youtu.be/dK_pJ_GwlAU

[Mark Hammer]

There is something about envelope control that can be immensely engaging to some of us.   I suspect it has to do with the outcome feeling like it's always different; like you're plugging in a new effect every time you plug in or stomp the switch.

[Kipper4]

Omg they have wifi in Scotland.
I like a pedal where I can get a good sound within a short time.
Have you seen the Bluebunny? Doesn't he live in that neck of the woods?
Mind the myxamitosis......

[dschwartz]

Just a suggestion.. why not to use the spare opamp as the input buffer and ditch the bjt?

[EBK]

Just a suggestion.. why not to use the spare opamp as the input buffer and ditch the bjt?

...unless there are other plans for that op amp.

[bluebunny]

Have you seen the Bluebunny? Doesn't he live in that neck of the woods?

Yeah, that's right.  I live in that part of Scotland known as "Berkshire".   

(Mercifully midge-free.)

[Kipper4]

Oh yer Marc it's the Iceman that lives in Scottieland.

This is a platform Autowah that is open to mods.
There's no good reason the spare op amp cant be used as a buffer.
It does leave the choices more open though for other mods if there's a spare op amp.
Now we're talking

[Kipper4]

Just a suggestion.. why not to use the spare opamp as the input buffer and ditch the bjt?

As per

[Fancy Lime]

Nice! This definitely deserved a bump considering the recent threads about similar filters.

Cheers,
Andy