MXR Envelope Filter & mods **verified**

[Zanius]

This was requested, I found an older topic but decided to start a fresh one since this is with mods.
I used the schematic from tonepad while taking peeks at the one at ggg too.
I've made a few layouts with standing resistors lately and I found them very useful, so there are a bunch of those in there :)

**Updated 11/1**

***Re-updated and verified 26/3***

[GrooveChampion]

Goddammit with these CMOS chips, I got the 4069, 4049 and the 4066, now I am missing another one...

[Strassercaster1]

did you verify it ? is this new i dont remeber seeing it a couple days ago Thanks Ill work on it in a couple of days i am waiting for one of the chips to arrive

[Strassercaster1]

thank you

[reddesert]

Cool. I have been building one of these on a perf version of the Tonepad layout (I didn't notice a vero version).

I see an issue with this layout: the only thing connected to +9V should be the 3K resistor, which drops to Vsupply for the entire rest of the circuit. That is, everything including the 47 uf cap and the Vsupply for each of the ICs comes after the 3K. This means the circuit runs off about 4-5V.  It isn't clear from the Tonepad or GGG schematic that the chips draw Vsupply from this dropped voltage, but it is from their PCB layouts.

[Zanius]

You're right. There's no marking on the schematics so I went standard practice :)
I will update soon.

[Zanius]

Updated!

Btw, this calls for 22Mohm resistors.. They are not easy to come by, most shops sell up to 10Mohms. Can anyone say if it would make a big difference if I used 10+10=20M?

[reddesert]

I don't know, but I doubt it will make a major difference. Those are in the envelope detector part of the circuit, where there's a stage that essentially has gain 1/2.2 (10M feedback resistor over 22M input resistor), and then another stage after the attack pot that has gain 2.2.

I got some 11M resistors from Tayda and teepeed them together to make 22M. I think I used 220K resistors in place of the 200K and 240K.

Try reading some of the diystompboxes threads about this effect. There are reports of people who did not get it to work using a TI brand CD4069 chip, and some reports of fixing that by changing the values in the R14-R16 voltage divider (62K-100K). The three inverters at the bottom of the Tonepad schematic make an ultrasonic oscillator, and it is possible that getting this to oscillate depends on the bias voltage and/or the supply voltage - and the supply voltage is dependent on the current draw of the ICs because of that 3K dropping resistor.  Long story short, you may need to tinker a little. I got it to work with basically the stock values. I used one of those Jye-Tech mini kit oscilloscopes to look at the high frequency clock and pulse modulation, which was very useful.

[Strassercaster1]

thanks again,   I will give it a try mid week. chips are due in soon. Have you made one yet?

[Zanius]

I've tried building it but only got clean signal through. No time for experiments now, I'll get to it again next week.

[Zanius]

Had some time to review this one today. Found the one mistake I had, it was an extra cut somewhere. Tried it with all the mods and everything works ok!

Not very pleased with the result though.The effect is pretty good but it sucks so much tone and volume, even with a buffer and a preamp I tried it with... Maybe it needs some fine tuning.

Anyway, This is now VERIFIED, updating the layout on the first post.