Old EHX Zipper Schematic Re-Draw

[Scruffie]

A Very Early Christmas Present to everyone... (especially for those with poor eyesight, which I don't suffer from yet, yet still struggled with the original!)

An EHX Zipper Schematic Re-Draw (Was the Original Posted by AMZ-FX? If So Thanks to Him/Her/Them) I think it's okay... (Assuming the Factory Original is Correct, would be handy if someone could verify this as some parts were very hard to make out) Maybe if the Bad Stone PCBs go down well too...



The Original This was Re-Drawn From - http://files.effectsdatabase.com/schematics/eh_zipper.gif

[Morocotopo]

Nice work Scruffie, thanks.
This is an envelope filter, right? Anyone ever built one? Or had an original? How does it sound?

[Scruffie]

Nice work Scruffie, thanks.
This is an envelope filter, right? Anyone ever built one? Or had an original? How does it sound?

Cheers 

Yup it's an Envelope Filter, I don't have one and haven't built one yet but by all accounts it's a vast improvement on any of the other EHX Envelope Filters (Dr Q etc.) and is a fairly sought after effect now from the old line of there Pedals (I beleive the new Tube Zipper is a completely different animal so I wouldn't try and compare them). No OTAs in this one which is nice too (as I don't have any) and only 3 FETs to match... could be worse.

[Morocotopo]

Seems like an easy one to try, no weird parts...
Right now I´m making a MXR env filter, but this looks like something worthwhile to try. Maybe I´ll breadboard it sometime.
I really like envelope filters, already made a Meatball and a Maestro Filter / sample & hold, but they are too big for the pedalboard...

I don´t get the function of Q4. Just a batt/pwr supply switcher?
Why do the fets need matching?

[Scruffie]

Seems like an easy one to try, no weird parts... this looks like something worthwhile to try. Maybe I´ll breadboard it sometime.

Yeah if you could and report back on how it works/ any issues with it anything like that, that'd be great!

I really like envelope filters, already made a Meatball and a Maestro Filter / sample & hold, but they are too big for the pedalboard...

Well if this gets verified I might consider doing a project like I just did for the Bad Stone Phasers (assuming the rest of the parties concerned agree) as i'd quite like an Envelope Filter for my board too and i'm on a bit of a run of reviving the Dead EHX Products as the second hand market for them has grown considerably and the prices have increased, plus the rarity and out of the ordinary sounds of alot of them in general... if it was on a professional PCB a fairly small layout should be possible.

I don´t get the function of Q4. Just a batt/pwr supply switcher?

Couldn't tell ya, someone else will have to chime in on that.

Why do the fets need matching?

I'm not sure they 'Need' matching but I think you'll get the most out of the pedal if you do... it may just be Q1 & Q2 that need matching as you see they're kinda set up like stages, both with the 160k Resistor and 5uF Cap with the 470R & 22R resistors before hand... someone else will also have to help clarify this but I think i'm right in saying matching will be a good idea.