Author Topic: Another shrunken Engineer's Thumb, plus more Circuit Salad + Sheltand Klony #3  (Read 3854 times)


  • Electron Doctor
  • *****
  • Posts: 7218
  • Jon P
    • View Profile
    • Midway Fair
Despite spending the later half of last week redesigning my clippers ship OD, I got through a couple boxes.

Moss Press, Ray Ring's new MOSFET compressor on a prototype PCB from the man himself. This thing's really cool and is, as far as I know, the only compressor that uses a MOSFET as the variable resistance element. Check out the schematic over here: Elsewhere on his site he has open source CAD files to get boards made.

Despite having suggested the Darlington (as noted in Ray's post), I ended up using a 2N7000 for now. It had a slightly brighter sound and I managed to find a quieter one. I also reduced the input resistor to 22K (high enough to prevent distortion with single coils on no compression but brighter sound). Overall, I really like this design, and he did a good job reducing some unnecessary complexity and accounting for gain loss due to the compression. (I had to *heavily* mod his opto-FET comp to get above unity on the highest compression settings.) This thing actually makes a good beefy boost. And the compression indicator LED (lights up according to the strength of the compressed signal) is really neat.

How's it sound? It's got a LOT of compression and sustain available. There's a slight perceived high end rolloff in higher compression settings (normal). The attack is slower than a FET and probably closer to a vactrol, but that can be altered. It has some really, really great "pop" on higher compression settings, the kind of sound that makes me think "I need to learn slap bass." The decay is absolutely flawless and fairly long thanks to the full rectification and rail-to-rail op amp.

I can highly recommend this if you want a smooth comp that isn't subtle. It's one step behind the Engineer's Thumb in noise (unless you use the Darlington) and tonal transparency (no way I can see to bring back in treble like in the Thumb), but as far as the actual performance of the compression goes, it's just about as good as you can get. Extremely well-engineered.

I know I had promised before to demo Ray's opto-FET comp. I'll do this one and that one in the same demo. (I was holding off once I knew he was designing this one.)

EDIT: here we go, demo!

[ Invalid YouTube link ]

Speaking of Engineer's Thumbs ...

A couple weeks ago a friend challenged me to get an Engineer's Thumb into a 1590A. I ended up building two boards because I didn't know that the op amps had to be JFETs (TL0x2) to work. This was the second one I made. I put the treble boost switch on the inside (it's a little slider switch in the bottom right of the board) because I never turn it off. The art is the same as the first one I made (, a hydrolic press with newly minted coins, a reference to the Sherlock Holmes story of course.

And finally, Sheltand Klony #3 on Jimmybjj's Apis board, kind of on the QT. Normally I wouldn't build a klone with the intention of selling it, but it's for the same guy that bought the second one I made (the one I built completely stock to verify the boards), so I was okay with it as long as he didn't put it around that I built it to order. (I have trouble telling people no.) He has two boards, one of which never leaves the house and he likes to keep them identical, so he "needed" a second. This means I now have pedals on TWO boards next to a King of Tone and Zen Drive 2.  :o

He asked for some less whimsical colors because the other one sticks out like a sore thumb next to all the gray pedals:

This one's stock except for OA1160s with particularly high clipping for that diode. They just sounded too good not to use ...

Just a reminder, Jimmy still has plenty of these boards for anyone looking to build one:
« Last Edit: December 10, 2012, 08:33:17 PM by midwayfair »
Myself's music & things I make: My band: PCBs of my designs from: (Bearhug Comp & Cardinal Harmonic Trem); (Hamlet+ delay & Blue Warbler envelope vibe); Snow Day OD/Flabulanche:


  • Electron Doctor
  • *****
  • Posts: 2103
    • View Profile
    • SJ Effects
Another load of lovely builds mate.

You are churning them out at the moment!


  • Electron Doctor
  • *****
  • Posts: 4792
  • Josh
    • View Profile
    • 1776 effects

Contract PCB designer


  • Solder Ninja
  • ****
  • Posts: 261
  • Jim B.
    • View Profile
Great job as usual Jon!!

No current affiliations

Lovetone Flanger


  • Electron Doctor
  • *****
  • Posts: 6173
    • View Profile
Yeah, some cool builds going on there.

I really want to build one of the engineer's thumbs.  I've been considering doing a 1590A friendly layout for it.

I agree with the Apis.  That is a cool shrink down of the Klon.
Function f(x)
Follow me on Instagram as pickdropper