Engineer's Thumb Compressor

Valve Wizard's excellent compressor design. Something a little different to the Dynacomp variants.

According to the write up this has five times more headroom and half the noise of the Dynacomp. Is that true? We wouldn't like to say, but it does sound good. Here's the horse's mouth.

We're offering this in a few configurations. You can keep it to an ultra simple two-knobber with just Compression and Level, but where's the fun in that? We all like to tweak those knobs. A four pot config adds Attack and Release controls. Add a fifth if you want a Threshold control. You can also add a Treble Boost toggle switch if you want to go the whole hog. We highly recommend this.

The kit is supplied with vertical-mount pots which have round shafts, so you'll need set-screw fitting knobs. If you're going for a 5-knob configuration keep them small - pot spacing is 17.5mm.

If you want the PCB without parts there's a link for that at the bottom of the page.

Partial kit: PCB, all board-mounted components, pots.

Full kit: As above, plus footswitch and appropriate daughterboard/components for your selected bypass type (see Downloads section for details of those), jack sockets, DC socket, battery snap, hook-up wire, LED.

Enclosure (pre-drilled) is available as an option with full kits, and will not take a battery. Knobs are not included.

Inspired by: Engineer's Thumb

Difficulty: Medium

PCB size: 50 x 47mm

Knobs required: 2/4/5

Enclosure: 1590B

Direct-Connect compatible (4-way)

Download the INSTRUCTION PDF

Product Code: EngThumb

Brand: Pedal Parts

Weight: 85.0g

Product Condition: New

Kit type* Circuit required* Treble Boost* Ribbon connector?*

£39.60 inc. tax

£33.00 ex. tax

? Tax based on United Kingdom.

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Customer Reviews

6 review(s) posted (write review)

Great Compressor, very versatile
"This is a great design for a compressor pedal. For me, a mix/blend knob is necessary in a compressor. It has this in the form of the ratio knob which I think changes the ratio and clean blend simultaneously. I made a 2-knob (plus hi-cut switch) version as I have found (with a 5-knob pedal I build) previously that I usually set the attack and release where I like it and leave it. Sometimes fewer options is more conducive to creativity. You should note that the volume for this pedal does not allow for any boost, so you will pretty much have it on full the whole time. I changed the 10ka for a 100ka (a=log) which is highly recommended. Theoretically it should give 2x volume boost on max. It probably changes the output impedance but it works for me." Matt - 05 July 2022

I built this in a day!
"I built this in a day. One day! It worked first time I laced it up. My first semi-complicated PCB from FuzzDog and it went together in a day and worked first time out. BZ guys. Nice project. I went from "what's a compressor" to one at each end of my pedal board. Not heavy compression. Just enough strengthen the signal up front and fatten it up at the end. That's where this pedal sits. For a non-optical device it has surprisingly little squash when set at a useable level. Classic design. Modern results. How do it know?" James Gale - 28 May 2022

Great compressor
"I got this to even out my clean playing and it worked perfectly. Had never used a compressor before buying this so still learning how the controls interact to get the best out of it. The immediate thing I noticed was no volume drop when splitting my humbuckers - really brings out the best in my guitar and gives me more options. As usual, great quality kit, great docs, and smooth build." Fabian Reynolds - 13 May 2022

Clean and musical compressor with piles of headroom
"Bought and built the 5 knob Engineer's Thumb compressor for my youngest son who was looking for a nice compressor. This compressor is quick, clean, and very musical in its sound. The design has a ton of headroom throughout the audio chain, and its all slipped into nice small physical package. I highly recommend it. My son loved it, and now his older brother wants one as well. I am a 35 year FOH and recording engineer with a family full of musicians. The build took me about 3-4 hours including measuring all my resistances before soldering (The old eyes don't see resistor color codes on small resistors like they used to). It was up and running without a hitch before my soldering iron had cooled down. One tiny thing caught me. I was getting some clipping with the threshold fully counter clockwise. I popped it up on the scope, looked at the schematic again, verified with some signals, and realized that CCW is high threshold, and CW is low threshold (more compression) -- opposite of what I was accustomed to as an engineer over the years. That pot orientation, however, made perfect sense to my guitar players. Makeup gain in the circuit was causing some clipping at that setting, so I will probably add a little extra resistance between the 4.5V rail and the threshold pot on my next one. And yes, there will be a next one soon!" Shawn - 30 July 2021

Incredible light bit of kit.
"This is a powerful little compressor with some serious overdrive/saturation type distortion if pushed really hard, I love it! Sounds amazing on an analogue synth. Really cool build too, got the full packagewwith ribbon connector and it's all finished really neatly. Was my first so a little tricky but as long as the time is taken to read all the resistor and component codes correctly, it's definitely achievable. Top marks!" Trevor - 22 August 2020

Excellent compressor and a great project!
"This is a fairly complex build so it was great to have it work first time wired direct to the sockets, then to have it fit into the enclosure after using the drill template. Not much spare room in there! Well worth the effort of putting it together as it's a really excellent compressor and you'd have to spend two or three times the build cost to get the same functionality from a manufacturer. I put all the controls and the switch in and glad that I did. This is a great project, total build time for me was about 5 hours. A ." jayjay - 13 January 2020