Microcompressor Stereo ttt





MICROCOMPRESSOR STEREO - compact stereo VC compressor for eurorack modular synthesizers. 16HP.



This compact but hi-quality compressor uses THAT4301 dynamics processor.

THAT 4301 Dynamics Processor, dubbed "THAT Analog Engine®", combines in a single IC all the active circuitry needed to construct a wide range of dynamics processors. The 4301 includes a high-performance, exponentially-controlled Blackmer® VCA, a log-responding RMS-level sensor and three general-purpose opamps.

Design is based on THAT Corp. design notes - Fully Adjustable Compressor / Limiter. This is a feedforward VCA compressor.


IMPORTANT! THAT4301 is obsolete. Please buy chips before ordering the kit (two of THAT4301 are needed). Or order replacement chiclet from Synthcube: https://synthcube.com/cart/that4301-replacement-pcb-chiclet-that4305-dip-20




  • Adjustable by potentiometers Treshold, Ratio, Attack, Release, Makeup gain.
  • Reduction LED which lights when signal level exceeds treshold.
  • Treshold, Makeup, Attack and Release can be controlled by CV.
  • Hard/soft knee switch.
  • Two timing modes are available -- auto and manual. In auto mode attack and release rates are linked, and depend on the non-linear capacitor circuit. In manual mode, variable, independent adjustments of the attack and release dynamics are possible.
  • Peak or Automatic timing detector options.
  • Sidechain in to external sidechain processing.
  • Envelope out allows to patch any VCA as compressor.
  • Full reverse polarity protection.
  • Power consumption: V+ 43mA, V- 30mA.


PCB - 2mm thickness, gold platted, black mask. $30


Two panels - 16HP front & back. Anodized alu, black print. $35


SMD parts + soldering. $15


Shipping per set: $5 - only board, $8 - board+panels.


TOTAL for complete set with shipping: $88


Paypal: info(at)greenexpo.by




MUFFWIGGLER forum thread http://www.muffwiggler.com/forum/viewtopic.php?t=101764


Short video demonstrating the Microcompressor features. This is quick test run I make on every new unit.

Warning! No music here. Technical data.




Soundsample. Tube VCA works as compressor modulated from envelope out of Microcompressor. Filter - Mutant vactrol VCF. No effects.




Sample made by Jim Sutherland www.jimsutherland.uk.com/

Distorted drums in punk style are heavy compressed. Jim modulated Makeup from Envelope Out to have extremally strong compression.










PCB top.


PCB bottom.


Front panel.


Back panel.






L-1 Stereo Compressor - Mouser shopping cart http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=4a34b f6189


Parts not included in Mouser shopping carts:

5 potentiometers (10K linear X 2, 50K linear X 3)
5 knobs
IC sockets - 20-pin X 2, 8-pin X 1.

Where to buy?

1. Thonk:
pots: http://www.thonk.co.uk/shop/alpha-9mm-pots/
knobs: http://www.thonk.co.uk/shop/synth-pointer-knobs/

2. Smallbear:
pots: http://smallbear-electronics.mybigcommerce.com/alpha-single-gang-9mm-r ight-angle-pc-mount/
knobs: http://smallbear-electronics.mybigcommerce.com/synth-pointer-2-colors/

3. Tayda:
pots: 50K http://www.taydaelectronics.com/potentiometer-variable-resistors/rotar y-potentiometer/linear/50k-ohm-linear-taper-potentiometer-round-shaft- pcb-9mm.html
10K http://www.taydaelectronics.com/potentiometer-variable-resistors/rotar y-potentiometer/linear/10k-ohm-linear-taper-potentiometer-round-shaft- pcb-9mm.html


I included into Mouser shopping cart 8 Kobiconn jacks. But they need to solder a leg for ground connection.
Better choise is Inline jacks:

1. Thonk: http://www.thonk.co.uk/shop/thonkiconn-3-5mm-jack-sockets-x50/






PCB with soldered SMDs:








(c) L-1 Synhesizer. E-mail: info@greenexpo.by