Shopping Cart


Your shopping bag is empty

Go to the shop

Union Tube & Transistor LAB Optical Compressor Boutique Guitar Effects Pedal


+ shipping

Up for sale, a Union Tube & Transistor LAB optical compressor pedal, brand new with Union's pedal crate. The LAB is an optical compressor which uses custom optocouplers to achieve up to 30dB of musical-sounding compression. Union was inspired by how in the recording studio, even with tons of compression, the old optical compressors such as the LA-2A sounded smooth and natural.

The essence of the LAB's sound comes from the fast attack and slow release times of the custom optocoupler. The optocoupler's behavior is quite complex, and program-dependent. It can't be modeled with simple resistor-capacitor networks. Union wanted the pure response of the optocoupler to define the LAB's dynamics, and not supplement that with RC filtering.

To that end, Union tried out just about every off-the-shelf optocoupler on the market, but ended up designing and manufacturing their own custom units. There's an interplay between dynamics, noise floor, distortion, and available compression on the one hand, and the opto's electrical parameters on the other. Since nothing commercially available fit the bill, Union built their own!

With just two controls – Compression and Gain make-up – the LAB is fast and simple to use. It sounds great on bass and electric guitar, and the noise floor is impressive – quiet enough for studio use. It really shines on acoustic guitar, vocals and drums.


-Power Requirements +9VDC @40mA
-Input Impedance 1MΩ
-Output Impedance 100Ω
-Frequency Response 20Hz–20KHz ±0.1dB
-Maximum Input Level +7.5dBu
-Maximum Output Level +10.0dBu
-Compression/Gain-makeup 30dB
-Noise Figure (Rs=10K) 3dB