CM1A is the Modular CL1B, with updated action!

The TUBE-TECH CM 1A Compressor is an optical, all-tube compressor. It features exactly the same tube circuit as our famous CL 1B Opto Compressor, but the action is different due to a different, carefully selected optical element and a fine-tuning of the control circuit.

This provides the CM 1A with an attack that enhances transients in a more punchy way, making it ideal for percussive material, yet still very well suited for vocals, bass guitar, etc.

The different optical element does NOT seriously change the the “classic” characteristics, known from the CL1B. The action of the CM1A places it somewhere between the LCA2B (Tube VCA) and the classic CL1B. CM1A has been extremely well received by numerous top engineers.

Note: Due to the high quality of the TUBE-TECH RM Series power supply and the pristine audio circuits, the Modular Series products deliver exactly the same uncompromised sound quality as our 19” units.


Features and Technical Specifications

The TUBE-TECH CM 1A Compressor features a gain-reduction element, positioned immediately after the input transformer. It is controlled by the sidechain amplifier, which also contain the two time control circuits – one for fixed and one for variable Attack/Release. The two time-controllers can either be used separately or combined.
This circuit contains semiconductor OP-amps for the entire control.

A tube-based push-pull amplifier follows the gain-reduction element with variable gain up to 30 dB. A dedicated Bus selector with three positions (Off, Link 1, Link 2) is used whenever you want to link several compressors together. Input and output transformers have a static-screen between the primary and secondary wirings. Input and Output is transformer balanced as well as fully floating.

  • Unique, low-distortion optical gain reduction element
  • All-tube based push-pull amplifier
  • Frequency response @ -3 dB: 5 Hz to 25 kHz
  • Low noise: < -75 dBU @ 30 dB gain
  • CMRR: > 60 dB @ 10 kHz
  • Variable ratio from 2:1 to 10:1
  • Continuously variable attack and release times
  • Variable threshold: Off to -30 dBU
  • Output gain: Off to +30 dBU
  • Input impedance: 600Ω
  • Interconnection of several compressors via two busses
  • LED display for monitoring compression and output
  • Conductive plastic potentiometers
  • Gold plated switches
  • Input and output are transformer balanced and fully floating


Sound Examples

Female Vocal (bypass)

Female Vocal (CM1A)



Male Vocal (bypass)

Male Vocal (CM1A)



Drums A (bypass)

Drums A (CM1A – light comp)

Drums A (CM1A – attack comp)

Drums A (CM1A – max comp)



Drums B (bypass)

Drums B (CM1A – light comp)

Drums B (CM1A – attack comp)

Drums B (CM1A – max comp)



Drums C (bypass)

Drums C (CM1A – light comp)

Drums C (CM1A – attack comp)



Snare (bypass)

Snare (CM1A)



Guitar A (bypass)

Guitar A (CM1A)



Guitar B (bypass)

Guitar B (CM1A)



Bass A (bypass)

Bass A (CM1A)



Bass B (bypass)

Bass B (CM1A)



RM Series Downloads

Manual RM2
Manual RM8
Manual PM1A
Manual EM1A
Manual CM1A

Tech Spec Sheets:
Specs PM1A
Specs EM 1A
Specs CM 1A

RM System

Recall Sheets:
Recall Sheet PM1A
Recall Sheet EM1A
Recall Sheet CM1A

Hi-res Images:
RM8 Perspective
RM8 Front
RM8 Rear
RM2 Perspective 1
RM2 Perspective 2
RM2 Perspektive 3
RM2 w.2CM1A Perspective
RM2 w.Micpres
RM2 Front
RM2 w.2CM1A Front
RM2 Back
RM2 at Console
PM1A Front
EM1A Front
CMA1 Front
PM1A Side
EM1A Side
CM1A Side