Item #1005200 Model #CL1B

Tube-Tech CL 1B Compressor Standard


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An all-tube optical compressor that can add just the right touch of magic to anything from delicate vocals to slammin' drums.

The all-tube amplified Tube-Tech CL 1B Compressor has become to go-to compressor for top studios, producers and engineers. Known for the marvelous sonic characteristics it imparts without making its presence obvious, the CL 1B particularly shines on vocals. The CL 1B also offers the ability to link up to ten units together and a unique attack/release feature, not found on other compressors, that enables two CL 1Bs to provide program-dependent, overall mix compression.

Tube-Tech CL 1B Compressor, First Take:
All-tube-amplified optocompressor
Non-degrading gain reduction element
Unique Fix/Man control allows automatic program-dependent operation
Link bus allows up to ten CL 1Bs to be linked together
Balanced I/O and floating transformers

All-Tube Ampifier

The amplifier consists of two tubes (valves) in push-pull configuration (one ECC 83 as the pre-amp and phase splitter, and one ECC 82 as the output stage), and an output transformer. The power supply for the preamp and phase splitter are stabilized and the heaters of both tubes (valves) are fed with a stabilized DC voltage. The whole amplifier (including input and output transformer) and the power supplies are placed on one PC-board. Both input and output are balanced (600 Ohms) and fully floating. The in/out key switches the compressor in and out without clicks.

The side chain is the only part of the compressor that contains semiconductors. They are used for three reasons: First, they do not affect the sound reproduction. Second, they have a high slew rate, which is of importance for the performance of the compressor in regard to how fast it responds to input signals, and third, they don't take up much room. It contains two J-FET quad op-amps, one npn-transistor and one FET-transistor, which handles the signal for the gain-reduction element.

Non-Degrading Gain Reduction Element

The CL 1B differs from many other compressors, in that the gain reduction element is made from a non-semiconductor element, which in itself has a very low harmonic distortion and none of the non-linearity problems involved when using most semiconductor elements. Furthermore there is no long-term degradation of the element thus giving it almost infinite life. This signal processor is placed after the input-transformer of the compressor and followed by an all tube-based amplifier with a gain of 0dB to +30 dB. Thus the signal is not fed through any semiconductor circuitry on its way to the output.

Unique Fixed/Manual Attack and Release Control

To control attack and release, the CL 1B contains two time constants circuits: fixed attack and release times and variable attack and release times. The three position attack/release select switch makes it possible to use these two circuits separately, or combine their functions. This setting (Fix/Man) provides a unique feature not available in other compressors. In the combined mode, the attack- and release controls make it possible to obtain a complex release-time slope that is program dependent. In this state, the attack time always fast, but the release becomes dependent on the input signal. This means that the time it takes for the selected release time to take effect after a peak disappears is determined by the attack setting. That is, the attack control now functions as a delay with the same time range as its normal setting. The more clockwise (longer) the attack control is turned, the longer time before the release control takes over. The more counter clockwise (shorter) the attack control is turned, the shorter time before the release control takes over. This function is valid only if the time of the peak is shorter than the setting of the attack control. If the peak of the program is longer than the setting of the attack control, or if the attack control has reached the full counter clockwise position, it will respond as in the manual mode. The fix/man mode acts as an automatic release function with a constant fast attack time and fast release time for short peaks and a longer release times for longer peaks. This setting is mainly intended for use on program material (overall compression).

Multi Link Mode

The input/output capability of the CL 1B's sidechain-circuit allows up to ten compressors to be linked together. Sidechain jacks for interconnection of several compressors are located on the rear panel. A switch on the front selects which compressors are interconnected, and on which bus they are connected. If you e.g. have 10 compressors in a rack, you can select compressor 1,5,7 and 8 on link 1, and compressor 2,3,6 and 9 on link 2, leaving compressor 4 and 6 in the off position. Compressors 1,5,7,8 would now be interconnected and all four will perform the same compression. This applies to compressor 2,3,6 and 9 as well. Compressor 4 and 6 are independent. The interconnection implies that the unit that performs the most compression is controlling the others. Additionally, you can choose which one you want to control the others.

Balanced I/O and Floating Transformers

Microphone Input/Output are balanced and have fully floating transformers with a static screen. Floating a transformer (not referencing it to ground) provides maximum electronic isolation for superior noise rejection. The static screens shield the transformer's secondary windings from the primary and prevent RF (radio frequency) electromagnetic noise from getting across. The power supply and the sidechain circuits are based on a solid-state circuit. With the exception of the anode in the output stage all DC voltages are stabilized. This prevents any variation in the DC energy when combined with the musical signal, which would otherwise cause certain types of distortion or hum.

About Tube-Tech

For over twenty years, Tube Tech has been one of the most prominent names in all-tube signal processing equipment. You'll find their gear in the best recording and mastering studios around the world. The company's founder, John Petersen is an electrical engineer who was factory trained at Solid State Logic, EMT, Studer, Sony, Neumann, and NTP Electonik (digital audio routers). He also designed tape recorder playback/recording amps for Lyrec tape recorders (found in the studios of the legendary Joe Meek and Vangelis). His first design under the name of Tube-Tech was an all-tube equalizer based on the legendary Pultec EQP 1A. Petersen continued to design and manufacture a number of innovative all-tube outboard processors including preamps, multiband compressors and summing amps. Thanks to John's dedication to high-quality analog sound you'll see Tube-Tech gear in the racks of pro audio legends such as multi Grammy Award winner Al Schmitt, (Frank Sinatra, Steely Dan, Toto, Quincy Jones, Natalie Cole, Diana Krall), Grammy winner Joe Chiccarelli, (Elton John, Beck, U2, Tori Amos, Counting Crows, Offspring), engineer Russ Long (Sixpence None The Richer, Wilco, Dolly Parton, Allison Moorer), producer-engineer Tony Shepperd (Elton John, Madonna, Kenny Loggins, Barbra Streisand, Lionel Richie, and Whitney Houston), and many more.

  • Frequency-response: 5 Hz - 60 kHz +0/-3 dB
  • Distortion (THD) (40 Hz): 0 dBU: < 0.15 %, 10 dBU: < 0.15 %, maximum output (1 % THD): +26,0 Dbu, maximum input (1 % THD): +21,0 dBU
    Noise: Gain = 0 dB: -80,0 dBU (Unweighted) -70,0 dBU (CCIR 468-3); Gain = +10 dB: -80,0 dBU (Unweighted) -70,0 dBU (CCIR 468-3)
  • Input impedance: 600 Ohms
  • Output impedance: < 60 Ohms
    Compression Ratio (cont. var.): 2:1 to 10:1
  • Threshold (cont. var.): -40 dBU to +20 DBU
  • Gain (cont. var.): off to +30 dB
  • Tracking between interconnected compressors: (0 to 30 dB compression): < +/- 1 dB


  • Non-degrading optical gain reduction element
  • All-tube amplification
  • Linkable for stereo applications - up to ten units
  • Sidechain
  • VU-meters showing output or compression
  • Fix/Man mode allows automatic program-dependent operation
  • Conductive plastic potentiometers
  • Gold plated switches
  • Clickless bypass relay
  • Analog Outputs XLR
  • Analog Inputs XLR