TUBE-TECH CL 1B - User Manual

LYDKRAFT ApS
Mose Allé 20, DK 2610 Rødovre
Denmark
1
Owners manual
TUBE-TECH
CL 1B Compressor
DESCRIPTION.
The TUBE-TECH compressor 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 element is placed after the input-transformer of the compressor
and followed by an all tube-based amplifier with a gain of - dB to +30 dB.
Thus the signal is not fed through any semiconductor circuitry on its way to the output.
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 pre-amp 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) and fully floating.
The in/out key switches the compressor in and out without clicks.
THE SIDECHAIN:
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 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.
The compressor contains two time constants circuits:
1. Fixed attack and release times
2. Variable attack and release times
The attack/release select switch makes it possible to use these two circuits separately or
combine their functions.
This gives a feature not normally obtained in other compressors:
In the combined (fix. /man.) state the attack- and release controls make it possible to
obtain a complex release-time slope. (See page 4)
(140919 jgp)

Summary

Description of the Tube-Tech CL 1 B Compressor

The Sidechain

Explains the side chain's role, semiconductor usage, and components within the compressor.

Compressor Interconnection

Controls

Gain Control

Explains the gain control for makeup gain, its range, and placement after the gain-reduction circuit.

Ratio Control

Describes the ratio control's function in varying the compression ratio and its continuous variable range.

Threshold Control

Defines the threshold as the point gain reduction begins, detailing its continuously variable range.

Meter

Details the VU-meter switch positions: Input, Compression, and Output for monitoring levels.

In;Out Switch

Explains the leverswitch for bypassing the compressor in/out of the signal path.

Attack Control

Describes the attack control's function in determining compressor response speed and its variable range.

Release Control

Describes the release control's function in determining response speed to signal decrease and its variable range.

Attack;Release Select

Bus Select

Explains how to interconnect multiple compressors using bus selection for synchronized operation.

Suggested Applications

Overall Compression

Provides recommended settings for final mix overall compression.

Standard Compression

Offers settings for standard compression on various instruments and vocals.

Heavy Compression on Instruments

Gives settings for heavy compression on line guitar and piano.

Compression of Drums

Provides settings for snare and bass drum compression.

Adjustment Procedure

Caution

Advises on unit heat-up duration and offset-voltage checks before adjustments.

Adjustment of Basic Gain

Details the steps for calibrating the basic gain of the unit.

Adjustment of Compression Tracking

Outlines the procedure for accurately adjusting the compression tracking.

Adjustment of the VU Meter Reading Compression

Adjustment of the Release Control

Explains how to set the release control for a specific time measurement using the VU meter.

Overview

1. Function Description
2. Usage Features
3. Maintenance Features

The TUBE-TECH CL 1B Compressor is a sophisticated audio processing unit designed to provide high-quality gain reduction with minimal distortion and long-term reliability. Its core gain-reduction element is a non-semiconductor component, which inherently offers very low harmonic distortion and avoids the non-linearity issues often associated with semiconductor-based elements. This design choice also ensures an almost infinite lifespan for the element, as it is not subject to long-term degradation.

Function Description:

The CL 1B operates by placing its unique gain-reduction element after the input transformer. Following this element, an all-tube-based amplifier boosts the signal with a gain range from -∞ dB to +30 dB. This architecture ensures that the audio signal never passes through any semiconductor circuitry on its path to the output, preserving the integrity and warmth of the sound.

The amplifier section is comprised of two tubes in a push-pull configuration: an ECC 83 serves as the pre-amp and phase splitter, while an ECC 82 handles the output stage. An output transformer completes the signal path. To maintain stable operation, the power supply for the pre-amp and phase splitter is stabilized, and the heaters of both tubes receive a stabilized DC voltage. The entire amplifier, including its input and output transformers, along with the power supplies, is integrated onto a single PC-board. Both the input and output connections are balanced (600Ω) and fully floating, ensuring robust and interference-free signal transmission. An in/out key switch allows for seamless engagement or bypass of the compressor without introducing audible clicks.

The sidechain, the only part of the compressor that utilizes semiconductors, is designed to have no impact on sound reproduction. Its components, including two J-FET quad op-amps, one npn-transistor, and one FET-transistor, are chosen for their high slew rate, which is crucial for the compressor's performance, and their compact size. The sidechain manages the signal for the gain-reduction element.

The compressor features two distinct time constant circuits: one with fixed attack and release times, and another with variable attack and release times. An attack/release select switch enables users to utilize these circuits independently or combine their functions. This unique capability allows for the creation of complex release-time slopes, particularly in the combined (fix./man.) state, offering greater control over the compression envelope.

Usage Features:

The CL 1B offers a comprehensive set of controls for precise audio manipulation.

• GAIN: This control compensates for the gain loss that occurs during compression. Positioned after the gain-reduction circuit, it does not influence the threshold setting. The gain control is continuously variable from off to +30 dB.
• RATIO: This control adjusts the compression ratio, determining how much the input signal is compressed. For example, a 2:1 ratio means a 10 dB input signal increase results in only a 5 dB output increase. The ratio is continuously variable from 2:1 to 10:1.
• THRESHOLD: This defines the point at which the compressor begins its action, specifically when the gain is reduced by 1 dB. The threshold is continuously variable from +20 dBU to -40 dBU.
• METER: A VU-meter switch provides three positions:
  • Input: Displays the level at the input socket.
  • Compression: Shows the gain reduction. Its rest position is "0 VU," with decreasing deflection indicating the amount of compression in dB.
  • Output: Displays the level at the output socket, with "0 VU" equivalent to +4 dBU.
  • Note: It is recommended to leave the meter switch in the "compression" position, as leaving it in "input" or "output" might introduce distortion.
• IN/OUT: This lever switch engages or bypasses the compressor in the signal path. The "out" position bypasses the entire compressor.
• ATTACK: This control determines how quickly the compressor reacts to an increase in the input signal. It is continuously variable from 0.5 to 300 milliseconds.
• RELEASE: This control determines how quickly the compressor responds to a decrease in the input signal. It is continuously variable from 0.05 to 10 seconds.
• ATTACK/RELEASE SELECT: This switch offers three settings:
  • Fixed: Provides a fixed attack time of 1 msec and a release time of 50 msec.
  • Manual: Allows for variable attack times from 0.5 msec to 300 msec and release times from 0.05 sec to 10 sec.
  • Fix/man: Combines the release times of fixed and manual modes, while the attack time remains as in the fixed mode. This mode provides an automatic release function with a constant fast attack time and fast release for short peaks, transitioning to longer release times for longer peaks. This setting is particularly useful for overall program material compression. In this mode, the attack control influences the time it takes for the selected manual release time to take over after a peak disappears. Turning the attack control clockwise increases this transition time, while turning it counter-clockwise shortens it. This function is active only if the peak duration is shorter than the attack control setting. If the peak is longer or the attack control is at its full CCW position, it behaves like the manual mode.
• BUS SELECT: This feature allows for the interconnection of multiple compressors on bus 1 or bus 2. If a compressor is left in the "off" position, it operates independently. When interconnected, the unit performing the most compression controls the others. To designate a master controller, set the attack/release time, threshold, and ratio on that unit, and turn the threshold fully counter-clockwise on the "slave" compressors. All interconnected compressors can also control each other simultaneously.
  • Important: When using interconnected compressors, ensure the ratio and gain controls are set to the same position on the "slaves" to prevent stereo image shifting during compression. The attack/release control on "slaves" will have no effect. The side chain circuit can link up to ten compressors using a standard 1/4" stereo jack/-jack cord (tip: bus 1, ring: bus 2). The two jack sockets on the rear panel are connected in parallel and serve as both input and output for the sidechain.

Maintenance Features:

The manual provides a detailed ADJUSTMENT PROCEDURE for maintaining optimal performance of the CL 1B.

• CAUTION: Before any adjustments, the unit must heat up for at least 15 minutes. It's crucial to verify that the offset-voltage measured at the side chain jack socket, with the THRESHOLD off, does not exceed +/- 15 mV DC in both "fixed" and "manual" positions (tip is bus 1, ring is bus 2). If this voltage is exceeded, IC1 or IC2 should be replaced.
• GRE Marking: Specific markings for the Gain Reduction Element (GRE) are provided based on serial number ranges:
  • For serial numbers up to 15891, the GRE should be marked between 1.225-1.285.
  • For serial numbers 15892 and onwards, the GRE should be marked between W1.20-W1.50.
• ADJUSTMENT OF BASIC GAIN: This procedure involves applying a 1 kHz, -30.0 dBU signal to the input, turning the GAIN control fully clockwise, setting the RATIO to 2:1, and then adjusting the pre-set GAIN (located on the amp/psu PCB) to achieve an output reading of 0.0 dBU.
• ADJUSTMENT OF COMPRESSION TRACKING: This involves turning the THRESHOLD control fully counter-clockwise, setting the RATIO to 2:1, and the BUS-select switch to 1. A 1 kHz, 0.0 dBU signal is applied to the input, and the GAIN control is adjusted for a 0.0 dBU output. Then, a +250.0 mV DC-voltage is applied to the side chain jack socket (tip), and the output level drop to -10.0 dB is observed. If this drop is not achieved, P 2 (P 1)* is adjusted. The trimpots in parenthesis refer to PCB 870316-0,1,2.
• ADJUSTMENT OF THE VU METER READING "COMPRESSION": This procedure involves setting the THRESHOLD fully counter-clockwise, switching the METER selector to "Compression," and setting the RATIO to 2:1. After applying a 1 kHz, 0.0 dBU signal and adjusting GAIN for 0.0 dBU output, P 4 (P 2)* is adjusted until the meter reads 0 VU. A DC-voltage of +250.0 mV is then applied to the side chain jack socket, and the output level drop to -10.0 dBU is observed. If this is not the case, the compression tracking (as described above) needs adjustment. Finally, P 3 is adjusted until the meter reads -10.0 VU, and steps 6-9 are repeated. The VU-meter accuracy should be within +/- 0.5 dB when reading compression.
• ADJUSTMENT OF THE RELEASE CONTROL: This involves setting the METER switch to "compression," the attack/release SELECT switch to "manual," and applying a 1 kHz, 0.0 dBU signal. The THRESHOLD control is adjusted to a -10 VU reading on the VU-meter, and the ATTACK and RELEASE controls are set to "fast" and "slow" respectively. The 1 kHz signal is then switched off, and the time it takes for the VU meter to return to 0 VU (approximately 10 seconds) is observed. If this time is not met, P 1 (P 5)* is adjusted to achieve a release time of approximately 10 seconds. The trimpots in parenthesis refer to PCB 870316-0,1,2.

The manual also includes an overview of the sidechain PCB, illustrating the locations of trimpots P1, P2, P3, P4, and P5 for different PCB versions (870316-0,1,2 and 870316-3), along with their corresponding functions (OVU, -10VU, Rel. 10 Sec.).

TUBE-TECH CL 1B Specifications

General

Maximum Output Level	+26 dBu
CMRR @ 10 kHz	> 60 dB
Type	Opto Compressor
Output Impedance	60 Ohms
Attack Time	0.5 ms to 300 ms
Release Time	50 ms to 10 s
Power Requirements	115 V or 230 V (factory wired)
THD @ 0 dBu	< 0.05 %
THD @ +10 dBu	<0.5%
Tubes	1 x ECC83, 1 x ECC81