Owner's manual

ManualsBrandsTube Tech ManualsAudio accessoriesLCA 2B Dual Channel Tube VCA Compressor

LYDKRAFT ApS

Mose Allé 20, DK-2610 Rødovre

Denmark

UsersManual

TUBE-TECH LCA 2B

compre ssor and limite r

DESCRIPTION:

The TUBE-TECH LCA 2B is a two-channel unit with an independent compressor and

limiter per channel. The unit is all tubebase d (except for the power supply and si-

dechain circuit). Output gaincontrol is placed between the VCA an d outpu t stage. The

VCA (1 dual triode) is pl aced between the i nput transformer and the output stage (2

dual triodes). The audio signal is pi cked up after the VCA and fed to the sidechain

circuit. The control signal from t he compressor and from the limite r is combi ned and

sent to the link switch and to th e control amp, which feeds the VCA. The bi-directional

link busses a re accessible at two 1/4" stereo jack sockets on the rear panel. The

channels can be linked toge ther for stereo appli cations and a lso linked to other LCA

2B's via the two link busses and a standard stereo jack/jack cord.

The compressor has six att ack/release presets as well as manual control.Thelimiter

attack/release is fixed an d equipped wi th an on/off switch.

The LED display is fed from th e control amp. T h e limiter LED is fed fr o m the limiter

buffer.

The audio path is fully symmetrical from input to output .

Input and ou tput have fully floating transformers.

All DC voltages are stabilised, except the anode voltag e for the output stage, which is

only filtered.

COMPRESSOR INTERCONNECTION:

The sidechain sockets for interconn ection of seve ral compressors are located on the

rear panel.

A switch (LINK 1, LINK 2) on the front sele cts which compressors are interconnect ed,

and on which bu s they are connected. If you select LINK 1 on both channels, they will

perform exact the same ga inreduction.

Having several connected co mpressors in a rack, you can sele ct which compressors

you will have working together.

By selecting e.g. LCA 2B no 1, ch . 1 on link 1, LCA 2B no 2, ch. 2 on link 1 and LCA

2B no 3, ch. 1 on link 1, they are now interconnected and all t hree will perform the

exact same compression.

The interconnection implies, that the unit, which performs the most compression, is

controlling the others.

To choose which one you want to control, select the a t tack/release time, the threshold

and the ratio on that unit, and turn the threshold fully counter clockwise on the

reminding compressors.

It is of co urse possible to have all the interconnected comp ressors control each other

simultaneously.

(150205)

Summary of content (8 pages)

PAGE 1
User s Manual TUBE-TECH LCA 2B compressor and limiter DESCRIPTION: The TUBE-TECH LCA 2B is a two-channel unit with an independent compressor and limiter per channel. The unit is all tubebased (except for the power supply and sidechain circuit). Output gaincontrol is placed between the VCA and output stage. The VCA (1 dual triode) is placed between the input transformer and the output stage (2 dual triodes). The audio signal is picked up after the VCA and fed to the sidechain circuit.
PAGE 2
CONTROLS: GAIN: The gain control is used to "adjust" for the gain loss, which takes place when the unit is compressing. It is placed between VCA and output stage. The gain-control is continuously variable from -6dB to +10dB. DISPLAY: The green LED display shows the gainreduction for both the compressor and for the limiter. A red LED shows if the limiter is active. The display is from the factory supplied in dot mode.
PAGE 3
ATTACK/RELEASE SELECT: This switch selects how the compressor reacts to an increase (attack) or decrease (release) of the input signal. There are two settings of the switch: 1. Manual. Attack time: from 0.3 mS to 10 mS Release time: from 0.07 sec to 2 sec 2. Preset. pos 1. pos 2. pos 3. pos 4. pos 5. pos 6.
PAGE 4
ADJUSTMENT PROCEDURE: CAUTION: Before making any adjustment let the unit heat-up at least 30 min. Always check the DC voltages at the power supply. When the VCA tube has been replaced, adjustment of: BASIC GAIN GAIN REDUCTION BALANCE shall be carried out. The adjustment procedure refers to channel 1. The trim pots in brackets are for channel 2. At the sidechain jack sockets at the rear of the unit, the tip is link 1 and the ring is link 2.
PAGE 5
ADJUSTMENT OF DISPLAY: 1) Turn the THRESHOLD-control for the compressor and limiter fully counter-clockwise. 2) Apply a DC-voltage of +5,000 V into the sidechain jack socket (tip). 3) Set the LINK-switch at LINK 1 and observe that the -15 LED just turns off and the -20 LED is on. 4) If this is not the case, adjust P8 (P108) at the sidechain PCB. TEST OF TRACKING: 1) Turn the THRESHOLD-control for the compressor and limiter fully counter-clockwise.
PAGE 6
ADJUSTMENT OF BALANCE IN THE VCA TUBE (V1, V101): As a quick check of the balance of the VCA tube, adjust the output to a level of 0dBU and turn the LIMITER THRESHOLD slow CW until the LIM led turns slightly on. If the led turn on abruptly or starts oscillating, the balance should be readjusted. 1) Turn the THRESHOLD-control for the compressor and limiter fully counter clockwise, and the GAIN-control fully clockwise. 2) Switch the LINK-switch to LINK 2.
PAGE 7
SPECIFICATIONS FOR LCA 2B >2k < 60 Input impedance: Output impedance: Distortion (THD+n @ 40 Hz): 0 dBU: 10 dBU: Max output (1% THD+n): Noise (Rg=200 ): Gain: 22 Hz-22 kHz: CCIR-468-3: Frequency response (-3 dB): Gain: Crosstalk (20 Hz-22 kHz): CMRR (@ 10 kHz): Tracking (0 to -20 dB gain reduction): LED display for gain reduction: < 0,15 % < 0,15 % > +26 dBU 0 dB < -85 dBU < -75 dBU Compressor: Ratio: Threshold: Attack (manual): Release (manual): Preset attack/release: 10 dB < -80 dBU < -70 dBU 5 Hz - 4
PAGE 8
SERVICE HINTS: (940530) SYMPTOM CAUSE ACTION Noise Unbalance in VCA tube Adjust balance Noise Noisy VCA tube (V1, V101) Replace and adjust Noise Control amp IC 4 (IC 104) Replace.