Tube Tech LCA 2A User Manual
TUBE-TECH LCA 2A
compressor and limiter
DESCRIPTION:
The TUBE-TECH LCA 2A 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). Input gaincontrol is placed
before the input transformer. The VCA (1 dual triode) is placed between
the input transformer and the outputstage (2 dual triodes). The audio
signal is picked up after the VCA and fed to the sidechain circuit. The
control signal from the compressor and from the limiter is combined and
sent to the link switch and to the control amp, which feeds the VCA. The
bidirectional link busses are accessible at two 1/4" stereo jack sockets
on the rear panel. The channels can be linked together for stereo applications and also linked to other LCA 2A's via the two link busses and a
standard stereo jack/jack cord.
The compressor has six attack/release presets as well as manual control.
The limiter attack/release is fixed.
The LED display is fed from the control amp. The limiter LED is fed from
the limiter buffer.
The audio path is fully symmetrical from input to output.
Input and output have fully floating transformers.
All DC voltages are stabilized, except the anode voltage for the outputstage.
COMPRESSOR INTERCONNECTION:
The sidechain sockets for interconnection of several compressors is
located on the rear panel.
A switch (LINK 1, LINK 2) on the front selects which compressors are
interconnected, and on which bus they are connected. If you select LINK
1 on both channels, they will perform exact the same gainreduction.
Having several connected compressors in a rack, you can select which
compressors you will have working together.
By selecting e.g. compressor 1 ch. 1 on link 1, compressor 2 channel 2
on link 1 and compressor 3 ch 1 on link 1, they are now interconnected
and all three 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 attack/release time,
the threshold and the ratio on that unit, and turn the threshold fully
counterclockwise on the reminding compressors.
It is of course possible to have all the interconnected compressors
control each other simultaneously.
2
CONTROLS:
GAIN:
DISPLAY:
LINK SWITCH:
IN/BYPASS:
The
gain
loss which takes place when the unit is compressing. It is placed before the inputtransformer.
The
gain
-6 dB to +20 dB.
The green LED display shows the gainreduction for
both the compressor and for the limiter. A red LED
show if the limiter is active.
The display is from the factory supplied in dotmode.
This can be altered to a bar by placing a strap on
U6 (U106) from pin 3 to pin 9
Interconnects several compressors on linkbus 1 or
linkbus 2.
If the compressor is left in the off position, it
works entirely independently.
This switch switches the compressor in and out of
the signal path. In the bypass position the entire
unit is switch out.
control is used to "adjust" for the gain
-control is continuously variable from
COMPRESSOR:
RATIO:
THRESHOLD:
ATTACK:
RELEASE:
The
ratio
input signal is compressed.
If the ratio selected is to 2:1, and the input
signal increases 10 dB, the output signal is only
increased by 5 db.The
variable from 1,6:1 to 20:1.
The threshold is the point where the compressor
begins its action. It is defined as the point where
the gain is reduced by 1 dB.
The threshold is related to the output level and is
continuously variable from off to -10 dBm.
The
attack
pressor responds to an increase in the input signal.
The attack control is continuously variable from 0.3
to 10 milliseconds.
The
release
pressor responds to a decrease in the input signal.
The release control is continuously variable from
0,07 to 2 seconds.
control varies the ratio by which the
ratio
control chooses how fast/slow the com-
control chooses how fast/slow the com-
control is continuously
LYDKRAFT Aps
Ved Damhussøen 38, DK 2720 Vanløse
Denmark
ATTACK/RELEASE SELECT:
This switch selects how the compressor reacts to a
increase (
signal.
There are two settings of the switch:
1. Manual.
attack time: from 0.3 msec to 10 msec
release time: from 0.07 sec to 2 sec
2. Preset.
pos 1. 1,5 mS 0,25 S
pos 2. 1,5 mS 0,8 S
pos 3. 3 mS 2,2 S
pos 4. 6 mS 5,0 S
pos 5. 3 mS 0,5/4 S
pos 6. 1,5 mS 0,5/4/20 S
The release time in position 5 and 6 is program dependent, that is:
pos 5, 6 for short peaks: 0,5 S
pos 5, 6 for long peaks: 4 S
pos 6 for continuously high levels: 20 S
attack
) or decrease (
attack release
release
) of the input
LIMITER:
THRESHOLD:
We recommend that the balance adjustment of the VCA, is carried out
every 6 month.
The threshold is related to the output level and is
continuously variable from off to 0 dBm.
ratio: 20:1
attack: 0,6mS
release: 0,5 S
LYDKRAFT Aps
Ved Damhussøen 38, DK 2720 Vanløse
Denmark
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