Tube Tech LCA 2B Dual Channel Tube VCA Compressor - Manual (Page 6)

LYDKRAFT ApS
Mose Allé 20, DK-2610 Rødovre
Denmark
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.
3) Apply a sine wave of 1 kHz, +15dBU via a 1K resistor into the sidechain jack
socket (ring).
(The +15dBU shall be measured before the 1K resistor.) *
4) Adjust trim pot P2 (P102) (located on amp/psu PCB) to a minimum reading at
the output.
5) Reduce the level of the sine wave to -5dBU.
6) Adjust trim pot P1 (P101) (located on amp/psu PCB) to a minimum reading at
the output.
7) Repeat step 3 - 6.
8) When both adjustments are at minimum, the level at the output shall be:
+15dBU less than -13dBU
+5dBU less than -14dBU
-5dBU less than -21dBU
If this cannot be obtained, the VCA tube shall be rejected and replaced with
new one.
* If the sine wave from the oscillator is observed on oscilloscope after the
1K stor, the negative part of the sine wave has been clamped to ground.
We recommend that the balance adjustment of the VCA should be carried out
every 6 month.
NOTE: 0 dBU = 0,775V
(941010)