Owners Manual

23
SLAM FACTORY ALIGNMENT PROCEDURE
Prep:
1) +4 dBu (1.23vAC), 1kHZ Oscillator fed into XLR LINE INPUTS
2) UNBALANCED LINE OUTPUTS feed Level & Distortion Analyzer.
3) Select LINE on SOURCE, L&R LIMITERS off, Phantom OFF.
4) Set INPUT & OUTPUT LEVELS for 12:00.
5) Set ELOP LIMITER & FET LIMITER fully CW.
6) Set SC HZ to FLAT, ATTACK to .1 SECOND.
7) Set LINK to DUAL MONO (off).
8) Set LED to PEAK, VU to I/P, VU to 0dB.
Power
1) POWER UP supply toggle – verify zero AC amps on external Variac current meter.
2) POWER UP front panel POWER – spikes and settles to 0.5 amps.
VU meters lit, POWER button lit RED. 3 internal LEDs lit. LED meter dances.
3) After 30 seconds mute relay clicks.
4) VU meters should read approximately 0 VU.
5) Adjust INPUT for 0 VU, which should be close to 12:00.
Tube Circuit Trims
1) Switch VUs to O/P. Disregard the reading for now.
2) Adjust LINE AMP BIAS. The gain should SLOWLY rise and distortion should drop to below
.05% (-65) or around –70dB. It helps to set it so the plate volts are about 170vdc. As you adjust the
trim watch the distortion and when it ‘nulls’, quickly note the plate volts then it is easier to trim for
that voltage than for the distortion ‘null’ because of the slow speed of this trim.
(FET Drain/Tube Cathode about 10-11vDC and FET Source/2K resistor about 5-5vDC, Plate
about 130-180vdc, gate about 27mvAC and gain about 34 dB on this stage.) Alternatively
and assuming no test gear, the highest gain corresponds to the lowest distortion. This is a
broad peak though and distortion may not be truly minimized but probably OK.
3) Adjust LINE AMP GAIN trim for 0VU (+4 dBu) with OUTPUT set to 12:00.
4) Verify distortion is nulled (or trim 2 is still at maximum gain)
5) Reduce Oscillator by 34dB (24.5mvAC), SOURCE select MIC. VUs should show near zero but
won’t necessarily. (no real trim for mic pre gain). Actually the INPUT pot typical +/-20% tolerance
is worse than the gain stage errors.
6) Adjust MIC AMP BIAS trim for maximum gain & lowest distortion. This is also a slow
moving trim and THD&N should drop below .02% or –65db. Noise and distortion may look similar
in amplitude. VU should read between -2 to +2 (24.5mVAC=0VU). Boosting gain by 20db, should
show smooth clipping . 400-80k noise floor should be below –65 dB (-70 typical).
7) SOURCE SELECT = Ø. Verify Polarity does reverse (and was correct).
8) SOURCE SELECT = 100 HZ. Verify approximately 3dB down at 100 Hz.
9) Raise INPUT 16 dB (.154vAC). Change input cable to 1/4” plug and insert it fully into
INSTRUMENT. SOURCE SELECT = DI. OP should read about 0VU.
10) Pull 1/4” INPUT half way out. Signal should remain near 0VU
11) Pull 1/4” OUTPUT half way out. Signal should drop 12 dB (-10dbv)
12) SOURCE SELECT = LINE. Raise oscillator by 14dB (back to normal +4 dBu). Check
BALANCED output for level and distortion (distortion ‘null’ might drift on a new tube).
13) If using AP run a frequency Vs level test to verify flat response.