Internal Jumpers and Adjustments (please see step 5 on page 2)
The motherboard has input cable shield ground selection jumpers to accommodate
different grounding schemes. It is recommended that all electrical equipment in the studio
is properly grounded by making sure that power cables have 3 pins and that the third pin
is connected to ground. The use of ‘ground lifts’ to clear up a buzz problem is frowned
upon by the international consortium of electrical safety agencies. If a ground noise
problem occurs, it may be cleared up by switching the jumper position on the connector
associated with the piece of gear that is having the buzz problem.
The shield lift headers have 2 posts. A jumper placed over both posts connects the chassis
ground to the cable shield. To lift a shield, pull the jumper off of the posts. It is a good
idea to put the ‘unused’ jumpers on one of the posts to keep from losing the jumper.
Master
should not need to be calibrated but in case it does, here is the procedure:
1.
Obtain a calibrated oscillator and level measuring device. These should be lab
quality (HP, Tektronix, Neutrik, Audio Precision, etc.)
2.
Place the
Master
on a clean, well lit table with a pad under it to prevent scratches.
3.
Remove the top to expose the motherboard for calibration.
4.
Hook up the power supply and turn on the unit.
5.
Set all controls to unity gain with all Function and Insert switches out.
6.
Set the oscillator for +4dBu and plug into Input 1. Feed both channels.
7.
Activate ‘Insert 1’ and measure the level coming out of the ‘Send 1’ jacks.
8.
Adjust P1 and P2 to m4dBu.
9.
Deactivate ‘Insert 1’ and adjust P3 and P4 to read +4dBu at ‘Main Output 1’.
10.
Adjust P5 and P6 to m4dBu at the ‘Monitor Output’ jack.
11.
Activate the ‘OUT MON’ function and adjust P7 and P8 to read +4dBu at the
Monitor Output jack.
12.
Pull the right channel’s input. Activate the ‘S&M’ function. Adjust the ‘xtalk’ pot
for minimum signal at the Right output. The signal should null below -70dBu.
6
