Tascam 122MKIII - Manual (Page 15)

Bias and Recording Level Calibration (122 MKIII only)
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Tapes differ considerably in the bias required to record on them and in their
sensitivity. The 122 MKIII allows fine adjustment of bias to exactly match the
tape being used ; also the reference recording level can be precisely adjusted to
compensate for difference in sensitivity among tapes.
■ Before starting adjustment, clean the heads, tape guides, rollers, etc. and
demagnetize the heads and all metal parts in the tape path.
■ In you intend to make adjustment while monitoring through speakers, turn
down their volume to avoid damage to them.
■ Have at hand a crisscross screwdriver which fits in with the BIAS/LEVEL
trimmers.
1. Load the tape.
2. Make the following settings :
INPUT level controls to 0 ;
OUTPUT level control to 0 ;
MONITOR switch to AUTO ;
DOLBY NR switch to OFF ;
MPX FILTER to OFF.
3. Press PLAY and RECORD to put the deck into Record mode.
4. Press ADJUST, then press OSC.
5. Turn the BIAS trimmers all the way to the left with the appropriate screwdriver.
6. Slowly turn the BIAS trimmers (one at time) clockwise for maximum reading
on the VU meters.
Suggestions : Turn the trimmers to the left and right alternately to "pinpoint"
the exact maximum position. If the meter needles deflect all the way to the
right, adjust the LEVEL trimmers until the meters read about 0 VU at a
maximum setting of BIAS.
7. Adjust the LEVEL trimmers (one at time) for 0 VU.
8. While alternating the oscillator signal between 10 kHz and 400 Hz by pressing
the 10 kHz switch on and off (still in record mode), adjust the BIAS trimmers
so that the VU meters show almost the same reading at both frequencies.
9. Set the oscillator to 400 Hz (10 kHz LED off) and readjust the LEVEL
trimmers for 0 VU.
Repeat the procedure each time you change the tape, especially when you change
the type of tape.
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