Manley TAPE HEAD PREAMPLIFIERS - Manual (Page 9)

ALTERNATIVE VERNIER CALIBRATION
Some mastering engineers have found that the following procedure helps with their day to
day use of these preamps. The procedure essentially gives a reference vernier setting that
shows them immediately if todays tape is “unusual”. It simply involves “moving” the
verniers so that a typical tape will read “50” on each dial. This is easy on all but the LF
control where a reference setting of “30” may be needed simply to have sufficient range of
this control. While easy, we recommend that an experienced technician perform the
procedure due to the shock hazard that exists working on powered high voltage equipment.
One does not want to touch the wrong thing while doing this.
We set these vernier controls at the factory to correspond to standard AES curves. This
does not include the effect of the individual head itself or other external factors not within
our control.
You will need a small Phillips screwdriver and a pair of insulated needle-nose pliers. The
thinnest needle-nose pliers are best for this. Rubber gloves are suggested for safety reasons.
1) This needs to be done in your normal set-up (not a shop), with heads and outputs
connected but monitors muted and preamps switched off.
2) Remove the small 4-40 machine screw holding the top perforated panel. It is located
above the back panel and towards the middle.
3) Slide the perforated top towards the back and remove it.
4) Set each vernier to “50” and loosen the Phillips set-screws that grip the shaft of the pots.
These will be just inside the front panel and now facing the top. Do not remove them - just
loosen them enough.
CAUTION -SHOCK HAZARD -THE FOLLOWING STEPS WILL BE DONE WITH
THE PREAMPS POWERED. HIGH VOLTAGE AND AND EXPOSED WIRING
EXISTS ON THE PRINTED CIRCUIT BOARDS. However there is only low voltages on
the pots and a metal shield between the pots and PCBs.
5) Power up the preamps, load a tape with good, typical tones and prepare toalign. Wait a
few minutes to allow for warm up (with monitors muted).
6) Use the needle-nose pliers to adjust each pot shaft while holding the vernier at a setting
of “50”. You will probably have to go back and forth between the 10 kHz VF vernier and
the 15 kHz VHF vernier to get it perfect due to some overlap or interaction. You may also
need to set the LF vernier to “25” or “30” in order to maintain the best control range.
7) Once you are happy with the alignment and the verniers are set where you
want
them - carefully tighten the screws holding the vernier to the pots. Do not overtighten -
it is not necessary because the pots turn freely and damaging the plastic pot shaft is good
thing to avoid.
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