McIntosh C108 -, Instruction Manual

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2. The C-108 and magnetic phonograph cartridges should
be mounted at least two feet from power transformers.
3. Inter-unit cables provide a complete ground system.
Alternate ground wires create ground loops which will
usually increase hum level.
4. The heaters of the 12AX7 tubes used in the C-108 are
returned to ground through a hum balancing potentiom-
eter in the power amplifier (or D-101 power supply if
used). This control requires an initial adjustment for
minimum hum, and should be readjusted each time one
or more tubes are replaced.
5. Grounding the turntable motor frame to the C-108
chassis near the input jacks may reduce the hum level
on the phonograph channels.
The output stage of the C-108 is a cathode follower. The generator r e s i s -
tance of this tube is 600 ohms, but should not be loaded with a capacitive reactance
of less than 10, 000 ohms at 20, 000 cycles. This is the reactance presented by
750 micromicrofarads, and is equal to that of a cable 30 feet long and having a
capacity of 25 mmf per foot. Under special circumstances where the C-108 must
be connected to the power amplifier by a longer cable, either lower capacity
must be employed, or the output must be reduced.
OPERATION
REDUCE TURNTABLE RUMBLE,
OR LOW FREQUENCY DISTURB-
ANCES ON ALL CHANNELS.
SELECT DESIRED BASS
COMPENSATION ON
CHANNELS 4 AND 5. SELECT DESIRED TREBLE
ROLL-OFF ON ALL CHANNELS. COMPENSATE FOR EAR
CHARACTERISTIC AT
REDUCED VOLUME ON
ALL CHANNELS.
SELECT ANY ONE OF FIVE
INPUT CHANNELS. UNUSED
CHANNELS ARE GROUNDED
TO PREVENT CROSSTALK.
CONTROL BASS RESPONSE
ON ALL CHANNELS.
CONTROL TREBLE RESPONSE
ON ALL CHANNELS.
CONTROL VOLUME ON
ALL CHANNELS. ON-OFF
CONTROL FOR C - 1 0 8
AND ITS POWER SUPPLY.