McIntosh MA 230 - SERVICS BULLETINS, Руководство пользователя

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as for TAPE input.
1. Set the TAPE MONITOR switch to
MONITOR.
2. Turn the MODE SELECTOR switch to
MONO (L+R).
3. Set the HF cutoff filter switch to FLAT.
(See page 15 ADJUSTING FOR SPECIAL
EFFECTS.)
4. Set the LF filter switch to FLAT. (See
page 15 ADJUSTING FOR SPECIAL EF-
FECTS.)
5. Set the LOUDNESS switch to FLAT.
(See page 15 ADJUSTING FOR SPECIAL
EFFECTS.)
6. Set the BASS CONTROLS and TREBLE
CONTROLS so that the dial indicators are
centered between the panel markings Land R.
7. Adjust the VOLUME control to the de-
sired volume.
8. Adjust the BALANCE control if neces-
sary.
POWER
The POWER ON-OFF switch controls the
AC power to the MA230 and the two black AC
receptacles on the back panel. The red AC
receptacle is not switched, and is on at all
times.
HEADPHONE
Two pairs of low impedance stereo head-
phones can be connected to the MA230.
Both front panel headphone jacks are con-
nected to the MA230 output through 100
ohm resistors. These resistors provide the
correct output volume level for headphone
operation.
ADJUSTMENTS
Two simple circuit adjustments are in-
cluded in the MA230. After extensive use or
when tubes have been replaced, these ad-
justments will insure top performance from
your MA230.
The DC bias of each 7591 output tube can
be individually set. Test Point jacks and bias
adjust controls are conveniently mounted on
the chassis next to each output tube. The
output tubes, Test Point jacks, and bias con-
trols are marked V, TP, and R, respectively.
The bias adjust control can be reached from
the top of the chassis with a small screw-
driver. Set the Bias controls for a DC voltage
of 0.7 volts from each Test Point jack to
chassis ground. Use a VTVM or sensitive DC
voltmeter. Check all voltages a second time
and readjust the controls if necessary.
A phase inverter AC signal balance control
is provided on each amplifier channel. These
controls are factory set with a harmonic dis-
tortion analyzer for minimum distortion at 20
cycles at 30 watts output. Normally just a
midpoint setting of these controls is ade-
quate to keep overall distortion to less than
0.5% at full output. If the necessary distor-
tion measuring equipment is available, set
each control for minimum harmonic distor-
tion at 20 cycles at 30 watts output. Balance
control R4 adjusts the left channel signal
balance, and R5 the right channel balance.
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