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Model SP9 MKIII
POWER/MUTING CIRCUIT
LED:
Glows green to
indicate unit is on and receiving power from the
power supply. Note that for approximately 45 sec-
onds after start-up or in "Mute" mode. this LED will
glow more dimly. indicating proper operation of the
muting circuit. In the "Operate" mode (after warm-
up). the LED brightens and your SP9 MKIII is ready
for normal operation.
MONITOR/SOURCE SWITCH:
In "Monitor" position
this switch "bypasses" the Input Selector and pre-
sents the signal to the main outputs from sources
(tape recorders. etc.) connected to the "Tape I" or
"Tape 2" input jacks on the rear panel. In the
"Source" position, the program source is controlled
by the Input Selector (Phono. Tuner, CD, etc.).
Connections
INPUT CONNECTORS:
All are clearly marked to
indicate use. All high level inputs are 50K ohms
impedance. Remember that impedance of "Phono"
input is controlled by soldered-in resistor values on
the main circuit board (see INPUT IMPEDANCE
ADJUSTMENT).
MAIN OUTPUT CONNECTORS:
There is one (1) set
of output connectors, which should be connected to
your electronic crossover or power amplifier.
The input impedance (load) of the power amplifier
or electronic crossover to the SP9 MKIII main out-
puts should be at least 20K ohms for maximum
sonic benefit.
NOTE:
At the performance level of the SP9
MKIII,
high-quality audio signal interconnect cables are crit-
ical to preserving maximum fidelity. Audio Research
RFI-shielded or unshielded interconnect cables are
highly recommended for connection to your power
amplifier(s) and to other ancillary equipment. See
your authorized Audio Research dealer for recom-
mended lengths and prices.
RECORDER I/RECORDER 2 OUTPUT CONNEC-
TORS:
Two (2) sets are provided. Recorder Outputs
should be connected to your recorder's "AUX or
"LINE" inputs. These outputs supply a source of
whatever is selected by the Input Selector Control.
Level is non-variable and approximately the same as
the selected input source.
All input/output connectors have heavy gold plating
and connect "ground" before "hot". (On disconnect.
"hot" is first.)
Installation Instructions
While the SP9 MKIII does not dissipate an unusual
amount of heat, it is important that it be provided
with reasonable airflow to assure long, trouble-free
operation. In addition, the following installation
guidelines will help insure maximum sonic perfor-
mance as well as reliable service.
1.
Upright and horizontal mounting is suggested if
extended operation (longer than one hour) is con-
templated.
2.
Do not "stack" the SP9 MKIII on top of a power
amplifier. Not only could this cause overheating.
but "hum" may be introduced into the phono cir-
cuits from the proximity of the amplifier's power
transformer.
3. Do not place or operate your SP9 MKIII on a soft
or irregular surface such as a rug. This will prevent
proper ventilation.
4. Do not operate your SP9 MKIII without the top
and bottom covers installed. These are required
both for safety as well as shielding from interfer-
ence (except in service operations, obviously).
5. If rack mounting is employed, use Audio Research
Rack Mount Ventilators (RMV-3) below and above
your SP9
MKIII.
6. If side-by-side mounting with other equipment is
employed. place the SP9 MKIII to the right of the
other chassis. so as to provide maximum spactng
between another power transformer and the SP9
MKIII's sensitive phono input circuitry.
7. In a cabinet or rack-mount installation which has
an enclosed back. an exhaust fan is desirable so as
not to operate the SP9 MKIII in overheated ambi-
ent air. Operation of vacuum tube equipment for
long periods of time in hot ambient air will short-
en tube life and increase chance of failure of other
component parts.
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