Specifications

he will use the inputs. A moving magnet phono
cartridge may be plugged into the PHONO input or any
high level source into the AUX. However the insertion
of an RCA plug into the AUX jack switches the phono
preamp off. Only one input may be used at a time.
The RECORD connectors are for the RECORD
PROCESSOR IN and OUT and for the three tape recorder
outputs.
The LISTEN connectors are for the LISTEN PROCESSOR
IN and OUT, SWITCHED outputs 1 & 2, and the MAIN
output.
A nine pin subminiature "D" connector is provided
for the SCR3 speaker switching accessory.
One unswitched and eight switched AC outlets are
provided for program source equipment.
TECHNICAL DESCRIPTION
ELECTRO-MAGNETIC SWITCHING
All signal switching in the C36 is done by ELECTRO-
MAGNETIC methods. ELECTRO-MAGNETIC switching
is an old and proven technology that has been blessed
with modern materials and manufacturing methods.
Each switch consists of a glass tube that is filled with
an inert oxygen-free atmosphere and sealed with tiny
leads protruding from either end. These leads extend
into the tube and overlap one another with a separation
of a few thousandths of an inch. The leads are made
from a ferrous material that is influenced by a magnetic
field. They are first plated with gold as a base material,
then with rhodium and ruthenium. Ruthenium is the best
contact material known. The glass assembly is then
placed in the center of a multi-layer coil of copper wire.
The entire assembly is molded together in a tough shock
absorbing plastic. The switch and coil connectors
extend from the bottom in the form of printed circuit
board terminals.
When a DC voltage is applied to the coil, current
flows and creates a magnetic field. The force of the
field causes the leads to bend and contact one another
inside the sealed glass tube. The inert gas eliminates
corrosion of the contacts, which insures a low'
resistance, distortion free switch.
PHONO AMPLIFIER
The phono amplifier uses a high technology integrated
circuit operational amplifier. Its differential input stage
has been optimized for low noise and low distortion
performance. Open loop gain of this integrated circuit
is 100,000. With high open loop gain, a large amount
of negative feedback can be used around the phono
amplifier to further reduce noise and distortion. The
feedback network also provides precision RIAA
frequency compensation. The network uses 1 % metal
film resistors and 5% polypropylene film capacitors.
To achieve low-noise performance it is essential that
the feedback network have very low impedance. As
a consequence, the preamplifier must be capable of
operating as a power amplifier to drive this impedance.
The actual power output capability of this preamplifier
stage is more than 100 milliwatts, a great margin
beyond that which is required.
Input sensitivity of the phono amplifier is 2.5
millivolts. The gain of the amplifier is 40dB at 1000Hz.
The phono amplifier has a very wide dynamic range.
At 1000Hz, the phono input circuit will accept 90
millivolts without overload, a voltage far greater than
the output of any current magnetic phono cartridge.
Phono input overload, therefore, is virtually impossible.
A signal level of 10 millivolts at the phono input at
1000Hz will produce 1 volt at the tape output. The tape
output has a source impedance of 100 ohms, designed
to operate into a load impedance of 10,000 ohms or
greater.
LOUDNESS AMPLIFIER
At the input to the high level or loudness amplifier,
the signal passes through the mono switch, then
through the volume control, and into the loudness
amplifier. In the past, loudness controls have typically
used simple passive circuits connected to a tap on the
volume control. As a consequence, compensation
accuracy was dependent on many variables such as
volume control position and differences in input level.
The C36 uses active loudness control circuitry. An
integrated circuit operational amplifier is used here. It
has two feedback loops. One feedback loop has flat
response. The other feedback loop has loudness
compensation. A potentiometer is placed between these
two feedback loops making is possible to select any
combination of the two from a flat response to full
loudness compensation. The overall gain of the
loudness stages is 20dB and is not affected at mid
frequencies by the position of the loudness control.
TONE CONTROL AMPLIFIER
The tone control amplifier uses high technology
integrated circuit operational amplifiers. Its output stage
has been optimized for the best transient performance
and minimum distortion. Another operational amplifier
C36 Product Preview/Page 4
MClNTOSH LABORATORY INC.. 2 CHAMBERS STREET. BlNGHAMTON, NEW YORK 13903