The Marantz
Power Amplifier has been designed and
constructed to give a long, trouble-free life of line listening quality. Here
is the type of performance and workmanship that previously was found only in
high quality Broadcast or Laboratory equipment. A built-in metered test
instrument permits simple, accurate adjustments for optimum performance.
"The
Model 2 power amplifier followed in 1956. largely completed by Sidney Smith, it
was a very successful tube design using EL34's in ''ultra-linear'' (push-pull)
configuration.
… some
sources cite the Model 2 as the beginning of Smith's exclusive concentration on
power amplifiers while Saul focoused his attention on preamplifiers,…"
(from
Marantz
History)
40 Watt / 20
Watt Switch
This unit
has been designed primarily as a 40 watt ultralinear amplifier. Speaker systems
of a lower power rating could easily be damaged by unwanted pulses coming
through at full power. To protect these systems we have incorporated a switch
which changes the output connections to Triode operation limiting the power
output to 22 or 23 Watts. This control, located near the output terminal strip,
is marked '40 Watt UL' and '20 Watt TRI'.
Input
Connections
There is a
choice of three input connections to the Marantz Power amplifier.
Pre-Amp:
This input is recommended for most preamplifiers. At this connection a 2 volt
signal will drive the amplifier to it's full output. A subsonic filter rolls
off frequencies below 20 cycles so as to supress speaker "breathing"
and other subsonic disturbances.
High Gain,
Filtered: For preamplifiers that have a low output voltage capability. Also may
be used where loudspeaker has very low efficiency. A signal of 0,7 volts is
required here for full 40 watt output. Subsonic filtering is also in effect.
High Gain,
Unfiltred: Same as above in sensitivity but without the subsonic filter,
response being maintained to below 2 cycles. This input is direct to the input
grid and is used in testing frequency response or for special applications
where subsonic response is needed.
Output
Connections
When not
using Variable Damping:
Use
"Ground Return" (center terminal) on loud speaker output terminal
strip together with impedance tap on right which matches speaker.
Variable
Damping control must be switched off for proper operation.
To use
Variable Damping:
Instead of
usual ground return, connect to corresponding "Variable Damping
Return".
Turn
"variable Damping" control on and adjust to desired damping factor.
Specifications
Power
Output: 40 Watts ( 80 Watts peak).
"Ultra-Linear" operation.
20 Watt
Triode Operation. Switch changes output connections to protect speaker of
low-power rating.
Output
Connections: 4, 8 and 16 Ω from Ground Return. 4, 8 and 16 Ω Variable Damping returns.
Input
Sensitivity for 40 Watts:
Two
High Gains Inputs: 0,7 V RMS into 105 k Ω
Pream
Input: 2 V RMS into 285 k Ω
Response
(has been deliberately rolled off approx. 5 dB at 100 kHz to control transient
response):
At 40 Watts
: Within 0,1 dB from 20 Hz - 20 kHz, within
1 dB from 15 Hz - 45 kHz
At ½ Watt : ±1 dB from 2 Hz - 50 kHz
Subsonic
Filter: In Preamp and High-Gain Filtered inputs, response is slowly rolled off
below 20 Hz (less than 1 dB at 20 Hz, 10 dB at 3 Hz; etc)
Distortion
Total
Harmonic Distortion at 40 Watts:
less than
0,1% at mid-frequencies;
less than
0,5% from 20 Hz to 10 kHz;
less than
1,5% at 20 kHz with resistive load (for
less at equivalent voltages with inductive speaker loads)
Intermodulation
Distortion at 40 Watts (equvalent 80 watt peak): Less than 0,5% (60 Hz /12 kHz 4:1
Distortion
below 30 Watts is largely of 2ad order and reduces rapidly with signal level.
Damping
Factors
Greater than
20 from 20 Hz to 20 kHz (without Variable Damping connections)
Continuously
Variable from 5 to ½ with Variable
Damping connections
Inverse
Feedback and Stability
23 ½ dB of overall feddback (20 dB in triode
position). Great care has been taken to ensure stability and low distortion
under widely varying loads, both resistive and reactive, such as are
encountered in loudspeaker systems. Power supply surges are balanced out of
signal channels providing excellent recovery from strong transients. Will not
oscillate under any condition of open circuit capactive load.
Hum
Better than
90 dB below 40 Watts (containing proportionately little of high order
components)
Meterd Tests
and Adjustments
Bias, D.C.
Balance, A.C. Balance (drive).All accurately adjustable with built-in
D'Arsonval meter and test switch
Power Supply
The use of a
transmitting-type oil input condenser, choke, telephone quality electrolytic
and the new type 6AU4-GTA as heater-cathode rectifiers provide, protection from
starting surge voltages, improved regulation and thorough filtering
Power
Requirements
Design
center; 117 volts, 60 Hz. Range 105 -125 volts. 150 Watts at Zero signal, 200
Watts at maximum signal
Tube
Complement
1 x 12AX7 /
ECC83
1 X 6CG7
2 X 6CA7 /
EL34
2 X 6AU4GTA
Size
and Shipping Weight: 15" x 9½" x 6½" / 47 lbs
