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professional grade power amplifier - MODEL 35MRM + 80MRM

The Model 35 MRM is a solid state power amplifier of superior quality and performance designed specifically for professional use.

  • Anmerkung : Das sind natürlich here Vorstellungen und lockere Marketing-Sprüche der Amerikaner. Denn in 1969/70 und auch vorher gab es bereits den CROWN DC300 und kurz darauf den DC300A Kraftverstärker. An diesen Geräten konnte jederman sehen, was es heißt, für professionelle Benutzung gebaut zu sein. Diese beiden C/M-Endstufen (aber vermutlich von vor 1965), - wir hatten nur die 35 MRM Kiste -, waren zwar riesig groß und schwer, aber für 35 Watt hoffnungslos überkandidelt und innen (auch) nahezu leer. Schlimmer war, daß es zwar zwei Kühlkörper wie in den Radio RIM Bausätzen gab, jedch keine Belüftung durch das geschlossene schwere Stahlblech-Gehäuse hindurch. Das war also in keiner Weise professionell. Es sah nur so aus. Von der 80 Watt Version gibt es keinerlei Unterlagen mehr.
  • Diese 35 Watt Endstufe ist vermutlich aus dem 35D abgeleitet und einfach nur als Mono-Block konstruiert.
  • Die 80 Watt Version könnte von der Folgefirma (nach dem Verkauf der beiden Gründer) stammen. Auch davon gibt es vermutlich nur eine Prototypen. Die Unterlagen sind spärlich.

Certain electrical properties of the 35MRM, unique in the field of audio amplification systems, are the prime reasons for its superior performance even when compared to conventional units of higher power ratings.

The 35MRM is a voltage amplifier with nearly zero output impedance. Therefore, not unlike a well regulated supply, power output will double for every halving of the load impedance until the power capability of the unit is reached.

As it is well known that maximum power transfer occurs when the load impedance is equal to the source impedance, it can be easily seen that power output will increase as load impedance diminishes and will reach a maximum at near short-circuit values. Limits on power output have purposely been imposed on the 35MRM to automatically protect it from over-dissipation resulting from short-circuits or otherwise improper loads.

The benefits derived from this characteristic in a power amplifier are several:
First, the high peak power available from the 35MRM is in the order of several times that of equivalently rated tube type amplifiers whose rated power and maximum power output occurs ONLY when the tube impedance is exactly matched to the load (frequently via transformer).

It is commonly recognized that resistor loads are NOT fair approximations of the loudspeaker as the impedance and voltage-current phase relationships of this type of load constantly changes over the frequency band. Continuous accelerations and decelerations of this motor, generator and mass combination consumes energy far in excess of the ordinary fixed resistor. It is therefore necessary, under continuing transients (as represented by music), to provide the loudspeaker with adequate peak power in order to reproduce the program material smoothly throughout the most complex passages.

Second, the high damping factor (low output impedance) lends itself naturally to multiple speaker installations as the levels of the individual loudspeakers are not affected by switching others in and out of the line. However, the most important benefit derived from high damping is that it increases the control over the mechanical movement of the cone providing greater clarity, transparency, and freedom from boom by reducing spurious cone and cabinet resonances. In this regard, it is now possible to increase the sound level in any given environment before acoustical feedback is introduced.

Finally, the reduction of spurious ringing and feedback further reduces intermodulation with the original program signal. This, along with the effective increase in the dynamic range of the system results in cleaner sound for any given level.

Combine these properties with the more fundamental requirements for quality reproduction (wide power bandwidths, fast recovery from clipping overloads, stable performance, and very low distortion at all power levels), and package it in one Model 35MRM. Result - superb performance, unequalled.


OUTPUT POWER 50 watts rms into 8 ohms, 40 watts rms into 4 or 16 ohms,
  20 to 20,000 cps continuous. Available peak power,
  200 watts. (Note 1)
FREQUENCY RESPONSE 20 to 20,000 cps, ±1 db at rated output; 1 cps to
  100,000 cps, ±3 db @ 1 watt.
INPUT SENSITIVITY Variable with input potentiometer. Maximum sensitivity,
  1.3 to .65 volts rms for full output for loads between
  16 and 4 ohms respectively. (Note 2)
INPUT IMPEDANCE 50k ohms minimum, 20 to 20,000 cps.
TOTAL HARMONIC DISTORTION Less than .5% between 20 cps and 20,000 cps at
  rated power into 8 ohm load.
INTERMODULATION DISTORTION Less than .5% at power levels between .5 and 50 watts
  equivalent single frequency amplitude into 8 ohm load
  (60 cps mixed with 6 kcs, 4:1). (Note 3)
OVERLOAD RESPONSE Recovery from clipping, 10 microseconds maximum.
  Automatic protection provided against short circuits,
  open circuits, or grossly mismatched loads.
DAMPING FACTOR Better than 200 for 8 ohm load, 20 to 20,000 cps.
HUM AND NOISE 80 db below rated output.
SOLID STATE COMPLEMENT 10 transistors, 2 rectifiers, 3 signal diodes, and
  1 reference zener diode.
POWER REQUIREMENTS 117 volts rms, 60 to 400 cps. 15 watts no signal,
  200 watts at full power. (Note 4)
CONNECTIONS Power, 3-wire grounding plug; input, Cannon XL-3;
  output, 3-terminal barrier strip.
DIMENSIONS Standard 19" rack mounting, 51/4" panel height;
  13" deep overall (measured from rear of front panel).
WEIGHT Approximately 32 pounds.
FINISH Blue/gray panel. Other steel parts cadmium plated.
AMBIENT TEMPERATURE 0 to 50 degrees C. operating. Natural convection
  cooling required.
RELATIVE HUMIDITY 0 to 85% without condensation.
PRICE Basic Amplifiers:
  Model 35MRM ..... $237.00
  Model 80MRM ..... $297.00
  Factory installed options: 70V (70 volt line output transformer) $ 36.00
  IT (600 ohm balanced line input transformer) .......... $ 21.00
  AL (audio lockout - guarantees instant distortion-free performance after initial application of power even with full audio input by automatically delaying signal until 'warm-up' period is over - approximately 3 seconds) .... $ 24.00

Unterschiede Modelle 35 und 80

Specifications for Model 80MRM identical to Model 35MRM except:

1) 80 watts for 8 ohm, 50 watts for 4 or 16 ohms, 300 watts peak
2) Sensitivity 1.5 to .75 volts
3) Intermodulation at .8 to 80 watts equivalent single frequency
4) 300 watts at full output

- Werbung Dezent -
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