What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Dynaco Dynakit Stereo 70

 The Stereo 70 is a dual 35-watt power amplifier, featuring the high quality and moderate price which has characterized earlier Dynakit amplifiers. Its electrical performance is matched only by manufactured amplifiers that cost far more.
The Stereo 70 can be used as apair of 35-watt amplifiers for stereo or as a 70-watt mono amplifier. Its power and distortion ratings are completely conservative. Its listening quality is unsurpassed. 
 Each channel of the Dynakit Stereo70 employs a 7199 triode-pentode and pair of EL-34 output tubes. The lower plate voltage used in the Stereo 70 assures long life for tubes and filter capacitors. In fact this amplifier's components are operated more conservatively than those in any other commercial amplifier we have used.
 The circuitry of the Stereo 70 is very similar to that of the older Mark II and Mark III amplifiers, except for the smaller output transformers. Somehow, the two amplifiers and their power supply have been packaged in a space not much greater than that of the older mono amplifiers, without crowding and apparently without running at a higher temperature.
The Stereo 70's frequency response is so flat that it almost seems pointless to plot it. The power response, in either mono or stereo modes, is nearly as good. The apparent discrepancy between the maximum power outputs shown in these curves and those suggested by the distortion curves is simply due to the different method of measurement. The power response shows the maximum power obtainable before some distortion of the output waveform can be seen on an osciloscope. Very small amounts of distortion can be numerical distortion values can be obtained at much higher power levels.
 The Stereo 70 will develop the eqivalent of 18 watts per channel into a 3-mld capacitive load at 10 kc, which makes it quite suitable for driving electrostatic speakers at high volume levels. It is absolutely stable and free from ringing under and conditions of capacitive loading.
Two power take-off sockets are provided to operate a pair of Dynakit preamplifiers. Each has its own heater winding to prevent interaction between channels.
Power Output:  35 watts continuous, 80 watts peak each channel
Frequency Response:  10 to 40,000 Hz ±0,5 dB
Power response:  20 to 20,000 Hz (within 1 dB of 35 watts at less than 1% distortion)
Harmonic Distortion:  immeasurably at power of 10 watts or less
IM Distortion:  less than 1% at 35 watts (less than 0,05% at 1 watt)
Hum an Noise:  Inaudible, better than 90 dB (below 10 watts)
Sensitivity:  1,3 volts RMS input for 35 watts out
Damping Factor:  15
Output Impedance:  4, 8 and 6 Ω
Minimum Channel Separation:  55 dB
Power Consumption:  190 watts 50/60 cps
Preamp provision:  Two power take-offs with independent heater windings to eliminate interaction. Each 6,3 volts 1 amp, 350 volts Dc 10 ma
Special Features: two separate power supply sockets for preamplifier; front panel switch to parallel outputs for operation as a 70 watts monophonic amplifier
Tube Complement:  4 x EL-34; 2 x 7199; 1 x GZ-34/5AR4; selenium rectifier
Dimensions (W x D x H):  13" x 9 ½" x 6 ½"
Weight :  32 pounds

Finish:  chassis and bottom plate bright nickel plated. Cover finished in charcoal brown vinyl paint.

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