Dynaco Stereo 400 Owners Manual

Page 1

SERIAL NUMBER

Nymaca

This number must be men-
tioned in all communications
5 I EREO concerning [his equipment.

INSTRUCTIONS FOR
ASSEMBLY
OPERATION

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Page 2

SPECIFICATIONS

Power Output:
20 Hz - 20 kHz, both channels driven:
200 watts rms per channel @ 8 ohms.
300 watts rms per channel @ 4 ohms.
100 watts rms per channel @ 16 ohms.
Monophonically:
600 watts rms @ 8 ohms.

Interlnodulation Distortion: Less than 0.1% at any power level up to 200 watts
rms per channel into 8 ohms with any combination of test frequencies.

Distortion reduces at lower power levels. Typically less than 0.03%.

Harmonic Distortion: Less than 0.25% at any power level up to 200 watts rms
per channel into 4, 8 or 16 ohms at any frequency between 20 Hz and
20 kHz with both channels driven. Distortion reduces at lower power levels.
Typically less than 0.05%.

Power at Clipping, Single Channel, 2500 Hz:
235 watts @ 8 ohms.
350 watts @ 4 ohms.
135 watts @ 16 ohms.

Power Bandwidth: 5 Hz to 35 kHz at less than 0.25% total harmonic distortion
-hali power output, 8 ohm load.

Frequency Response: +0, -1 dB, 8 Hz-50 kHz @ 1 watt into 8 ohms.
10.5 dB, 20 Hz-20 kHz @ 200 watts.

Hum and Noise: Greater than 95 dB below rated output, full spectrum.
Greater than 100 dB below rated output, 20 Hz-20 kHz.

Input: 50,000 ohm load; 1.6 volts for 200 watts @ 8 ohms.
Slewing Rate: 8 volts per microsecond.

Damping Factor: Greater than 80 to 1 kHz into 8 ohms.
Greater than 30 to 10 kHz into 8 ohms.

Channel Separation: Greater than 60 dB by IHF standards.

Connectors: Inputs: phono jacks. Outputs: color coded 3-way binding posts
with standard 3h spacing.

Dimensions: 17 wide; 14 deep; 7" high.
Weight: Shipping weight 58 lbs. Net weight 52 lbs.
Power Consumption: 120 v.a. quiescent; 11 amps maximum; 50/60 Hz, 120 VAC.

Bob01605@aol.com

Page 28

2) Dynaguard circuit {left and right)

3) Voltage doubler and accumulator-C10, D1, D2,
011; 012, R9, R10; P1.

b) Logic-D3, D4.
c) Function-~ICI, D5. D6.
d) Light control-P2, Q3, D7, Q4.

3) Relay Circuit
3) Low pass filter~----C18, R28, (319, R29, C20.

b) Double-ended limit detector-102, I03, D8, D9,
D10, D11.

c) Switch-Q5. Q6.

Preamplifier / Filters

This may be described as a Darlington-connected
emitter-follower with approximately unity gain, since the
voltage at QlE is always slightly more positive than the
voltage at its base. The driven transistor in the Darling-
ton pair, Q2, provides high current amplification with
very low output impedance.

Basic 6 dB/octave single section filters are enhanced to
an actual 8 dB/octave characteristic by C36 and the pre-
ceding impedance forming an additional low-pass section
of the high filter, and 09 and its following impedance
forming an additional highmass section of the low filter.

Dynaguard Circuit

The amplifier-9 output voltage is proportioned by the
setting of the front panel switch and level trimpot P1.
It is clamped by C10 and D1, and rectified at peak nega-
tive value by D2 and CH. The rectified voltage is then
stored in the accumulator (312, R9, R10 which is designed
to bleed on the charge at the prescribed rate.

D4 is a +0.7 volt reference voltage source. D3 will
start conducting when the voltage at its cathode becomes
more negative than --0.7 volts, and any increase there
will also appear at the anode of D4, shutting it off as a
positive voltage source.

Two operational amplifiers in [CI serve as a 20 dB
voltage amplifier and inverter. When D4 conducts, the
amplifier feeds about 5.5 volts to the cathode of D5, which
is then inverted with unity gain for the anode of D6.
Thus, when D4 is conducting, D5 and D6 are heavily
reverse biased and do not. affect the signal.

However, when high amplifier output voltage causes

' D3 to conduct, the voltage input to 101 will start drop-

ping to zero, and the voltages on D5 and D6 will de-
crease. The amplifier output will exhibit Dynaguard
action when the D5 and D6 voltage becomes low enough
to cause the input signal voltage to start limiting. The
lowered output. will in turn decrease the signal to I01.
thus keeping the limited voltage constant.

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