Dynaco Stereo 410 Power Amplifier

View the
parts list,
amplifier schematic
for the ST-410. You may want to right-click (Mac users click/hold) to save these, as they will slow your browser down significantly.

Kevin Boales has provided an excellent article on fixing an ailing ST400; give it a look!


The Dynaco Stereo 410 is a basic two channel power amplifier employing all silicon semiconductors. They include 38 transistors, 2 zener diodes, 24 diodes, and 3 thermal sensors. The output circuitry is of the full complementary symmetry design. The entire amplifier, except for an input network, is direct coupled. Its measured distortion levels approach the threshold of much laboratory test equipment, not only at the commonly specified full power ratings, but more importantly at very low power outputs as well. This is the result of circuit techniques which eliminate any discernible crossover notch at low levels, and contributes to the Stereo 410's freedom from listening fatigue. Its accurate, uncolored sonics have been achieved on a wide variety of loudspeaker loads, including electrostatics and multiple drivers with complex crossovers.

The design of a superb power amplifier implies the necessity of several protection techniques for the amplifier, and for the speaker load. In addition to the AC line fuse, four separate B+ fuses are supplied. Electronic volt-amp limiting ensures safe operation of the output transistors, and an independent thermal cutout for each output stage protects from high temperature. A large radiating area for the heat fins, which are attached to an aluminum back panel, and cooled with a thermostatically operated two speed fan, form a highly efficient heat sink. Speaker fuses protect the load.


Power Output Ratings: Less than 0.1% total harmonic distortion at any power level up to 200 watts continuous average power per channel into 8 ohms (100 watts per channel into 16 ohms) at any frequency between 20 Hz and 20 KHz with both channels driven. Distortion reduces at lower levels.

Available Power Output:

20 Hz to 20 KHz, both channels driven:

200 watts continuous average per channel @ 8 ohms;
300 watts continuous average per channel @ 4 ohms;
100 watts continuous average per channel @ 16 ohms.

Intermodulation 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.

Power at Clipping, single channel, 2500 Hz, less than 1% distortion:

235 watts @ 8 ohms;
350 watts @ 4 ohms;
135 watts @ 16 ohms.

Half-power bandwidth: 100 watts per channel at less than 0.25% total harmonic distortion from 5 Hz to 35 KHz into 8 ohms.

Frequency Response: +0, -1 dB, 8 Hz to 50 KHz @ 1 watt into 8 ohms; ±0.5 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 to 20 KHz.

Input: 20,000 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 3/4" spacing.

Dimensions: 16-5/8" wide, 14-1/2" deep, 7-1/4" high.

Weight: Shipping weight 50 lbs; Net weight 44 lbs.

Power Consumption: 120 VA quiescent; 11 amps maximum; 50/60 Hz, 120/240 VAC.

Designed by:

Wade Burns, Richard Pley (Engineers), with James Bongiorno, Erno Borbely, Harry Klaus (400/410 circuitry), Hans Frank

Year Introduced:



$399.00 kit
$599.00 assembled


A budget version of the Stereo 400, replacing the overdesigned chassis and heat sink with a smaller set of heat sinks and a fan but retaining the massive power supply and output circuitry. The Dynaguard and buffer were also omitted, resulting in what some people feel was a better-sounding amplifier. Later revived and reissued by Stereo Cost Cutters/Sound Values as the "Black Box" 410 when they inherited the Dynaco parts inventory, until they officially ceased Dynaco support in the early 1990s.

This page created and maintained by Greg Dunn.
Copyright © 2000 Greg Dunn