The Dynaco ST-70 is nothing short of legendary. It was one of the best selling stereo components of all time. Every list of the most important tube amplifiers features this amp. Ask an audiophile what their first tube amp was, and you'll likely hear ST-70 as the answer. This piece has the character typical of pieces this age, but is in top electronic condition. Recapped, biased, and ready to go.
- Full 30-point service check
- Replaced multisection capacitor
- Replaced bias capacitors
- Replaced rectifier
- Cleaned controls, switches, and chassis
Power output 35 watts per channel into 8Ω (stereo)
Frequency response 10Hz to 40kHz
Total harmonic distortion 1%
Damping factor 15
Input sensitivity 1.3V
Signal to noise ratio 90dB
Speaker load impedance 4Ω to 16Ω
Driver Board PC-3A (upgrade)
Tube complement 4 x EL34 (JJ), 1 x GZ34, 3 x 12AT7
Finish nickel plated chassis
Dimensions 13"W x 9.5"H x 6.5"D
Weight 32 lbs.
ON DECK ST-70 Owner's Manual
The History of Dynaco
Founded by hi-fi pioneer David Hafler and Ed Laurent in 1955, a small company by the name of Dynaco unknowingly would become the most popular tube amplifier company of all time. Five years prior in 1950, David Hafler and his friend Herb Keroes started up the company Acrosound, dedicated to building audio quality...
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The Dynaco Stereo 70 is a complete dual 35 watt power amplifier kit which offers the highest possible fidelity, at low cost and in a compact arrangement.
It uses a patented circuit of outstanding performance characteristics, along with top quality parts, including the new Dynaco Super-Fidelity A-470 transformers – the finest available.
The measured specifications show that the Stereo 70 is an amplifier of unequalled performance, and its listening quality is also unrivalled by any regardless of price.
This amplifier has characteristics and power rating ideal for either stereophonic or monophonic use. The two non-interacting 35 watt channels provide adequate power, in a stereophonic or two channel system, for loudspeakers of any level of efficiency.
The channels can be paralleled for a full 70 watts of low distortion output, suitable for practically any monophonic use even where several loudspeakers are in use in different areas.
The high power capability and low internal impedance provide excellent damping for all types of high quality speaker systems without need to make adjustments to match specific speaker installations.
The design features of your Dynakit which contribute to its superior listening quality include some which are not revealed by the customary steady-state laboratory measurements.
For example, it does not exhibit bounce and flutter when pulsed with a transient signal. Thus a sharp percussive signal like a drum beat or a piano note will be reproduced with sharpness and clarity and neither overhang nor muddiness.
The Stereo 70, unlike many other amplifier circuits, has been designed to provide its specified performance on a loudspeaker load, not just under laboratory measuring conditions. Therefore, the connection of a loudspeaker to the amplifier does not deteriorate its performance or listening quality.
In addition, due to the high quality of the output transformers used, the Dynakit’s power handling capabilities are maintained over the entire audio band without the sharp rise in distortion that characterizes most amplifiers at the extremes of high and low frequencies.