Dynaco

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Dynaco is an American hi-fi manufacturer, founded by David Hafler and Ed Laurent in 1955, that earned enduring fame for its wide range of affordable component kits. Dynaco is best known for its highly regarded Stereo 70 vacuum tube amplifier. Introduced in 1959, the 35 watt per channel Stereo 70 (or "ST-70") was sold until mid-1990. With more than 300,000 ST-70s produced, it is the most popular tube power amp ever made. Dynaco electronics were available either factory assembled or in do-it-yourself kits, Dynakits. These kits were different from the popular Heathkit products because of their preassembled circuit boards. These boards were wired at the factory, tested and packaged with the unassembled chassis. The builder was left, largely, to attach the switches and controls to the chassis pieces, assemble the chassis and power supply and solder connecting wires to the circuit boards. This saved considerable time and reduced errors on the part of the builder. Because of their excellent sound quality, low noise, and reasonable prices, Dynaco tube amps were often referred to as "the poor man's McIntosh." Even today, upgraded components, rebuild kits, and even a complete improved reproduction of the ST-70 is available.

Dynaco is also well known for its line of transistor components. Beginning in 1966 with the introduction of the Stereo 120 model power amplifier (60 watts/channel) and the PAT-4 preamplifier in 1967, the company affirmed its ability to design reliable solid state equipment at an affordable price. In the 1970s, the Stereo 400 was developed and marketed. This was a high power amplifier at 200 watts per channel that offered automatic protection circuitry to prevent electrical destruction of the loudspeaker. The FM-5 tuner was offered as was the SCA-80 integrated amplifier in the early 1970s time line. There was also the Dynaquad system which allowed the user to simulate a quadrophonic sound by using out of phase signals at the speaker terminals. It apparently was a success and offered good four-channel sound at budget price.

Dynaco also distributed the famous SEAS 'A-Series' of bookshelf loudspeakers that were manufactured in Denmark, using input from Dynaco's David Hafler. The A-Series were marketed between 1970 and Dynaco's demise in the 1980s. The Dynaco A-25 model proved to be extremely successful, selling over 600,000 units. A modified aperiodic bass reflex design in a handsome wood cabinet, it combined quality sound reproduction with a budget price (under $100), making it highly competitive with much more expensive loudspeakers. The patented aperiodic (essentially non-resonant) woofer design utilized a highly-damped vent instead of a reflex port, whose acoustic resistance is very carefully controlled. The resistant venting action lowered the "Q" of the system and reduced impedance variation near resonance in the A-Series speakers. Dynaco followed the A-25 with the slightly larger A-35, which featured a dual-chambered, non-vented design in a walnut-veneered cabinet with even greater transparency and fidelity. Over time, Dynaco marketed a wide range of loudspeakers, ranging from the small A-10 model to the floor standing A-50 series. After some 30 years, these loudspeakers still command good prices in markets such as eBay, and are a testimonial to their quality.

Concurrent with A-25 production, Dynaco introduced a system whereby 4-channel sound could be easily derived from stereo material by using a rear channel speaker matrix. This "Dynaco patent" required a single resistor and a threeway potentiometer for the two rear speakers for generating sufficient phase difference signals for a feeling of ambience. The system worked best when the stereo sound had been recorded via two bidirectional microphones on the same spot. When microphone set-up changed to the use of multiple directional microphones and multitrack tape recording and postprocessing (i.c. in the CD era), the Dynaco patent lost its market value.

The Pan Orient Corporation (later Panor Corporation) acquired the Dynaco trademark in the early 1990s and began marketing electronic components with the Dynaco brand. Panor even reintroduced some of the older Dynaco designs. Among collectors, the Panor/Dynaco ST-70 is not as desirable in comparison to vintage ST-70s of the 1960s (the earliest ST-70s with cloth-covered transformer leads are the most sought-after models among audiophiles and collectors).

[edit] Dynaco tube equipment

Dynaco introduced the following tube audio amplifiers, tuners, and preamplifiers between 1955 and 1976.

Model Type Channels
(Power)		 Year Introduced
Dynaco Mark II Power Amp Mono
(50 watts)		 1955
Dynaco PAM-1 Preamp Mono 1957
Dynaco Mark III Power Amp Mono
(60 watts)		 1957
Dynaco Stereo 70 Power Amp Stereo
(35 wpc)		 1959
Dynaco PAS-2 Preamp Stereo 1960
Dynaco Mark IV Power Amp Mono
(40 watts)		 1960
Dynaco FM-1 FM tuner Mono 1961
Dynaco Stereo 35 Power Amp Stereo
(17.5 wpc)		 1963
Dynaco SCA-35 Integrated Amp Stereo
(17.5 wpc)		 1964
Dynaco FM-3 FM tuner Stereo 1964
Dynaco PAS-3 Preamp Stereo 1966
Dynaco Mark VI Power Amp Mono
(120 watts)		 1976

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