amplifier (60 wpc). Because of early problems involving circuit, power supply, and transistor failures, the ST 120 was not as popular as earlier Dynaco tube amplifiers. Numerous small circuit changes were introduced by Dynaco over the years in an attempt to improve the stability and reliability of the ST 120, without much success. With the PAT-4 preamplifier in 1967, the company affirmed its ability to design reliable solid state equipment at an affordable price. In 1969 the Dynaquad 4-channel matrix decoder system was introduced, helping to start the quadrophonic sound craze. 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. Dynaco's solid-state kits were different from the popular Heathkit products (and Dynaco's own vacuum tube kits) because of their preassembled circuit boards. These boards were wired at the factory, tested and packaged with the unassembled chassis. It remained only for the consumer 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 error in assembly. Dynaco also distributed the famous SEAS 'A-Series' of bookshelf loudspeakers that were manufactured in Denmark, using input from Dynaco's David Hafler and SEAS's Ragnar Lian. The A-Series were marketed between from 1970 until Dynaco's demise in the 1980s. The Dynaco A-25 model proved to be extremely successful, selling between 600,000 and 1,000,000 units. A modified aperiodic bass reflex design using SEAS speakers in a handsome wood cabinet, the A-25 sold for $79.95 each in 1969 making it 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