Mark III

About the Mark III

The Dynaco Mark III is a classic tube monaural power amplifier kit rated at 60 watts RMS output, originally sold as a Dynakit for user assembly. It uses a push-pull output stage with two KT88 or 6550 power tubes, a 6AN8 driver/input tube, and a GZ34/5AR4 rectifier tube, with a C-L-C filtered power supply that includes the Dynakit C-354 filter choke. Manufacturer specifications give total harmonic distortion below about 0.5-1% at 60 W, with frequency response rated essentially flat from 20 Hz to 20 kHz at low distortion and extending out to about 6 Hz-60 kHz within ±0.5 dB. The amplifier is designed as a mono unit; a pair of Mark III chassis is used for stereo operation. It provides output taps for 4, 8, and 16 ohm speaker loads via A-431 output transformers, and is known for clean, dynamic sound, good transient response, and relatively low distortion for a vintage tube design. The chassis is a compact, sturdy steel design with a P-782 power transformer, C-354 choke, and PC-1 driver board, with front-panel controls limited mainly to power and traditional output tube bias adjustment. Originally sold as a kit with straightforward construction and significant upgrade potential, it remains a highly respected amplifier among tube audio enthusiasts.