Power amplifiers stereo — Gryphon Audio Mephisto Stereo

The Mephisto Stereo from Gryphon Audio Designs is a stereo amplifier running entirely in class A, designed and built in Denmark, with exterior styling by Flemming E. Rasmussen and electronics by Tom Moller. It has since been succeeded by the Hyperion, which keeps the same basic topology.

Key specs that matter

Output is 2 x 175 W into 8 ohm, 2 x 350 W into 4 ohm and 2 x 700 W into 2 ohm, all in class A. Gryphon quotes bandwidth beyond 350 kHz despite the absence of global feedback, and distortion of 0.006 percent. Gain is 31 dB, and the inputs are balanced only, through gold-plated Neutrik XLR connectors. The chassis measures 52 cm wide, 34 cm high and 71 cm deep and weighs 108 kg, in brushed aluminium with a black finish. Two mains cords are required, one per channel. Gryphon also claims up to 6000 W per channel of peak class AB power into half an ohm. The US price was USD 57,000.

Engineering and use context

The layout is pure dual mono. Two Holmgren toroidal transformers with internal magnetic shielding feed the channels, and the capacitor bank totals 500,000 microfarads, including eight 56,000 microfarad low-ESR capacitors for the output supply. Separate power supplies serve the amplifier circuits and the digital control. The output stage uses 40 high current bipolar transistors, and the signal reaches Gryphon gold-plated binding posts through solid copper rails with no output relays in the path to keep output impedance low. DC servo coupling is used in place of coupling capacitors. Bias can be set manually to Low, Mid or High, or left to the automatic Green Bias mode. A 3.5 mm control jack carries a 12 V trigger for remote switching, and a non-intrusive protection system guards the circuit. A soft start sequence at power-on prevents tripping fuses or circuit breakers in the home, the circuit boards are double-sided military specification types, and damping stays constant across the frequency range.

Pairing

The source ahead of it must offer balanced XLR outputs, and the ability to double output each time the load halves makes difficult loudspeakers a suitable load. Because of the weight and class A heat, the amplifier needs a solid floor position with free air around it.

Alternatives

The Gryphon Hyperion in its stereo version is the newer class A power amplifier from the brand, rated at 180 W into 8 ohm and 720 W into 2 ohm per channel.