Power amplifiers stereo — Gryphon Audio Apex Stereo

The Apex Stereo is the two-channel version of the Apex power amplifier made by Denmark's Gryphon Audio, introduced in 2022 and also offered as a monoblock. Gryphon designs and builds it in Denmark. The circuit operates entirely in Class A, each channel is laid out as a pure dual mono design, and no global negative feedback is applied.

Key specs that matter

Output is 2 x 210 W into 8 ohm, 2 x 420 W into 4 ohm, 2 x 800 W into 2 ohm and 2 x 1,490 W into 1 ohm. THD+N is below 0.02 percent at 50 W into 8 ohm, and IMD (DFD) is also below 0.02 percent at that level. Output impedance is 0.015 ohm, and the -3 dB bandwidth spans 0.3 Hz to 330 kHz. Gain is +31 dB with an input level of 1.16 Vrms, and the balanced input impedance measures 20 kohm. Noise is below -80 dBV unweighted from 20 Hz to 20 kHz and below -86 dBV A-weighted. The chassis is 59.3 x 37.1 x 88.6 cm and weighs 202 kg net.

Engineering and use context

Sixty-four very high current bipolar devices make up the output stage, fed by a capacitor bank of 1,040,000 uF, more than 1 farad. Two custom 2,000 VA toroidal transformers sit in individually decoupled castings. The input begins with a Class A J-FET buffer of very low capacitance, and after it come dual differential balanced Class A input stages with symmetrical voltage gain. The voltage amplifying stages have a fully regulated low-noise supply, the damping factor does not vary with frequency thanks to DC servo coupling, and Zn foil capacitors handle local supply decoupling. The four-layer boards use copper up to 105 um, and internal signal and power wiring is Gryphon silver. Maximum consumption is 3,700 W, while idle draw is 1,000 W, 660 W or 320 W depending on the high, mid or low bias setting, and standby stays under 0.5 W. Mains power connects through two C19 inlets, and firmware is updated over USB.

Pairing

Inputs are gold-plated Neutrik XLR only, and speaker cables go to custom gold-plated Gryphon binding posts. A 12 V link allows remote power switching, and the automatic Green Bias link to a Gryphon preamplifier can replace manual bias selection. The protection system is non-intrusive. Gryphon states that the large power reserves let the Apex behave uniformly into any loudspeaker load. The shipping crate measures 102 x 81 x 67 cm and weighs 265 kg.

Alternatives

For a far smaller Gryphon stereo amplifier, the Essence also runs in pure Class A and weighs 45 kg.