The GB150D features my new fully symmetrical discrete power amplifier topology that achieves absolute Hi End performance at low cost. The design features very high PSRR for reduced sensitivity to power supply quality and the output stage Class AB commutation artefacts superimposed on the supply impedance, which causes the harshness and loss of timbral and spatial detail in lesser designs. The 4 x 150W common source complementary MOSFET output stage swings to within 2V of the supplies, maximizing power output for greater power efficiency than conventional designs, achieving 150W into 8ohms on unregulated +/-55V supplies! The unique topology eliminates the Vas stage which compromises conventional designs, instead employing positive feedback to achieve highly linear and very high first stage gain. Then a complementary 300MHz Class A buffer drives the MOSFETs with only feedback lead compensation for excellent stability with all loads. The amplifier is ideally suited to electrostatic loudspeakers with typ < 0.001% THD at 100 ohms, and less than 0.025% mostly second harmonic distortion at average listening levels.

The amplifier may be configured as a simple AC coupled design, or DC coupled to eliminate signal path capacitors, with onboard DC nulling and bias adjustment. The kit includes all matched components (input diff'ls to 5% Hfe, MOSFETs to 10mV on Vgs), quality metal film resistors, polystyrene, silvered mica and polypropylene capacitors, 105 degreeC long-life electrolytics and fully ground planed and through hole plated PCB, with detailed component overlay. All components for AC or DC coupling are included. Full assembly and support hardware instructions are provided, including a variety of options and tweaks as well as simple modifications to introduce 0.25% second harmonic 'bloom' for a 'fuller' more tube-like sound if desired. The amplifier may also be configured in pure Class A to 50Wrms at 8 ohms on +/-32V supplies. Hints for optimal operating conditions are provided to extract the best from the design.

NOW AVAILABLE GB150D Stereo Kit (Including case, psu, transformer etc)


 Power Output
150Wrms max into 4/8ohms
 Idle Power
11W on +/-50V supplies
 Freq. Response
20Hz - 20kHz 0.15dB @ 1W
1Vrms for 100Wrms/8ohms
 Input Impedance
27k // 330pF
 Slewing Rate
>15V/uS into 8ohms
<0.025% @ 100W/8ohms
<0.01% 2hD @ 10Wrms
 Damping Factor
>500 @ 50Hz for 8ohms
 Hum & Noise
< -100dBA w.r.t 1W
100mm x 50mm x 30mm