The Amp No. 1

1988. 80 watts. An unlikely beginning.

Built in 1988, The Amp No. 1 began with an unlikely circuit: a high-current driver originally intended for stepper motors. Reworked for audio, it became a quasi-complementary MOSFET amplifier delivering around 80 watts into 8 ohms.

An unconventional starting point, but one that proved remarkably well suited to driving loudspeakers.

The dual-mono idea was taken literally. Each channel has its own transformer, rectifier, power supply and amplifier section; only the chassis is shared. Rear level controls allow the input sensitivity to be reduced for higher signal levels and make small channel differences easy to correct.

The low chassis was deliberate. Only the electronics remained inside; the transformers and heatsink were left visible above it. There is a distant echo of classic valve amplifiers — without trying to imitate them.

Nearly forty years later, the marks are still there.

Separate rear level controls allowed the amplifier to be driven from a higher source level, keeping noise low while retaining the ability to correct small channel differences. Soft start, delayed speaker connection and DC protection were built in from the beginning.

Parts already mattered. Black Gate capacitors, WonderCaps and carefully selected components found their way into the circuit.

No CAD. No PCB software. Schematics on squared paper; PCB artwork by hand on transparent film, using transfer symbols and lettering.

The enclosure took shape on the same squared paper. Low chassis. Transformers and heatsink above it. The basic architecture was already there.

The first boards hummed. So did the next ones. Four redesigns later, the grounding and current paths were finally right. That lesson stayed with me.

Built in 1988. Still working.

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