Power amplifiers stereo — Pilot Radio 232

The Pilot Radio 232 Stereophonic Power Amplifier is a stereo valve power amp from the American brand relaunched by Barak Isidor Epstein, great-grandson of company founder Isidor Goldberg. The relaunch is a family revival rather than a purchased trademark. The 232 is based on Pilot's Curtain of Sound circuit of 1959, redesigned by Damon Coffman of Coffman Labs, and it is built in Portland and Dallas. It was unveiled at the Southwest Audio Fest in Dallas at USD 4,790.

Key specs that matter

EL84 output valves give 15 W per channel, and Pilot describes the design as pure Class A. The transformers are custom made in the USA. Speaker terminals are provided for 4 and 8 ohm loads, and the inputs include balanced connections. Each channel has its own sensitivity control, and there is also a balance control. Construction uses point-to-point hand wiring and vintage oil-in-paper capacitors.

Engineering and use context

The original Pilot company was based in Brooklyn. It made radios from the 1920s and hi-fi electronics in the 1950s and 1960s, among them the SA-232 stereo amplifier of 1959, the SP-210 stereo preamplifier, the SA-260 60 W stereo amplifier and models marketed as Curtain of Sound. The new 232 takes its name from the SA-232 and keeps the circuit concept of that design while modernising the execution. The EL84 is a small power pentode. In Class A the output valves conduct over the full waveform, so there is no crossover error, but efficiency is lower and power stays modest. Point-to-point wiring joins the components directly without a circuit board, a traditional valve construction that is easy to service. The oil-in-paper capacitors in the signal path were common in the era of the original design. Separate taps on the output transformers let the owner match the amplifier to the speaker impedance, keeping the valves at their intended load, and the per-channel sensitivity controls adjust the input level to the source or preamplifier.

Pairing

With its modest output, the 232 needs efficient speakers of 90 dB or more and a gentle impedance curve, for example Klipsch Heritage, DeVore Fidelity or Audio Note models, in rooms of 12 to 25 m2. It is driven by a valve or solid-state line preamplifier.