Pioneer A 339

Forty honest watts, a 0.02% distortion spec, and a service manual that quietly admits it's a dressed-up A-337.

HiFI-Stereo (May 1992, p.101) ran classified listings for secondhand audio equipment of this era. Amplifiers like the A 339 were circulating through the used market long before collectors took an interest.

Overview

The Pioneer A 339 is an integrated stereo amplifier, and the first thing to know comes straight from Pioneer's own service documentation: the A-339/KU, HE, HEWZ, and SD types are, in the company's words, "the same as the A-337/HE type with the exception of the following sections." That's not a knock - it's an honest statement from a manufacturer that usually let model numbers imply more novelty than they delivered. It's a regional-variant amplifier from Pioneer's 1990 service literature, sold under a handful of destination codes that mostly describe which wall voltage the thing expects.

The power requirements explain why A 339s turn up in odd places. The KU type runs on AC 120 V only. The HE type is switchable between AC 220-230 V and 240 V. The SD type has the widest range, switchable across AC 110 V, 120-127 V, 220 V, and 240 V. The KC variant is AC 120 V only. A buyer hunting one today should check the rear panel rather than assume. The same model designation can be a North American amp, a European amp, or an export-market amp, and the primary wiring differs accordingly. Pioneer's own manual notes that changing between the switchable voltages requires a primary wiring change, not just a flip of a selector.

The amplifier section is where the A 339 makes its case. Pioneer rates it at 40 watts per channel continuous average power output, minimum, at 8 ohms from 20 Hertz to 20,000 Hertz, with no more than 0.02% total harmonic distortion. Read that spec the way an engineer would: 40 watts is not a big number, but the conditions attached to it are strict. Full-bandwidth rating rather than a single-frequency figure, both channels driven, and a distortion ceiling of 0.02% across the entire audio band. Pioneer also footnotes the distortion measurement as taken with an Audio Spectrum Analyzer, and the power figure as measured pursuant to the Federal Trade Commission's Trade Regulation rules on Power Output Claims for Amplifiers — the rules that were supposed to stop manufacturers from quoting inflated, one-channel, 1 kHz power numbers. An amplifier rated this conservatively tends to behave well with real speakers, because the number isn't a peak and isn't a fantasy.

The rest of the amplifier section reads like a competent late-eighties integrated. Phono (MM) input sensitivity and impedance are specified at 1 kHz with THD of 0.02%. The phono stage holds a frequency response of 20 Hz to 20 kHz within ±0.3 dB. The line-level inputs (CD, TUNER, LINE, TAPE) get their own sensitivity and impedance figures, and the tone controls are conventional: bass ±8 dB at 100 Hz, treble ±8 dB at 10 kHz, with a loudness contour specified at the volume control's −30 dB position. There are two switched AC outlets on the rear. One footnote in the spec block notes a measurement taken with the DIRECT switch set to on, so the signal path can be shortened when the tone controls aren't wanted.

On the evidence of its own documentation, the A 339 is not a flagship. Nothing in the service literature gives this chassis the higher-tier A-449's 60-watt rating. The A-449 is a separate model in the same manual, and the A-339's own amplifier section is the 40-watt, 0.02% specification. The chassis architecture is shared across the A-337, A-339, and A-449 families, which makes parts commonality good for restoration, and the sections that differ between types are documented rather than guessed at.

Production years aren't documented in the surviving record. The service manual carries a 1990 copyright from Pioneer Electronic Corporation, and the manual's own scope note directs technicians to a separate service manual (ARP2043) for the A-447/HE and A-337/HE, which suggests the A-339 sat within an established family rather than launching a new one. Beyond that, any dating is speculation.

The A 339 is a serviceable, conservatively rated integrated amplifier with a good phono stage on paper and a distortion figure that most modern budget amplifiers would be embarrassed to publish. The complication is regional. Between the KU, HE, HEWZ, SD, and KC types, and the A-339-S variant that Pioneer describes as identical to the A-339 except for color, there are enough permutations that buyers should verify the exact type code and voltage configuration before committing. The manual also carries the usual warning that some components are marked with a triangle symbol for safety-critical characteristics, and that substituting non-equivalent parts can create shock or fire hazards. That's standard language, but it applies to a thirty-plus-year-old amplifier with mains wiring inside.

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