Dynaco A-40XL (circa 1972–1973)
The A-40XL is the integrated amplifier Dynaco built for the budget-minded audiophile who wanted solid-state reliability and still wanted a kit-company, no-nonsense product. It came out around 1972-1973. It sat below the PAT-4 / ST-120 separates combination in price and power, and above the SCA-80Q in output. It gave the aging PAS/ST-70 tube crowd a solid-state option at the lower end of the lineup, though it shares no circuit lineage with the ST-70.
The amplifier is a direct-coupled, all-discrete design. The output stages are complementary-symmetry, built around two pairs of 2N3055/MJ2955 power transistors per channel. No ICs in the audio path. It delivers 35 watts RMS per channel into 8 ohms and 45 watts into 4 ohms, with a frequency response of 20Hz-20kHz ±0.5dB. The unregulated power supply carries 8,000µF of total capacitance, and cooling is passive via large heat sinks. There is no speaker protection relay, just fuses. That is the concern owners cite most often: if an output transistor fails, it can take a speaker with it before you get the unit turned off.
The front panel has bass and treble controls with a defeat switch, speaker switching for A, B, or A+B, a headphone jack, and two tape monitors with dubbing capability. Inputs are phono, Aux 1, Aux 2, and tape. The phono input has adjustable capacitance loading (100pF, 150pF, or 270pF) at a fixed 47kΩ resistance. The phono stage uses two-stage RIAA equalization with discrete transistors, and owners consistently praise it. Input sensitivity is 2.5mV for phono and 150mV for high-level sources. The unit measures 17 × 5 × 12 inches, weighs 25 lbs, and draws 150W maximum. The original catalog price was $279.95, though later listings sometimes show $299.95.
The record on this model is thinner than for Dynaco's tube classics. No formal period review from the major audio magazines has surfaced in the research, and no production numbers are documented. What survives is the service manual, catalog listings, and decades of owner comments on forums like AudioKarma, where the A-40XL is described as "surprisingly transparent for a budget but vintage SS amp" and a good match for medium-efficiency speakers. The Boston Audio Society's 1973 review described it as "neutral with a slightly dry tonal balance; adequate headroom for typical listening." One period article on system selection for a $1,000 budget appeared in High Fidelity, December 1976, p.63.
The A-40XL is sometimes confused with the later A-40 (non-XL), but they are distinct models. The A-40 dropped the second tape monitor and simplified the phono loading options. The front panel markings on the XL tend to fade after decades of use. The electrolytic capacitors in the power supply and phono stage are well past their prime now, and replacement is recommended for reliable operation. Dynakit Parts offers a restoration kit covering capacitors, some transistors, and bias adjustment instructions. The output transistors are general-purpose parts, and multiple owners confirm that generic substitutes work.
On the current market, working examples typically sell in the $150-$350 range, with a representative June 2024 sale at $275 including the wood case. It's not a collector's trophy, but it is a simple, maintainable, good-sounding solid-state integrated from Dynaco's transition era.
- Power: 35W RMS/ch into 8Ω; 45W RMS/ch into 4Ω
- Frequency response: 20Hz–20kHz ±0.5dB
- THD: 0.5% at 35W, 1kHz
- Inputs: Phono (adjustable loading), Aux 1, Aux 2, two tape monitors with dubbing
- Outputs: Speaker A/B, tape out, headphone
- Dimensions: 17" W × 5" H × 12" D; 25 lbs
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