Audio Research D-79 (1979)
A high-powered tube amplifier built in the USA with a regulated power supply and forced-air cooling for sustained high-fidelity performance.
Overview
The Audio Research D-79 is a powerful tube-based stereo amplifier introduced in 1979. Built in the USA, it was designed for audio perfectionists seeking high-definition sound reproduction across a wide range of speaker systems. With a robust construction using near-military-grade components, the D-79 delivers 75 watts per channel and features extensive engineering for stability and clarity, even under reactive loads. It is known for its ability to resolve subtle sonic details and maintain performance with minimal maintenance when equipped with high-quality tubes.
Specifications
| Power Output | 75 W/C RMS at 16 ohms from 30Hz to 15kHz with less than 1% THD |
| Power Bandwidth | 15Hz and 40kHz (-3dB) |
| Input Sensitivity | 0.75V RMS for rated output |
| Input Impedance | 80Kohms, nominal |
| Output Regulation | Approximately 1.5dB, 16 ohm load to open circuit |
| Overall Negative Feedback | 13.5dB |
| Damping Factor | Approximately 8 |
| Distortion (Intermodulation) | Less than 0.5% at 1dB below rated output |
| Slew Rate | Approximately 10V/µs |
| Rise Time | 5µs |
| Hum & Noise (Wideband, unweighted) | more than 90dB below rated output |
| Hum & Noise (Line components) | more than 80dB below rated output |
| Tube Complement | 6 x 12AX7, 8 x 6FQ7, 5 x 6550 |
| Dimensions (W x D x H) | 48.5 x 48 x 27 cm |
| Weight | 40 kg |
Design
The D-79 uses a pentode output stage operated in ultralinear mode, driven by a high-energy, well-regulated power supply featuring Audio Research’s patented balanced and cross-coupled circuitry. Forced air cooling is provided by three built-in fans to manage heat in the output stage. The unit is constructed with high-reliability components and designed for excellent service accessibility.
Context
The D-79 was developed in response to demand from audio perfectionists seeking high-fidelity power amplification. It shares design lineage with other models in the 79 series: the 'A' version uses a D76A front end, the 'B' incorporates the D90 front end, and the 'C' (and 79C-MKII) are based on the D115 and D115 MKII designs respectively.
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