Denon PMA-700Z (1975)
Overview
The Denon PMA-700Z is a pre-main amplifier released in 1975, combining a high-precision preamplifier with a powerful amplifier section in a single chassis. Built during a period when Japanese audio manufacturers were rapidly gaining global recognition for their innovation and quality, the PMA-700Z exemplifies Denon's commitment to high-fidelity sound reproduction and solid engineering. It delivers 70 watts per channel into 8 ohms (85W into 4 ohms) with less than 0.05% total harmonic distortion at rated output, making it a competitive performer for its time. The unit supports both moving magnet (MM) and moving coil (MC) inputs via separate phono stages—Phono1 and Phono2—with dedicated sensitivity and impedance settings, offering flexibility for analog enthusiasts.
Frequency response spans an exceptionally wide 8 Hz to 150 kHz (±0.5 dB), and power bandwidth extends from 8 Hz to 30 kHz at 0.1% THD, indicating strong transient handling and stability across demanding loads. Input sensitivity varies by source, with Aux, Tuner, and Tape inputs at 320mVrms; the main amplifier section has an input sensitivity of 1 Vrms, with input impedance of 80 kΩ ±20% across the 20 Hz–20 kHz range. The tone control section features selectable fold points at 320 Hz and 640 Hz for bass, and 1.6 kHz and 3.2 kHz for treble, with a variable range of ±10 dB in 2 dB steps. A loudness compensation circuit boosts low and high frequencies at reduced volume levels, with a characteristic lift of +6.5 dB at 100 Hz and +6 dB at 10 kHz.
Design
The preamplifier section delivers a rated output of 1 Vrms (10 kHz, THD 0.05% or less) and can supply up to 14.2 Vpeak maximum power output. Output impedance is kept low at 0.16 Ω or less (below 10 kHz, pure resistance), ensuring strong damping and control over speaker loads. The RIAA equalization accuracy is tightly controlled, with deviation within ±0.3 dB from 20 Hz to 20 kHz. The tone defeat mode maintains a wide passband of 7 Hz to 300 kHz (+0/-1 dB), preserving signal integrity when tone controls are bypassed.
Market
The Denon PMA-700Z had an original retail price of ¥145,000 in Japan at launch. Its dual phono inputs—supporting both MM and MC cartridges with distinct sensitivity settings (3.2 mVrms for MM, 0.32 mVrms for MC)—positioned it as a serious choice for vinyl-focused listeners. Signal-to-noise ratio for the Phono1 input is rated at 62 dB or more (IHF-A weighted, input shorted), with a higher figure of 78 dB listed in a separate catalog, suggesting optimized noise performance under specific conditions.
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