Denon DH-710

The Denon DH-710 (most commonly referenced as DH-710F or DH-710S in variants) is a mid-to-late 1970s high-end professional/consumer stereo reel-to-reel tape recorder, produced approximately 1976–1980 (manufactured in Japan by Nippon Columbia/Denon). It was a flagship model in Denon's DH series, highly regarded by audiophiles and engineers (notably praised by legendary designer Tim de Paravicini as his favorite/road machine). The DH-710 series combined broadcast-grade engineering with audiophile appeal, featuring half-track (2-track) recording with quarter-track playback capability in some configurations (versatile for both pro and consumer tapes), three-motor direct-drive transport, two-capstan system, and exceptional tape handling.

Variants include:

• DH-710F: Often the "pro" or export version (sometimes with XLR I/O or refined features).

• DH-710S: Frequently the "home" or single-box integrated version.

• Some sources note a two-box setup (deck + separate preamp/amp in early or pro configs).

It was built for durability and performance, with a massive chassis and precise engineering that made it a favorite for critical listening and recording.

Key Technical Specifications

• Recording/Playback System — Half-track (2-track) stereo recording (with quarter-track playback head in many units for versatility); 2-channel stereo/mono compatible; records and plays stereo on tracks 1-2 forward (no reverse pair without manual flip); mono compatible; sound-on-sound/multiplay overdub facilities; no auto-reverse.

• Tape Speeds — Two professional speeds:7½ ips (19 cm/s)
  15 ips (38 cm/s)
  

• Reel Size — Up to 10½ inches (26.5 cm) NAB hubs (professional large reels for extended playtime).

• Frequency Response (approximate, within tight tolerances; varies by tape/condition):At 38 cm/s (15 ips): 30 Hz – 30 kHz ±2 dB
  At 19 cm/s (7½ ips): 30 Hz – 20 kHz ±2 dB Outstanding bandwidth for the era—hi-fi capable with excellent extension.
  

• Wow & Flutter — <0.02% WRMS at 15 ips (exceptional stability from three-motor direct-drive, two-capstan transport, and electronic AC servo tension control).

• Signal-to-Noise Ratio — >66 dB at maximum recording level (514 pWb/mm); >58 dB at standard level (200 pWb/mm) (very high for transistor design with low-noise tape).

• Total Harmonic Distortion — <0.5% at 1 kHz (with Scotch 206 tape or similar; low saturation in recording amp).

• Heads — 3 heads: separate record, playback, and erase (newly-developed Sendust alloy or hard permalloy; 2.1 mm track width for excellent S/N).

• Drive System — Three motors (1 × 6-pole out-rotor AC servo capstan motor + 2 × AC servo reel motors); direct-drive two-capstan system; electronic tension AC servo (minimizes load fluctuations/start-up issues); one-way air damper for tension control; fast wind/rewind; precise braking.

• Electronics — Fully transistorized; printed circuit board amplifier; NAB equalization; maximum recording amp output >+30 dB @ 1 kHz (to match pro gear; low saturation distortion).

• Inputs —Microphone (low-level).
  Line/radio/phono (standard line level).
  DIN-style connectors (some pro versions with XLR I/O).
  

• Outputs —Line out (~1 V).
  Headphones (monitor).
  External amp/speakers.
  DIN-style.
  

• Features —Twin illuminated VU meters (needle type; active for record/playback).
  Electronic logic transport (smooth push-button).
  Off-tape monitoring (source/tape switch).
  Input mixing.
  Pause function.
  Portable/tabletop design with lid/handle; vertical/horizontal orientation.
  

• Power — AC mains (100 V Japan standard; multi-voltage variants); consumption ~130 W (deck + amp in some configs).

• Build & Dimensions — Massive tabletop case (often wood/teak or metal finish); deck approx. 505 × 420 × 310 mm (WHD); amp unit ~490 × 180 × 330 mm (in two-box versions); combined weight ~27 kg (deck) + 8.5 kg (amp) — very heavy and robust.

• Manufacturing — Japan (Denon/Nippon Columbia).

Performance & Legacy Context

The DH-710 series (especially DH-710F) was hailed as a "full-fledged high-performance open-reel deck for audiophiles" — with tape handling described as "marvellous" thanks to the three-motor direct-drive, two-capstan system, and electronic AC servo tension (minimizes start-up load and tension fluctuations). It offered ultra-low wow/flutter (<0.02% WRMS at 15 ips), high S/N (>66 dB max), wide frequency response (30 Hz–30 kHz at 15 ips), and low distortion. The Sendust heads and generous recording amp headroom (>+30 dB) ensured clean, professional-grade results, with the ability to play both ½-track and ¼-track tapes in some configs (like Technics RS-1500 or Otari MX-5050). Tim de Paravicini favored it as his road/travel machine for its reliability and sound.

Common issues today: Belt/idler degradation (goo/melting—kits needed), dried electrolytic capacitors, transistor aging, dirty heads (3-head alignment critical), worn idler tires/clutches, and occasional servo/tension faults. Restorations are rewarding—many units achieve superb performance post-service. Service/user manuals available (HiFi Engine, Audio Database—schematics, alignment).

Compared to siblings:

• DH-610S — Similar flagship (often considered close or variant; some prefer DH-710 for refinements).

• DH-510 — Related but sometimes seen as slightly less advanced.

• DH-710 — Balanced high-end with pro specs (15 ips, NAB 10.5" focus, two-capstan).