Denon DH-630S

The Denon DH-630S (including variants like DH-630S/00) is a late 1970s high-end consumer/professional stereo reel-to-reel tape deck, produced approximately 1978–1980 (manufactured in Japan by Nippon Columbia/Denon). It was a flagship model in Denon's DH series, serving as the 4-track (quarter-track) counterpart to the DH-610S (which is the 2-track/half-track version). The DH-630S is highly regarded among collectors as one of the best-sounding Japanese open-reel decks of the era, praised for its massive build, exceptional stability, wide frequency response, and professional-grade features like three-motor direct drive, glass-ferrite heads, and separate left/right bias adjustment.

It was designed for serious audiophiles and semi-professional use, with NAB reel compatibility (10.5" reels), direct tension servo for gentle tape handling, and outstanding performance that rivals high-end Swiss or European decks when serviced.

Key Technical Specifications

• Recording/Playback System — 4-track (quarter-track), 2-channel stereo/mono compatible; records and plays stereo on tracks 1-4 forward and 3-2 reverse (manual tape flip required for second pair); 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 or Type 26/No. 10 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 – 26,000 Hz (or up to 30 kHz in some claims)
  At 19 cm/s (7½ ips): 30 Hz – 22,000 Hz Outstanding bandwidth—among the widest in late 1970s consumer/professional decks.
  

• Wow & Flutter —At 38 cm/s: ~0.025–0.035% (WRMS)
  At 19 cm/s: ~0.03–0.05% Ultra-low thanks to three-motor direct drive and direct tension servo.
  

• Signal-to-Noise Ratio — 64–66 dB (DIN weighted; very high for the era with low-noise tape).

• Total Harmonic Distortion — <0.1–1% (low distortion at normal levels).

• Heads — 3 heads: separate record, playback, and erase (hard permalloy or glass-ferrite for record/playback + ferrite erase; high-quality construction for longevity and superior high-frequency performance).

• Drive System — Three motors (direct-drive capstan + two reel motors); direct tension servo (automatic tape tensioning); electronic logic transport; variable spooling speed; fast wind/rewind (~2 minutes 30 seconds for No. 10 reel with 740 m tape); precise dynamic braking.

• Electronics — Fully transistorized; printed circuit board amplifier; variable/stepless bias adjustment (separate L/R); NAB/IEC equalization switchable at 38 cm/s.

• Inputs —Microphone: low-level (~0.2 mV).
  Line/radio/tuner/phono/aux: ~100 mV.
  DIN-style connectors standard.
  

• Outputs —Line out: ~1 V / 50 kΩ.
  Headphones (monitor, 6.3 mm jack, 8–2000 Ω, ~40 mW at 600 Ω).
  Monitor output: 0–1 V adjustable / 11 kΩ.
  DIN-style.
  

• Features —Twin illuminated VU meters (needle type; active for record/playback).
  Electronic logic transport (push-button with smooth response).
  Separate L/R bias and equalization.
  Input mixing/attenuators.
  4-digit tape counter.
  Off-tape monitoring (source/tape switch).
  Pause function.
  Optional DIN 5-pin remote control.
  Vertical/horizontal operation; massive chassis.
  

• Power — AC mains (100 V Japan standard; multi-voltage variants); consumption 75–80 W.

• Build & Dimensions — Massive tabletop case (often wood/teak or metal finish); approx. 530 × 527 × 230 mm (20.8 × 20.7 × 9 inches); weight 25 kg (very heavy due to motors, heads, and chassis).

• Manufacturing — Japan (Denon/Nippon Columbia).

Performance & Legacy Context

The DH-630S (as the 4-track version of the DH-610S) was Denon's ultimate late-1970s open-reel flagship—celebrated for its massive scale, quartz-like precision (ultra-low wow/flutter from direct drive and tension servo), glass-ferrite heads (long life and HF extension), and wide 30 Hz–26 kHz response at 15 ips. The quarter-track format offers more channels/recording time than half-track (DH-610S), though with slightly narrower tracks and marginally lower S/N per track. It delivered superb clarity, dynamics, stereo imaging, and low noise—often described as "studio-grade" or "one of the greatest unknown decks" in collector circles. Serviced examples frequently exceed factory specs and are highly sought after.

Common issues today: Belt/idler goo (multiple belts need full kits), dried electrolytic capacitors, transistor aging, dirty heads (3-head alignment critical), worn idler tires/clutches, capstan motor faults, and electronic counter/logic issues. Restorations are complex but yield outstanding results. Service/user manuals available (HiFi Engine, Elektrotanya—full schematics, alignment, bias info; Japanese originals common).

Compared to siblings:

• DH-610S — Nearly identical but 2-track/half-track (wider tracks for better per-channel fidelity; often preferred by purists).

• DH-510 — Similar but sometimes seen as slightly less refined.

• DH-710F — Earlier/high-end predecessor (Tim de Paravicini's favorite; similar three-motor/3-head design).

• DH-630S — 4-track flagship with pro specs (15 ips, NAB 10.5" focus, glass heads).