Technics RS-B605 (1987 to 1990)

A Japanese-built stereo cassette deck with high-end noise reduction and precision tape handling, sold for ¥54,800 in 1987.

Overview

At 4.3kg, the Technics RS-B605 sits solidly on the shelf—light enough for portability, heavy enough to signal serious engineering. This stereo cassette deck, manufactured in Japan from 1987 to 1990, was built for listeners who demanded more than basic tape playback. With a frequency response stretching to 19 kHz on metal tape and a dbx noise reduction system that pushes the signal-to-noise ratio to 92 dB, the RS-B605 was positioned as a high-performance option in Technics’ late-’80s lineup. Its 0.06% wow and flutter (W.R.M.S.) rating suggests tight speed stability, important for maintaining pitch integrity during playback, while the inclusion of Dolby B, Dolby C, and dbx systems gave users flexibility across tape types. Input sensitivity is rated at 60 mV for line and 0.25 mV for microphone, with impedance matched to standard consumer gear of the era, and the 400 mV line output ensures compatibility with most preamps. Housed in a 430 x 114.5 x 287 mm chassis finished in Technics Brown, the deck draws 17W from a 100 VAC supply—modest power demands for a machine packing this many features.

High Hardness Permalloy Heads with Double-Gap Ferrite Erase

The RS-B605 uses a high hardness permalloy head for recording and playback. It was chosen for durability and consistent high-frequency response. It resists wear even with frequent use, and it helps the deck reach 19 kHz on metal tape. The erase head is a double-gap ferrite type, which erases both tracks completely and keeps crosstalk and residual noise down. Both heads suit high-output tapes that need precise magnetic control.

dbx, Dolby C, and HX-PRO Noise Reduction Integration

The RS-B605 supports three noise reduction systems: Dolby B, Dolby C, and dbx. Dolby B gives about 10 dB of noise reduction and works on high-frequency hiss on standard tapes. Dolby C goes up to 20 dB and suits CrO₂ and metal formulations. The dbx system does the most. It measures 92 dB signal-to-noise ratio when engaged and nearly eliminates tape hiss, though it needs careful calibration to avoid "pumping" artifacts. Dolby HX-PRO is also fitted. It's a pre-emphasis system that dynamically reduces bias current during high-frequency passages, which increases headroom and reduces distortion.

ClassAA Recording Amplifier and Custom Regenerative IC

The RS-B605 has a ClassAA recording equalizer amplifier, a circuit design unique to Technics. It splits voltage control and current drive into separate amplifier stages. The output waveform is set only by the voltage amplifier, which isn't affected by load variations, so the recording signal is cleaner and more stable. Technics also developed a single-chip custom IC for the regenerative equalizer amplifier, which cuts component count and keeps the signal path consistent. That level of circuit specialization was uncommon in mid-tier decks, and it suggests Technics aimed the RS-B605 at semi-professional users and critical listeners.

2-Motor Full Logic Transport with FL Peak Metering

The transport is a quiet 2-motor full logic mechanism. It uses electronic sensors and solenoids to move the tape, with no mechanical linkages. That reduces wear and improves reliability, but it leans heavily on rubber parts like drive belts and idlers, which are common failure points in aging units. The meter is a wide-range 3-color FL (Fluorescent) peak level display with distinct color zones for setting levels. LED indicators give additional status, and the electronic counter handles basic cueing and timing. A music selector function jumps to the start of the current or next track HiFI-Stereo (May 1989, p.100).

Timer Rec & Play, Auto Rec Mute, and L/R Mic Inputs

The RS-B605 also has several features for home recording and automation. Timer record and playback allows scheduled operation, handy for catching radio broadcasts or running timed playback. Auto Rec Mute silences the record path when no input signal is detected, so blank sections don't get recorded. The deck has L/R independent microphone inputs, a rarity at this price point, so stereo mic recording works without an external mixer. That made it a workable option for field recording, voiceovers, or live performance capture, especially with high-sensitivity dynamic or condenser mics.

Historical Context

The RS-B605 was introduced at ¥54,800 around 1987, late in the high-fidelity cassette era. CDs had begun to climb by then, but cassette decks still appealed for portability, recording capability, and lower cost. It was built in Japan, at a time when offshore manufacturing was becoming more common among competitors.

Collectibility & Value

Service manuals and instruction guides are available through online archives, so restoration is feasible for technically inclined owners. Specialty vendors like WebSpareParts offer the plunger (Pos.25) and idler assembly (Pos.24), at $14 and $39 respectively. A replacement power cable is available for under €6. Common issues are degraded rubber components, particularly the pinch roller and drive belt, which can make the deck stop during playback. One owner noted that a stable power regulator contributes to "firm bass" and "crisp, clear treble," implying that power supply integrity matters for performance. Market conditions vary widely. A unit in excellent used condition was listed on Reverb for $135 plus $35 shipping, and a Catawiki auction closed at €135 against an expert estimate of €150. A Reddit user in December 2024 reported picking up a unit for just $38 and called it a "good deal."

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