A portable stereo cassette deck built for field recording and mobile use, with Dolby NR and dual power options.
Overview
The Technics RS-646DS is a portable stereo cassette deck made for high-quality recording outside the studio. It was built with professional use in mind and works as a self-contained field recorder. It runs on AC power or eight D batteries. It was used in scientific audio capture, including field recordings of cranes with external microphones. It has a 2-head configuration, Dolby noise reduction, and a built-in 10 cm monitor speaker with 0.8W output. It's big and heavy, but it's designed for mobility and reliable operation in remote locations.
Specifications
| Power consumption | Approx. 9W |
| Power sources | 100 VAC, 50Hz/60Hz; 12 VDC (8 D Batteries) |
| Frequency characteristic Normal | 30 Hz to 14 kHz |
| Frequency characteristic CrO2 | 30 Hz to 16 kHz |
| Signal-to-noise ratio Dolby out | 50dB |
| Signal-to-noise ratio Dolby in | 5 kHz or more, 10 dB improvement |
| Wow flutter | 0.08%(WRMS) |
| Input Sensitivity / Impedance Mic | 0.25 mV (-72dB) / 400 Ω ~ 10k Ω |
| Input Sensitivity / Impedance Line in | 60mV(-24dB) |
| Output Level / Impedance Line out | 420mV/50k Ω or more |
| Output Level / Impedance Headphone | 65mV/8 Ω |
| Monitor output | 0.8W |
| Speaker | 10 cm cone type |
| Head configuration Recording | LH For |
| Head configuration Erase | Double Gap Ferrite |
| Motor used | One electronically controlled DC motor |
| Semiconductor used | Transistor: 39; IC: 2; Diode: 22 pcs |
| External dimensions | Width 363x Height 106x Depth 280 mm |
| Weight | Approx. 5.7 kg |
Design
The RS-646DS uses an electronically controlled DC servo motor for stable tape transport. It has a full auto-stop mechanism with a silent stop function to reduce mechanical noise. A level lock handles smooth fade-ins and fade-outs, and a built-in limiter prevents distortion on high-input recordings. The Dolby NR circuit reduces tape noise. A 2-stage tape selector adjusts bias and equalization for Normal and CrO2 tapes. The erase head is a double-gap ferrite design for efficient erasure. The recording head is an LH type, known for durability and re-recording performance. The amplifier prioritizes linearity and low noise, with help from integrated circuits. Power can come from AC, D batteries, or a car battery. A battery check switch and a meter light switch make it easier to use in the field.
Product Family
A related model, the RS-686D, is a three-head variant and may be considered a sibling unit in the Technics portable cassette lineup.
Market
The Technics RS-646DS turns up on eBay, often with belt replacement kits available. That points to deteriorated rubber belts as a common maintenance issue. The chassis is labeled as having no user-serviceable parts inside.
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