RFT GC6131

Dates

General

• Manufacturer: VEB Elektronik Gera (Germany, GDR)
• Model: Geracord GC6131
• Type: Stereo cassette deck, shelf unit (HiFi component)
• Years of manufacture: 1985 - 1989
• Manufactured in: Gera (Germany, GDR)
• Color: metal housing black, front black or silver metallic
• Remote control: not available
• Power consumption: 15 W (according to the imprint on the back of the device)
• Dimensions: 390x130x272 mm (WxHxD)
• Weight: 4,8 kg
• Original price approx.: 1.350 M (DDR)

Connections

• Number of inputs: 4

Audio/Tape (5-pin DIN socket, current sink, sensitivity 0.5 mV/kOhm source resistance, requires approx. 150-500 kOhm series resistor in the source device or in the cable, otherwise overload of the input amplifier even before the recording level controls) Phono (5-pin DIN socket, without equalization amplifier, for high-impedance ceramic pick-ups, sensitivity 500 mV at 1 MOhm load)

• • 2x microphone (5-pin DIN socket separately for left and right channel, sensitivity 0.6 mV, >6 kOhm)
• Number of outputs: 2
  • Audio/amplifier (5-pin DIN socket, also used as audio/tape input, output > 500 mV at load >= 10 kOhm at reference level)
  • Headphones (5-pin "cube" DIN socket, >= 3 V at load impedance >= 60 Ohm)

Technical Data

• Audio heads: 1 record/playback, 1 RF erase head.
• Erase/pre-magnetize frequency: approx. 83 kHz
• Motors: 1
• Synchronisation fluctuations: <= 0.18 %
• Average tape speed deviation from set point: <= +/- 1.5%
• Tape types: Type I, II and III (FeCr)
• Frequency response: 35 ... 12500 Hz (Fe2O3 type I band), 35...14.000 Hz (CrO2 type II band), 35...14.500 Hz (FeCr type III band)

Distortion factor: K3 <= 3%, K2 <= 2%

• Fremdspannungsabstand: für alle Bandsorten ohne Rauschminderung >= 45 dB, for Cr/FeCr with DNR compander: >= 48 dB
• Noise-to-noise ratio:
  Type I 48 dB without NR / 51 dB with dyn. low-pass "RVS" / 56 dB with compander "DNR
  "
  
  Type II 50 dB without NR / 54 dB with dyn. low-pass "RVS" / 58
  
  dB with compander "DNR"
  
  
  Type III 55 dB without NR / 62 dB with dyn. low-pass "RVS" / 67 dB with compander "DNR
  
  
  "
  
  
  
• Crosstalk attenuation (1 kHz): >= 30 dB
• Cancellation attenuation >= 65 dB
• Sidetrack attenuation (1 kHz): >= 60 dB
• Auto-Reverse: not available
• Title search: not available
• Dolby: Dolby B compatible noise reduction system "DNR
• MPX filter: yes, switchable
• Recording control: 2 knobs separately for left and right channel
• Pitch control: not available
• CD synchro recording: not available

Special Features

• mechanical 3-digit tape counter with zero stop function from all tape run functions (memory).
• LED output indicator (2x10 LED)
• Rec Mute button (function to insert pauses, button locks)
• Noise reduction system "RVS" (only on playback side, attenuates level-dependent high frequencies)

Noise Reduction System "DNR" (Compander System, Dolby B Compatible)

Remarks

The GC613x series was a further development of the GC603x series to meet the HiFi standard. The drive was given an electronically controlled DC motor that ran permanently when the unit was switched on, but was not convincing in a vertical installation position (originally designed for horizontal installation in the Geracord GC6010, 6020 and 6030 top loaders), not least because of the exclusive use of plastic parts. The mechanical workmanship is, although the device is robust, quite poor. Sharp-edged front panel, fixation of the cassette in the cassette compartment insufficient (tilted slightly when retracting the headstock), adjustment of the drive switches partly insufficient (tape end cut-off triggers when pause button is held fully depressed in anticipation of a recording), danger of loose contact due to oxidation of the A/W switch mechanically moved by the drive via a metal rail on the circuit board.

The sound head X2C70 was subject to high wear (abrasion).

The robust device could be operated completely manually (no automatic tape selection etc.) and was therefore very popular with disc jockeys.

Achievable recording quality was amazingly good, if exactly calibrated to the tape type (internally on the circuit board). "West" tapes required new calibration from 1990, otherwise extremely treble-heavy and pumping effects of the DNR compander due to higher tape sensitivity than with GDR tapes.

Headphone amplifier very powerful, but clear distortions when falling below the minimum headphone impedance of 60 ohms. Simple bridging of the stereo channels at the headphone plug to judge the audio head azimuth setting results in strong distortions due to mutual loading of the output stages of both channels.

Please note: above data from the original service manual refer to the GDR standard TGL 27616/02 and HiFi according to TGL 28660/04, which was based on the DIN standard. Especially the frequency response should not be compared to that of Japanese decks, which were often measured 20 dB below standard level to hide the tape saturation in the highs.

Balance in 2017: the present specimen still works completely, belts and slip clutches are intact original parts, now 30 years old.

Other models of the same series: GC6132, GC6133.
These variants were visually adapted to other HiFi components, but were only produced in small numbers.

Pictures

[[1]]

Links

RFT-HiFi.co.uk: GC6131

References

Technical data from: Service manual HiFi cassette deck GC6131, VEB Elektronik Gera, printed matter no. III/29/1 Mn 102/86 (1986).



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