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Arcam Delta 80 AM/FM Stereo Tuner

Arcam are a British hifi company based in Waterbeach near Cambridge in the UK.

They have produced a wide range of quality hi-fi components over the years. In the 1980s they had two levels of components - an entry level range called Arcam Alpha and a the higher priced and more exotic Arcam Delta range. This web-page is about the Arcam Delta 80 AM/FM tuner.

This tuner has excellent sound quality as you'd expect from an Arcam product. However, it's also an interesting device because it doesn't contain on the inside quite what you'd expect having looked at the front.

External views:


A clue to the unusual insides of this tuner comes from the controls on the rear. While it has the appearance of a digital synthesized tuner on the outside, the insides are actually of a traditional analogue tuner. It simply has a digital frequency display instead of a "stick on a piece of string" tuning indicator. The presets are set here by hand, and separately for AM and FM tuning. LW and MW share their presets.

This odd combination of analogue and digital is not necessarily a bad thing. Many people believe that analogue tuners sound better than digital tuners, and of course given that DAB is broadcast with such a low bitrate (especially in the UK), a good FM tuner provides the best off air sound quality you're likely to get.

I don't know how many of these tuners were made, but my serial number is just 45.

Inside the box

Compared with a more modern digital synthesized tuner, this box filling, and apparently hand drawn, PCB contains a huge number of components with lots of space between them. No wonder it was an expensive tuner when new ! Just behind the tuning control at the front right you can see a flywheel on the ball bearing potentiometer used for manual tuning voltage. This gives a nice heavy feel to the tuning action. The back panel tuning presets also are small potentiometers, and front panel switches give a choice of voltage derived from these or from the front panel manual tuning control.

Circled in Yellow are the CMOS 4000 series logic chips which operate the front panel frequency display. Circled in red is the actual analogue tuning and audio output circuitry.

The top right hand corner is the power supply, using a single LM317 regulator chip.

The analogue circuitry

The analogue circuitry is, I think, fairly typical of the time this was built. An FM front end in a metal box is labelled FC1U129A / 6J73107A, and there are CA3189 for FM IF, TCA4500A stereo decoder, LM324 quad op-amps. I can't help but feel that the LM324 is perhaps not the world's greatest quad op-amp chip. All these chips are socketed, so changing the LM324 for a more modern quad op-amp would not be difficult to do and might improve sound quality further.

The AM radio uses a TDA359 IC.

Comprehensive silk-screening on the board will help with any maintenance that might be required in the future. Apart from the LM324s which seem to have been hanging around since 1984, the other analogue chips have 1988 date codes, and I believe that was the year of production of this tuner.

The digital circuitry

The digital circuitry consists of a 3.2768MHz crystal and a bunch of CMOS 4000 series logic chips: CD4013, CD4020, CD4029, CD4069, CD4073 and CD4543, all oddly with 1986 date codes and all soldered to the board.

Silk screening here shows which chips decode which digits of the display (MSD - Most Significant Digit, LSD - Least Significant Digit).

No modern device would contain so many parts as this. Even if the aim was to produce an analogue tuner, this counter could easily be implemented on the corner of a custom chip.

Specifications and manual

The FM tuner specifications are as follows:

  • Sensitivity 1.4uV
  • THD: Mono < 0.15%, Stereo < 0.25%
  • s/n ratio: Mono 74dB, Stereo 70dB
  • Frequency response: 20Hz - 12kHz +/- 0.5dB, typically -2dB at 14kHz
  • Channel separation at 1 kHz: > 40dB
  • Pilot tone suppression: > 50 dB
  • Alternative channel suppression: > 60 dB
  • AM suppression: > 50 dB
AM tuner specifications:
  • Distortion typically 0.4%
  • s/n ratio: 50dB
Misc:
  • Size: 430 mm x 265 mm x 60 mm
  • Weight 3 kg

Arcam have the original manual for free download on their webpage.

Conclusion

The Arcam Delta 80 is a good tuner and FM radio remains a high fidelity source of highly enjoyable music if you find a good radio station (e.g. NPO Radio 4 here in the Netherlands, BBC Radio 3 in the UK). If you find one of these tuners for sale, it's probably a bargain in comparison with it's original 1988 price of about £400.

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