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Old 28th February 2010, 10:29 PM   #11
Cobra2 is offline Cobra2  Norway
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Old 30th July 2013, 11:53 AM   #12
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Originally Posted by fftulip View Post
I suggest that you try the QuadrophonicQuad Forums for ideas:
QuadraphonicQuad Forums
There is at least one design there (Dorren, under Discrete LP Formats) that uses up to date, near state of the art circuitry.

I have a vintage Panasonic CD4 decoder and matching cartridge ("semiconductor"), but I've only listened to it briefly so far. The decoder design is only what I would call "mid-fi", using mostly discrete parts plus a few old style op-amps (lots of Japanese parts probably obsolete nowadays, no audiophile grade caps, etc). I managed to pick it up for fairly cheap but if you want audiophile sound you can probably do a lot better using modern IC's and better quality parts. I've heard that the Technics version of the decoder is better quality than the Panasonic but have no first hand experience with it.

You don't really need a "special" needle for CD4, just a good cartridge that has extended high frequency response to well over 20KHz. A Shibata style tip will help do that, but it's not absolutely necessary.

The new Dorren CD-4 demodulator seems to be on hold, as Lou Dorren has not been active at the QQ forum for over half a year. I propose people should get some old 4DD-5 on ebay, and modify these according to some postings on the web. I do not have a link handy... Or maybe even implement a more modern front end. By that I mean replace the RIAA stage with something designed after 1972.
Or if the quad LPs from our youth maybe now are available on SACD, DVD-Audio or BluRay, and in surround, buy these instead.
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Old 30th July 2013, 02:42 PM   #13
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There are many sites offering free schematics of old equipment, one is HiFi Engine | Download Free User/ Service Manuals, Amplifier, Receiver, CD, Tape, Tuner, Video or Nostalgia Air my fave is Audio Circuit Denmark but this site is temporarily down. I am sure you will be able to find a circuit but getting the ICs will be a bummer! E
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Old 30th July 2013, 02:46 PM   #14
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You must re-use the demodulator parts. Just replace the input amplifier with RIAA with something newer. And probably the power supply.
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