Digital Isolation ......and a few hints on CDP and DAC mods

Discussion in 'DIY Discussion' started by zanash, Jun 20, 2003.

  1. zanash

    zanash

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    This is again a hangover from the old place.

    The current status is that one of the devices is out there, its either in or on its way to a voulenteer. These rare people who out of the goodness of thier own heart, will have a listen, make a few notes and then pass the device to the next due gooder on the list.

    Well thats the idea anyway, currently It's with number one or intransit to number two.

    I'm still to get number ones views......so if your looking at this and you know who you are " send me the bl**dy questionaire !! ".

    For those who read this and haven't foggiest, here's a summary.

    The device is a pulse transformer, normally used in digital communications. I read a piece on the web and a thought occurred to me that this could be used in between CDP and DAC. A long look at current devices seem's to show no one implimenting the idea.

    So a device was built and installed between my test bed transport and DAC, well stunned I was, gob smack. Took it out listened again yes a lot missing, put it back........ hell's teeth.

    So the question was what level of gear does the effect stop, or become less apparent. Hence the test, by the good people mentioned above.

    I'll colate the returns and now display the results on this forum !!



    Oh yes I hear you ask so what CDP and DAC did you use.

    The CDP is an old Denon dcd920 [£25 from one of those modern pawn brockers]

    I 've done a little work on it though [sic]
    In order of the magnitude of improvement

    A. swapped the bog standard diodes for 11dq10's schottky diodes. This was a supprise to me and was one of the last component mods, I carried out.
    B. Changed the Op amps for BB opa2604 biased into class A.
    C. replacement of caps in the audio output stage by stargets
    D. replacment of caps in audio and digital stages with Oscons. The bypassing of all electrolytics with 1uf wima's
    E. This may be interchangable with D. Repacement of all resistors in the digital and output stages with holco's
    F. disconection the headphone output, no I don't know why but it definatley sound better without it.
    G. Removal of the silly feet and beefing up the box, which includes damping the sides top bottom and base this rubber and bitumen sheet.
    H. Earthing and shelding using copper foil of all chips and flying leads, which are then grounded to a star earth.

    I. Must be something else, but my memory has not been the same since my blow to the head [RTA] Oh well.

    The DAC is a Music Fidelity X-DAC [again second hand but bought through the local paper]

    So I did all the above except to damping the unit. But the biggest difference came when I changed the wallwart plugin transformer. The unit takes 230vac and reduces it to 12vac. So when I saw in a local Government surplus store, a 300va ish 230v ac to 12v ac. I had to have it. "A tenner to you mate" was the princely sum. A bit of internal surgery, ie a mains lead and 12v output lead, a small plug and roberts a close relation to your mother.
    Stunning difference, It's no wonder MF came out with there own version. From a unit that only got used now and then its now a perminent feature to run the CDP.

    Comments and qusetion are welcome....though I might not know the answers.
     
    zanash, Jun 20, 2003
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  2. zanash

    LiloLee Blah, Blah, Blah.........

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    Eh? I don't have anyone in my Family called Robert. Is my Mum having an affair?:eek:

    Lee
     
    LiloLee, Jun 20, 2003
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  3. zanash

    zanash

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    Isn't Bob your uncle ? Sorry my mistake !
     
    zanash, Jun 21, 2003
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  4. zanash

    lhatkins Dazed and Confused

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    I'm glad your keeping this one going Pete, cos I would certainly like a look in next time its doing the rounds.
     
    lhatkins, Jun 21, 2003
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  5. zanash

    zanash

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    No problems .......

    How are the plug ?, still tight I bet !!

    I'm looking at bullets now as well as the Profi's
     
    zanash, Jun 21, 2003
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  6. zanash

    MO! MOnkey`ead!

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    this still going? Where's it at now?
     
    MO!, Nov 4, 2003
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