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Arcam Delta Black Box

Discussion in 'd.i.y.' started by barrymidd, May 26, 2010.

  1. barrymidd

    barrymidd Who me?

    There are bound to be knowledgeable people who can help me with this; I have just retrieved the above DAC from the loft where it has resided, unloved, for the last 10 years or so. When I put it there, it was working fine, but I have just tried it and it gives out no signal from either channel output.
    What is likely to have gone wrong with it just by sitting in the loft for 10 years? Also, if I have to repair it, this would seem the ideal opportunity to upgrade it and as it was a really good DAC in its day I would imagine many people have had a go at improving its performance over the years.
    I am wondering just how good you could make it by comparison the modern high end DACs.
    Any help/advice/links would be much appreciated.
    Barry
     
  2. yairf

    yairf Trade: Teddy Pardo Audio

    I wouldn't bother.
    Yes, it does have a TDA-1541A inside, but the rest is nothing to write home about.
    In case you insist, you'd need a scope to trace the signal...
    Yair
     
  3. prowla

    prowla pfm Member

    I had a listen to one of those in the 80s, and it sounded pretty good.
     
  4. barrymidd

    barrymidd Who me?

    That is why I was looking at upgrading
     
  5. yairf

    yairf Trade: Teddy Pardo Audio

    I once considered picking up a BB1 for free. Then I looked at the diagram and gave up the idea: the digital receiver section is old fashioned and far from current standards. The analog section can be rebuilt with ease but then you'd need a perfect digital transport to get something out of it.
    Another alternative could be something like this:
    Take a good digital receiver board (SPDIF or USB, or both) such as DDDAC, and hook its I2S output directly into the 1541, then throw away the whole analog section and replace it with a line transformer (for I/V) and maybe a gain stage.
    On a second thought - putting together a DDDAC will get you there quicker and without the mess...
    Yair
     
  6. rontoolsie

    rontoolsie pfm Member

    I heard the original Black Box when it first came out. It sounded not too different from the standard ouputs of my Phillips CD80 at the time.. which is to say soft, fuzzy and with very little in the way of PRAT. Upgrading the parts (yes modding digital gear back in 1986 was in its nascent stages) made a considerable improvement. I think one of the (many) weak points -as mentioned above- was the Yamaha receiver chip.
     
  7. zanash

    zanash pfm Member

    its probably the caps ..that have dried out
     
  8. RustyB

    RustyB Registered Ginga

    I have modified about half a dozen BB1's and BB2's. In stock form they sound pleasant but veiled. Upgrading a host of passive components removes the veil and results in a DAC that is highly enjoyable, in a warm and involving LP12-ish manner. A proviso is that a really good transport is essential to realise this performance. Note that the circuitry is all discrete and DC-coupled at the output.

    Obviously even the modified BB won't compete with DAC's using more modern D>A technology in terms of detail resolution, but the continued popularity of machines using the TDA 1541A proves there are people out there who value the musicality higher.

    At a guess I'd say you've probably got some dead electrolytics somewhere. Starting point would be to measure DC volts around the circuit.
     
  9. yairf

    yairf Trade: Teddy Pardo Audio

    There is no receiver chip per-se, it is made out of stand alone line drivers, decoders and PLL components. Interesting effort but far from current standards.
    Yair
     
  10. barrymidd

    barrymidd Who me?

    I am a fan of the Philips chip (the Black Box has the single crown version which is V good) and have just been through an evaluation process of very high end DACs with fellow fish IWC Dopple. They all do things very differently, but we came to the conclusion that differences in digitally generated signals are much harder to pin down and make conclusions about than pure analogue signals that can be more easily recognised. The conclusion we both came to was that overall the compromise was always between resolution/prat and overall emotion and musicallity. The Philips chip does the latter really well but I would be disappointed with a dull or veiled sound to go with it. I generally find "Vintage sounding" kit much more to my taste than "The Naim Sound" which can be too reveiling and dry at the expense of emotion and just pure "listenability" to me. I say all this to try and explain why I think the Black Box may be worth upgrading. I use a Marantz CD80 which although getting on, has an excellent quality transport mechanism and a very good, switched digital output and the Black box would be used with this player.
     
  11. darkmatter

    darkmatter pfm Member

    Very interested in the mods you have carried out as I may have a go at modding a one or a two in the near future, any preference between the two DACs?

    Cheers,

    DM :)
     
  12. RustyB

    RustyB Registered Ginga

    I'd go for the BB2 as a preference, different input board with Toslink socket.
     
  13. darkmatter

    darkmatter pfm Member

    Thanks for that, what mods did you carry out, did you NOS them?

    Cheers,

    DM :)
     
  14. RustyB

    RustyB Registered Ginga

    Pretty extensive.

    Starting at the front, I remove the RCA socket from the i/p board, replace with panel-mount BNC hard-wired with 75 ohm mic cable.

    Most of the PSU caps get replaced with Pana FC's, diodes with 11DQ10's, small elcaps with Stargets, resistors downstream of the DAC with Vishay-Dales, analogue outs repleced with decent quality panel-mount sockets. Sometimes I omit the 0.8V output.

    The last one I did was NOS'ed, using the NET Audio board designed for the AA5. I only had time for a quick listen before it went to it's new owner, but it did seem to be well worth doing.

    Also damp the case and lid with Soundcoat.
     
  15. darkmatter

    darkmatter pfm Member

    Thanks for the detail.

    It is the NOS mod and how it would sound as a stand alone DAC that is of real interest to me, if I find a BB2, perhaps we could have a chat?

    Thanks :)
     
  16. RustyB

    RustyB Registered Ginga

    Yep, sure.
     
  17. niek024

    niek024 New Member

    it's an old thread, but maybe someone is still listening.

    I'm fairly adept at soldering, but complex electronics still elude me sometimes. So I was hoping for some practical advise on the Arcam Black Box 1 that i recently bought because of its TDA1541-chip.

    The biggest disappointment about the machine is the fact that the unit doesn't seem to decode 48kHz signals (I hadn't thought of that, unfortunately). I've read that people do some extensive modifications, and I wondered if anyone around could advise me on how to get the machine to accept 48kHz?
    Using a different spdif-receiver and feeding the i2S-data to the TDA seems to be a possibility, but ebay only shows me rather expensive input-boards... Wouldn't it be possible to modify the original Input Board?

    The second worry is the -6.2V that the DAC is fed. I've read about two possible ways to fix that:
    1) changing resistor R309 from 490 to 360 Ohm (which, IIRC would also affect the -6.2V that the inputboard is using), or
    2) replacing the 'wire link' (meaning TP36?) with a resistor.

    Which of these solutions would be preferable? And what value should i use for the resistor on that 'wire link'?
     
  18. RustyB

    RustyB Registered Ginga

    What's the problem with the -6.2v feed?
     
  19. niek024

    niek024 New Member

    I was under the impression, the -6.2V is exceeding the -5V specifications from Philips, leading to an early demise of the chip. But maybe i'm too concerned about it?
     
  20. Nigel

    Nigel pfm Member

    Regarding these DAC's, Black Box 1 & 2, technically, which should be the better output? The 0.8V line level or the 2V CD level output?
     

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