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Best CD clock upgrade?

Discussion in 'd.i.y.' started by hacker, Dec 7, 2005.

  1. hacker

    hacker Delicious and nutritious

  2. cliveastro

    cliveastro pfm Member

    I have Trichord clock 4 which works with the never connected psu. But I did have to clean up the mains supply to get the best out of it.

    Clive
     
  3. ian r

    ian r 401's Nakman

    This is intersesting chaps .....some ... er much more detail would be walcum
    ianr
     
  4. Andrew L Weekes

    Andrew L Weekes Senior Reverse Engineer

    Carl,

    I'm not getting involved over there...;)

    In answer to your question, the first problem is none of the aftermarket clocks are specified. Ask the manufacturers for verified specs and you'll meet with silence, with one sole (AFAIK) exception - Guido Tent's oscillator module.

    Here's my suggestions: -

    1. Buy a Tent oscillator module (cheap) and add a good PSU - I can help with that ;). Needs a bit of work to get it right though.

    2. Buy a complete Tent oscillator / PSU solution.

    2. Buy one of those Audiocom ones from eBAY and fix it (I can help with that too, as I have one here). It's a nice small board and adding a single cap and resistor can lower PSU noise 15-20dB (which will lower jitter). The downside is they seem to have used some nasty logic for squaring up the o/p which has a nasty PSU load, the rest of the circuit is competent though and the oscillator cct is good. I'm hoping to report more on this once I've had chance to do some proper measurements (once I've built a phase noise measuring system!).

    3. Read this and build one of Jocko's circuits.

    4. I suspect the latest LCAudio clock is very good, but to be honest it's too pricey, in my view.
     
  5. hacker

    hacker Delicious and nutritious

    Thanks Andy.

    I used a Tent XO module in my last player, the CD6000KI. PSU was a crappy little c/t trafo. rectifier, smoothing and one of your SRs at 5v. It worked a treat although I suspect the psu could still have been made a lot quieter.

    Martin Clark has helped me out (see this thread: http://www.pinkfishmedia.net/forum/showthread.php?t=17825) and we've come up with a nice capacitance multiplier circuit to keep out the noise:

    [​IMG]

    This is to be fed into one of your superregs before feeding the clock. I may just go down the route of getting an XO2 and build the above PSU for it, as I'd never be able to construct as good a PCB for a diy XO module.

    Les reckons the Trichord4 is a good clock in the Naims though... ah, the choices.

    You mentioned that you could help with a psu for a Tent clock. Care to share any tips?

    Cheers,
    Carl
     
  6. ian r

    ian r 401's Nakman

    Chaps
    this item is beginning to hum but its the 'sound of people talking' not a harmonic from the OEM chip!

    I want more of this detail ...... if possible...... best wishes
    ianr
     
  7. Andrew L Weekes

    Andrew L Weekes Senior Reverse Engineer

    The best PSU I've ever built for a clock supply was based on an AD797.

    The ones I've done were a modified super-reg, but I reckon it could be simplified a lot - the AD797 has enough current capability from it's o/p stage to supply most clocks.

    The AD797 needs a supply (a simple 3-terminal or maybe just the mutliplier supply above would do it on it's own) it then just needs configuring as a simple reference supply, buffering a suitable reference (e.g. a 2.5V LM336). For the cheap seats an LED and an adjustment on test of R2 / R3 to set output V could do just as well, LED's are quiet devices and you get a visual indication something's working ;)

    I've attached an idea, which I've not built myself but should work - the clever bit is C2, we'll see if anyone can work out what it does (clue, read the AD797 data sheet. Martin Clark is excluded, 'cos he knows!).

    C5 may need some experimentation for stability, you gotta do something yourselves :)

    For a dirt cheap version you could use almost any old op-amp with suitable curernt capability and eliminate C2, the bipolar AD797 is great for low noise (and the C2 'magic' is only available with this device), but not so good for EMI immunity, hence the o/p choke.

    Andy.

    P.S. Don't forget to add some op-amp decoupling
     
  8. martin clark

    martin clark pinko bodger

    Hey Andy that looks rather like the one in my 3.5 ;) It's been running two years without a hitch.

    Later this week when home I'll post a pic. It's all dead-bugged together, uses a 7812 as a pre-reg with the 7812 reference leg driving an LED as the reference (since this a very convenient constant-current source). The cap multiplier precedes it all to kill noise on the psu rails.

    As a quick n' dirty trial an NE5532 works well. C5 is essential with a '797, the opamp will oscillate without. 10uF tantalum or oscon is ideal. Best measurements come from 47-100nF SMT ceramic right at the tent XO also; there's nothing I can see on the scope except just 2mV of ripple at the clock frequency :)
     
  9. Andrew L Weekes

    Andrew L Weekes Senior Reverse Engineer

    That's smart (and cheap); I like it!

    Andy.
     
  10. trancera

    trancera pfm Member

    Post the working (clever) circuit please martin, im watching Carl's latest bodge with interest ;)
     
  11. S-Man

    S-Man Kinkless Tetrode Admirer

    Distortion reduction at hf
     
  12. martin clark

    martin clark pinko bodger

    Yes, but it's the side effect that has we're interested in. Look at Fig21 on the datasheet...
     
  13. S-Man

    S-Man Kinkless Tetrode Admirer

    Ahah!
     
  14. RichardH

    RichardH Bodging pleb

    Andy - do you mean the Superclock2? I'm still girding my loins to attach one of these to my CD17, so if there's some little extras I can do to it before it goes in, then I'm all ears!
     
  15. Andrew L Weekes

    Andrew L Weekes Senior Reverse Engineer

    Yep, that's the beastie - give me a day or two, I'll gather details.
     
  16. Andrew L Weekes

    Andrew L Weekes Senior Reverse Engineer

    I think Martin means something like this - this is one of the rare cases where maybe a blue LED (or similar high Vf LED) could be better, the voltage will have to be adjusted using R2 / R3 to set Vout to the required voltage.

    Andy.
     
  17. martin clark

    martin clark pinko bodger

    Yes that's about it.

    BLue LEDs have a forward voltage of c.3v but seem to have higher dynamic impedance and noise. I used a plainjane green LED, which gives about 1.94v.
     
  18. martin clark

    martin clark pinko bodger

    ...since here's the circuit as-built in a diagram I never got around to posting on the 3.5mods page:
    [​IMG]
    The LED reference gives a hair under 2v, which is well filtered by the 10k/3.3uF filter - the 3.3uF caps are film types to avoid leakage noise. 10uF types can be tantalum or oscons; the 47uF cap ditto - this rolls off noise gain and is recommended. L1 is simply a ferrrite bead placed right next to the oscillator package power pin, which is also decoupled with a 47nF ceramic SMT cap. Note the opamp is supplied via a 0.5ohm resistor ; this does double duty, stoppig the 7812 oscillating with the film cap on its output, and providing a convenient place to monitor current draw. With the Tentlab XO running on the output the whole thing draws about 20-21mA; if you measure 30mA or more it's highly likely the 797 is oscillating at HF (an easy way to check for those without an o'scope).

    This circuit also works very well with an NE5532, which actually makes it very cheap and effective. It's all put together freehand on a piece of copperclad PCB material about 30 x 60mm including the XO module.

    BTW input to the left of the circuit is supplied from a very simple centre-tapped transformer/fullwave rectifier/1000uF PSU, the only wrinkle being a 60uH/0.4ohm choke (from the bits box) before the 1000uF electrolytc which completely kills the reverse recovery spike from the cheap diodes. All remaining garbage is swept up by the simple cap multiplier at the input.
     
  19. joecrow

    joecrow pfm Member

    some advice please,
    I am mainly clueless about clocks and power supplies,but am trying to learn
    i am visiting uk from australia and have picked up a Teac t1 transport and have been advised to fit a tricord 4 clock and never connected power supply,circa £400 fitted
    i will be using the transport with a dac that has the latest anagram module in it (audiomecca)
    is this the best bang for the buck given that I am highly skilled at diy only if it involves timber and I dont want to stuff up a mint demo Teac transport
    Cheers
     
  20. RichardH

    RichardH Bodging pleb

    I've done a few DIY modding jobs, and when I recently got a new clock for my CD player, and merrily popped it open, I wasn't quite prepared for the tinyness of the components which you need to remove and then replace. I closed the lid again and took a few deep breaths, and ran away to PFM for advice. I'll be attempting it shortly, but if I were you I'd open the transport up and look inside BEFORE buying any bits - see if you feelyou'll be comfortable working on it.
     

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