My new DIY USB headphone DAC+AMP (photos)

Discussion in 'PC Audio' started by MWP, Sep 1, 2005.

  1. MWP

    MWP Member

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    I have to show off my latest creation :)

    Its a fully USB powered headphone amp + dac which uses:
    - PCM2707 (USB reciever)
    - PCM1798 (DAC, Dynamic Range: 123 dB, THD+N: 0.0005%)
    - OPA4228 (for I/V)
    - TPA6120 (Current-Feedback headphone amplifier, Dynamic Range >120dB, SNR 120dB)

    Its mounted in a Hammond extruded aluminium case.
    The case is slightly smaller than a credit card.

    All done & working:
    [​IMG]
    [​IMG]

    The innards:
    [​IMG]
    [​IMG]

    Schematic is here:
    http://www.overclockers.com.au/~mwp/temp/usb-headphone-dac.gif

    It sounds friggin awesome ;)
    Well... compared to the amps, soundcards, etc ive used before it does anyway.

    Very smooth freq response, excellent bass response, clear highs (maybe a little too bright).
    Perfectly slient when nothing is playing (very important to me, i HATE background noise).

    It draws around 500mA at idle, around 600mA while playing music at an above normal level.

    To have it work out this well after a few days working on it, im a very happy camper :leet:
     
    Last edited: Sep 1, 2005
  2. Circa_Survive

    Circa_Survive Member

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    awesome, now only if i could read that crap and had the skill to make one myself id be set, haha

    dont feel like making one for me too? it looks very nice
     
    Last edited: Sep 1, 2005
  3. MrSmith

    MrSmith Member

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    Thats awsome!

    I WANT ONE! does the quality differ through this little black box? :D (better/worse?)
     
  4. Snufkin

    Snufkin Member

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    Nice work! :)
     
  5. dakiller

    dakiller (Oscillating & Impeding)

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    The tpa6120 is a very nice headphone amp chip, my current headphone amp is designed around it and for what it is, it is very hard to beat in performance
    Though I didn’t go for the USB to I2S to DAC to I/V in mine, I just got a simple USB to analog pcm2702 chip for the moment that does a very nice job. But I do have a full blown dac on the way (after I replace 2* pcm1704 DAC chips that will set me back over $80 to get)
     
  6. mAJORD

    mAJORD Member

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    looks great , WD with etching yourself too, looks like it came out well :thumbup:
     
    Last edited: Sep 1, 2005
  7. Robzy

    Robzy Member

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    Correct me if im wrong, but didnt i see that posted on head-fi just a couple of days ago? ;)

    Did you use eagle to design it? If not what did you use?

    Rob.
     
  8. d-cee

    d-cee Member

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    wow how much did it cost?
     
  9. OP
    OP
    MWP

    MWP Member

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    Yup i did :)

    I used Protel DXP 2004 SP1.

    Actually, just the price of the box... $17.
    Everything else i already head or got via samples.
    There is probably >$80 worth of parts in it though.
     
  10. TripleAI

    TripleAI Member

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    Awesome! :thumbup:

    btw, where did you get the Hammond case?
     
  11. SilverRayne

    SilverRayne Member

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    You can get those extruded al hammond cases from altronics - I think K&W and Wiltronics sell them cheaper though.
     
  12. sagey

    sagey (Banned or Deleted)

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    Serious, only $100 worth of parts.

    I'd make one if i knew how :(

    Nice job btw :thumbup:
     
  13. Robzy

    Robzy Member

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    Any chance of getting a copy of the schematic? Pretty please! :p

    Rob.
     
  14. Robzy

    Robzy Member

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    I was hoping a copy of the actual file... so that i can build the same DAC ;) (Of course due credit given to you).

    Rob.
     
  15. Robzy

    Robzy Member

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    I was hoping a copy of the actual file... so that i can build the same DAC ;) (Of course due credit given to you).

    Rob.
     
  16. OP
    OP
    MWP

    MWP Member

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    Possibly.
    The schematic and PCB will need a lot of design changes first... i completley screwed up the design around the PCM2707.
     
  17. Robzy

    Robzy Member

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    Eep... dont worry then. The reason i was asking for it was so that i wouldnt need to do the design around the PCM2702 and all that jaz.

    Thanks anyway, and awesome work!

    Quick question, what is on the green boards?

    Rob.
     
  18. mAJORD

    mAJORD Member

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    ahh , so you're not blind then ;) , sorry.

    should have known, i too hate having to redo everything from essentially a hard copy :)

    MWP, did you prettymuch take it from the datasheet for the headphone amp? im sure its either that IC or maybe the DAC that has an example of something similar to what you made.

    I wouldn't mind making a reasonably high end spdif-DAC, these SUB dac's sound interesting tho. How do you actually use it as a virtual 'soundcard' from windows, and what options are there.

    im acutally surprised at the low number of ppl DIYing decent dac's, and im not sure why it is, considering a commerciald one is so expensive :Paranoid: . the problem with the spdif outs of most cheaper soundcards from what i can gather is the high jitter rate in the clock, and it can't be unsyncronised afaik. perhaps its not worth doing.
     
    Last edited: Sep 2, 2005
  19. aXLe

    aXLe Member

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    Wow - nice project :)

    I think 600mA is a little too high (by 100mA) for USB bus powered devices if sticking strictly to the specification, but no doubt it works fine though.

    Is that chip natively recognised by the OS without installing drivers etc?

    How do you direct the audio via the chip? I guess this would be what they use in the USB headphones etc these days?

    Must look up the specs on it - sounds good :)
     
    Last edited: Sep 2, 2005
  20. OP
    OP
    MWP

    MWP Member

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    Voltage step up/down converters (5V to +12V and -12V).

    Yeh, the DAC->IV->TPA came from the TPA data sheet.
    Although the resistor values around them have changed now for a lower gain.

    All the TI USB "soundcard" ICs are natively supported by Win98 & newer and Linux also.
    Plug it in, it finds the device (no drivers needed), away you go... use it like a normal soundcard.

    Well component size would be scaring a lot of ppl away.
    It takes some experience to solder these small pitch SMD ICs.
    Also if you cant get the ICs via samples, they can be very hard to buy in small numbers (and very expensive).

    Most decent sound cards can be modifed to use a better clock.
    This is why USB is a good thing... the TI USB ICs are quite low jitter.

    Yeh it is a bit high :(
    Its ok on my Laptop.
    Its ok on my PC.
    The USB2 hub i have doesnt like it due to the plugin surge.

    Yup, see above.
     

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