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Starting Point Systems portable NOS DAC

Discussion in 'Portable Source Gear' started by cjg888, Mar 12, 2014.
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  1. earwego
    Well here's the result - after half and hour of not playing music but leaving the system on (I just stopped the music playing on Daphile which uses the LMS engine) - the DAC had still not charged enough to remove distortion. But after leaving the system on for about an hour and a half the DAC was charged enough to play cleanly.

    Christophe Mariac thinks that this old Lenovo S10-3 netbook of mine is not providing enough charge to top up the batteries while playing - from his words "Yes the DAC can power from USB, and charge and keep the batteries topped from USB alone. However, it need quite a bit of current (in the 400mA region)" - so I can only assume that this netbook via USB is not providing enough current which would be the logical conclusion.

    I still have further questions for Christophe - but I want to keep this DAC as it "does" sound very good indeed - but I cannot have it being an operational pain. My perfect solution would be to have the music playing continuously without ever running out of charge by way of a USB connection to computer - so I guess this old Lenovo S10-3 doesn't have enough current and I have to find a computer that does. Shame as the netbook has served me well otherwise.
     
  2. gvl2016
    Find a powered usb hub, or better yet get a Schiit Wyrd or use an external linear low noise PSU.
     
  3. earwego
    The Schiit Wyrd looks good - I was about to say I'm investing quite a bit into making the SPS DAC 3 work for me, but, I believe the Wyrd would be a good investment anyway for 'any' USB based DAC.
     
  4. gvl2016
    One thing about USB, this DAC, at least the revision I have, doesn't use any of the known well recognized USB audio interface chips, instead it relies on the USB interface built-in into the MCF51JM64VLD microcontroller and likely some custom code to make it appear as an audio device and process incoming data. Because of it I'm curious how well this DAC deals with jitter on the USB input. It took non-trivial engineering efforts for the companies XMOS to design a robust USB audio interface chip. So forget about asynchronous mode, and 16kB of DRAM on the microcontroller is pretty tight for a bit-accurate reclocker. Because of this I wonder if an external USB to SPDIF converter like Schiit Eitr or the like could bring noticeable improvements.
     
    Last edited: Sep 10, 2017
  5. earwego
    If you look at his video he mentions that he prefers adaptive USB connectivity with good re-clocking - and explains why (Beresford also thought that async USB was not as good as we all think it should be). This is meant to be both a sophisticated re-clocker and DAC in the same bit of tin so I would assume that nothing more was necessary.

    However, because I would need a longer playing time than just the 2 hours on battery, I would prefer to invest in a clean external power source due to the fact (as I mentioned earlier) the jitter aspect has already been engineered into the DAC. So, for me, the Schiit Wyrd would suit my circumstances better and I would therefore trust the de-jitter engineered already into the unit. The essence of making this DAC sound so good is the clean power supplied by the batteries, so keeping it clean with the backup power supply is a logical move.

    The DAC sounds very good so, I want to get the best out of it.
     
    Last edited: Sep 11, 2017
  6. gvl2016
    I've been also using a Jameco DFU240050F1121 linear regulated 24V/500mA PSU with this DAC, I got for under $15 from Amazon. Works fine. I couldn't detect any meaningful differences between that and the USB power. There is also a 12V/1A version of the PSU from Jameco, I probably should have gotten it instead of the 24V as the DAC runs noticeably warmer on 24V than on USB power, the reason I got the 24V supply was that the DAC switches from USB to external at around 11.5V, and I thought 12V might not work reliably, but it should run from 12-24V per product description. There are also DC regulators inside the DAC so I think overall it doesn't really need an uber stable external PSU, so you might be able to just use an unregulated linear wallwart that are even cheaper, something like 16V/1A will probably work best.
     
    Last edited: Sep 11, 2017
  7. earwego
    Yes the designer warned about how some 12v supplies drop to 11.5v - so ideally I need to find a good quality 15v power supply (if I choose to use a power supply) - or alternatively a high quality USB power supply that doubles as the connection to the computer hence the Schiit Wyrd idea.
     
  8. gvl2016
    I like it too, but given the reclocker works as advertised is there a big value in it? I'd just slap a $10 linear PSU on it first and see what happens. The DAC should stabilize the voltage internally.
     
  9. earwego
    Ok - so where to find a 10 dollar linear PSU which fits in the DAC 3 and is 15 volts.
     
  10. gvl2016
    Ok, looks like it will cost a bit more than $10 with shipping.

    This one is 18V/1A unregulated: http://a.co/52N8eNy

    I have this one, it is regulated but 24V/500mA, seems price went up as I got mine for $15 shipped: http://a.co/cJvrkJ3

    Also check out http://www.jameco.com, they have more models listed there, most are available through Amazon or so it seems.

    These are hefty transformer-based wallwarts, not the typical small switched noisy types you get these days.

    There is also 15V iFi iPower, it is not linear but supposedly designed to suppress HF crap from the switching supply, but at $50 it isn't exactly cheap.
     
    Last edited: Sep 11, 2017
  11. richard51
    I will try a 12 volt Ankaka lithium battery for external power complete isolation of the dac from the system and a 12 volt 1.5 A psu for comparison... The battery solution is not cheap for sure, but i have one already...
     
  12. gvl2016
    FYI, after the external battery drops below 11.5V the DAC will switch to internal batteries.
     
  13. earwego
    For now I've settled into using power from the plug of a USB charger (borrowed from the Chromecast Audio) so now there should be sufficient power into the USB socket of the DAC 3.

    So from the computer I'm going from its feeble (power wise) USB port into a USB to SPDIF to converter instead.

    From what I've learnt so far this should allow for continuous play while giving the batteries a healthy charge in the process.
     
    Last edited: Sep 11, 2017
  14. gvl2016
    This should work. SPDIF input on this DAC uses DIR9001 chip with its own jitter corrector that is independent from the USB reclocker.
     
  15. richard51
    Yes and if i understand correctly, when the battery control button and the main power button are on. the external battery will charge the 2 small internal batteries continuously... at the end i will have to charge only my external battery from times to times.... is it correct?
     
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