Right I've been busy and got a load of rmaa results on this! I've done a battery vs usb power comparison

I'm a RMAA n00b, but I think I got it figured. When I changed sample rate I also changed it in Patchmix to match. Everything seemed to work ok, even if it didn't it doesn't matter, it was the same for either the usb power or battery power tests so they are vaild to compare.

I used the emu0404 to record with, I couldn't test loopback because I don't have enough adaptors..
My dac has all the trimmings, the axial inductor and blackgates.

First we have the battery power tests which are here!

It doesn't look too bad to me, way better than onboard sound so I'm happy

I tired the test with two aa's but it didn't happen, voltage was too low to make the tests at 48khz work (white noise) so instead I used 4 aa's which measured at 5.25v. On 2 aa's (2.65v) the volume was considerably less than usb power or 4 aa's, I had to adjust 5db more in patchmix to get the level up for Rightmark.

Here we have results for usb power!

It looks worse than it is and in listening it doesn't sound too bad, I couldn't really tell them apart to be honest apart from infrequent HD noise. That said it is a fairly big gap performance wise...I am wondering if I should go back back on my plans and use battery power now.

I have a comparision of the two here so you can see the results side by side.

I'll try to get some results via my laptop tomorrow to see if power is cleaner there.

To jump back to a subject brought up earlier in this thread: a USB DAC with S/PDIF output. There is a great little USB soundcard made by Voyetra Turtle Beach called the Audio Advantage Micro.

It has a single analog output (headphone amp claimed, but 3rd party reviews call it a bit lacking in power). The great thing is that it can do S/PDIF via a Toslink optical out instead of the analog jack (they use a proprietary adapter, included). $30 shipped from places like Amazon and Newegg.

Could meld this into some DIY external DAC project and none would be the wiser

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There are a bunch of USB cards with digital out. There are also some people now modding DACs by internally adding various flavors of these cards to them. Search the computer audio forum here for lots on this.

-d

very nice sound. what config should i use it in foobar? should i resample to 96k ?

also how does this usbdac compare to something else diy such as the nonoz III ?

(on which page can i find the schematic of the DAC all you guys are talking about? :S)

Rob.

http://www.mellowparenting.demon.co....er/usbdac.html

Hrrm... does anybody know of a substitution for the WIMA caps? I managed to aquire 8 of them (thank you, Guzzler!), but I don't want to have to put in a minimum order of 50 from Mouser to get the remainder for the second DAC. I thought for a bit I had found a cap that was a similar pitch, but now I can't find it anymore on the Digikey website (wasn't a box cap, but a radial lead poly disc cap... I think).

But in other news, the first DAC is coming along well. Hopefully by Sunday I'll have it all assembed sans casework. You can guarantee I'll have pics by then.

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I have three left over from my other two USB DACs - if someone else can supply you with the remaining 5, I can send you the three your way.

I've been fiddling again!

Got my Toshiba Tablet laptop out to give it a whirl with the USB Dac and RMAA. I got some intersting, if expected results!

You can find them here

Same as last time, input to the same pc with the 0404. I powered the dac via usb with the lappy plugged in, with the laptop on batteries and finally with it powered via 5.25v's worth of NIMH's.

All the results are so close I doubt you'd ever tell! Certainly sounds the same! Its way better than when powered from my pc

I have a meaty main pc but I blew the good Antec psu up, so I'm on a no-name one at the moment. A new Truepower 430 arrives next week so I will also test on that just out of interest.

Solves my dilema anyway, I'm building it into an enclosure with no batteries because I'll be using the laptop with it. I'll put a power jack on the outside should I ever need to use it on a desktop.

That's very interesting! I should build my second DAC with USB power and see how it performs. I was just hesitant because my bypass-modded OptoPlay had a pretty high noise floor.

Thanks for the results!

Im wondering...

Is it possible to connect this device to the USB output of an Ipaq pocketpc? I have problems with the noise levels from the headphone out and I would be extremly happy if there was an alternative. Iwe understood that the Headroom bithead only works with cds or "wave out", so if a program would be installed to send this (wave) information through the usb, then it could technically work?

Daniel

To my knowledge, the Bithead line and this DIY USB DAC are both a "Standard USB Audio Device". Any OS that supports things falling into this specification should support them (Windows, Linux, OS X...).

I don't know if Palm or PocketPCs support this, but Google probably does.


p.s. Nice avatar

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Thanks

Well it seems I was completely off with the wave and cd stuff, well at least when I checked with the bithead stats, so probably the same with 00940 and guzzlers usb dac (correct me if I’m wrong). I’m going to try this and hopefully I will have a new favourite portable music source in the near future.

Got it nearly done.. got all components soldered in except for C17. I noticed this was an addition but noted for if you were going to use the USB supply. Does it need to be in if you're going to use batteries? If it's not essential, I'll just add it later when I put in the next order of parts to Digikey.

Otherwise.. it's almost there. Need to buy a USB cable, find a suitable case, and wire up the RCA jacks.

I have a question...

Is it safe to connect four batteries in series? I am getting frustrated with the short battery time of connecting 2x2. I got a brand new pack of cheap alkalines and they lasted like three hours.

With rechargeables it should be fine since 1.2V x 4 = 4.8V but with 1.5~1.6V it's going to be over 6V... Will this damage the switching trans?

Yesterday I was watching Troy at full volume since the volume encoded in the movie was rather quiet... I had put in the batteries like half an hour before the movie started but towards the end of the movie the nasty white noise came out at full volume and I thought my drums were being blown out.