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Hi!
I have an Apple Airport Express which has an analog output, a digital optical output, and USB + Ethernet connections.Can I use the USB connection with a DAC that has a USB input? (I'm considering building an Audio Note 2.1 DAC kit.)
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You would end up with the jitter from two PLL's if you did this, one in the AE and one in the USB DAC, not to mention the jitter from the Toslink output. Better to get I2S interface directly from the AE or at least improve the clock in the AE and get S/PDIF output.
Steve,Common... you would not get jitter from 2 sources let alone the toslink.
If you went out the printer port USB there would be only the jitter assoiciated with the interface. It would have nothing too do with the toslink or the PCM270x part in the AE.
Why go I2S it is not even a specification. The only dac he could use is one of yours.
Since the AE basically has a host USB controller it would not take much at all to send the USB Audio signal out the Printer port as compared to the PCM270x part. It would merly take changing the address one bit. Then it would be no different than say a PC or a MAC in delivering data to the USB Dac.
I dumped the analog board for a customer and hardwired a usb cable to the header and it work fine. Not something I want too do but it did work just fine.
From what I can discern, there is nothing that can pass a USB audio signal wirelessly, so if the AE can be modified to do so it seems to me it would be a huge seller and you guys would be foolish not to offer this service.
Belkin demonstrated wireless USB at CES last January. They have had a few technical problems bringing it to market though, evidently passing FCC emissions is part of it...To change the AE to output USB audio would require firmware changes I believe. You would have to have the original source code to make these changes. I dont think Apple will be forthcoming with this...
The 802.11G WiFi that the AE uses is quite excellent actually. I have Off-Ramp WiFi versions of this that have great transmitting range and the audio quality is only limited by the TI interface chips, the 270X series. Both the S/PDIF-AES and I2S versions sound better than CD players, albeit not quite as good as USB interfaces. They are limited to 16/44.1 kHz unfortunately, where USB is not.
Gordon - one PLL, of course you are correct.As for I2S DAC's, you can get an Audiologic, P-3A or Northstar, all stock with I2S interfaces. I have my own versions as well as mods of these above too.
Also evidently some Zanden models have I2S inputs.
i think only the 5000 signature dac has it. When ppl ask abt the ultimate computer setup i always tell them to get it + your offramp i2s or get a wavelength silver crimson.
AG,The USB at this point can only be used for the printer. It's ashame as the analog/SPDIF is USB so they could literally change from port A to port B and the output would go out the USB port.
Thanks so much for the replies.Would love to have a mod for the Airport Express that would enable me to convert the USB printer output to stream audio (or at least an RCA unbalanced digital output).
Hmm.... I guess my other choice is to run a long (40-60') USB cable from my PC to the DAC.
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