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Author Topic: Testing various DAC inputs (coax digital, optical digital, UBS, AES)  (Read 7283 times)

mojave

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I have a Ross Martin Audio Super Beast DAC that accepts two optical digital inputs, two coax digital inputs, adaptive USB, and AES. It has a switch that lets you immediate change which input is being used.

I decided to try connecting several inputs and switching them to see if it sounded different. I have a Steinberg MR816x that has both coax and optical digital outputs. I setup a zone in JRiver with 12 channels and ASIO output and copied the Left and Right to channels 9 & 10 (optical) and channels 11 & 12 (coax). Playback in this zone goes via Firewire to the MR816x and then out both digital outputs simultaneously.

I also connected a USB cable from the computer to the Super Beast DAC and set a zone for WASAPI output.

I linked both zones and now all three outputs play to the DAC at the same time. I just need to rotate the DAC's input switch to change source.

Even thought the same DAC is getting the same digital signal, it sounds a little different with each input. I had no idea when starting whether one would sound different and if they did which would sound best. I decided I like the optical digital best followed by the adaptive USB and then the coax digital.

My HTPC at home also has AES output via a Lynx AES16e card and coax and optical output via the motherboard. I'm thinking about connecting 6 inputs into the DAC and switching among all six just to hear if I can detect a difference.

Just for fun I also went via adaptive USB to a Tascam US-144 MKII, coax digital out from the Tascam to the coax input on the Steinberg MR816x, and then optical digital out from the Steinberg to the Ross Martin Super Beast DAC. It sounded fine and I couldn't tell any degradation in quality by going through 3 audio devices.
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johncaul

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Re: Testing various DAC inputs (coax digital, optical digital, UBS, AES)
« Reply #1 on: June 10, 2013, 08:46:05 am »

Thanks for sharing. I did something similar and also preferred optical spdif, despite the consensus on most forums i've read being that coax should sound better. I suspect it might be because an optical connection isolates the dac from ground hum and other electrical muck coming from the PC. Cheers
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bobkatz

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Re: Testing various DAC inputs (coax digital, optical digital, UBS, AES)
« Reply #2 on: June 10, 2013, 09:19:43 am »

I'm not surprised different inputs sound a little different. First see this reference:

http://dagogo.com/benchmark-media-dac1-review-part-1      referring to John Watkinson's article in Resolution titled "The Cable Snake"

Another excellent reference are the white papers at the Grimm Audio Website, where they have the high resolution measurement tools to measure slight improvements in low frequency jitter performance even when feeding into a phase locked loop, from a "more perfect" digital clock source. These people know what they are talking about and can buttress their claims with facts, not fancy.

That's the technical side of the argument in favor of the placebo effect being the dominant factor here.

However, despite all this above placebo-likely situation, it appears to be true that despite many DAC makers' claims of "complete" jitter immunity, there is a small residual possibility of audible jitter due to different input topologies or cable differences being audible, due to the DAC's inability to reject all of the incoming jitter. HOWEVER, this residual with a well-designed DAC is usually so low that it takes a real expert to reliably hear the difference on a very high resolution playback system and even then there is room for doubt. These kinds of audible differences are so subtle that it is not the kind of thing that sounds "obvious". Especially if you do successive playbacks after minutes of silence, a sure recipe for the placebo effect.

Bottom line: if you start worrying about your DAC performing or sounding different with different inputs, then get a life and get a job! Or get a better DAC! There are more important things to worry about, the differences assuredly (with a well-designed DAC) are at the threshold of audibility and inconsequential even to the most critical audiophile's listening system, in my not-so-humble-expert-opinion.

JItter is audible, though, and I urge those of you wishing to train your ears to hear it. Visit http://www.cranesong.com/ and click on the link to learn what jitter sounds like. David Hill of Cranesong has induced various types of jitter into a file and made it obvious for ear education. Take advantage of this education so you can be sure that you know what you are talking about and what the real sonic symptoms of jitter are.

Best wishes,

Bob
I have a Ross Martin Audio Super Beast DAC that accepts two optical digital inputs, two coax digital inputs, adaptive USB, and AES. It has a switch that lets you immediate change which input is being used.

I decided to try connecting several inputs and switching them to see ...
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mojave

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Re: Testing various DAC inputs (coax digital, optical digital, UBS, AES)
« Reply #3 on: June 10, 2013, 04:58:28 pm »

Thanks, Bob. I later listened again with a different song and still thought it sounded slightly different. However, my order of preference changed.  :) I decided not to pursue it further and spent my time perfecting my Audiolense filters. I have, however, been following the Acourate forum.  ;)
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astromo

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Re: Testing various DAC inputs (coax digital, optical digital, UBS, AES)
« Reply #4 on: June 10, 2013, 07:32:43 pm »

JItter is audible, though, and I urge those of you wishing to train your ears to hear it. Visit http://www.cranesong.com/ and click on the link to learn what jitter sounds like. David Hill of Cranesong has induced various types of jitter into a file and made it obvious for ear education. Take advantage of this education so you can be sure that you know what you are talking about and what the real sonic symptoms of jitter are.

Thank you for this. I really appreciate this kind of input. It gives people like me a reliable reference point. I'll have a listen to do some audio education as suggested.
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