MacBook: S/PDIF or USB?

pkane

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Jan 6, 2017
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I just discovered that my Macbook Pro has a Toslink S/PDIF out. I've been using the Mac for years, and somehow never knew this!

Up until now, I've been using a simple USB to SPDIF converter to feed into my DAC. While I do have some jitter reduction built into the system, I still find that SQ is better when played on a CD transport than from the Mac through the USB port. Perhaps I need a better USB-to-SPDIF converter (maybe with async capability?)

Today, I got the mini-Toslink to regular Toslink cable and connected it between Macbook and DAC. The sound is now really close to what I get from the CD: when doing A/B comparisons, level-matched, I can occasionally hear very slight differences. Sometimes the CD sounds a touch better, sometimes the Mac over S/PDIF. Overall, I feel they are very closely matched now.

So, the question is: do you folks use (and prefer) the S/PDIF output on the Macs directly or is a high quality USB-to-S/PDIF converter a better choice? Are there some software limitations with Mac S/PDIF output that do not exist with USB, or are they equivalent from software perspective?
 

Joe Whip

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Feb 8, 2014
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Personally, I prefer the USB out of my Mac Book air to CD playback through two transports I have to use, a Sony ES SACD player via coax and believe it or not, an old laser disc player via toslink which sounds very good but still not a match to my computer play back. I use a Jitterbug and a Schiit Wyrd in the system and am thrilled with the result. You may want to try one of the USB isolation devices and see what you think. I have heard that there are several interesting ones coming out in 2017.
 

pkane

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Jan 6, 2017
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Personally, I prefer the USB out of my Mac Book air to CD playback through two transports I have to use, a Sony ES SACD player via coax and believe it or not, an old laser disc player via toslink which sounds very good but still not a match to my computer play back. I use a Jitterbug and a Schiit Wyrd in the system and am thrilled with the result. You may want to try one of the USB isolation devices and see what you think. I have heard that there are several interesting ones coming out in 2017.

Thanks for the information, Joe. I'm actually very happy with my CD-transport playback. I've put together this system many years ago and have not touched the components since -- really didn't have the urge or the need to. Only recently I started adding PC (Mac) music playback to the system, and found the USB playback lacking in transparency. I did research into various USB clean-up solutions, including Wyrd, but I'm not sure if these will improve on the Toslink/SPDIF output from the Macbook.

I'd be curious to hear from anyone who has done such a comparison in their system: Macbook->USB->SPDIF->DAC compared to Macbook->SPDIF over toslink->DAC and what USB converters/clean-up devices they used.

A related question: how is the SPDIF output generated from the Macbook audio card? Hopefully the digital output is kept digital all the way through, and not converted to analog and then back to digital. It doesn't sound to me like it's being double converted, but you never know ;)
 

asiufy

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Jul 8, 2011
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Hi Paul,

I think the issue here is the USB to SPDIF converter you have to use for the USB connection. That must be surely degrading the performance quite a bit, as the Toslink is widely known to be a very jittery connection.

If your DAC doesn't have a native USB port, and you want to enjoy computer audio, you might want to look for a streamer (with proper SPDIF, not Toslink) instead of the Mac, or at least get a new DAC with a USB port.

cheers,
alex
 

pkane

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Jan 6, 2017
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Hi Alex,

I think you're right, it does come down to which interface is more jittery, Toslink or the the USB connection on my Mac. I do have a different DAC that supports USB (Emotiva XDA-2). Interestingly, it sounds very good with the USB connection from my Mac, but sounds horrible with the CD transport connection. So, I'm stuck with two DACs, one that works well with USB, the other works well with CD source, and neither works well with both :(
 

Joe Whip

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Feb 8, 2014
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You can try the if I spdif purifier. With it, you can take the spdif out of the Mac and do either toslink or coax into your DAC. Not expensive at all.
 

pkane

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Jan 6, 2017
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You can try the if I spdif purifier. With it, you can take the spdif out of the Mac and do either toslink or coax into your DAC. Not expensive at all.

Thanks, Joe! This is really interesting. I was looking at the iFi USB iPurifier, and wasn't convinced that it would help since it seems to only de-jitter and recondition USB clock and not the audio clock, which is where I believe my problem lies. But SPDIF iPurifier looks like a well designed product that de-jitters SPDIF signal using a memory buffer, something I've seen only in much more expensive products.

I'll definitely try this, as I can use it on the direct Toslink output as well as after the USB to SPDIF converter to see where it does the most good. Thanks again for the suggestion, I didn't know this gadget existed!
 

pkane

New Member
Jan 6, 2017
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I just received the iFi SPDIF iPurifier. It appears to be well made. It's supplied with all the adapters needed to connect to the system, including BNC to RCA, mini-toslink to toslink, etc. So far I only had about 30 minutes with it, but there is a subtle but noticeable improvement compared to my system without it. It shows up as a much more layered sound stage. The depth to the different instruments is much more obvious than without it. I'll spend more quality time with it, do more testing and post my findings here.
 

pkane

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Jan 6, 2017
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Joe's suggestion of the iFi SPDIF purifier worked out, but not enough to fix the problems with USB output. It did improve the SQ of the SPDIF toslink output from the MacBook, though, and for that I'll keep it in my system. The USB output improved, but not enough to use it this way.

While I was already happy with the toslink output from the mac, the iFi purifier added a little depth and perspective to the sound that was obvious on some tracks, but not on some others. It never hurt the sound, but didn't always improve it. I assume it has to do with the quality of the recording. For reference, my system consists of:

2011 Macbook Pro -> toslink -> iFi SPDIF purifier -> DEQ2496 -> DTI Pro32 -> I2S -> Uther II DAC

DEQ2496 is acting as an all digital parametric EQ, while the purifier and DTI Pro are acting as dejittering devices. I tried placing the purifier in different positions (before DTIPro, for example, or after) but it seemed to have the best effect just before DEQ2496, so I assume most of the jitter was being introduced somewhere between the mac and the toslink cable.

I have to conclude that my USB to SPDIF converter is the main culprit in the poor USB performance, as even with the purifier, the USB output doesn't sound nearly as good as the toslink connection. For now, I'll keep using the toslink with iFi purifier, as that sounds very sweet indeed :)
 

Legolas

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Dec 27, 2015
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Joe's suggestion of the iFi SPDIF purifier worked out, but not enough to fix the problems with USB output. It did improve the SQ of the SPDIF toslink output from the MacBook, though, and for that I'll keep it in my system. The USB output improved, but not enough to use it this way.

While I was already happy with the toslink output from the mac, the iFi purifier added a little depth and perspective to the sound that was obvious on some tracks, but not on some others. It never hurt the sound, but didn't always improve it. I assume it has to do with the quality of the recording. For reference, my system consists of:

2011 Macbook Pro -> toslink -> iFi SPDIF purifier -> DEQ2496 -> DTI Pro32 -> I2S -> Uther II DAC

DEQ2496 is acting as an all digital parametric EQ, while the purifier and DTI Pro are acting as dejittering devices. I tried placing the purifier in different positions (before DTIPro, for example, or after) but it seemed to have the best effect just before DEQ2496, so I assume most of the jitter was being introduced somewhere between the mac and the toslink cable.

I have to conclude that my USB to SPDIF converter is the main culprit in the poor USB performance, as even with the purifier, the USB output doesn't sound nearly as good as the toslink connection. For now, I'll keep using the toslink with iFi purifier, as that sounds very sweet indeed :)

I would try AOIP, sounds better than my previous (many) USB chains. The Rednet 3 is the one I use with my Mac Mini and sounds very liquid and smooth, unlike USB which is edgy and very digital.
 

pkane

New Member
Jan 6, 2017
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I would try AOIP, sounds better than my previous (many) USB chains. The Rednet 3 is the one I use with my Mac Mini and sounds very liquid and smooth, unlike USB which is edgy and very digital.

Interesting. Rednet 3 appears to be overkill for what I need (a single connection from Macbook Pro to my digital system via AES/EBU or Toslink). Are there other AOIP products that are more limited in scope ...and price?
 

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