Why USB to SPDIF and not optical?

Using a Mac Mini as my music server, and was wondering why the sound would be better converting the USB to SPDIF to my Bel Canto Dac3 as opposed to just hooking up a mini to Toslink? If there is a valid reason, what is a less expensive alternative to the Bel Canto USB Link?
There is no "valid" reason. It's a question of well the solution is implemented on a unit by unit basis.

Apple has hung its hat on optical and most everyone seems very happy with the results they are getting from the Mini using the best Toslink cable they can buy.

FWIW, a good SPDIF cable - and this is definitely one of those cases where there are real differences between cables - is both more expensive and shorter then either Toslink or USB.
So you are saying there would be little reason to spend $500 on the Bel Canto USB link, for example. Performance enhancement likely wouldn't be that noticeable? I thought I might need a similar device because the soundcard in the Mini is lacking?
The Toslink out from the Mac Mini has very poor jitter performance. It would be worth comparing that to USB from the Mac Mini directly to the Bel Canto DAC3, which has a USB input.

An inexpensive USB to SPDIF converter, such as the HagUsb, may or may not be an improvement over Toslink. Bel Canto's USB add-on gets you 24/96 via USB and, I expect, also gets you much better performance across the board. A device like the Empirical Audio Offramp takes it up another notch or two and leaves Toslink in the dust.
Okay i have the same confusion... i also have a DAC3...which has spdif AND USB inputs.. and i read on the Bel Canto site...

"The USB Link 24/96 includes a Stereovox XV2 BNC/BNC cable with RCA adaptor to feed your audiophile DAC of choice – most likely a Bel Canto DAC3!"

So... all i can derive from this is that the device must just be a usb based sound card?
I've seen first hand gains from going other than USB into the DAC3. Each step up by way of interconnect seems to gain a darker backdrop, and more ease and detail. Depth as well. the best connection thus far that I've used is via the BNC input jack on the BC DAC3 through a Stereovox xv2 IC.

Via coax things get better over TOS by way of jitter reduction and sound stage acquisition. The DAC3 seems to catch the info and reproduce it with a stronger grasp.

With even the use of an adapter, things are better using coax into BNC... especially by way of ambient recall or retreval of the orig recording venue.

these are incremental increases, yet descernable without too much care in listening. Most noticeable is the jump from USB to coax. IMO.

If of course your ripped info was encoded at more than 16/44.1, then even TOS WILL BE A DECENT LEVEL OF improved refinement over it's USB imput.

These items I've noted too might also be, in part, the result of the jitter or dejittering characteristics of the cable interface being used.

I found it impossible to find a maker of all 3 sorts of cabling, USB COAX, & BNC of the same level of quality to experiment with, so keep that in mind too.

Given all the cables I used are quite modestly priced, I'd submit my findings seem valid enough. No uberexpensive wires have yet to remain here, though several were tried.... some upwards of $750 MSRP per 1M.

Perhaps, having another sound card installed with your choice of interface (coax or BNC) would be an option, and possibly save you on many accounts.

Good luck
I believe the USB Bel Canto Link is just that, a soundcard. Maybe my original question should have been - do I need to upgrade the soundcard of a Mac mini?
Generally speaking, Macs don't have sound cards that can be upgraded. You can run an external sound card, such as a Lynx, in a Mac desktop. There is no way to put one into a Mac laptop or Mini, although I believe there are some external solutions.

I think it's erroneous to call the Bel Canto Link a sound card. It is a converter with added value.
One last potentially obvious question...

I have a minipc (like a mac mini, but wintel based - made by Aopen) with a realtek high definition audio output section on the motherboard...

If i was to hookup up one of these Bel Canto usb gadgets we started the thread with, then i would be bypassing the Realtek to use the bel canto in the digital bitstream on it's way to my Dac3?....

The reason i asked.. is that i just installed the foobar2000 player with the wasapi plugin that bypasses all the windows digital processing and volume controls.

That actually made a huge difference already...

wondering what the bel canto doohickey would do in addition (assuming it might do anything)?...

Maybe TTVJ is on my next email agenda for a try out... :-)
Just improving the Toslink from the Mac will reduce jitter a little, but it does not change the clock inside the MAc, which is the true source of the jitter.

If you go USB to S/PDIF, there are three advantages:

1) Eliminate the Toslink optical conversions as a source of jitter
2) Establish a new low-jitter clock to replace the one in the Mac
3) Output from S/PDIF coax to the DAC, whic has the opportunity to have lower jitter than the Toslink (depending on implementation)

BTW, this can still give you galvanic isolation (just like the optical) providing the converter is properly transfomer coupled.

Steve N.
Empirical Audio

Since you seem to be an expert in "jitter", can you provide a link to any qualitative data explaining this phenomenon, in layman's terms?

I just spoke with the folks @ Bel Canto...

and they essentially mirrored Steve's comments

(not that i didn't believe you Steve... i just didn't know you had responded :-) )

I asked why i'd want this 24/96 doohickey if i already had a Dac3 and a 24/96 toslink connection from my computer to the Dac3.

First (according to Bel Canto) the usb->spdif conversion in the 24/96 link is a better implementation than the one already in the Dac3 (plus the fact that the usb input doesn't do 24/96).

Secondly, he believed the optical Toslink from the computer didn't perform as well as the usb anyway.

So that's the retransmission of my conversation this afternoon.. :-) Enough for me to try one..

Happy listening
I am a little concerned about the statement that it is compatible with native Windows drivers. Do you know how the Link product interacts with XP's audio subsystem? The literature says it accepts 24/96 but I think parts of the XP subsystem probably needs to be bypassed to get 24/96 cleanly through the OS. So does it have drivers that bypass KMixer and the like and will any software product (iTunes for me) work with it directly or do you need special drives (like ASIO) to use it? Any information would be useful.
In addition, XP generally upscales 44.1 files to 48 unless special drives are installed. Does the 24/96 link help with that problem?
FYI, y'all:
My system - PC, Windows XP, ASIO4ALL, JRiver Jukebox > Belkin USB out to Giga Lab Moon USB DAC(NOS). My DAC also has coax and optical ins.

On a whim this afternoon, I inserted a $30 Behringer USB headphone amp (which also converts USB to optical) between the PC and the DAC (optical from the Behringer to the DAC). I was amazed to hear at least a 10% sound improvement, especially on my FLAC downloads from HD Tracks.

Apparently, my DAC prefers optical over USB, but I don't know why.
Mmarvin19 - The JRiver and ASIO configuration is one I am intertested in but have not tried yet. Can you tell if you get 44.1 MHz out of both the Belkin and the Behringer? And do both pass higher frequency without re-sampling? I check this by hooking it up to my HT receiver which reports the input signal sampling frequency. Thanks.
"XP generally upscales 44.1 files to 48 unless special drives are installed."

Not true. My USB converter uses the native drivers and it outputs 44.1 on XP. There are several ways to avoid kmixer, including:

1) unmapping the device
2) Kernel Streaming

Steve N.
Empirical Audio
Steve - Let me re-phrase - "XP generally upscales 44.1 files to 48 unless special software is installed to bypasses the XP upscaling". You are correct that is not only a driver issue. Unfortunately the simple solution of unmapping the device often disables the device so it is not a general solution - at least for me The specific issue I was addressing is whether the Bel Canto managed to bypass this upconversion. If there is no additional software other than the native drives, I would suspect that the upconversion still happens. Do you concur? Does your converter get 44.1 out of iTunes? As I understand it, neither KS or ASIO is available for iTunes. If that is incorrect I would love to know a general process for bypassing the upconversion when using iTunes. I like the iTunes interface, but am frustrated by the uponversion. Any insight would be appreciated.
Correction - not mapping through the device does not disable my devices, it just does not seem to stop the upsampling. The "do not use audio functions" option is the one that disables the devices. Sorry - I got the 2 options mixed up.
"If there is no additional software other than the native drivers, I would suspect that the upconversion still happens. Do you concur? Does your converter get 44.1 out of iTunes?"

No, not with Vista and my converter. It changes 16/44.1 into 24/44.1, so Vista is bit-perfect.

With XP, there is something changed if you dont use Kernel Streaming, but it is not necessarily 44.1 to 48. I believe there is volume adjustment DSP, just like Vista does with 16-bit data.

I dont recommend using iTunes on any PC with any device, even WiFi. Use Mac with iTunes.

Have you tried Jriver?

Steve N.
Empirical Audio
I just installed J River Media Center 13 last night and am still getting 48 MHz output on XP. I installed ASIO4ALL and upconversion still happens. I still need to do some experimenting to be sure I have everything set up correctly. Do you get 16/44.1 out of J River? If I read your comment correctly Vista converts 16/44.1 to 24/44.1, so I would not call that bit-perfect. Is your software adding the bits or is Vista? The purist in me would still like to get the original 16/44.1 out to my DAC without the any changes happening in the PC. I sometimes feel like I am losing the battle with this. Might try foobar next, but I am not sure I can live with the interface. Thanks for your help.
"Do you get 16/44.1 out of J River?"

Yes, but with my USB converter it's 24/44.1. With some devices attached to my Pace-Car, it's 16/44.1. The Sonos is also 24/44.1, but bit-perfect.

"If I read your comment correctly Vista converts 16/44.1 to 24/44.1, so I would not call that bit-perfect."

Vista and XP both change 16/44.1 into 24/44.1 with my USB converters. It's bit-perfect. The data is not modified. The noise floor is just lowered.

"Is your software adding the bits or is Vista?"

Both, its the firmware of the USB interface talking to Windows audio stack S/W in XP and Vista.

I think your problem is iTunes. If you use Jriver or Foobar and either unmap or use Kernel Streaming with XP, you will be bit-perfect. The sound quality will be a lot better too. I recommend Foobar 0.8.3.

Steve N.
Empirical Audio
Hey dtc.

"The purist in me would still like to get the original 16/44.1 out to my DAC without the any changes happening in the PC."

Why do you prefer 16/44.1 over the higher resolutions? I am under the impression that 16 bits is better than 24 and 48kHz is better that 44.1 and 96 is better than 48, etc...
Am I missing something?

Hey Steve.

Why is Kernel Streaming better than ASIO for KMixer avoidance?
Mmarvin19 - I would rather have my DAC (Musical Fidelity) do the upscaling rather than some unknown software buried in the PC. So I am looking for a simple USB to optical or coax converter that will bypass the XP upscaling. The 44.1 to 48 upscaling may not have much effect on the final sound, but I would still prefer to be able to control it. I would think you would also prefer 44.1 for files ripped from CD for your NOS DAC. Part of the idea of a NOS DAC is to not do any upscaling. Can you tell if your Behringer is putting out 44.1? I assume with ASIO it probably is. I have tried a couple of devices today with J River Media Center and ASIO4ALL but they do not work with ASIO4ALL. So I am still looking for new options. I am very happy with what I am currently getting, but want to see if I can get it to another level.
"Hey Steve.

Why is Kernel Streaming better than ASIO for KMixer avoidance?"

Because at least with XP, every ASIO plug-in that I have tried sounds different. I dont trust them anymore. Unmapping has a clarity that ASIO just does not delivery IME.

Steve N.
Dtc - it turns-out that hardware upsamplers are mostly inferior to software upsamplers. Makes perfect sense. There are limitations to what you can do in hardware and how long it takes to do it. It usually a compromise.

Software on the other hand is more flexible for editing and integrating the latest algorithms, and for file re-writes (such as R8Brain and Adobe Audition), the S/W can take all night to do the upsampling task, and it often does. More time to do it equals better quality. Not all upsampling algorithms are equal either.

Steve N.
Empirical Audio
Steve - I agree in principle. The comparison here is between the real time up sampling from 44.1 to 48 done by XP versus the up sampling done by my DAC. I would prefer to not use the XP upsampling because I do not think it adds anything to the chain and depending on how it is done may degrade the sound - although probably only slightly. Once I can bypass the upsampling I can try it both ways and see if I can hear any difference.