[FallenAngel]

Quote:

Originally Posted by Lil' Knight /img/forum/go_quote.gif I've just found out that my laptop has a 3.5mm S/PDIF output. So, I just wonder if there's any difference between using it and USB?

3.5mm S/PDIF output : you have an S/PDIF transport built into the laptop, most built in are not bit-perfect and usually crappy quality. 3.5mm is very far from ideal 75 Ohm connection required for S/PDIF.

USB : A connection to a USB transport built into a DAC. The transport is inside the DAC, no extra requirements on laptop. Usually quite a nice option.

Quote:

Originally Posted by ironmine /img/forum/go_quote.gif Use your laptop spdif output, but upsample the signal first in Foobar2000.

Why? See differences above.

 

[Greeni]

The Blue Circle USB Thingee appears to be primarily designed for converting USB to SPDIF, and received some good reviews:

GoodSound! Equipment Review -- Blue Circle Audio USB Thingee Digital Converter (5/2008)

If possible I would also avoid all these intermediating conceptions, cables, etc., with a USB DAC instead....

 

[mrfloopy]

Quote:

Originally Posted by audioengr /img/forum/go_quote.gif 1up is correct. If you spend $100-200 on a USB to S/PDIF converter it will be poor compared to a built-in interface like the Benchmark DAC-1 USB has. On the other hand, if you buy a really good converter and spend $800, this will be better than the built-in USB interface. There are a number of reasons for this, three of them are: lower jitter clock than the built-in interface, separate power system and galvanic isolation between computer and DAC. Because a DAC upsamples asynchronously, this does not make it immune to jitter. This only reduces jitter. Steve N. Empirical Audio

I'll add my vote to this lot – it all depends on how well the bit of equipment has been designed and implemented.

For example, I've got a NOS DAC with USB, optical SPDIF and coaxial SPDIF inputs. The DAC's designer specifically states that the DAC's clock design is simple, because the design philosophy is to rely on the quality of the incoming signal timing-wise.

Having a listen to the same stuff via USB and then via a relatively inexpensive USB-to-SPDIF converter, the USB connection sounded inferior – my inference is that the USB audio information + DAC's USB receiver resulted in a more jittery signal than the SPDIF out of the USB-to-SPDIF converter.

 

[leberserkfury]

Interesting post mrfloopy. I'll keep this in mind when i buy my DAC. Thanks

 

[hubsand]

This is such a difficult question to answer generically.

First, each DAC implements its inputs differently: some just seem to favour USB, coax or - even - optical.

Second, cables matter: a poor coax often sounds worse than a bog standard USB cable, and cheap optical cables sound awful - from which much of its poor reputation springs. Audio grade USB cabling is a science in its infancy.

Third, the PC-side implementation matters, and varies: USB from my Mac Mini, for instance, sounds conspicuously worse than USB from my MacBook, even when the laptop is powered.

Fourth, USB->SPDIF conversion is often lossy and depends on the quality of the converter. The money you need to spend on a top-notch converter would more smartly be spent on a better DAC.

What I can tell you does work is the VdH Optocoupler which, for $60, completely changed my opinion of optical connection.

 

[Andrew_WOT]

I was getting surprisingly better results with HR MicroDAC by running M-Audio Transit as external USB->SPDIF converter.
With Stello DA100, directly feeding it from USB sounds better than USB-Transit-SPDIF Stello.

 

[mackman]

16 bit 44 kHz is perfectly fine for CD rips but if you're listening to music DVDs or other high def audio you'll need to use S/PDIF to your DacMagic. It looks like the M-Audio Transit would provide that. Also, if you want to experiment with some PC-side DSP effects (such as various tube simulators or even just replaygain) you'll need the higher bit and sample rates.

 

[athenaesword]

edit: using a usb -> spdif converter with a 24bit/192khz DTS track playing, is the input into the DAC 24bit/192khz or 16bit/48khz and subsequently upsampled by the dac to 24bit?

 

[theeviljesus]

So is the general consensus that if a laptop is the only source, it's better to buy a good DAC with USB input (for ex. DAC1/Stello Signature) than a not so expensive (~200$ max) converter (may it be USBtoSPDIF/I2S) and a good DAC without USB input (for ex. North Star 192/vintage DAC)?

@athenaesword: Correct me if I'm wrong, but isn't the output of the dac an analog signal? Does the 24bit question not only concern digital signals? Or do you mean balanced/unbalanced?

 

[athenaesword]

Quote:

Originally Posted by theeviljesus /img/forum/go_quote.gif So is the general consensus that if a laptop is the only source, it's better to buy a good DAC with USB input (for ex. DAC1/Stello Signature) than a not so expensive (~200$ max) converter (may it be USBtoSPDIF/I2S) and a good DAC without USB input (for ex. North Star 192/vintage DAC)? @athenaesword: Correct me if I'm wrong, but isn't the output of the dac an analog signal? Does the 24bit question not only concern digital signals? Or do you mean balanced/unbalanced?

oops i think i ought to clarify my question:
using a usb -> spdif converter with a 24bit/192khz DTS track playing, is the input into the DAC 24bit/192khz or 16bit/48khz and subsequently upsampled by the dac to 24bit?

 

[mackman]

The M-Audio Transit mentioned by the original poster will max out at 24bit/96kHz which will be upsampled by the DAC to 24bit/192kHz. A straight USB connection to the DacMagic will downsample it to 16bit/48kHz on the PC and then upsample it on the DAC back to 24bit/192kHz. There are some USB DACs that support 24bit/96kHz with custom USB software drivers (which is how the M-Audio Transit works), but the DacMagic isn't one of them.

 

[athenaesword]

Quote:

Originally Posted by mrfloopy /img/forum/go_quote.gif I'll add my vote to this lot – it all depends on how well the bit of equipment has been designed and implemented. For example, I've got a NOS DAC with USB, optical SPDIF and coaxial SPDIF inputs. The DAC's designer specifically states that the DAC's clock design is simple, because the design philosophy is to rely on the quality of the incoming signal timing-wise. Having a listen to the same stuff via USB and then via a relatively inexpensive USB-to-SPDIF converter, the USB connection sounded inferior – my inference is that the USB audio information + DAC's USB receiver resulted in a more jittery signal than the SPDIF out of the USB-to-SPDIF converter.

you received a more jittery signal on the USB->dac than through a usb-> spdif converter? i thought USB is supposed to have minimal jitter?

sorry if I seem to be asking silly questions I'm trying to pick things up as quickly as possible

 

[Fidelity]

USB does not provide a smooth constant stream of data it sends bursts (chunks) of data at a time, unlike SPDIF.

 

[Andrew_WOT]

Quote:

Originally Posted by Fidelity /img/forum/go_quote.gif USB does not provide a smooth constant stream of data it sends bursts (chunks) of data at a time, unlike SPDIF.

Except that most USB DACs work in Isochronous transfer mode, which is a continuous stream.

 

[Fidelity]

Yes but the packet sizes are not 100% consistent, no guarantee that each packet will arrive 100% on time, IIRC some buffer mechanism is used.