Does USB to S/PDIF converter gives better sound?

[murillollirum]

Hi, I use a Musical Fidelity V-DAC MKII and guy told me that USB does not give the same sound quality as SPDIF, so he suggested me to buy a hiFace II USB to S/PDIF converter, is that true? I do not understand, what noise or quality should I loose if digital is only 00000000 or 11111111?

 

[abraxalito]

Noise is carried over the USB cable from the very noisy source (computer). Many DACs with in-built USB adaptors are poorly isolated from this noise, whereas with S/PDIF, a transformer provides a degree of isolation.

 

[DF96]

See here for an interesting set of measurements. The conclusion I draw is that basic USB is simply not suitable for high quality audio, as it does not maintain (and was never intended to maintain) proper timing.

 

[Hugh Jazz]

Logic / binary is 0 1. Spdif digital is high voltage to low voltage with rise, bounce, noise, time error, etc. Logic is perfect. Digital is not perfect so can be good, bad, better, etc.

Asynchronous USB not need to worry for problem with USB time error. Hiface is asynch, so is CM6631A, so is XMOS ( no spdif ?) , so is Xilinx... many to choose.

CM6631A is best value to try IMO.

Here is test to show it is good.

Archimago's Musings: MEASUREMENTS: [UPDATE] Adaptive AUNE X1, Asynchronous "Breeze Audio" CM6631A USB, and Jitter...

 

[murillollirum]

See here for an interesting set of measurements. The conclusion I draw is that basic USB is simply not suitable for high quality audio, as it does not maintain (and was never intended to maintain) proper timing.

wow!!! outstanding info! great weekend reading! thx man.

 

[SY]

IME, you don't need anything as fancy as a HiFace- I got essentially identical results with a cheap Chinese USB-to-SPDIF converter. The fellow who sold HiFace converters was very unhappy about my results...

 

[DF96]

Perhaps anything which acts as a half-decent FIFO can do the job. USB delivers the bits (which it can do quite successfully) and then they just need sending on at a strictly regular rate.

 

[Redshift187]

See here for an interesting set of measurements. The conclusion I draw is that basic USB is simply not suitable for high quality audio, as it does not maintain (and was never intended to maintain) proper timing.

That information is specific to the DACMagic only, and the DACMagic does not specific whether it's isochronous or asynchronous. My guess is isochronous given the timing issues.

Every additional data conversion adds jitter. A properly done USB DAC is better than USB -> SPDIF -> DAC. Many DACs simply add a crappy USB interface as an afterthought to increase the feature set for advertising.

 

[Pano]

Define "Crappy".

 

[abraxalito]

Adding a USB board as an afterthought means its power supply arrangements aren't engineered optimally - particularly the grounding. I've noticed this with an Audio-gd USB interface for example. I take it that's what's meant by 'crappy' here.

 

[nigelwright7557]

I would have thought a digital USB signal would not care too much about grounding.
So long as it is not affecting the 1's and 0's then it should be fine.

Grounding affects analog signals more due to their nature.

 

[abraxalito]

You're quite right - the digital signal doesn't care, its differential anyway. But the DAC's analog circuits do, as do downstream analog boxes like preamps and amps.

 

[linuxfan]

See here for an interesting set of measurements. The conclusion I draw is that basic USB is simply not suitable for high quality audio, as it does not maintain (and was never intended to maintain) proper timing.

The keyword here is "basic USB", or poorly implemented USB audio. Yes, it's mediocre.

But well implemented asynchronous USB audio, and especially the new UAC2.0 interfaces such as Lorien's WaveIO, Amanero's Combo384, and exaDevices exaU2I, are claimed to be the best-available digital front ends (currently) for computer based audio.

And don't assume S/PDIF is ideal! S/PDIF TX adds jitter, and S/PDIF RX adds jitter.
Sure, a S/PDIF TX stage might "iron out" the jitter from a poor USB receiver, but it would be more sensible to use a better USB receiver in the first place!
The only good reason to use a USB-S/PDIF interface is for people who have an existing investment in a good quality DAC with S/PDIF input ...
... which leads us to murillollirum's V-DAC MKII. This is a modestly priced DAC, and it's not clear (to me) how good its USB receiver might be.
Would a separate USB-S/PDIF interface feeding the V-DAC be better than the V-DAC's own USB input??
murillollirum, you might need to experiment, yourself.

he suggested me to buy a hiFace II USB to S/PDIF converter

Mmm, there are cheaper options -
for $60 there's a well-regarded (XMOS based) USB-S/PDIF interface here -
XMOS 384kHz high-quality USB to I2S PCB with ultralow noise 6.5uV regulator | eBay

for $55 the miniDSP miniSTREAMER is TE7022 based -
miniSTREAMER | miniDSP

or for $40 CM6631-based -
CM6631 24bit 192kHz USB to Coaxial and Fiber WLX | eBay

But you're spending money to improve the front end of a DAC that is not exactly high end. This money might be better put towards a good DAC/USB receiver combination -
$145 will get you the well-regarded Objective DAC (ODAC) with ES9023 DAC chip, plus the respectable TE7022 USB receiver -
Objective DAC (ODAC) - RCA Version

The same component choices, though not quite of the same construction quality, are available from HiFimeDIY for a ridiculous $60 -
HiFimeDIY Sabre USB DAC 2. External PSU, 96khz/24bit - ES9023+TE7022 + Coaxial OUT

 

[Redshift187]

I would have thought a digital USB signal would not care too much about grounding.
So long as it is not affecting the 1's and 0's then it should be fine.

Grounding affects analog signals more due to their nature.

You can't separate the digital ground from the analogue ground of a DAC, or it won't work. Yes, you need to do it right and there are wrong ways, but they must be connected.

 

[Redshift187]

Define "Crappy".

What I mean by crappy is an isochronous implementation with little regard paid to circuit design, including layout, ground and power.

 

[tiefbassuebertr]

regarded sound reproduction by compact disc (PCM-CD, 44,1 KHz sample rate and 16 bit) the way of setup number #4 is the best - go to
http://web.archive.org/web/20070411084050/http://www.lessloss.com/types.html
As to read about asynchronous reckocking this kind is not the preferable solution (only the best possible solution for those who wish not to modify at their existing digital audio components).

What is now the golden rule, when I want to optimize the sound quality by HDD or SD via USB (or Ethernet) wire? And what is the reason for large differences in sonic transmission by the use of different USB cables ? Also Jitter?

For me a very great problem is a so called "BLACK BOX" for the USB-I2S (resp. USB-SPDIF) conversion instead a detailled circuit diagram.
What happens exactly by the different kinds of components ?

 

[SY]

You can't separate the digital ground from the analogue ground of a DAC, or it won't work. Yes, you need to do it right and there are wrong ways, but they must be connected.

The entire problem (assuming that it actually is a problem) goes away with about $5 worth of parts (transformer and hex inverter). EC8010 and I have posted similar circuits here in the past.

 

[qusp]

I cant believe we have the same old stuff dug over here in 2013 that has been put to rest years ago for those paying attention...

yes a clueless badly managed USB audio connection is probably worse than a bog standard spdif, but especially as a member here, the problem goes away with $60 on the amanero and a half decent power supply, among other options. It by no means only started to be worthwhile recently, it just became more affordable recently and UAC2 became more fully supported on windows finally.

yes the afterthought USB 'feature' added by many designers to round out the feature set is responsible for there STILL being badly done USB when it ceased to be even a close run race a few years ago.

DF96: sorry mate, but I have no idea where you got the idea that USB timing still has any impact at all on the timing of USB audio data transported on it; for any designer that has even the vaguest idea.

ground is the only possible problem and even that relies on some pretty average PCB design to create an issue. Thats if you leave ground intact and dont isolate before reclocking, not all USB devices call for ground from the host

 

[DF96]

Every additional data conversion adds jitter.

No, not if the data is properly re-clocked as any USB-SPDIF converter would have to do.

DF96: sorry mate, but I have no idea where you got the idea that USB timing still has any impact at all on the timing of USB audio data transported on it; for any designer that has even the vaguest idea.

Some people still seem to want USB to deliver both bits and timing. The fact that it can, badly, do it means that people use it. If they just wanted USB to deliver bits and leave the timing to something else then all would be well. Normal computers can't do timing, as they don't have a proper real-time operating system and usually have fairly poor interrupt handling and DMA too. I suppose the right dedicated hardware in a computer could generate well-timed USB packets but I don't think anyone does it this way.

A built-in USB port on a DAC would be fine provided that it had a large FIFO and proper re-clocking.

 

[murillollirum]

The keyword here is "basic USB", or poorly implemented USB audio. Yes, it's mediocre.

But well implemented asynchronous USB audio, and especially the new UAC2.0 interfaces such as Lorien's WaveIO, Amanero's Combo384, and exaDevices exaU2I, are claimed to be the best-available digital front ends (currently) for computer based audio.

And don't assume S/PDIF is ideal! S/PDIF TX adds jitter, and S/PDIF RX adds jitter.
Sure, a S/PDIF TX stage might "iron out" the jitter from a poor USB receiver, but it would be more sensible to use a better USB receiver in the first place!
The only good reason to use a USB-S/PDIF interface is for people who have an existing investment in a good quality DAC with S/PDIF input ...
... which leads us to murillollirum's V-DAC MKII. This is a modestly priced DAC, and it's not clear (to me) how good its USB receiver might be.
Would a separate USB-S/PDIF interface feeding the V-DAC be better than the V-DAC's own USB input??
murillollirum, you might need to experiment, yourself.


Mmm, there are cheaper options -
for $60 there's a well-regarded (XMOS based) USB-S/PDIF interface here -
XMOS 384kHz high-quality USB to I2S PCB with ultralow noise 6.5uV regulator | eBay

for $55 the miniDSP miniSTREAMER is TE7022 based -
miniSTREAMER | miniDSP

or for $40 CM6631-based -
CM6631 24bit 192kHz USB to Coaxial and Fiber WLX | eBay

But you're spending money to improve the front end of a DAC that is not exactly high end. This money might be better put towards a good DAC/USB receiver combination -
$145 will get you the well-regarded Objective DAC (ODAC) with ES9023 DAC chip, plus the respectable TE7022 USB receiver -
Objective DAC (ODAC) - RCA Version

The same component choices, though not quite of the same construction quality, are available from HiFimeDIY for a ridiculous $60 -
HiFimeDIY Sabre USB DAC 2. External PSU, 96khz/24bit - ES9023+TE7022 + Coaxial OUT

lot of good options here, thx for the great info.