M2TECH Hiface USB->SPDIF 24/192Khz asynch

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jkeny

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Joined 2007
Charles said:
Your findings are interesting.

Reclocking the Master after isolated I2S transmission IMO is a good idea, but at the same time this is what people normally want to avoid first place by going I2S instead of S/PDIF.
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Well yes, that is true so I'm wondering if the whole I2S thing is not such a good idea when dealing with USB transports which have possible dirty grounds?

However being connected to the computer's power noise in any way is a pain, and it will always limit playback quality.

In the end ... reclocking the I2S master clock - or - reclocking the master clock after optical S/PDIF transmission and clock extraction is not so different an approach.

The quality you get in the end is that of the reclocking solution.

What do you think ?

Charles :)
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What you say is indeed possibly true - there ain't much difference between re-clocking I2S or SPDIF. There is one question I can think of - SPDIF receivers are known to introduce data correlated jitter - this is addressed by re-clocking - might there be other detrimental effects that re-clocking may not alleviate?

I was going to go balanced, anyway - so what do you think of this approach?
 
C

Charles

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Joined 2002
altmann.haan.de
jkeny said:
Well yes, that is true so I'm wondering if the whole I2S thing is not such a good idea when dealing with USB transports which have possible dirty grounds?


What you say is indeed possibly true - there ain't much difference between re-clocking I2S or SPDIF. There is one question I can think of - SPDIF receivers are known to introduce data correlated jitter - this is addressed by re-clocking - might there be other detrimental effects that re-clocking may not alleviate?

I was going to go balanced, anyway - so what do you think of this approach?
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The only way to completely avoid this problem is going optical.

A transformer makes it better, yes, going balanced may also improve things, however those methods do never offer a complete solution.

Optical means complete isolation.

Yes you get a bit more jitter, but that 'can' be solved on the receiving side, and it can be solved very close to 100%.

Charles :)
 
S

Spartacus

Member
Joined 2002
For those wanting to isolate their Hiface

While investigating a popping/clicking issue with my Hiface using the Windows DirectSOund driver, I tested the USB through-put:

@44.1KHz, 24bit
Average bit rate: 3.216 Mbps
Max bit rate: 4.447 Mbps

Seems like the 480Mbps High-speed figure is the max allowable bandwidth the bus will support. I think there's a fair chance that a 12Mbps full-speed isolator will work ...
 
J

jkeny

Banned
Joined 2007
Hi Leo,
That would be interesting indeed - I'll try it when I get a chance but won't be soon, I think.

I've set up a web-site about these Hiface mods & will be adding to it with the DIY instructions that are in this thread. Home (Hiface Mods)

I've also boxed up the modded Hiface. Boxed unit contains 2 batteries, modded Hiface & connectors specified below. It's about the same dimensions as an iPhone but thicker

Front shows USB-in connector
Back shows BNC-out, On/Off switch, socket for charger

Pics:
An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.
 
S

Spartacus

Member
Joined 2002
Hi John, it's Dan actually ..... would like to lose the "Spartacus" handle as I chose it years ago when I was really into online gaming. Feels a little .... young .... these days. :)

I'll give the ADuM isolator a go some time soon hopefully, but I'm waiting for the next driver to sort out an issue with popping noises I've been getting. Then I'll start modding my Hiface in earnest, borrowing from some of your tips and pictures. I'll probably use regs instead of batteries though.

Good luck with the modding venture by the way. The case looks a good idea ... how about an I2S output?
 
J

jkeny

Banned
Joined 2007
Sorry Dan, why did I think you were Leo from AOS?
Good luck with the modding - I would still advise a battery for the clocks for best sound & if you have one in there then ....... :)
Thanks - I2S is not a standard & not really of use to most people unless they can mod their DAC to take I2S in. If they can do that then ............
 
J

jkeny

Banned
Joined 2007
Spartacus said:
Hmmm, where do you get them from?
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Oh you doubting Thomas (Dan)

From their web-site:
ANR26650M1A: The ANR26650M1A is A123 Systems’ pioneering product, originally designed for a new class of power tools. Applicable to a wide variety of system designs and currently in mass production, the 26650 cell offers excellent price-performance.

Power: Over 3000 W/kg and 5800 W/L
Safety: Excellent abuse tolerance and environmentally friendly
Life: Excellent calendar life, 10X cycle life vs. conventional lithium ion

Our batteries use a new type of cell construction based on a dual plate tubular design optimized to deliver very high power with high efficiency. This new design does not use crimp seals and instead opts for a more advanced “all laser welded” construction optimized for very low humidity penetration over the life of the battery as well as stronger, thicker dual plate headers.
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J

jkeny

Banned
Joined 2007
Sure,
Drop me a email - I have a PH shunt that I just ordered which I wanted to compare against the batteries too. What other regs do you have?

Specwise, the battery is stupendous - <8mOhm impedance, 2300mAH, 120Amp discharge for 7 seconds 70Amps continuous, - no measures of noise but other scientific papers that I've read about battery noise (not the TNT one) show broadband noise down in the -180 to -200dB for NiCd batteries AFAIR.

You have a Buffalo? Might be interesting to power it with these - certainly cheaper than PH regs. That's how I'll be powering my ESS AckoDac :)
 
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R

regal

Member
Joined 2004
jkeny said:
I have noticed a sharp edge to the sound of my modded HiFace set-up when using I2S as compared to SPDIF. I've been thinking that one explanation for this might be the SPDIF transformer providing galvanic isolation from the DAC. So I'm back to this old chestnut again of galvanic isolation. Here's my summary of the info about this in the thread so far:
- high-speed USB 2.0(480Mbps) cannot be so isolated with currently available technology.
- isolating I2S will introduce jitter (using ADUM, etc)
- this could be an acceptable trade-off Jitter Vs ground Noise
- if MCLK is rec-clocked after the I2S isolation it might be more acceptable.

One further thought occurred to me - what about splitting the I2S signal & going differential to two DACs i.e one DAC process R+/- & the other processing L+/-. I don't suppose the simpler version of one DAC processing R+/L+ & the other processing R-/L- would remove common noise (as effectively or at all?).

Would this achieve the same result as galvanic isolation in that it would remove common noise?

Can it be done effectively at 24/192 speeds?

I'll start a new thread on this as it applies more generally than just the HiFace
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What about the wireless USB hubs, http://www.iogear.com/product/GUWH104KIT/ Would be easy to give one of those clean ground. Also I don't do Hirez so I could live with USB1.1, is the Hiface compatible with 16/44.1 USB1.1?
 
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analog_sa

analog_sa

Member
Joined 2002
regal said:
Would be easy to give one of those clean ground. Also I don't do Hirez so I could live with USB1.1, is the Hiface compatible with 16/44.1 USB1.1?
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Clean ground but at the expense of how much jitter? An optic isolator is a much better solution.

There is no reason to worry 16/44 compatibility but USB1.1 ports are to be avoided. For reasons i don't understand they sound much worse.
 
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