M2Tech hiFace Asynchronous USB To S/PDIF Converter Review

MR · August 25, 2010

to the HiFace. I lived with one for more than two months while I waited in line for another company's async USB->S/PDIF converter (the Legato -- costing almost 3x as much). The HiFace can't compete and shouldn't be expected to. I believe it's the close contact with computer power and grounds that causes the sound of my DACs to lurch forward, with some of the spitty-ness we call glare or haze. The more expensive interface box has its own all-out power supply and doesn't bring the USB power lines into the USB cable. The jkenny power mods to the HiFace back up what my ears hear. So much of this depends on the DAC -- how good its defenses are against ground and power noise in addition to how well it handles jitter. Some low-end DACs might sound the same with almost any interface -- and some high-end DACs may have the defenses to do the same. (For example, the Theta Gen VIII buffers the S/PDIF stream and then re-clocks it inside the DAC -- such a technique should tend to minimize jitter-based sonic differences among inputs).

In our avocation, there is no "always and everywhere." No component *always* sounds better and no component *always* sounds worse. One thing I have learned from computer audiophilia is that component matching is critical given that we have the freedom to do so.

BTW, I have a HiFace EVO as well, and to my ears it outperforms the HiFace by a good bit. It's not always the case . . . but in this case, maybe that's why it costs more.

kamil · August 25, 2010

MR, so how does the Evo compare then to the Legato in your system?

Tipper · August 25, 2010

I’m beginning to wonder if I read the same review as some of those who have commented.

What I got from Chris’s review was while he thought the Hi Face excellent value for money even at such a low price there were a few obvious issues that should be addressed by any company marketing such a product.

1) The drivers were not particularly satisfactory and the company has some history of supplying the wrong drivers for the product. It seems Chris also found the uninstalling the drivers from other user reports problematical.

2) Chris also notes the lack of galvanic isolation in the device; something that for USB connection is pretty standard for both other USB to SPDIF converters and other USB Dacs around this price range.

3) He also raises a valid point regarding whether or not any drivers are required for a device such as this. Perhaps the Hi Face may have done better to forgo the 192 capability for OS that do not support it natively.

4) The fact that the Hi Face has a considerable overhang when attached directly to say a laptop could also be an issue in his opinion as could be the blocking of other USB ports.

Add to this he didn’t find the overall construction particularly good and what he considered to be a sonic performance one might expect from a product at this price level then his opinion that perhaps this is a product that has been somewhat over rated seems more reasonable.

While I agree with many of the people who have commented on the relevance of comparing this product with “reference grade components” it seems this is pretty much standard practice for most reviewers.

Audio_ELF · August 25, 2010

@Tipper ... I generally agree with your assessment of Chris' review however... "While I agree with many of the people who have commented on the relevance of comparing this product with “reference grade components” it seems this is pretty much standard practice for most reviewers."

While that is true, most reviews compare components within a reference grade system and also withing price comperable system - i.e. in this case yes use Weiss DAC202 and berkely Alpha, as reference grade system, but also needs using with £500 - £1000 DACs (Musical Fidelity X-DACv8, Cambridge Audio DACMagic, Lavry DA10, etc).

MR · August 25, 2010

in with the EVO to say. I am letting it break in on a system with no amp (separate J River zone). All of my regular listening is through the Legato, with which I am well pleased. Maybe I will have an opinion in a few weeks.

I should point out that I use a Jurrasic-era DAC (Theta Gen Va 96K balanced), vintage 1993.

weib · August 25, 2010

comm'on chris wrote a review and that's his decision.

Fair or not fair..well if you felt it was represented wrongly, you can always create your own site and write your own review.

give it a rest already.. any comments now trying to defend the hiface only makes it sound it's from a religious zealot.

Andrew S. · August 25, 2010

I liked the review. Reflected an opinion honestly held.

I agree it is not without problems but is a great little device for inexpensive usb - spdif transfer.

Audio_ELF · August 25, 2010

@weib...

Actually this is a forum. Chris wrote a review and by the nature of a forum he's opening it to questions and comments. Chris hasn't complained about this, in fact he encourages it. Everyone has a different view / point of view.

I don't think anyone has out and out disagreed with Chris anyway, just wondered if his context is quite valid for this product...

Eloise

HaMa · August 25, 2010

hello,

as I'm new to the CA forum let me briefly talk about myself. I'm with 2ch hifi since more than 30years now and still like it :-) - the equipments I refer to is named at the end. I'd like to send you my report as I identified myself as one of these guys which are believed to be the hiface users...

I'm running my T+A digital preamp since more than 8y with the according CD transport. I believe when I got this devices it was either already the end of a decade showing CD transports w/o a DAC or the start of this new decade with separate DACs again.

However I liked the idea of having an excellent (but expensive) digital converter which may be used not only for the CD player but for my desktop TV or DVD in some future.

Years ago I tried the integrated SPDIF output of my notebook (never had an desktop)just to check this option with my Pre. Immediatelly it worked and I got easy access (and was impressed) to lot's of compressed music, but the sound was so disappointing that I used it randomly for some netradio. I thought there is much more to gain with a source, but after learning about XP, the kernel, the drivers, the soundcards and all the other concerns I simply gave up due to time limits and the experienced results.

From time to time I tried again to find a sufficient way on computer audio but instead found even more obstacles like ripping file formats, bit perfect data transfer or just the fan noise of a computer to be wiped out. I was even more frustrated about the endless list of concerns found in the internet. Professionals talked easy: just spend a considerable amount of cash, forget your existing DAC and that's it! But I was still very much concerned about using a PC as music source at all.

Lately, getting more in touch with a variety of digital and also high resolution music again, I tried another attempt...(and I needed a good reason for myself to skip the old notebook)

Nokia issued a netbook with a solid touch (cast metal- low resonance), style (husbands know what I talk about) and a fanless design (even the HDD is super silent). Moreover 10hrs. of operation, I still like the idea of a battery powered music source.

Hiface was issued claiming to be easy to use and all the other nice things mentioned in the review. foobar was recommended with KS and requires low CPU power even with large files. A must as the netbook is pretty weak due to it's fanless CPU and long battery time. It offer's an SPDIF which is the only access to my existing digital Pre.

All in all less than 1k$ just give the whole idea again a (final) chance for me. It just took me 2-3 hrs. to set up the whole chain - and it works, and how it works !

It did not compare the sound 1:1 with my transport up now, but it is immediatelly good enough to continue the story in the future. For me the success of hiface is due it's sound per expenditure potential and the simple integration into my existing environment.

In a sentence, I like the detailed review with all the pros and cons, but concluded a different result for me. That is what a good review is for.

HaMa

PeterSt · August 26, 2010

... and that is a priceless virtue of the HiFace.

Which is all you wanted to say of course.

Nice story and very well said.

And welcome here of course !

Regards,

Peter

Lowlands · August 26, 2010

Chris,

I re-read the review. My eye fell on:

<cite>"Async USB transfer mode has nothing to do with asynchronous sample rate conversion (ASRC) even though some manufacturers would like listeners to believe ASRC is an equivalent competing technology addressing jitter reduction." <cite>

I am afraid I am such a listener..

I understand USB transfer & ASRC to be unrelated, however, I was of the impression that ASRC requires a re-clock by an oscilator at the DAC, since the conversion rate differs from the offered sample rate. Or is ASRC typically implemented by a PLL+math solution on the incoming signal? If ASRC is generally implemented by a dedicated clock at the DAC, independent of the clock of the incoming signal, does that not qualify as 'a-sync'..?

Just trying to understand...

Hans

BobH · August 26, 2010

a lot of the terminology used is confusing, I agree. My take on it is not to try and sort it all out, but to ask 'why'. Why pick the same term to describe two completely different processes? Well, in order to confuse people, of course!

Why would you choose to deliberately try and confuse people? Well, the only logical answer is that you don't want them to fully understand, you want to leave as many little unknowns as you think you can get away with! They can make you a lot of money! Have a look around the high end hi-fi world at how many products are offered to 'solve' all the 'little unknowns' that have been created!

Now for something useful! When you see 'asynchronous' and 'USB' used together, substitute 'duplex' for the 'async' bit, it makes much more sense and is a much more accurate description of what is being made to happen.

When you see 'async' being used in any other context, start out by ignoring it and see if it makes any difference. If you can still understand what is being said then you don't need to worry about it!

Hope this helps.

PeterSt · August 26, 2010

<cite>Why pick the same term to describe two completely different processes?</cite>

Well, because it isn't the case ? haha

ASRC is about two clocks not running synchronously, therewith creating a new "jitter base".

Asynchronous communication (in the sense of USB) is about a clock drawing data from the PC (briefly said).

I don't see much the same in these two different terms.

<cite>even though some manufacturers would like listeners to believe ASRC is an equivalent competing technology addressing jitter reduction."</cite>

If I may ... I don't understand where this one is coming from (yes, from the review). Of course it is an equivalent means addressing jitter reduction. It is even better, although that won't have been the intention from Chris to say. But :

The means is so totally different that one can wonder what the result is for sound quality. So on that matter the "statement" may well be right. But now *I* like to know where the sortout of this one is (written). But of course I miss a lot, so why not this one.

Maybe this is not the thread for this subject, but the review seems to claim something which I not had accepted. Maybe Hans has the same problem. Maybe more people have.

Maybe it will be so hard to explain (which is different from "telling") that nobody is going to ...

... for sound quality, hence net result !!

Peter

John · August 26, 2010

@ Hans You are nearly right in your decription of ASRC. Yes it is implemented with a dedicated local clock at the DAC. However, the independence of impact that clock from the input clock is not 100%.

Timing errors in the input clock do not result in phase errors in the output samples; that piece IS independent. However there is an averaging process going on (phase aligning the two clock's edges) to tell the output clock which of the filter co-efficients to apply to calculate the interpolated output sample. So phase errors in the input clock translate into data errors in the outputed samples (wrong sample gets calculated albeit by vanishingly small amounts). This is not as bad as it seems unless the jitter is high and certainly should be better that just using a vco based pll. However it is not as good conceptually as slaving the transport to the DAC with async usb or firewire or whatever.

- John.

BobH · August 26, 2010

the same bit would be the use of the word 'asynchronous'. Incorrectly in both cases, as it happens! That was my point.

Asynchronous means 'not synchronised'. If we try and make it mean something else, by using it incorrectly, then we create misunderstanding and confusion.

In the case of sample-rate conversion, what is actually happening is that the algorithm is guessing. It's no more complicated, or scientific, than that. But scientists and software writers have a problem with the word 'guessing', so they come up with the wholly inappropriate use of a perfectly good word to cover up what they really mean. They could have used 'Interpolate', but everyone knows that's just intelligent guessing! Doesn't sound clever enough when you put it like that!

In the case of USB connections my suggestion of 'duplex', whilst still not entirely appropriate, is still better than saying that the connection is not synchronised. Not sychronised with what? Would it be better if it was synchronised? How does it produce superior results by virtue of being not sychronised with something? What would be wrong with simply saying '24/192 capable', or even Full HD!! At least people would be able to place that phrase into a real world context.

In case you hadn't guessed, this is my pet hate in computer audio. In fact it's my pet hate in high end hi-fi.

fredhammersmith2 · August 26, 2010

Hama

I'd like to know which Nokia netbook it is, since I am in the kind of pre-shopping phase...

PeterSt · August 26, 2010

LOL Bob. Thanks.

In the case of async USB ... what about the SIZE of the "packet(s)" taken per draw ? I'll bet that matters.

IOW, how async is async if that would be, say, 2 samples only.

No, never mind. You are right. It is as hard as it is already for someone who thinks he's experienced in the area.

Wasn't that you who (a very long way back) told me that it's nog Kg but kg ?

Maybe not, but anyway I didn't know, and always thought it was Kilo, not kilo.

Sorry to be off topic.

Peter

Wavelength · August 26, 2010

There seems to be a lot of confusion about what the differences are between Asynchronous USB and Asynchronous Up/Resampling.

Asynchronous USB in the basic sense means we have a fixed oscillator (usually 2 to support both 44.1/88.2/176.4 or 48/96/192) that controls the dac chip. This oscillator is also feed back into the USB controller and the I2S or other audio protocol is created from this oscillator. Since the host computer is not in sync with the Asynchronous DAC another USB stream or what we call pipe is sent back to the host computer to tell the computer to send more or less data to assure the Asynchronous DAC does not run out or over run it's local buffer to the dac chip.

Asynchronous Up/Resampler is a form of Fourier/LaPlace ideas that in math say that we can take an input sample at one frequency and either up or downsample (resample) each of the original samples into a new fixed asynchronous output. In all cases the input stream will usually never perfectly match the input stream and all the data used for this will work on the relationship between the input sample rate and the output sample rate.

Personal note, I am not a fan of Async Up/Resampling. Basically what we are talking about is reformatting the data to fit a new (asynchronous) sampling rate. The problem is that with this type of math there is a lot of low level information that gets washed out of the new sample because of the the manner in which these chips work. They all work on fixed math and see the basic idea which comes from LaPlace and Fourier in the early 1800's is that you take a infinite table of samples and multiply that by an equal table of coefficients and then you add this all up and it's your new sample at the new sampling rate. The problem is that all the coefficients are less than 1 and all of these chips use fixed point math which means that division has to happen and with that becomes remainders and most of this gets thrown away. Well that and the table cannot be infinite it has to be finite in some way. The other problem is that this math is usually carried out with little overhead, sometimes... well most of the time with on a 24 bit accumulator which means, again the loss of data. The other problem comes when you try and up/resample to say an odd frequency. Many can see that if we had say 44.1K and upsampled this to 88.2K that things would be pretty cozy. But taking 44.1k to 92K or 192K is usually not a real good sounding situation.

Both of these concepts have the plus side of having a fixed oscillator on the DAC chip which means that it will have (usually) better jitter than that of a product which has moving clock oscillators at the dac chip like PLL type oscillators do.

The main caveat here is that any designer can choose to do any of this and the results will vary widely.

Thanks

Gordon

BobH · August 26, 2010

that's the point I was trying to make. ;~)

Audio_ELF · August 26, 2010

Gordon said... "There seems to be a lot of confusion about what the differences are between Asynchronous USB and Asynchronous Up/Resampling."

I think the confusion comes just because the two terms both use asynchronous in their title and (maybe deliberately) some companies word product descriptions ambiguously as to weather they are ASRC or asynchronous USB.

Eloise

HaMa · August 26, 2010

@ fredhammersmith2

attached some reports on the nokia netbook I choosed as first computer music source. I do not know if it is available anythere else than europe.

http://www.timesonline.co.uk/tol/travel/business/article6985047.ece

http://www.metacafe.com/watch/3207910/nokia_3g_booklet/

http://www.nokia.de/produkte/mini-laptops

HaMa

barrows · August 26, 2010

thanks for your description of the problems/limitations inherent in asynchronous sample rate conversion (or commonly referred to as "upsampling" vs. "oversampling"). That is the best description of the ASRC process I have heard so far.

It is interesting to note that many high end DACs still are using some form of ASRC (Berkeley Alpha, Weiss DAC 202, dCS). It seems to me that not all ASRC hardware choices, or proprietary ASRC in software are equal in how much damage they may do. My experience with the common ASRC chips (4192, etc) has shown to my ears to my ears that there is some sonic compromise going on with these pieces of hardware.

I know you do not use the onboard ASRC in your implementation of the ESS 9018, I am currently building a DAC that will use the ESS ASRC, as some seem to believe ESS' implementation of this is better than that in standard hardware devices. I am interested to hear what the ESS 9018 can do with its onboard ASRC. Maybe eventually I'll figure out how to control the ESS chip, and provide a master clock to avoid the onboard ASRC as well, but right now I do not have the knowledge to be able to control the chip myself.

Richard Dale · August 26, 2010

J. Gordon Rankin: "..There seems to be a lot of confusion about what the differences are between Asynchronous USB and Asynchronous Up/Resampling.."

As a computer programmer we normally talk about a 'asynchronous api call' to mean that you pass a callback function to the asynchronous function, meaning 'tell when you have done stuff' which gets called after the 'asynchronous event' has occured. In contrast, if your program is 'synchronous' and you make a function call your program just stops (blocks) until the function call has completed.

However, in the USB specification it only ever talks about 'isosynchrous' protocols. There is a good explanation in in this Wikipedia entry <a href="http://en.wikipedia.org/wiki/Isochronous">Isochronous</a>

"..Isochronous : From Greek iso, equal + chronos, time. It literally means to occur at the same time or at equal time intervals. In general English language, it refers to something that occurs at a regular interval, of the same duration; as opposed to synchronous which refers to more than one thing happening at the same time. The term is used in different technical contexts, but often refers to the primary subject maintaining a certain interval, despite variations in other measurable factors in the same system.."

In the USB specification the data is sent every milli-second, whether you have an 'Asynchronous DAC or an Async one'. The only difference is 'flow control' which is about which end of the connection can say 'please stop my buffers are full'. With what we call 'asynchronous USB connections' the DAC end can say no and use its own local accurate clock, whereas with the normal type of USB connection the computer end is in charge, and the DAC end has to 'muddle through' with clever algorithms.

I am the very happy owner of an HRT Music Streamer II+ DAC which describes itself as 'asynchronous', and I am not bothered whether or not that is an accurate term in computer programming terms. As long as we know what it means in DAC terms, I don't think it matters.

jkeny · August 27, 2010

I see my mods & modified Hiface were mentioned a couple of times & I wanted to say that I did offer Chris my modified Hiface for review but it was rejected. I still extend this offer.

AFAIK, I introduced the idea of using attenuators on the Hiface in order to cut down the high output from it's SPDIF but more importantly to reduce any reflections to negligible levels. I have noticed that the Sabre DAC, for instance, clips when used with the high un-attenuated SPDIF signal from the Hiface. This high signal may well cause problems with other DACs & I suggest to Chris to buy a few different dB minicircuits attenuator for $12 & have a listen & maybe report back. More important than this output level reduction, the attenuators will remove the jitter inducing reflections & this is immediately noticeable in the sound.

I was at an audio meeting last night of about 7 people & a squeezebox was being used into a Paul Daniels NOS DAC. The difference in sound between without/with attenutor was noticeable within the first few seconds of playback.

There are 2 reviewers currently looking at the modified Hiface in comparison to other similar devices including the stock Hiface, Evo, Halide Bridge, Audiophileo & others. One of these reviews will be published shortly, I believe.

In relation to the idea of a "bad" Hiface crystal on the Head-fi thread - I think the jury is still out on this matter?

I'm interested in the bit about the higher level of jitter on the synch part of the signal - can this be explained in some more depth, please? BTW, I agree about the single digit jitter figure being an almost useless measure but that is often the way it is presented unfortunately & leads to the general misunderstanding about jitter & it's sonic effects.

Matias · August 27, 2010

John, where can I buy this cheap attenuator and test it myself? eBay?

Edit: already found it here.

http://www.minicircuits.com/products/attenuators_coax_fixed.html

M2Tech hiFace Asynchronous USB To S/PDIF Converter Review

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