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Enjoythemusic review of jkeny modified Hiface

jkeny

Banned
2007-02-06 12:43 am
Dublin

jkeny

Banned
2007-02-06 12:43 am
Dublin
Some time ago I mentioned that I had scope shots of the stock Vs modified Hiface & of the effect of RF attenuators. I couldn't post these pictures as they were to appear in a review. That review has now been published MK1 Boxed M2Tech hiFace Evo USB To S/PDIF Converter Plus the Halide Design Bridge and John Kenny Mk1 boxed hiFace A 'bit' more rambling about USB to S/PDIF interfaces. Review By Mike Galusha

So I can now post these pics:
- the two pics shown in the review show the rise/fall time decrease from 6.1ns to 3.92ns as a result of the PS modifications.
- Below is a pic showing the fall time
[IMGDEAD]http://dc185.4shared.com/img/ys1OcuU6/JK-Hiface_fall_time_no_attenua.jpg[/IMGDEAD]

I'm looking for a reasonable/possible explanation for this reduction in the transition time due to the PS modifications!

- Below is a pic showing Hiface without RF attenuators
[IMGDEAD]http://dc233.4shared.com/img/ZCKJSdn1/JK-Hiface_no_attenuators.jpg[/IMGDEAD]
- And a pic with RF attenuators (10dB + 6dB)

[IMGDEAD]http://dc233.4shared.com/img/099mlw3C/jkhf-attenuators-20ns.JPG[/IMGDEAD]


The RF attenuators noticeably reduce the squiggles on the top of the SPDIF waveform. These are interpreted as reflections of the SPDIF signal. A reduction in these reflections can result in the reduction in jitter.

There are other scope shots from other sources which show the same effects for the RF attenuators.
 

jkeny

Banned
2007-02-06 12:43 am
Dublin
The two scope shots below show the effof ect that a better PS has on the SPDIF waveform.

The better PS speeds up the rise/fall time slope of the SPDIF waveform. Somewhere about half way up the slope of the line is the decision point. I believe that the faster/steeper slope makes for a more accurate decision point with a better chance of it matching the timing of the decision point in the recording. Any variability in this timing match leads to jitter.

The modified Hiface with better PS showing a faster rise-time
[IMGDEAD]http://dc180.4shared.com/img/HyZmRo3K/s3/JK-Hiface_rise_time_no_attenua.jpg[/IMGDEAD]

The stock Hiface showing a slower rise-time
[IMGDEAD]http://dc180.4shared.com/img/O6q-cMJA/s3/USB-HiFace_rise_time_no_attenu.jpg[/IMGDEAD]

The second picture seems to show a kink in the rising slope - could this be a reflection falling on the slope?
 
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John,

Something is a bit strange here.
The stock Hiface has 1.5nsec rise time. I have shown 1.8nsec rise time in the RF attenuators.. thread long time ago, later on re- measured with some real fast scopes and it had settled down at 1.5nsec.

Then lately had got a most recent unit, still stock. It's even faster, 1nsec.

Ciao, George
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
I have some scope shots that I will post ASAP of the hiface SPDIF stream.
They show the same overshoot as seen in other shots. But the BNC attenuators do seem to reduce that overshoot twice as much as they reduce the signal.

Not that it makes any difference. Without the attenuators I was able to make a bit perfect recording via USB<->SPDIF<->USB from one computer to another and also from the same computer to itself.

So the Hiface is capable of sending a bit perfect stream, I have no doubt about that. And that's a complex musical signal, just in case you were wondering, not a test tone.
..
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
Listening

Finally got a chance to lsiten to the modified hiface in action and compared to 2 other USB/SPDIF devices.

The Hiface sounds better.

I compared it to a cheap USB dac I got years ago off eBay. One of those 5.1 Dolby things with Toslink in and out - cost about $20.
Also compared to an M-Audio USB card that has coax SPDIF in and out.

The Hiface was "clearer." That's the best way I can describe it. More detail, more space, more ambiance, cleaner textures. It even sounds a bit more dynamic, but that has to be my imagination. Tonal balance is slightly cooler than the other adapters - maybe because the Hiface sounds more open, fuller.

On classical music it is the most obvious, from small string quartets to big choir with orchestra and pipe organ. On country and pop voices were more present and tactile. Cymbals more detailed, bass fuller.

I am not talking about huge differences here, not night and day. But maybe morning and mid afternoon. ;) It is definitely more pleasant to listen to.

Important Caveats
  • This was not a blind test. I did the switching.
  • All listening done via headphones.
  • I have not heard the unmodified Hiface, so don't know if it's different.
  • The cheap adapter is optical only, which may make a difference.
  • I did not expect to hear a difference.

I do need to set up a blind test and will try to do so. I do believe that I can pick the hiface in a blind trail better than chance. But only the test will tell.

So far, that's what I've learned.
..
 

jkeny

Banned
2007-02-06 12:43 am
Dublin
Thanks Pano,
You have confirmed my & others scope shots above & the prediction that the attenuators reduce the perturbations by twice the value of the attenuation. This is predicated on the idea that it is reflections that are being reduced by this amount & reflections make a round trip i.e pass through the attenuator twice before reaching the DAC (or in this case the scope).

Nobody claimed the attenuators effected the bit-perfectedness of the SPDIF data stream. What they do effect (reduce) are these reflections. And as I have said before these reflections are directly related to the production of jitter effects at the DAC. I'm not the only one to claim this or that the attenuators work in this way.

I look forward to your scope shots & to your listening test results on the attenuators & the modified Hiface.
 

jkeny

Banned
2007-02-06 12:43 am
Dublin
Ah, I see we crossed posts.

Yes, thank you for this honest report. Your caveats are spot on & I look forward to your blind tests on both the attenuators & the modified Hiface.

Yes, a comparison against a stock Hiface would reveal the effects of my modifications & vindicate my lauding of battery power instead of USB power. I have stock Hiface units but shipping to US from Ireland & back is too costly. Maybe someone locally has one?
 

jkeny

Banned
2007-02-06 12:43 am
Dublin
I'll try the attenuators, tho I don't think they will matter. Who knows, maybe that peaky waveform is what makes it sound good. ;)

Well, I believe the exact opposite - reducing/removing those reflections (peaky waveforms) will help the sound. Let's see who's right - maybe neither - maybe it will harm the sound :). You should be good with about 20dB on the output of the Hiface. Try a smaller value on the output of your M-Audio. BTW, have you looked at it's SPDIF output waveform?
 
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jkeny

Banned
2007-02-06 12:43 am
Dublin
A couple of other things, Pano, if I could ask of you:
-Can you use something other than a DCX as a DAC? Maybe some friends have a DAC?
- This thread is off the beaten track of the forum & I don't believe those that followed the RF attenuator thread will look at this so they will be denied the exposure to this new information.
-Could a post be put in the RF attenuators closed thread that points to this as the continuation of that thread. Would you be able to do this please? OR
- Do you want to reopen that thread with this new information or do you have any objection to me opening up another thread to put this in the main part of the forum?
 

sandyK

Member
2007-04-27 12:54 am
Sydney
A bit of serendipity - a reviewer in Australia has just published this glowing review of the MK2 Hiface & the RF attenuators John Kenny modded M2Tech HiFace MK2
John
Some friendly fire !;)
A nice review. However, who is this John Darko ?
What are his qualifications, and why nothing more than subjective reports ?
I have no problem accepting much of what he is saying, due to my own findings in this area, but his review fails to do more than confirm other subjective reports.
Alex
 

jkeny

Banned
2007-02-06 12:43 am
Dublin
Yes, Alex, you are correct, it is a purely subjective review with no attempt to measure or do blind tests. I guess it will be ignored by those who insist that a double blind test is the only yardstick by which they judge such subjective comments. This just adds to the weight of subjective evidence that has already been accumulated. However, I would also draw your attention to Pano's statement above
I do believe that I can pick the hiface in a blind trail better than chance. But only the test will tell.
Of course, I hope that this doesn't negate the blind testing that he is intending as it does introduce an expectation bias. However, is it the case that an expectation bias only works on a blind test when the expectation is that no difference will be found?

Anyway, looking forward to Pano's further test results.

Pano, did you manage to get that scope shot ready for posting yet? It could be interesting.
 

sandyK

Member
2007-04-27 12:54 am
Sydney
Anyway, looking forward to Pano's further test results.
John
They would be much more meaningful if Michael is able to obtain a standard Hiface to do some comparisons against.I agree with your comments about a different type of DAC being desirable as part of the tests, but I applaud Michael's decision to use headphones, which are far more revealing of small differences in the absence of much higher resolution living room systems.
Alex