Enjoythemusic review of jkeny modified Hiface

[jkeny]

The review of the modified Hiface has finally arrived 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
It compares the M2tech Evo & the Halide Bridge to the JKHiface. Remember this is the MK1 version that is being reviewed so the battery comments don't apply to the MK2 & are somewhat incorrect for the MK1 anyway!

[jkeny]

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


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

- And a pic with RF attenuators (10dB + 6dB)




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]

Can't seem to post these pics in a larger form! Here's the link to them 4shared - pics - shared folder - free file sharing and storage

[julcat]

Hello JKeny

Interesting article, i recently buy one modded mk2 from you, still waiting for it, did you know where to get the RF attenuators mentioned in the article??

[jkeny]

Yes, Julcat, I got your order on 26th - next week for delivery!
Also note that the MK2 sounds better than the MK1

There is a lively discussion about these attenuators here RF Attenuators = Jitter Reducers

The minicircuit site for these is mentioned in the first post

[jkeny]

More scope shots showing effect of attenuators on stock Hiface taken by Joseph K:

First stock Hiface SPDIF waveform with no attenuators


Stock Hiface with attenuators

[jkeny]

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


The stock Hiface showing a slower rise-time


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

[Joseph K]

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

[jkeny]

OK George, let me run some tests here & get back!

[Pano]

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.
..