Originally Posted by regal
I still think these reports may point to anomalies in the Hiface jitter spectrum. I know Slim is very high on the 1nS jitter spec but if all that jitter is under the digital recievers PLL cut-off point (unlikely) it could point to an issue. My guess is that the power supply upgrade would fix this problem. My point is Jitter can't be summed with a single number, you have to look at what frequencies the jitter is peaking at. A good transport will have the jitter spread almost equal across 20-20khz, this is much less audible than jitter centered at say 300hz.
I think that except for the last few pages, the majority of the people described the hiface as being an excellent transport and better than CD based and computer based transports.
However, at the same time, some people like Shahrose and h.rav didn't like the sound of the hiface that much.
I don't think that the distribution of the jitter spectrum is the cause. I am pretty confident that if we measure it on a good computer, it will give better figure than CD spinners or other soundcards (even on the low frequencies).
I have thought about what might be the origin and I have came up with a few ideas/speculations:
1. Type of the DAC: upsampling vs. non upsampling, de jitter functions, DSP...
2. type of computer: motherboard, usb sockets...
3. Power supply to the computer
4. Vibration control of the computer
Point 1 - the type of the DAC
When people use any transport with a DAC that has an ASRC or a DSP like the one used in the audio-gd ref-1, results are unpredictable. If you read the specs and understand how they work, the jitter of the source should not be relevant at all since they don't treat the data in real time but they buffer it.
If you look at jitter measurements of the Benchmark DAC1 which uses an ASRC to "reclock" the data, you will see that even high amounts of jitter at any frequency do not affect the jitter measurements taken by an Audio Precision system 2 at the analog outputs. So any jitter in the Benchmark DAC1 would be generated after the ASRC. As long as we have bit perfect data, there should be no measurable difference in jitter figures whit most usb deviced (even the poorly constructed ones).
So if we assume the AMB Y2' ASRC is properly built (which I think it is), it wouldn't show any measurable difference in jitter figures regardless of transport.
The same thing apply to DSPs such as the one used in the Audio-gd Ref1 and audio-gd DAC19dsp. In theory, the transport shouldn't matter as long as it is bit perfect.
However, listening tests seem to indicate that there are other factors because different transports and digital cables affect the sound of thoses DACs.
Funny thing, Kingwa (the designer behind the audio-gd gear) encourages people using a high quality transport despite the fact that theory and some measurements say it shouldn't matter.
To sum up, I don't think we should make assumptions about the jitter spread of a transport when listening to such equipment. At least, in my opinion, it is not a safe assumption to speculate that by miracle all the jitter of the hiface is centered at 300hz. If that was the case, everyone who has listened to the hiface wouldn't have liked it.
I am not saying that the hiface is perfect, but it is highly unlikely that it has some highly unusual spread of jitter just because a few isolated people didn't like it their system.
So far, the only measurement we have is the 1ns figure and it is a good one and speculating that the hiface has an exceptionally weird jitter spectrum is just trying to find an excuse to comply with the listening experience of a few people.
I think that by doing that, we are looking at the problem from the wrong side, I think that there are a other factors that affects the sound of a transport beside the jitter figure.
So what are those factors? Honestly I don't know. Even Kingwa (the designer of audio-gd) acknowledges that there are differences between transports besides the jitter measurement. But he didn't go into too much details about it.
Point 2/3 & 4 are just based on my own listening experience: all of them made noticeable changes to the sound of the hiface. So by proxy, I am assuming that different opinions on the hiface (a lot of people liking it and a few not so much) are partly due to those points.
Point 2 - different computers
I have tried the hiface on 2 different notebooks connected to the same dac with the same digital cable and it sounded slightly different. (The emu 0404 usb showed however more differences between the 2 notebooks).
Also, it has been reported by many that different usb sockets sound differently.
Point 3 - Power supply
The power supply to the computer is important. I am plugging my notebook to a separate power filter than the rest of my chain. I have also noticed than running the notebook from battery changed the sound.
Point 4 - Vibration control
I never thought a computer performance in streaming audio would be affected by vibration. It happened to me by accident when I was switching the place of my notebook from a glass shelf (in my living room) and I put it temporarily on my wooden floor. The sound changed and it took me a while to understand what was happening.
I will spare you the details of I tried after but I have finally settled on Herbies's Audio Tenderfoot under the notebook. I am also using a thick acrylic shelf (instead of glass).
Those small tweaks made a big and noticeable improvement on the hiface. I have had a lot of friends laugh at the decoupling of the notebook when they first saw it. But usually, as soon as they listen to the sound, they forget about those weird "tweaks".
So my speculation is based on how the sound changed with those tweaks. I can imagine (or even create) a situation where the hiface is plugged in the wrong usb socket, where the power supply to the computer is not (or is poorly) filtered and where it suffer from a lot vibration coming from the computers.
Contrary to many other converters, the hiface is directly "hard wired" to the computer which must make it a lot more sensitive to some of the things I described.