Review: Jkeny’s modified Hiface - Page 3

There a lot of factors that can affect the performance of the transport: clock jitter, phase noise clock, power supply, ground traces, output transformer, output impedance, quality of the connectors, ...

The Elite Pro and the Essential were not build from the ground up to serve as a transport. For example they don't use true audio clocks. It means that when you are listening to 44.1 CD (or any multiple such 88.2 or 176.4), their clock has to be derived from a 48 multiple which makes things even worse.
The Esi Julia use true audio clocks (one for 44.1 multiples and one for the 48 multiples). I remember reading a user (on the m2tech thread) saying that the hiface was a pretty big improvement over the Pro PCI Esi Julia.
I would also like to see the clock phase noise of the clocks being used in those soundcards. (The hiface clocks for example are -78db at 10hz and -140db at 1khz which is relatively low). Those figures are far more important than ppm for example.

Jkeny's mods have addressed the one weakness that the hiface had: the power supply. The hiface draws its power supply from the computer: even if you put the best commercial computer power supply, it will still have much higher noise levels than the battery power supply he is using for his mod. By bypassing the 3.3 voltage regulators and "injecting" directly the very low noise battery power supply, the benefits of that battery power supply are even more appreciated. Even the best voltage regulators (regardless of the power supply) will have some kind of noise.

As for the Audio-gd DAC you are mentioning, I did my tests with a similar one (the dac19dsp) and it is defintely sensitive to the quality of the transport. Kingwa, the designer of the dac, also says that while in theory it shouldn't be affected by the quality of the transport, it is the case in practice.

I haven't listened to neither the Elite Pro nor the Essence in my system, so I can only speculate. However, my best guess given everything I know about jitter and digital design is that the Elite Pro or the Essence ST are no match for his modded hiface. The stock hiface already had better measurement than the professional PCI LynxTwo card (which is a few steps above consumer cards such as the Elite Pro and the Essence ST), so it would be highly unlikely if the modded hiface didn't outperform by a very large margin consumer PCI cards such as the Elite Pro and the Essence ST.

ps: the measurements about the hiface I am referring to are here: http://www.head-fi.org/forums/f46/us...ml#post6063226
pps: I am making my assumptions about jitter and transports, simply because a good measuring and sounding transport doesn't happen by accident as there are a lot of conditions to fulfil to do so.

Sorry, my explanation wasn't very clear I think. The Elite Pro might be perfect but the problem lies in the way the clocks are being handled.
For instance, the X-Fi seems to have only one clock at 24.576mhz which is perfect for playing back 48khz as it a 512x multiple.
Let's assume that you want to play a 44.1khz, if the data is bitperfect, the 24.576mhz has to be derived someway to give the 44.1 frequency. If you do the math, the 24.576 has to be divided by a non integer (557.278911...) which is not easy to do and will undoubtedly increase the jitter. So even if the x-fi used an ultra low jitter clock (which it doesn't seem to be the case), it would still have to go through a lot of steps.
The Hiface (and other high end units) use 2 clocks to avoid that problem.

So it is not a problem about the data (bit perfectness) but rather about the timing of the data (clock jitter, clock phase noise, ...)

Concerning your question about the "jitter clock", there are many ways to connect a transport to a DAC. You can read this article here: The Digital Forest : LessLoss high end audio power cables, video power cables, audiophile power cables, audiophile cables
The way we connect our DACs to the transports (by slaving them) is the least effective way but it is also the easiest to implement.

By the way, you seem to misusing the term "jitter clock". Maybe you mean "low jitter clock"? But in any case, I doubt that you will find a low jitter clock in a consumer device such as the Elite Pro.