Mac vs. PC differences to Airport Express?

The data stream from the AE is identical whether it is PC or MAC. The audio quality is the problem - very jittery. You can get decent "background music" with a glass Toslink, but that's all IMO. If you want to transform the AE into something world-class, then I recommend this:
http://www.empiricalaudio.com/frPace-Car.html

Steve N.
Empirical Audio
Manufacturer

Kana13 - you've got to be joking right?

This will never compete with a Pace-Car. I dont care how good the clock is. I also do a mod to the AE called the Off-Ramp Wi-Fi. Same thing as the French company, new clock, new power supply, new S/PDIF output circuit. It's not even remotely close to what the Pace-Car does. I have only sold a few of these. I dont even try to sell them anymore. Pace-Cars is what sells because they are amazing.

Steve N.

TomEdison - the Modded DAC-1 would probably be more smooth and listenable IMO.

Most unmodded gear has sibilance as well as jitter. Eliminating the sibilance is probably more important than reducing the jitter. However, both are needed to achieve a really fatigue-free sound with the best clarity.

BTW, nice invention, the lightbulb, but they are quickly becoming relics.

Steve N.
Empirical Audio

Juanitox - you dont have to trust me, although I wish you would.

I rely mostly on posts on the forums - customer feedbacks for advertising. I sell all of my products word-of-mouth. No advertising to speak-of. My advertising budget for the year is about $250. Even with this, I have had a 5 month backlog all year.

I post on these forums mostly to dispell misinformation and prevent people from making bad choices.

Steve N.
Empirical Audio

Mhfun -

1) because the jitter is not almost nothing IME. I mod the DAC-1 and DAC-1 USB, so I get to hear them both frequently on my reference system. (The DAC-1 USB is a significant improvement over the DAC-1 IMO, particularly the USB input) I can plainly hear these differences. The only explanation that I have is their system must not be very resolving or other sibilance is masking the jitter if they cannot hear the difference. There are other things that they say they cannot hear, so I believe this is a reasonable explanation. I have found that even many famous magazine reviewers systems are sub-par, so this is not unexpected.

2) The Pace-Car is only similar in function to only one other reclocker, and that is the Genesis Digital Lens. This one also stores the data in a FIFO memory and clocks it out with a totally isolated, independent clock. The difference is that the Genesis is designed to work only with CD's of a limited length. The memory in it will eventually overflow, so it cannot be used with computer and long playlists for instance. The Pace-Car does not overflow.

The other reclockers that you mention are primarily ASRC, or asynchronous sample rate converters, similar to what is done in the DAC-1, Bel Canto and others. They change the data stream using various chips that upsample the data to a higher resolution. This asynchronous process does reduce jitter significantly depending on the chip used, but I have yet to encounter a chip that has complete immunity to the incoming jitter. Also, the quality of the clock used to drive the ASRC chip is critical. A $2 oscillator is not sufficient to get inaudible levels of jitter. A Superclock, Tent clock etc.. is required IMO.

The other way that other reclockers work is to use multiple levels of PLL or phase-locked-loops. Each PLL locks onto the incoming stream and reduces jitter a little. After passing through several of these, the jitter can be reduced significantly, but there is always some sensitivity to incoming jitter. The clock quality again is very important too, this time of every stage. If there are 4 PLL's, then you need 4 Superclock4's for instance. This can get really expensive.

Another difference with the Pace-Car is that is also has I2S output. If you have a DAC that can accept this interface (DAC-1 can be modified), this is a more direct route to the D/A chip and reduces jitter even more compared to the typical S/PDIF input.

Steve N.
Empirical Audio

Thomasedison - I would keep the DAC-1 or DAC-1 USB in calibrated mode, and change the balanced output jumpers to max output level.

I replace the fuses with 3 amp fast blo. This is sufficient to protect the transformer and board, but maybe not the chips on the board. Chips are cheap, but transformers and boards are more expensive. This does seem to make a difference. You can also try the silver fuses in fast-blo.

A good power cord also makes a world of difference. I have one custom-made for my Spoiler DAC and I use this one on my DAC-1's. It is over $1K and silver though.

Steve N.

Mark02131 - your logic on Toslink would seem to make sense, but it is flawed. The only benefit is galvanic isolation, and you can get this with coax also.

The optical-electrical conversions add a LOT of jitter to the digital signal that is carried to the ASRC chip. It is my least favorite means for digital transmission. Fine for data, but not for real-time timing-sensitive signals.

Steve N.