Mac vs. PC differences to Airport Express?

Thanks for all of your advice, guys. I have decided to get a Trends UD-10.1 USB converter for now. I will use my iBook laptop attached to an external hard drive. I will go

Mac iBook >Trends USB converter > S/PDIF cable > Benchmark DAC-1 > analog out > Musical Fidelity A5 Integrated > speakers.

Down the road I will either mod my existing Benchmark DAC or upgrade to a USB DAC, but for now this looks like the best way to improve my sound greatly for just $150.

The only question I still have is what cable format to from USB converter to Benchmark DAC. I can use my existing Stereovox HDXV S/PDIF to BNC cable
or
I could use an XLR cable between the two.
Any feedback on that?

I would use XLR first any maybe compare to see what sounds best.

Jax2,
I agree the more steps along the path the more chances to signal derogation. I think light pipe is less suspetable to problems than electrical signals and can cary 8 channels of 24/96 audio, thats a lot of room if you are only using it for 2. one way you convert digital to electrical signals the other to light. We always use fiber in high end computers to large disk arrays because it a better, faster medium than electrical signals.

Thanks, Mark. I already own the coax cable, so I'll try that first.

Steve, would you keep the Benchmark's volume in 'calibrated' or 'variable' mode?

Would replacing the stock fuses make a difference?

Audioengr - I also stream my music via PC iTunes to an Airport Express, toslinked into my Benchmark DAC-1.

1) May I ask what is the reason to use Pace-Car reclocker while Benchmark DAC1 already has UltraLock that claim to reduce jitter to almost nothing?
2) How is your Pace-Car compare to other reclocker devices such as Audio Alchemy DTI, Meridian 518 or Monarchy DIP 24/96?

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