Posted this elsewhere, but thought it might be of interest here as well. I've been listening to USB audio for the last several years, and over time have ripped most of my 1500 CD collection to HD, using iTunes, in Apple Lossless. My system has gone through numerous changes, and today consists of: 12" Mac PB G4, 867mhz, 1GB RAM Generic USB Cable out to HagUSB 1M Belkin PureAV Coax to Musical Fidelity CD/Pre24, which automatically upsamples to 24/96. 2M Tara RSC to Red Rose M150 mono-blocks 8' Ocos to Vienna Acoustics Beethoven In general, it sounds really good, particularly via the CD/Pre's built-in CD player. For those of you not familiar with the CD/Pre, it's an Analog Preamp, CD Transport, DAC and A2D converter in one box. There's also a full digital tape loop, and all digital signals, whether from the CD or the SAC are automatically upsampled to 24/96. The CD transport provides a handy reference w/ which to compare the performance of the DAC when driven by other transports. Most of my listening these days is via iTunes however, and although the sound is quite good, it's not as good as the CD, sounding somewhat flat by comparison. So i've been considering trading it in for a USB DAC and separate preamp. Before doing so however, I wanted to make sure I had a good picture of the quality of the CD/Pre's DAC, and determine if the problem lay not there, but upstream, w/ cables, the HagUSB, or perhaps the Mac itself. I tried several different Coax interconnects, including those from Staightwire and DiMarzio. The differences were subtle, but readily apparent, and for me, the Belkin offered the best combination of smoothness, transparency, even response, depth and space. and it's cheap! I'd earlier upgraded to the HagUSB from an Edirol UA1D, and the Hag made a huge improvement. So that left the mac. Fortunately, I had another machine to compare it to, my wife's 13" Intel based MacBook, which has a Toslink out. So i hooked the MacBook up to the one input on CD/Pre via toslink, using the Monster mini Toslink cable, and the Powerbook via USB/Coax to the other, and switched back and forth between the two. Tunes we on an external firewire drive connected to the PB, and the MacBook accessed them via iTunes sharing. Both machines were running Tiger, and iTunes 7.5. The difference was immediately apparent, not just to me, but to my wife as well. The MacBook/Toslink combo sounded more dynamic, more open, the PB sounding softer and more restrained by comparison. further listening revealed the MacBook was also more forward in it's presentation however, the PB more laidback, and this lent greater immediacy to the sound. ultimately it also sounded brasher, which grew somewhat fatiguing over time. but i wanted that immediacy and "life" w/out sacrificing the rounder, more relaxed presentation of the PB. So i plugged the HagUSB/Coax combo into the MacBook... Eureka! this had everything, depth, space, incredible openess, immediacy, detail, but not etched. it short, it sounded as good as the CD. So the question of whether the DAC was the problem was answered. But why did the two laptops sound so different? Was it a question of Intel vs. Motorola processors, or something else? There was one more variable- the MAcBook was running on battery power, the PB plugged in. So i plugged the MacBook in and compared it to the battery, via USB. The differences were slight, but apparent, and not as great as those between the PB running on AC and the MacBook running on battery. So i unplugged PB and compared the two laptops running on battery power, again via USB. There was no discernable difference- both sounded tremendous, and easily as good as the built in CD. If I had to rank the various combos, it might look like this: 3rd: Tie between the PB on AC via USB and the MAcBook via Toslink. There were real differences, but both were equally good, or not so good, depending on your taste for forward vs. "behind the proscenium" presentation. 2nd: MB via USB running on AC 1st: MB/PB via USB running on battery Conclusions: The CDPre24 has a tremendous DAC. USB is superior to toslink, and battery power makes a real, audible difference. now i just need a dedicated long-life battery supply.
actually, i wonder whether the difference would e as pronounced if i had access to a glass toslink cable, rather than the plastic one.
