Shadorne...The "Clock" is sometimes embedded in the data, so that no separate clock signal is needed. Check out "Manchester 2" code, one of the first.
Digital Playback Comparison
Which sounds better: Original CD, CD burned from harddrive, playback from computer HD through USB, or optic cable, or Airport Express? I cleaned my contacts, installed NOS Amperex tubes in my preamp, had new tubes installed in my Trivista SACD/CD player, and had a go at a comparison test for these playback methods. The HD used was from my MacBook Pro. The piece of music used for a comparison was the Hallelujah chorus from Handel's Messiah, Solti and the Chicago Symphony Orchestra and Chorus (Decca 1985). See my system for equipment used. The USB playback was via a HagUSB via S/PDIF into the Trivista coax input. Here are the conclusions, going from best to least good sound quality:
1. (Tie): HagUSB and Burned CD (CD was burned from HD at 4x, from Apple Lossless file). I couldn't tell a difference between these two after extended listening including other music besides the test music. Great dynamic range, wide and deep soundstage, a "rightness" to the sound (at least within the limitations of digital) that made you want to quit analyzing and just listen.
2. Original CD. I read somewhere recently (some of you might know the source) that there is an explaination for why burned CD's sound better than original, but until I made the comparison, I was skeptical. The original had a slight loss of "presence", and seemed slightly compressed compared to the #1 playback methods.
3. HD through toslink. 1 & 2 are closer in sound than 2 & 3. There is a noticable shrinking of the soundstage and air with the optic cable. The cable is a good one--Van den Hull glass cable with mini-plug out from Mac. I was disappointed in the sound from this method.
4. Airport Express and optic. A significant drop in sound quality here. If you have been using this method I suggest doing what I will now do which is run USB out of computer to HagUSB ($119) via long run of coax (Canare for me) to your DAC. The Airport Express is OK for "working around the house on the weekend" listening, but is a serious compromise from what you can get with only a minimal incremental investment.
Notably absent from this comparison are music servers, or a good quality USB DAC, or good reclocker/converters that could be used with a computer HD and conventional DAC. Hopefully someone else can do comparisons of the burned CD with some of these methods to see what is the best sound for, let's say, a $2000 or less investment (obviously not including the cost of a computer). That is a level that many of us might be willing to make if there is a significant improvement over the #1 methods above.
1. (Tie): HagUSB and Burned CD (CD was burned from HD at 4x, from Apple Lossless file). I couldn't tell a difference between these two after extended listening including other music besides the test music. Great dynamic range, wide and deep soundstage, a "rightness" to the sound (at least within the limitations of digital) that made you want to quit analyzing and just listen.
2. Original CD. I read somewhere recently (some of you might know the source) that there is an explaination for why burned CD's sound better than original, but until I made the comparison, I was skeptical. The original had a slight loss of "presence", and seemed slightly compressed compared to the #1 playback methods.
3. HD through toslink. 1 & 2 are closer in sound than 2 & 3. There is a noticable shrinking of the soundstage and air with the optic cable. The cable is a good one--Van den Hull glass cable with mini-plug out from Mac. I was disappointed in the sound from this method.
4. Airport Express and optic. A significant drop in sound quality here. If you have been using this method I suggest doing what I will now do which is run USB out of computer to HagUSB ($119) via long run of coax (Canare for me) to your DAC. The Airport Express is OK for "working around the house on the weekend" listening, but is a serious compromise from what you can get with only a minimal incremental investment.
Notably absent from this comparison are music servers, or a good quality USB DAC, or good reclocker/converters that could be used with a computer HD and conventional DAC. Hopefully someone else can do comparisons of the burned CD with some of these methods to see what is the best sound for, let's say, a $2000 or less investment (obviously not including the cost of a computer). That is a level that many of us might be willing to make if there is a significant improvement over the #1 methods above.
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BTW - that you had issues with airport express is not surprising if you think about it ... a tiny little box with SMPS power supply sandwiched close to the rest of the circuitry. However it is the analog that stereophile took exception to and not the optical out. Perhaps the PLL design in your Tivista did not like what Airport express was doing jitter wise? How close was the Airport express to the other gear....as I mentioned the packaging of this thing means it is more likely to raidate EM/RF noise.... Thanks for sharing - interesting |
Shadorne, The CD itself of the 1985 performance is new, but I've gotten the same results from other CD's tested this way, so I'm thinking the difference is in the playback medium, not the particular CD. But, I'm glad to learn about the bronzing problem--something I did not know about. The AE definitely has limitations, but they are much less when you use the digital out vs analog out. When I sent the TriVista back for retubing and to have the power supply rebuilt I had to go from the AE directly to the preamp to play iTunes playlists. There was a HUGE drop in quality going this route (similar to Drubin's "FM radio" results reported above). I thought that if this was the best my system were capable of reproducing I'd end up never listening to music. I think the lesson from my experiments and that of others such as Drubin, is that we need to do some direct comparisons of digital playback metods and equipment to learn how to get the best quality sound when using a computer as a source. The recent report in TAS is a start, but much more needs to be done to see if there are ways of getting great sound without having to make a five figure incremental investment. |
My own system consists of an Apple G5 with CDs burned using lossless into the Slimdevices Transporter via an ATT Gateway Modem to my Audio Aero Capitole using the AES/EBU digital connection. This sounds really good and much better than streaming audio. However most of my original CDs sound better on the Capitole which means that I have degraded the signal along the way or, I suspect, the Audio Aero was designed to do it's best with an original CD. I still prefer using the Audio Aero DAC over the really audiophile quality DAC in the Transporter as the Audio Aero sounds 'warmer' while the Transporter is much more analytic. Either way I like the system and I use the Computer generated music set an random song mix. |
I have been listening to the following digital playback chain for a while now and can report on the quality compared to the other playback methods described in my original post: iMac-->USB cable-->Hagman USB-->9m of Canare coaxial cable-->Trivista as DAC. Cost: $119 for Hagman, $102 for cable. So, for a little over $200 I can use my computer in another room as the digital source for playing iTunes playlists. The sound quality? Excellent, the equivalent of a CD-R burned from the hard disk, and therefore tied for the best digital sound of all the options described in the original post. This is better in every way than using the Airport Express and Toslink output, and it isn't a subtle difference, either. You can obviously do much better with a high end transport and DAC, or one of the high end servers tested by TAS, but you'll spend a lot more than $200!! I guess the point here is that it wouldn't cost you much to try something like this setup, if you already have a good DAC, before you drop five figures on a transport/DAC or music server. You might end up putting that money somewhere else in the system where you can't get such good results from a $200 expenditure. YMMV. |
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