Rob has presented a theory that the DAC's ability to reduce transport transmitted jitter will determining whether the transports will sound virtually identical or not. Rob has done some empirical testing that he feels proves his theory. A question for Rob: were any of the transports that you used in your testing of exceptional quality?

Elroy, you mentioned that you didn't hear a difference between transports using Dingus's EAD DSP-1000. According to Rob's theory the Kenwood & Wadia would need to have nearly identical transmitted jitter in order to sound virtually identical on the EAD. In AB testing at my home running a Denon DCD-1500 and a Yamaha CDX-10000 through the EAD, the Yamaha clearly sound better through than the Denon. According to Rob's theory that means that the EAD does not possess sufficient transmitted (received) jitter reduction capability to reduce it to a non-audible level.

I think additional testing is called for. I for one will test this as soon as I can acquire a "Rob approved" DAC, and a mediocre transport.

Now guys, don't make it out like I am trying to trash your DACs. I am just trying to better understand why we had such a variety of observations, while testing transports.

I will definitely need to sit down and do some more specific listening myself. Unfortunately I sold my Adcom GDA-600 to offset some of the cost of the equipment I bought in the spring, so I can't test with that DAC. I know the GDA-600 had excellent the Burr Brown PCM63 DACs, but I don't know which input receiver it used. I can still test with with my PS Audio Ultralink Two. My Adcom GCD-750 CD player also has a digital input which allows it to be used as DAC, and my Sony DTC-75ES DAT deck can also be used as a DAC.

For transports I have available, an Adcom GCD-575, a $25 Cyberhome DVD player and Marantz DV4001, DV6001 and DV7001 DVD players. The DV7001 in particular is a really nice unit that retailed for $800. Sadly my Adcom GCD-750 has only a digital input, not an output.

Once I get a day to sit and listen I will share my observations.

Rob

I didnt take it at all like that, other than calling me a cheap chinese hose monster,

I am really enjoying this thread, I think next week I am going to take my DAC and new Yamaha CDX-2020 to dingus's and do a little comparison. He doesnt know that yet, but oh well, should be interesting.

I think we could run each DAC separately, and see if there is a difference between them and their respective transports.

elroy

what i have found in my limited experience is that the transports that did better with my DAC were those that i perceived to be of higher quality, ie; heavier and better build (such the Wadia and Kenwood) while lesser built players (Denon 1500 and Luxman d-113) delivered a less solid presentation and were not as smooth. further testing is sorely needed and it will be interesting to see what Elroy's CDX-2020 reveals.

also the article referenced from Stereophile is fairly limited in its scope and (at least for me) did not shed much light in regards to the benefits of a good transport or DAC. one example from the article states " With no input signal, the CS8412 will introduce 200ps of clock jitter. the EAD DSP 1000 use the Crystal CS8412, but the EAD manual states units jitter at <100 picosecond rms. this indicates that the Crystal CS8412 is not the limiting factor for how much jitter a DAC will introduce. there is more to a device than one of its components. also i remain somewhat skeptical to what extent jitter effects what we hear since (as far as i know) i've never heard it.

I think the less jitter you have, the better the sound, I dont think you can hear the jitter per say, but I think the more jitter equals less definition, and clarity. jmo

yes but what amount of jitter is detrimental to the sound and at what point is it audible?

quit asking me the technical questions, I have no idea

What about less of definition and less of clarity in analog setups where jitter is out of the equation.....?! Don't blame everything on jitter, there are other more apparent audio problems that cause audio listening fatigue less definition and clarity than little old jitter.

Given that the adverse effects of jitter are not measurable, may not be audible, are at least arguable and, if real, likely to only be revealed by the most revealing/expensive systems, i'd venture that the practical path would be to start with a good an inexpensive DAC and see how it sounds. If it doesn't sound as better than your cdp did, use it as a reference when auditioning other DACs, clocks, etc…
If it does sound as good or better than you cdp, get off the internet and listen to music.

Been there, done that, with the simple 16/44.1 from my Audio Alchemy in the 90’s.
Also, do not believe that an answer to a less jitter interface lies on an outboard dac. There are many good cdp’s with much lesser jitter than many dac’s.
I’d use to have the AA with a Roksan dp1 transport and every mag audio critic says at the time that was a great transport, bla bla bla... ‘til one day I bought a cd recorder from Philips and try it out directly to my amp – a Mission Cyrus, at the time – bypassing the dac, and….i found out that I have a much better sound coming from the Philips cdp than coming from the Roksan plus the Audio Alchemy dac. Sometimes re-clocking a jittered signal may help, other times don’t.
BTW, later I found out the problem was in the transport, not in the Audio Alchemy dac. Of course!

Certainly there are plenty of things that can affect the overall sound quality of CD music. I don't think anyone doubts that. However, the context of this thread was a discussion about why some people have been able to clearly hear a difference between various CD transports, while others cannot. In this context the answer must lie in the digital realm, as the analog sections are identical in each person's comparison tests. Given these constraints, jitter is certainly a primary suspect.

Rob

Of course.
IMHO, one of the most important differences between an average cdp and a great cdp lies into the power supply design.
Any leakage current (interference) between the servo mechanism controlling the speed of the spinning disc and the crystal oscillator controlling the output of the buffer may unstabilize the crystal oscillator enough to add jitter to the clock signal. As a matter of fact this is one of the reasons i moved to computer as a source.

The hard drive uses an asynchronous interface - SCSI. The disc is always spinning at the same high speed and the heads land on the spot you need when the data is requested. The data coming out is completely unclocked (it comes out in bursts) and has to pass through the SCSI barrier into a buffer located in a different chassis than the hard disc (the computer)... thus, there is great distance between the varying currents of the spinning disc motor and the oscillator driving the output of the buffer in the computer chassis. Since the computer power supply only has to power the output oscillator, the result imo can be much more stable. Same for a cdp or transport... there are "audiophile cd players" where great attention has been made to power supply design, and these players exhibit much less jitter and better sound.

Not to derail the thread but has anybody tried a Blue Ray player as a transport?
I bought a Pioneer BDP-51FD recently and have toyed with the idea.
It is a full size unit with some mass to it.
It has Wolfson DAC s on board.
I had good luck with my Pioneer Laser Disc player in that capacity.

I use a Blu-Ray player - LG- GGC-H20L - in my comp and the differences between the LG and the Plextor dvd are not subtle. I don't know if this is because it uses the BlueRay laser diode or the construction of the mechs itself....IMO, because both matters - the Blu-Ray is a better transport than the Plextor.

From the Blu-ray site: "A blue-violet laser (405nm) has a shorter wavelength than a red laser (650nm); this makes it possible to focus the laser with even greater accuracy..."

That is not proven, since the transports used in the testing were different.

Mark, I am not sure I get your point.

My point was that in the tests where a difference in sound quality was noticed, the transports being used for the test differed substantially in quality. Everything else being equal, any difference in sound quality could be attributed to the difference in quality between the transports.

In a test in which 2 medicre transports were used the expected result would be that little if any difference in sound quality existed between them. Similarly, if 2 superb transports were used for the test, the expected result would be little or no difference in sound quality. In either of these scenarios, it would be misleading to conclude that the lack of difference was due to transports having no affect on sound quality.

To properly test whether transports affect the sound quality, the transports used for testing must have a significant difference in quality between them.