All transports are NOT the same

[Mr Peabody]

I recently had a chance to speak with a factory technician for a "high end" company who assured me that there is a difference in brands of transports. We were discussing using digital outs of disc players and preamp DAC's vs stand alone players and DAC's. He says the difference is in how much jitter is caused when the information is read from the disc. Better transports will have less jitter and less of a problem to be corrected. He felt I would get better sound from my Krell transport than my Denon into the same DAC. Some day I will get energetic and see.

Those who use mega disc changers and feed the signal into an outboard DAC seem to be satisfied yet it sounds like better sonics could be had. Has any of you ever compared a single disc digital out to the jukebox? I would think the jukebox would be the worst possible transport.

[mtrycraft]

I recently had a chance to speak with a factory technician for a "high end" company who assured me that there is a difference in brands of transports.

His evidence would be his word in this? Anything else? Perhaps he has an interest in telling you this silliness?

He says the difference is in how much jitter is caused when the information is read from the disc. Better transports will have less jitter and less of a problem to be corrected. He felt I would get better sound from my Krell transport than my Denon into the same DAC. Some day I will get energetic and see.

See under level matched, DBT listeing? Did he offer any evidence?

Those who use mega disc changers and feed the signal into an outboard DAC seem to be satisfied yet it sounds like better sonics could be had.

Yep, that is the initial supposition but evidence is more powerful.

Has any of you ever compared a single disc digital out to the jukebox? I would think the jukebox would be the worst possible transport.

That is understandible. Thinking is not evidence, again.

[skeptic]

"I would think the jukebox would be the worst possible transport."

Why? A jukebox is nothing more than a single disc transport with another machine to select which of the discs in its magazine will be played one at a time.

While it is true that the degree of rotational speed variation from ideal which we used to call wow and flutter but in a digital age we call jitter can vary, ALL of them are much worse than is needed for reproduction of audio or video signals. How is this overcome? By reclocking. The pulses for each data point must enter each cell of a buffer register within a certain time interval. When the register dumps each cell, its data is reclocked to conform to the timing of a quartz oscillator which is rock steady. If it fails to happen, the entire process breaks down and you won't get any music or picture at all. Therefore, reducing digital jitter in the transport doesn't result in a better digital data stream. This is one of the great advantages of the digital system of storage and retrieval of analog signals. It doesn't depend for quality on a super precision transport unit to play it back, it's independent of it as long as it meets the minimum requirements necessary for it to function at all. Your misconception is all based on the myth implied by many manufacturers that if you optimize every conceivable element in a system, each one will contribute to superior performance. Some elements are less important and some merely have to be present in any working form.

[RGA]

The best thing to do is go and listen - I compared a 300 disc Pioneer Elite changer versus a super expensive Wadia and Enlightend Audio Designs transport through a Cal Labs DAC and high end Bryston monoblocks and Martin Logan speakers. No one heard a difference even sighted. The dealer himself dumped the transport for the changer. The Dac was another matter.

There may be a difference - but I would rather spend it on speakers room treatments etc.

I run a changer and a dedicated single disc player - the Cambridge is probably better - but given the price - if I ad to do it over again I would take the Sony 300 disc player - and buy a second and third one instead of the CD-6.

And hey the 300 disc player does have a digital output if you really want an external DAC - and best of all you can always take an external DAC home to try out before you buy.

[E-Stat]

Therefore, reducing digital jitter in the transport doesn't result in a better digital data stream. This is one of the great advantages of the digital system of storage and retrieval of analog signals. It doesn't depend for quality on a super precision transport unit to play it back, it's independent of it as long as it meets the minimum requirements necessary for it to function at all.

Great theory as usual. It's a shame the theory doesn't work that way in the real world. Ever burn your own CDs? I've done hundreds. With data disks, I rarely have experienced any trouble using several different burners. Burning music disks, however, is a different matter. Doesn't matter whether I burn WAVs or MP3s. Even with my pretty fast 2.2 Ghz P4, I must slow down the burn from 32x down to 4x to prevent horribly obvious clicking and other timing artifacts.

rw

[skeptic]

And how do you account for the fact that you don't get these errors burning data cds but you get them with audio cds?

Ever consider that your A/D converter may not be quite up to the higher speed? This is the most likely cause of your problem. And it may be due to power supply voltage fluctuations, not the A/D chip itself. Blaming the cd transport is the last place to look for the answer not the first because on playback, either the PLL locks or it doesn't. If loss of lock were due to jitter, the problem would be constant with the artifacts occurring all of the time. This is the only conceivable marginal situation and would indicate that the entire cd recording process was on the verge of complete breakdown. There are no halfway situations like there are in analog systems. The naive one time use of green felt tip pens and plastic rings on the outer rims of discs which audiophiles swore made a drastic improvement in sound, shows that many of them have only a rudimentary understanding of the radical difference between digital and analog systems. The belief in more expensive precision transports is simply a way for manufacturers to exploit exactly this same widely held misconception that steadier rotation will somehow improve the ultimate sound. It just can't because the process doesn't work that way. The jitter was anticipated and compensation for it is built right into the process or the buffer registers wouldn't have been necessary. If you want an indication of how really effective they are, consider a portable unit which has to absorb enormous jarring and yet still usually maintains a steady audio output.

[E-Stat]

And how do you account for the fact that you don't get these errors burning data cds but you get them with audio cds?

Think about the fundamental difference. A data file really doesn't care about the speed or pace at which it arrives because it is not acted upon until the file has been entirely transferred. This is true for executables, image files, word processing files, etc. That is in stark contrast to the continuous nature of a wav based audio stream getting transferred.

rw

[Resident Loser]

...I have found that most, if not all CDPs, use either Sony or Philips transports as the basis for their units...any difference in the transports seems to be mechanical in nature...the long service life for a pro unit requires things like metal parts, glass lenses, that sort of thing...regardless of all the tomfoolery, a zero is a zero and a one is a one. It seems that when you get into the DACs is when the specific "sonic signatures" are futzed with...

As I recall there was a recent thread re: a German piece of "sonic artwork" which used the same transport as a very less(make that very, very, very less)expensive Marantz unit...limited production etc., the machined housing and laser-cut faceplate of the former, contributed to it's price and, as it always seems, that price was equated to by some, to be what elevated it to the "best"...what ever that means. As I recall the DAC had "timbral adjustments" or some other less-scary-to-the golden-eared euphemism for tone controls.

jimHJJ(...and solder is solder, and wire is wire, and the green grass grew all around...)

[woodman]

I recently had a chance to speak with a factory technician for a "high end" company who assured me that there is a difference in brands of transports. We were discussing using digital outs of disc players and preamp DAC's vs stand alone players and DAC's. He says the difference is in how much jitter is caused when the information is read from the disc. Better transports will have less jitter and less of a problem to be corrected. He felt I would get better sound from my Krell transport than my Denon into the same DAC.

Just because someone has a job with a "high-end" company does not mean that they are actually knowledgeable. In this case, the factory technician is talking directly out of his a** - just like Jim Carrey did in his film "Ace Ventura - Pet Detective". It's absolute, total BullSh!t. Skeptic spelled it all out in his reply here ... he is 100% correct.

Some day I will get energetic and see.

I certainly hope so. Then, you can cease and desist posting this sort of audiophoolery.

[RobotCzar]

I recently had a chance to speak with a factory technician for a "high end" company who assured me that there is a difference in brands of transports. We were discussing using digital outs of disc players and preamp DAC's vs stand alone players and DAC's. He says the difference is in how much jitter is caused when the information is read from the disc. Better transports will have less jitter and less of a problem to be corrected. He felt I would get better sound from my Krell transport than my Denon into the same DAC. Some day I will get energetic and see.

Those who use mega disc changers and feed the signal into an outboard DAC seem to be satisfied yet it sounds like better sonics could be had. Has any of you ever compared a single disc digital out to the jukebox? I would think the jukebox would be the worst possible transport.

The technician is right that there may be differences in jitter, which is due to clock errors in the player. OK, but the real issue is: does it make a difference we can hear?
Jitter errors will show up in standard THD measurements (I have previously published a reference for this but find it yourself in The Audio Critic or online). Almost all CD players (I am aware of --to please certain readers) have distortion measurements below the ability of humans to distinguish. So, if you are worried about jitter or the quality of the playback of your transport, just check its distortion specs or measurements. Jitter is one in a long line of high end "concerns" that are mere smoke to sell magazine and let English and journalism majors pretend they are technical. Bottom line is that there is no logical scientific reason to think there are audible differences in transports and when people have been tested they can't tell them apart. Of course, that is to my knowledge and perhaps Superman can detect audible differences in CD transports--but he hasn't been tested yet. "Listening" for differences is folly, you are much more likely to hear differences due to level mismatches or your biases.

Perhaps "factory technicians" of high end stuff are not the best source for reasonable information. Why not ask a designer (EE) of a reasonably priced product?

[skeptic]

It is entirely likely that cd players do not all sound alike. That is my experience and that of many other people as well. But these differences IMO have nothing to do with the transports. Early 16 and 18 bit D/A converters in the early to mid 80s were usually awful. But in the last 15 year or so with 20 and 1 bit converters, the only discernable differences are usually do to minor differences in analog frequency response. Therefore they are insignificant and of no consequence to anyone smart enough to use a graphic equalizer to achieve optimal tonal balance.

[E-Stat]

It is entirely likely that cd players do not all sound alike. That is my experience and that of many other people as well.

D'ya think?

But these differences IMO have nothing to do with the transports.

My experience suggests otherwise. BTW, with regard to your last post, the quality of the DAC in my computer with burning CDs is completely irrelevant because it is not used at all by the software. Time for a new theory.

But in the last 15 year or so with 20 and 1 bit converters, the only discernable differences are usually do to minor differences in analog frequency response.

Do you really believe is no audible difference whatsoever between the necessary analog circuitry between an $.80 op amp and a discrete stage using the finest components?

rw

[RobotCzar]

D'ya think?

Do you really believe is no audible difference whatsoever between the necessary analog circuitry between an $.80 op amp and a discrete stage using the finest components?

rw

The cost of a chip (or a section) is probably correlated to performance, so your inferrence is not totally off the wall, but the fact that you want to talk about price instead of performance does illustrate where you are coming from.

Why assume that there is an AUDIBLE difference between an opamp chip and a discrete stage based on price or cost? Why don't we just measure and see which has the better electrical performance? Armed with this information we can then make a better guess as to possible audible differences (with a much better chance of being right). Of course, even the cheap opamps sometimes outperform "high-end" tweako discrete designs (in terms of measured performance). And, of course, the performance of even very cheap opamps is these days almost always below audible thresholds. Pehaps that is why people can't tell them apart in listening tests (duh)?

[skeptic]

Excellent point. The price of semiconductor chips is almost always inversely proportional to the number produced up to a point. This is because once the development and tooling cost are amortized, the production cost per unit is almost zero. Op amps find their way into so many different applicatons and have been under development for so long that it would be surprising if there aren't many which can perform the function of signal level audio amplification just about perfectly for next to nothing.

[E-Stat]

Why assume that there is an AUDIBLE difference between an opamp chip and a discrete stage based on price or cost?

Because there are a sum total of zero state-of-the-art preamps that are chip based.

Of course, even the cheap opamps sometimes outperform "high-end" tweako discrete designs (in terms of measured performance).

Which shows you how totally useless such measurements are. The absolutely dreadful Crown IC-150 preamp had GREAT specs.

And, of course, the performance of even very cheap opamps is these days almost always below audible thresholds.

On what, test tones? LOL.

rw