Digital Source Comparison - An audible difference?

I'm trying to compare with my own ears the difference that people hear, or claim to hear, between digital sources. I realize that it's entirely possible that my system isn't quite to the level where difference are audible but it's pretty simple to do a comparison.

Source 1: Pioneer Elite PD-D6-J SACD Player (on Nordost Sort Kones)
Source 2: Integra CDC-3.4 CD Player (multi-disk)

My plan would be to use two Toslink cables since the Integra is already connected using one and it's fairly easy to obtain another one.

Considering the rest of my system includes an Integra 50.1 AVR, Focal Chorus 836v speakers, and DIY Cat5 speaker cables, would you predict that I will hear a difference?

There is a distinct difference between the two CD players using analog connections, but if they are reduced to being transports that rely on the DAC in the AVR will there still be a difference?
I predict not but you don't know until you try
With the same CD in either player, It only depends on how well the receiver handles jitter and how jittery the signals are.
I suggest you ask an uninterested party to listen as you change sources and make comments on paper not verbally to you. Then let them change between the two sources or not back and forth and then compare notes. If neither of you can score better than six out of ten correct there is no significant difference in the two as transports.
Yes, you will hear a difference. A good portion of the difference you hear between the two players has a lot to do with the transport. As you use the players as a transport you will notice the sound will take on the character of the transport being used.
The differences with those low fi players will be minimal .
Tmsorosk - I can handle my Integra multi-disk player being low fi as it's obviously intended to be convenient first and foremost, but I disagree that my Pioneer Elite SACD player falls under that impossible to define category. It's a pretty solid unit that gets great reviews, especially for the price. I just don't see low fi being applied to a component that is clearly designed with performance in mind within the limits of the price point. It's clearly a better player when used as an analog souce.
MC, I think you made the point that Tmsorosk was, that the Pioneer is designed with performance in mind within the limits of its price point. Which means it needs to be built for about 1/4 of its selling price to allow for the necessary mark-ups/profit.

Low-fi was probably not a fair term, I agree with you, but the closer two items are (CDPs especially) in price, typically the less likely you are to hear a difference. And I think that was his point. I think there are a lot of $1,000 CD players that few could hear a difference in comparing them to $400-$500 players (new prices of course).

You would expect to get more bang for your buck from a high volume manufacturer like Pioneer Elite than from a boutique company (Ayre, ARC, even Rotel, etc. . . ) when paying the same price for a CDP.

I think your approach may have some major flaws. I am not a fan of toslink. Regardless of my opinion it is a fact that toslink and S/PDIF outputs are different beasts and not treated equally by manufacturers. Sometimes toslink is not much more than an afterthought.

You need to find out if either CD player manufacturer or the DAC manufacturer recommend a preferred output/input. I doubt if the CDP manufacturers make any recommendation for digital out but the DAC manufacturer may make a recommendation for a preferred input.

If you want to compare sources you have to make sure everything else in the chain is up to the task. I think you are already in trouble with your choice of toslink. At least that is my experience with inexpensive toslink cables on equipment where S/PDIF or AES/EBU were designed to be the primary in/outs.
OK, Before someone jumps on me because TOSLINK is also classified as S/PDIF I need to clarify. I was trying to differentiate between optical and electrical inputs and outputs. Namely TOSLINK vs RCA and XLR (AES/EBU).
Ckoffend, Since when are Ayre, ARC and especially Rotel considered "boutique" companies. Ayre, for example, has an extensive dealer network not to mention distribution in nearly 50 other countries.

It is not likely you would get more for your money with Pioneer than the other companies you mentioned.
Rrog, my point is that these are all low volume product companies (in most industries, they would be considered specialized or boutique like companies that rely on high profit margin per sale versus lower margin compensated by high volume).

Pioneer probably sells as many single item component (take any model CD players of theirs) as these other companies sell between their entire product range. How many actual products do you think Ayre sold last year - between all the products they make? 2,000 - 3,000 - 5,000 - 10,000? I doubt 10,000, actually I doubt even 5,000 total products shipped from their facilities in 2010.

Now, how many individual products do you think Pioneer shipped?

Think about a $1,000 Pioneer Elite player, probably a total run of 10,000-25,000 pieces produced, if not way more. Now compare that to an Ayre CD player that sells for $1,000 (I don't think they could make one that cheap in reality). How much does Ayre pay for the case? The circuit boards, including their design/engineering, the connection sockets, heck, even the screws that hold the unit together. For Ayre to just get the same quality that Pioneer can deliver, they would spend more than twice as much to produce it! So, do they forego the profits or have to sell the similar product for a lot more?

That is why I say/suggest that these "small" companies cannot make a $1,000 CDP that is notably better than a Pioneer Elite CDP or other $400-500 big brand CDP. The finances just don't add up.

Now, when you start talking about a lot more money, that is where you see the real differences in performance vs. the more mass market stuff.

Just think about it from a business perspective first.

Don't get me wrong, when it comes to this hobby most of us ignore the business or logic aspects of it. We own $20,000 speakers that sound incrementally better than mass market speakers that could be had for a few hundred.

We have thousands of dollars in cables that in reality are only incrementally better than lamp wire (I say incremental because a passing by non-audiophile is very unlikely to immediately hear or note any difference).

But we spend the money trying to get every last drop of performance out of our systems for the discretionary money we each have available to do so. The variety of speakers I have in my house right now exceeds the value of the two cars I own (a BMW 5 station wagon and a Dodge Durango SUV). So I am not bashing the industry, just recognizing that at certain budget points there are two real logical options: get the best mass market stuff you can afford or buy higher priced items on the used market thar are heavily discounted vs. their original list price.
I would not expect much difference, most likely not near as much as the effect of two different DACs, but some is possible due mainly to potential differences between the two in regards to jitter.
Don_s - I have no issue with getting pair of both types of digital connections and doing the comparison that way.

Blasphemy Warning: Because I'm probably closer to the "bits is bits" belief I'm not convinced that I should hear any difference related to a digital source or cable, but it seems only fair to make any comparisons using identical cables.

My AVR has two Toslink inputs so it makes for an easy A/B switch for comparison and I suspect I can do the same with the other style of cable.

One of these days I want to visit my hi fi shop and connect an Integra CDP and one of their $10k CDPs to the PS Audio DAC using identical cables and then see what I can hear. It should be significant I would hope.
I do know how much difference you will hear between those two, but I will say that the transport makes as much difference as the DAC...or more.
Comparing optical vs RCA connections might be the most telling.
In addition to sonic differences that may or may not result from differences in transport-generated jitter (depending on the amount of that jitter and on the jitter-rejection capability of the dac), if the connection between transport and dac is via an electrical cable you may or may not hear differences depending on:

1)The length of the cable, and the happenstance of the relation between that length and the risetimes and falltimes of the output signals of the transports. Those risetimes and falltimes are usually unspecified. See this paper for further explanation. In other words, you may hear a difference when one cable length is used (with both transports), and not hear a difference when another cable length is used (with both transports).

2)The amount of groundloop-related electrical noise current that the transport and dac collectively may cause to flow through the shield of the interconnect cable, which in turn will affect jitter. That effect is, again, unpredictable happenstance.

3)The degree of mismatch between the output impedance of the transport and the impedance (more properly, the "characteristic impedance") of the cable. That will affect waveform integrity, and may thereby affect jitter.

4)The degree of mismatch between the input impedance of the dac and the characteristic impedance of the cable. That will affect waveform integrity, and may thereby affect jitter. That effect on jitter may be sensitive to which transport is used, because the consequences of the waveform reflections caused by the impedance mismatch depend on the other three effects. In other words, an impedance match between dac and cable which is less than perfect can cause differences to be heard between transports.

Toslink is not susceptible to any of those effects, but I have no reason to doubt what seems to be the prevailing consensus that more often than not it will provide inferior performance compared to electrical interconnection.

None of those four factors have any strong correlation with component quality or component price. Transmission of digital signals between components should be viewed as a system-level issue, which is dependent on interactions between both components and the cable connecting them.

-- Al
I presume you are talking about 44.1K/16 bit native output from the players. For that frequency and bit depth I doubt if toslink will show any difference with coax, assuming you use glass fiber toslink and not plastic optical fiber.

If upsampled digital output from the players is used, all bets are off. I did this with a CA 840c (feeding a Bryston BDA-1) and found significant loss in sound quality when using the upsampled outputs (up to 24 bit/192K)of the 840. This was compared to the 840 alone feeding the same pre-amp/amp as the Bryston. At the high frequencies and bit depth the toslink would not allow the Bryston DACs to lock, whereas coax did. When I sent native 16 bit/44.1 KHz from the 840 to the Bryston, sound quality improved significantly.
Al - I can understand the concept of reflections in a digial cable, but is there concrete evidence that these reflections will actually cause an error in the transmitted data? Can the reflections actually cause the "pulses" to be outside of the acceptable range? I would assume that the DAC is looking for specified ranges with some tolerance applied.
Hi Mceljo,

Assuming that the impedance mismatches are within limits that are not totally unreasonable (such as might occur if the connection of the shield in a coaxial cable were broken), the resulting reflections will not cause any errors whatsoever in the digital data as received by the dac.

The issue is that the waveform distortion caused by reflections, in combination with noise that will invariably be riding on the signal to some degree, will result in small but significant fluctuations in the TIMING at which the dac senses the transitions between bit intervals. That is what the term "jitter" refers to. Depending on the jitter rejection capabilities of the dac, that can and often will have audible consequences, even though all the bits will be correct. See this paper for further explanation.

Best regards,
-- Al

I passed the two main links along to an EE friend of mine that's my sounding board for all things electrical. Here's part of his response.

"Those are the first articles you've sent me where I completely agree with everything written. This guy is obviously a well-educated electrical engineer.

How noticeable corrections to these factors will be, I do not know. I don't believe that crystal oscillators used in today's computer equipment are much farther off timing-wise than a belt-driven turntable."

In any case, he generally give me a list of things he considers to be "bunk" in the things that I pass along.

On a somewhat related question to the information in the links. Do you think jitter is a significant contributer to the difference in sound that I get between my Onkyo iPod dock and Ethernet connected Pandora Radio? The other obvious factor is the difference in DACs that are being used. Pandora is using 128 MP3 files and it takes at least the Applelosses on the iPod to sound consistently and sometimes even that doesn't sound as good.

I find myself turning off the iPod because it just sounds subpar, but Pandora runs for hours at a time.
Hi Mceljo,

Thanks for providing the feedback from your EE associate!

I have no particular familiarity with iPods, docks, Pandora, etc. But assuming that the DAC function is being performed by the component into which you are connecting the dock's cable and "universal port" connector (as opposed to being performed by the dock itself), yes, it is certainly conceivable that jitter could be a significant factor. The magnitude and character of the resulting effects would be dependent on the iPod, the dock, the cable, the input circuit of the component containing the DAC, any noise that may couple onto the relevant signals, and the jitter rejection capability (if any) of the particular DAC.

Another thing to consider, though, especially when dealing with mp3 files, and considering the poor engineering of many recordings generally, is that increased reproduction accuracy can often result in less enjoyable sound. A traditional audiophile dilemma :-)

Best regards,
-- Al