How much does transport matter?

PhilNYC · « **Reply #20 on:** 8 Feb 2005, 03:29 pm »

This is one of those topics that has been discussed/debated a lot. I've had enough discussions with engineers to reach the conclusion that there are definitely audible differences between transports, and some explanations (ie. jitter resulting from numerous things, including signal reflection in the SPDIF connection, error correction, etc) make sense to me, while others don't (eg. why re-clocking doesn't solve jitter issues). Having said that, there is no question whatsoever to me that transports need to do far more than just get the 0's and 1's right.

FWIW - JeffB, from what I understand, the issue with the slewrate/rise-time is not that picosecond jitter differences are audible...but that variations in the slewrate/rise-time (or simply variations in the shape of the squarewave) in an SPDIF interface will cause signal reflections if the SPDIF interface is not truly 75ohms the whole way through; and it is those reflections that cause confusion (and ultimately jitter) at the receiving end of the SPDIF interface.

As to why re-clocking doesn't solve jitter completely, I am at a complete loss. I wish it did solve it...my DAC (Dodson DA-218) has a state-of-the-art FIFO buffer and re-clocking design, yet the differences between various transports is audible even to my wife (who is the biggest skeptic of audio tweaks I know)...

Adarsh · « **Reply #21 on:** 8 Feb 2005, 04:07 pm »

Today I connected a very basic JVC CD player to my system. Although I wasn't very disappointed, I could tell the difference between it's sound and the sound of my laptop. My laptop sounds better, the bass is stronger, the highs are clearer that of course with all equalizing switched off.

I don't know if this is due to the transport of the JVC. Can someone shed some light.

BTW, I've also enabled ATH Strong Noise Shaping on my laptop, would this be another reason?

Thanks,

-A

BobM · « **Reply #22 on:** 8 Feb 2005, 04:25 pm »

Here's a link to a comparison of the CD Pro2 transport and the EA Modded Sony 7700. Both designed and implemented very well. Both with a very noticeable difference in sound.

http://www.audiocircle.com/index.php?topic=16390

Then we tried my modded Toshiba SD4960 and yes, the sound was noticeably different (not nearly as good by itself or into the DAC).

Same DAC, different transports, different sound. Absolutely noticeable to everyone in the room. Now there was a clear majority winner in this shootout, but it was not unanimous. One person liked the CD Pro2 better than the Sony.

Different styles for different people.

Enjoy,
Bob

Adarsh · « **Reply #23 on:** 8 Feb 2005, 09:37 pm »

Today I connected a very basic JVC CD player to my system. Although I wasn't very disappointed, I could tell the difference between it's sound and the sound of my laptop. My laptop sounds better, the bass is stronger, the highs are clearer that of course with all equalizing switched off.

I don't know if this is due to the transport of the JVC. Can someone shed some light.

BTW, I've also enabled ATH Strong Noise Shaping on my laptop, would this be another reason?

Thanks,

-A

PhilNYC · « **Reply #24 on:** 8 Feb 2005, 10:44 pm »

Adarsh,

Are you saying that you connected the digital out on your JVC to an AV receiver or DAC? or did you connect the JVC's analog output to your system?

If you are comparing analog outs from your JVC vs. your laptop, then the differences could be any of a hundred different reasons (different designs, different DAC chip, different power supplies...essentially you are comparing two completely different machines). There's no way to isolate why the differences exist asides from saying "everything is different".

If you are hooking up the digital out of your JVC to an AV receiver or DAC, and comparing it to a digital out from your laptop, then there might be more isolated reasons why things sound different...

Adarsh · « **Reply #25 on:** 9 Feb 2005, 06:14 am »

Phil,

I've been using an analog signal for both the JVC and the laptop.

Thanks a lot,

Adarsh

Mad DOg · « **Reply #26 on:** 9 Feb 2005, 07:08 am »

Quote from: Adarsh

Phil,

I've been using an analog signal for both the JVC and the laptop.

Thanks a lot,

Adarsh

then you're not comparing transports...

Adarsh · « **Reply #27 on:** 9 Feb 2005, 02:27 pm »

I think I understand.

So it could also be that the DAC of the JVC is of lower quality?

Note: I'm playing the same CD on both devices.

PhilNYC · « **Reply #28 on:** 9 Feb 2005, 03:47 pm »

Adarsh,

It could be the DAC, but it could also be a lot of other things...quality of the power supply, the sophistication of the overall design, the quality of the parts in the output stage, etc.

_scotty_ · « **Reply #29 on:** 9 Feb 2005, 10:20 pm »

Adarsh, what is the model no. of the JVC player you are listening to.
Scotty

JeffB · « **Reply #30 on:** 11 Feb 2005, 07:29 pm »

Well, after skimming two very long winded boring articles on jitter, the picture is a little clearer.

http://www.stereophile.com/reference/193jitter/index.html
http://www.stereophile.com/reference/368/index.html

Jitter wrecks the output waveform by producing the correct wave amplitude, but at the wrong time. The second article has a picture that is quite telling. Apparently our ears do indeed hear jitter in the picoseconds. Probably any form of electronic clocking has some jitter, which may explain why buffering and clocking out the signal is not sufficient.

What I don't understand from the article is whether transports favor an accurately spinning table over buffering and electronically clocking. In other words is jitter best eliminated via electronic means or mechanical means. In any event, it appears that there are many places in the audio path between the transport and the dac where jitter can creap in.

JLM · « **Reply #31 on:** 11 Feb 2005, 10:35 pm »

Like most things in the audio chain, the best way to deal with distortion is not to allow it into the system to start with. Usually fixes help relieve the problem to only a degree while adding another problem. Another vote for KISS.

Its scary how little we know about what makes vinyl or digital sources sound good. Current widely accepted science cannot reveal why two different transports with similar specifications sound different or why two different DACs sound the same with one transport but different with another.

Note that the belt drive CEC's are reported to have very low jitter and a good jitter profile.

audioengr · « **Reply #32 on:** 14 Feb 2005, 07:10 pm »

Quote from: JeffB

Well, after skimming two very long winded boring articles on jitter, the picture is a little clearer.

http://www.stereophile.com/reference/193jitter/index.html
http://www.stereophile.com/reference/368/index.html

Jitter wrecks the output waveform by producing the correct wave amplitude, but at the wrong time. The second article has a picture that is quite telling. Apparently our ears do indeed hear jitter in the picoseconds. Probably any form of electronic clocking has some jitter, which may explai ...

Jitter definitely has a better chance of being minimized in an all-electronic scheme, whether this is buffering or driving it from a computer. These all-electronic means will always be better than that from a transport with moving parts.

I proved this at CES, where my reference Sony 7700 was put up against my USB-to-S/DIF converter in A/B single-blind tests with lots of listeners. The listeners always picked the Computer driven source over the transport without exception. The only time they were found to be identical was when we played a specially written CD on the transport where the pits were precision timed (developed by Mark of Z-Cable). In this case the 44.1 from the computer and the 44.1 from the Transport were indistinguishable. This says two things:

1) the pits in the average CD are a LARGE source of the jitter that you get from the transport. No matter how good the transport is, this jitter will always be there unless you rewrite the CD with better timing.

2) the 7700 is really an excellent transport to be indistinguishable from a computer source that has no moving parts and a Superclock that determines the bit timing.

Steve N.

MttBsh · « **Reply #33 on:** 14 Feb 2005, 08:09 pm »

"2) the 7700 is really an excellent transport to be indistinguishable from a computer source that has no moving parts and a Superclock that determines the bit timing"

Steve, are you refering to the stock 7700? If that is true, how could mods possibly improve the 7700s transport? I have a stock 7700 (I did put in an IEC to accept a better power cord) feeding a Tubedac Plus and a Clari-T amp. If your statement above is true, this should be about as good as it gets.

Thanks

Matt

Marbles · « **Reply #34 on:** 14 Feb 2005, 08:30 pm »

Matt, Steve has heavily modified his S7700.