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What is the difference in CD transports?

This may sound stupid, but what makes one transport better than another? I have an old Theta Data Basic transport that I'm using with a Musical Fidelity Tri-Vista DAC 21. The DAC made a world of difference compared to my Theta Gen. III or Conrad-Johnson D/A-3. I can understand that because we're dealing with newer technology, faster and more powerful computers, better decoding chips, etc. A transport however, simply has to read the 0's and 1's, or pits. A CD reader in a computer costs practically nothing and reads fine (I assume), so why should a reader that costs almost $2000.00 be less than spectacular at reading and interpretting data correctly? When Theta tells me that the Data Basic II gives a wider soundstage and deeper bass, why would it? When I hear the Theta Jade is even better, what makes it better? I guess what I'm asking is "Is there a difference, and if there is, what transports are there that will feed my MF Tri-Vista DAC 21 more and better data?" Thanks, this is just puzzling!
krell_man
bombaywalla's avatar
bombaywalla
1,958 posts
 
A learned engineer @ one of the well-known & respected digital player companies wrote this once. I have picked this snippet up from his post:-

There are really only 3 three main parts to any transport.
1) the CD mechanism to read the data off the disc
2) the clocking and digital output methodology.
3) the powersupply

CD mechanism overall rigidity, smoothness of operation of the lens as it reads the disc, clamping the disc to reduce/eliminate wobble in (1) all have an effect on sound. Maybe subtle but there.
Clock stability in (2) above reduces jitter & hence read errors.
Poor power supply design in (3) can pollute quiet supplies with clock infested supplies. This could create spurious energy in the output data stream & reduce SNR &/or dynamic range thru an elevated noise floor.

Better designs pay more or much more attention to these details & the price goes up accordingly.
sean
6,231 posts
 
Logic would dictate that using a common reference clock for the transport and DAC would improve performance. Has anybody ever thought about finding a quality transport & DAC and using one lab grade ( like HP, etc... ) external clock for both of them? Sean
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bombaywalla's avatar
bombaywalla
1,958 posts
 
Sean,

I think that your logical thinking is on the right track!
I think that Wadia uses 1 clk for both transport & DAC when one buys their 270 transport & 27 DAC. The clock is in the DAC unit & is fed back to the transport using a glass fibre (ST) cable. They call this their "Clock Link" technology, I think. I believe that they do the same thing inside their CD players but it is transparent to the users as the routing is all internal. I think that the fed back clock is put in a FIFO & this FIFO can be compensated for time (which is phase) delay. The time delay, of course, occuring in the fed back clk signal.
FWIW.
fatparrot
1,314 posts
 
I believe that the discontinued Sonic Frontiers T/P combo used a common clock, as well.
psychicanimal
1,738 posts
 
Also consider direct drive vs belt drive transport differences.
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