PC or CD transport

You will find many claims on the internet like:
"My CD transport sounds superior to my PC"
"My PC blows my CD transport out of the water"

 

Some cannot believe that a PC can be as good as a $5000 transport.
As we are talking PCM-audio, we have to deal with the bits (the samples) and the timing, the sample rate.

 

A CD transport must do two things.
Reading the bits
This must be done in real time as it has to feed a stream of data to a DAC with a very constant bit rate.

 

Ripping a CD on a PC is a far simpler job.
Read the bits.
It can do it at its own pace as nobody is listening.
The timing (the jitter) is completely irrelevant as this is a copy from one digital media (the CD) to another (the hard disk).

 

If a reading error occurs e.g. scratches on the CD, all a transport can do is interpolate or mute.  In case of a PC, the ripping software can re-read the damaged sector as long and as often as it likes. Some use up to 80 times to find out what is the best possible representation of the damaged sector.

 

Rippers like dBpoweramp calculate a checksum after the rip is completed.
This checksum is compared against the AccurateRip database.
This allows you to compare the result with those of others.

 

As a transport will never tell you it is interpolation and doesn’t have the option to verify the data against a database, the PC is the better of the two in reading an audio CD right.

 

A high quality transport will feed a DAC with excellent timing.
It will have a clock with a very low jitter driving the SPDIF or AES/EBU into a DAC.

You won’t find PC’s with pristine SPDIF out.
Here the transport shines.

 

Inherent to SPDIF is that the DAC is slaved to the sender. That’s why a transport can make a difference.
Inherent to SPDIF is that it will always generate a certain amount of input jitter as no clock is perfect.

Today there are many DACs with an asynchronous USB input.
This means the DAC is no longer slaved to the transport (the PC) but the DAC it self is in charge of the timing.
By using an asynchronous protocol, the DAC in principle has zero input jitter.
Combine this with galvanic isolation and we finally have a true digital solution, a DAC fetching its data at its own pace and not disturbed by any stray signal from any source.

 

Theoretically, the PC when used in this way as a transport should be superior to any other solution!