Reference Transports: An overall perspective

I am not referring to any specific CD/DVD player. In our hypothetical CD/DVD player, the entire song can be uploaded to RAM (i.e. computer memory). This is very inexpensive. Once the song is in RAM which is a digital circuit, it can be read out and processed by the other digital circuits of the CD/DVD player. These circuits perform error correction decoding and filtering. These are typical circuits in any CD/DVD player.
The key point here is that once the song has been uploaded to RAM, the transport is no longer part of the signal path. It is effectively non-existent. You can think of an Ipod Nano as a CD/DVD player which has the song loaded into RAM. Of course the loading of this data is performed from a PC and not a transport.
Once the digital signal has been processed by the digital circuits, this signal has to pass thru a D/A converter. The quality of the D/A converter as well as the clock which clocks the D/A converter can effect the sound quality. If the clock is sufficiently jittery, you will hear this.

the idea of a computer as a transport is intriging however, there are too many variables right now (os, software, hard drive integrity etc....)

a minimist approach with a buffered transport or dac is very, very attractive...

are there any ram buffers (not clocks) that can be added to exsisting transport or dac's ?

As you know any computer today can play a CD/DVD. But a CD/DVD player does not have to be as complex as a computer. A CD/DVD player does not require an operating system. However, it does have firmware, i.e. software which runs the hardware. Dont forget that all CD/DVD players are digital systems anyway so they already have RAM memory. If properly designed, a CD/DVD player can offload all data into RAM prior to playing the music hence relegating the responsibility of the transport to merely a temporary storage for the music. Furthermore once the data has been offloaded into the RAM buffer, the transport no longer has an effect on the quality of music. Just think of the CD/DVD disc as inexpensive storage and the transport as a means of transfering the data on the CD/DVD to digital circuits. You can decouple the processing from the storage (the disc) by using a RAM buffer for intermediate storage.

Lktanx, so if error correction is only for gross errors, then it seems logical that the transport becomes a very important part of getting the data correct, particularly if it can minimize the random errors that occur in all physical systems. If errors are correlated, then adaptive error correction would be helpful, but how are random errors corrected once they occur?

I agree that once the data is read to RAM, the only meaningful influence on the digital signal, other than digital filtering and D/A conversion, is the precision of the clock. Still, to get the data into RAM you need to read it via a transport, and unless you're claiming that all transports are perfect, I don't see how the transport is not a meaningful link? We could debate the significance of this link, but that's another issue altogether.

Transports are not perfect i.e once in a while they make errors but these errors are detected and corrected by a digital circuit. If the system makes a huge amount of errors, such as when your car CD player skips when you drive thru a bump on the road, then you will hear this. A skipping CD player is an example when too many errors are made which "overloads" the error correcting capability of the circuits.
Note that we a talking about a digital means of data delivery. This is not an analog system like a turntable where subtle issues i.e. spin rate of the turntable can be coupled into the music. The digital system with transport is tranferring 1's and 0's into RAM. It does this with the utmost reliability. Dont forget you are trusting such a system of data transfer when you use your computer on a daily basis.