Replace DAC in CD player

[John Richards]

Been reading about the DIY non oversampling DACS and plan to build one. I
will initially use the digital out coax on my current CD player but was
wondering if it would be practical to gut an older CD player except for the
drive and the remote funtions. My hope is that the CD drive and remote
would remain fully functional while replacing the DAC (and the power supply
as needed)? The ideal situation would be the existing DAC connected to the
drive via a ribbon cable and a lot of open space to mount the new DAC and
power supply. Does this sound doable and do you have any suggestions for
specific CD players (cheap) that might meet my requirements?

Thanks
John

 

[LASERandDVDfan]

Been reading about the DIY non oversampling DACS and plan to build one. I
will initially use the digital out coax on my current CD player but was
wondering if it would be practical to gut an older CD player except for the
drive and the remote funtions.

Are you sure you'd want to do that?

There are distinct advantages to having an oversampling filter. One,
primarily, is that it will allow a far simpler analogue section. If you don't
have oversampling, you have to rely on brickwall analogue filters to stop
aliasing noise. It is very difficult to build an analogue section with proper
brickwall filtering. Aliasing noise on a non-oversampling rig will occupy the
upper frequency range of the sample, which is why you have a maximum frequency
response of 22,050 Hz with CD audio. The extra 2,050 Hz is headroom for
aliasing noise. But to construct a filter that will cut off between 20 KHz and
22.05 KHz without any audible artifacts by itself is very difficult and
generally expensive.

Oversampling in the digital domain merely pushes the aliasing noise further
beyond the audible spectrum by increasing the sampling rate of the audio. 8
times oversampling simply means that a 44.1 KHz sample is turned into a 352.8
KHz sample. Since the aliasing noise occupies the upper range of the sample,
the aliasing will be out of the audible range. Although this is a rather
simple explanation, it explains the basics behind oversampling. It is also why
insanely high oversampling rates is overkill.

Perhaps a better solution, provided that you have a decent CD player to begin
with, would be to concentrate on improving a CD player's analogue section and
possibly the power supply. In regards to analogue sections, a lot of CD
players use inferior opamps as an example. Two particular opamps are the
JRC4556 and JRC4560. Replacing these opamps with something along the lines of
a Burr-Brown OPA2604 or a Burr-Brown OPA2134 will help to improve the sound.

Changing the rectifier diodes to something more substatial would also be
another improvement as it supposedly lowers the noise floor, although this by
itself is subject to debate.

A final note: don't buy into audiophile gimmicks like blue LED lights, green
magic markers, and rotation stabilizer rings. Regardless to their fantastic
claims, they do nothing except take money out of your pocket and into the bank
of the seller.

The things that I think would make a great CD player is one that is solidly
built, has a refined transport, a precise digital section with dual D/A
converters, and a clean and faithful analogue section. All powered by a clean
and refined power supply and controlled with a clean and simple interface. -
Reinhart