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RE: A very technical curiosity - how to assess the quality of a spdif stream ?

Posted by Thorsten (M) on May 19, 2015 at 10:18:45

In Reply to: RE: A very technical curiosity - how to assess the quality of a spdif stream ? posted by beppe61 on May 19, 2015 at 04:33:50:

Hi,

> I am not an expert but as someone i think did, to use a cheap
> cd rom to fill a 1 GB buffer and then read with good clock from
> that buffer should not be that difficult and expensive.

Early PC based "Memory Players" did precisely that and got good reviews. I never experienced those, because at that time I was already on file based for digital.

Before that, the only platform that used read CD "asynchronously" were very early (first gen) DVD Players that lacked a separate laser and chipset for CD-Replay. It meant they were no-go for CDR, but some CDRW+ blanks recorded did work.

I owned one, from pioneer, which incidentally featured the same HD "Legato Link" DAC chip as the Stable Platter Pioneer CD-Player used by Tom Evans for the legendary EIKOS modification.

I had a lot of fun modding this unit, it was extremely responsive to tweaks and once I was done made both an exceptional Player via analogue out (using LC Audio Zero Feedback "Zap-DFilter" anlogue after the DAC - fully balanced) and via digital out (a reclocker plus 16.XXXMHz clock that also fed the CD Playback with separate PSU etc) into DAC's.

I had it beat the Eikos via both analogue and digital outs and among others a Teak VDRS Transport as well as Pioneer Stable Platter, CEC Belt Drive etc. The Mechanism was an early plastic DVD one, plastic drawer, cheap and nasty as they go.

The key was that the CD was read as "Data Rom" and stored in RAM before leaving the DVD Chipset. On errors it would re-read (it was fun to watch this one with damaged CD's with the Top Off). It was possible to stop the disk for a moment and playback would continue, if the disk was released sufficiently quickly to restart reading before the buffer ran dry, playback would be uninterrupted.

Later DVD players put in effect a full CD Player back in, cancelling all the good stuff.

I sold the unit many years ago in a cleanout, a year or two it came for sale and was still going like a trooper (unlike many early SACD Players). So I think that there is some merit to your ideas. No need for 1GB, IIRC DVD had 16MB RAM...

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

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