Not much jitter reduction and reclocking was done.
The DAC would synchronize on the received SPDIF clock and often just jitter along or slightly reduce jitter with a slow PLL loop which had its own 'noise' and 'analog' issues.
This made it a hit or miss exercise in those days.
in case anybody knows, what is going on here, I am very interested!
There are a number of variables we don't know.
The sweep itself. How was it generated and how did you verify its accuracy? There could be some out of band content that is causing issues with certain D/A designs.
The quality of the actual recording on the disc itself.
The eccentricity or relative flatness of the disc.
I remember the first time I copied one of my reference test discs, verified it was error free and identical data (on a PC) and then tested a player with it, only to find distortion that wasn't present on the master disc in the same player.
As for the alignment and defects discs, they cannot be duplicated as they are verified optically flat, concentric and contain various pressing (deliberate) defects in the data stream ranging from burst dropouts, continuous and repeated incremental length dropouts, changes in track pitch, length and eccentricity.
OTOH, I don't think anyone has ever done a double blind, matched level listening test on CD transports...
from the assumably redbook encoded test CD-DA with external CD drive
I do not think there is a need for level matching of digital transports. This should make the test simpler.
As an engineer I have always been sceptical of the VRDS idea. I think it is cockeyed thinking, or marketing linked to record player mythology.Asked myself a similar Q whether to keep a nice transport (famous Teac VRDS-10 w. disc clamping, perfectly according to spec) and still use it with a new RME ADI-2 fs ADC/DAC.
A recorded disc (CDR) is not Redbook compliant by definition. It's yellow book or is it green, can't remember.
Too many books. https://en.wikipedia.org/wiki/Rainbow_Books
Unlike an LP, however, a CD is constant linear velocity source, and spinning relatively fast too, so anything increasing the inertia of the disc will increase the servo power required to keep the frequency right on an eccentric disc.
There is literally zero benefit in increasing the inertia of a CD, the opposite in fact.
Surely one needs both?Eccentricity is accounted for not with rotational velocity adjustments but with small lateral movement of the entire objective lens assembly.
I believe it's high time those books were put into the public domain, or at least made available at physical cost, without effectively paying the license fee at the same time.Too many books. https://en.wikipedia.org/wiki/Rainbow_Books
Still not that simple as it would be impossible to get them synchronized so switching inputs on a DAC is bound to result in issues. But amplitude variations in the final output won't be a problem.
In the end: CD transports all differ but the final result should be they all sound 'the same' on the same external DAC unless that DAC is very crappy and can't deal properly with jitter and/or signal levels/quality.
Audibility of this thus depends on several factors and cannot simply be answered with 'yes' or 'no' in all cases.
Further, the Pioneer stable platter players, (like the 6 disc magazine players) placed the laser assembly above the inverted disc, and as time marched on, the adhesive holding the lens failed, and the lens fell off, rendering the machines dead. All it took was careful re-gluing of the lens and the machines would live on- that is, if it hadn't fallen out a hole somewhere when someone angrily shook the player...
I saw it for the first time in the late 90s. Opened a Pioneer PD-8700 drawer and the lens was on the rubber platter mat.
Since I only have the Philips CD-100 (analog out) here, I can say that there is a whole bunch of beating tones audible between, say 14-20KHz, listening level around -10dB below clipping with Stax L700 & SRM-353x
That's not due to the transport but rather the effect of the used digital (upsampling) filter and the sampling frequency.
Chances are when sweeping a NOS DAC this way you will also hear beating tones.