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restorer-john
Grand Contributor
Bear in mind every CD player from day one had ~16K of RAM in it for buffering between the transport/ram control/error correction and the D/A. Jitter was never an issue in a single box machine.
restorer-john
Grand Contributor
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.
eliash
Senior Member
...just as side info, the sweep was generated using WaveLab 5.0 at 44.1KHz/16bits (.wav). WaveLab has a sweep function, duration set to 3mins (log/time frequency rise from 20-200-2K-20KHz per minute), level -20dB.
Perfectly playing on the PC as digital file or from the assumably redbook encoded test CD-DA with external CD drive...the beating frequency, heard on both CD-players, was clean in itself and reproduceable, so I do not think that the test CD has a burning issue...but that´s why I put it to discussion...btw. these self-burned CD-DAs play otherwise perfectly, even on that 37y old Philips CD-100 mentioned...
restorer-john
Grand Contributor
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
solderdude
Grand Contributor
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.
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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.
Clearly keeping the disc flat will reduce some laser servo activity. 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.
No idea if any of this could be the cause of your weird artefact though.
solderdude
Grand Contributor
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
wiki said 'orange book' for CD-R.
restorer-john
Grand Contributor
Eccentricity is accounted for not with rotational velocity adjustments but with small lateral movement of the entire objective lens assembly. More easily done with the Sony system than the swing arm Philips system. The buffer could handle the cyclic fluctuations from eccentricity and clock it out perfectly. Even the 1st gen Philips mech (CMD-0 and 1) could do 1mm.
But I agree, the belt drive (Teac), Stable Platter (Pioneer) and even Sony's XA-xx series were a completely illogical and pointless exploit. You are dead right, it was about grabbing the high-mass TT crowd. Not only that, they were terribly unreliable, offered poorer tracking, track search and were slower at doing anything. The low mass BSL driven, linear motor mechs from various manufacturers were the gold standard IMO.
Surely one needs both?
The lateral movement of the objective assembly would clearly be needed but the disc would also have to increase and decrease speed twice per revolution to maintain constant linear velocity, though allowing the laser objective system to correct circumferentially and laterally together could achieve the same I suppose.
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.
wgb113
Active Member
As others have mentioned, the biggest difference I've encountered between CD players is their ability to read certain discs - some being very particular and others more forgiving. I've not heard a difference in sound quality.
I've been pleased with the Cambridge Audio CXC's ability to read discs of varying quality. The Rega Planet 2000 it replaced was a little more particular which is a shame as I do prefer top-loaders as there's less that could go wrong.
I've been pleased with the Cambridge Audio CXC's ability to read discs of varying quality. The Rega Planet 2000 it replaced was a little more particular which is a shame as I do prefer top-loaders as there's less that could go wrong.
restorer-john
Grand Contributor
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.
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.
eliash
Senior Member
They should sound similar, thought so too,
therefore just re-did the whole thing, generated a new 44.1/16 sweep file, burned it and compared once again.
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 (my ears still ringing...). Using the PC+RME ADI-2 fs at exactly the same level showed less and quieter (but some) beating tones @44.1/16, absolutely no beating tones @96/24 (similarly generated file). So it may have something to do with out-of-band-tone downmix...
A late remark: Eventually bit-depth might have something to do with this as well, need to check later...
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eliash
Senior Member
Yup, somehow there is a structural mismatch between the massive mechanical construction of the TEAC VRDS and its tiny rubber-belt based tray and clamp drive. Took me almost 3h to renew them, no messing around, just straight working hours...
solderdude
Grand Contributor
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.
solderdude
Grand Contributor
I remember servicing a Pioneer the first time and found out the 'stable' platter was a very thin and lightweight platter that weighed even less than the usual magnet clamp. The platter felt incredibly flimsy once inside the player. Only in the open drawer did it feel substantial.
eliash
Senior Member
Yes, sure,
finally I just checked the influence of bit-depth or resolution as well.
Comparing the a. m. 44.1/16 file with a similar 44.1/24 file via PC/RME, the latter showed absolutely no beating tones...(same as 96/24)