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Measuring CD Players?

Χ Ξ Σ

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I looked at the review index, and It seems like Amir has never measured a CD player (or did I miss it?). I did find measurements of CD players from other members though.

Has anyone ever offered a CD player to Amir?
 

VintageFlanker

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I looked at the review index, and It seems like Amir has never measured a CD player (or did I miss it?). I did find measurements of CD players from other members though.

Has anyone ever offered a CD player to Amir?


Correct me if I'm wrong, but @amirm can't test CDP (without digital inputs) the same way he does for DACs. He would have to use a specific CD running static noises (or sweeps?) and this will interact differently with the Audio Precision. I'm not sure this would even be able to produce apples to apples comparaisons...
 

restorer-john

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@amirm 's Audio Precision cannot control a CD player directly. It can of course analyze the signals one produces.

So, he would need to obtain the original industry standard test CDs which are getting virtually impossible to find in perfect condition anymore. People like to burn their own, but they are not really good enough for testing players. The test discs have specific run out/flatness/pit to land transistion and reflective standards that cannot be achieved with a CD-R.

As for the interuption to data tracks for error correction/interpolation tests etc, there's really only the Pierre Verany test set, the Philips 5a and a very rare Sony YEDs. The standard CBS CD-1 was used by Stereophile, Audio and many other magazines for decades along with the AP systems.
 

mkawa

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use a cd player with spdif out and use the dac measurements. there is no difference between modern read mechanisms. it could be a 12v powered 5.25" reader with the spdif pins tapped and it would have zero difference in measurement from a 10,000$ cd player with spdif out. any other implication is snake oil
 

restorer-john

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There are CD players that have digital (USB or optical) inputs, which allow the player to be used essentially as a D/A converter, but that defeats the primary purpose which is performance of the disc player itself.
 

mkawa

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what differences do you expect to see in optical read mechanisms?
 

restorer-john

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what differences do you expect to see in optical read mechanisms?

Enormous differences. The abilities of players to accurately retrieve data from compact discs varies wildly.

People who propose otherwise, clearly have never set up, aligned, repaired or tested CD players.
 

Chrispy

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Enormous differences. The abilities of players to accurately retrieve data from compact discs varies wildly.

People who propose otherwise, clearly have never set up, aligned, repaired or tested CD players.

Can you define enormous and how it impacts audibility?
 

Doodski

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Can you define enormous and how it impacts audibility?
Enough that enormous includes entire a entire system of proprietary circuitry that comes with the laser assembly design usually from Sony, Philips, Pioneer, Matsushita, Sanyo etc. There are many kinds from car audio, personal audio, home, boat and portable and they all handle the bumps and thumps differently and sound different because they are different but close sounding at the same time. I don't go as far as saying they all sound the same but they sound similar.
 

amirm

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The standard CBS CD-1 was used by Stereophile, Audio and many other magazines for decades along with the AP systems.
I had the CBS disc years ago but I think I lost it around the same time.
 

restorer-john

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Can you define enormous and how it impacts audibility?

My reply was to what differences I see in optical read mechanisms as posed by @mkawa . The visible differences are enormous. Some RF (eye patterns) are a wasteland. By the time the signal is demodulated, buffered, error corrected/interpolated those differences can be non-existant or still present in the form of heavily interpolated data or even (ramp-down-ramp-up) mS semi-mutings. That is what testing uncovers.

High frequency pure sines are the easiest to see interpolation effects- the THD skyrockets. Don't forget, the digital filter and D/A converter just process the incoming bitstream. To those chips, the signal is golden, they don't know if its accurate or not- they just do what they're told and convert it.

But for testing CD players, you are testing the system as a whole. It's abilities with actual discs. For that, you need absolutely perfect, unmarked discs pressed to unwavering tolerances. They were very expensive at the time and impossible to find now. You also need discs with deliberate errors, eccentricities, pit-land length errors, data interruptions etc to accuractly determine the performance of the optical/servo/tracking/error correction and other systems.

Just because a disc plays, doesn't mean it is reading 100% perfect data.
 

amirm

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Has anyone ever offered a CD player to Amir?
I have a Linn CD player I could test one day. I don't think I have any other pure CD player anymore.
 
U

UKPI

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there is no difference between modern read mechanisms. it could be a 12v powered 5.25" reader with the spdif pins tapped and it would have zero difference in measurement from a 10,000$ cd player with spdif out. any other implication is snake oil
I wouldn't say that with certainty. Different optical reading mechanisms would result in different initial readings from the same disc. That difference might matter when reading a disc with damage which exceeds the capability of the error correction mechanism of CDDA. Different CD drives/players also have different interpolation mechanisms to cope with unrecoverable errors. Because of this, some drives/players would have less audible clicks and pops or click at different places even when the same damaged CD is played.
 

restorer-john

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I had the CBS disc years ago but I think I lost it around the same time.

I have only 1 myself. Otherwise I'd send you one.

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Original Philips 3/5/5a test set with calibrated data interuptions
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restorer-john

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@amirm The Denon 38C39-7174 pressed in Japan is pretty easy to get hold of.

99 tracks and was also a standard test disc. Plenty were sold in record stores at one point. Nippon Columbia and Acoustic Laboratory of Waseda University.

I can keep an eye out on eBay, they pop up quite often, but you need to know which one to get. And it has to be absolutely unmarked to be of any use for THD etc tests.

This one:
scan545.jpg
 
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RayDunzl

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As a practical matter, after I opened up my CD player, watched it change rotational speed up and down, and stuck my thumb on the spinning disc, slowing, releasing, and even stopping the spin, and the music output remained undisturbed (unless the buffer emptied), I stopped being concerned with much of what I imagined it had to do.

Using the digital outputs to an external DAC eliminated other possible concerns or curiosities.

Having only one or two (obviously problematic) discs that don't play well pretty much ended another thread of possible investigation.
 
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