The key is to fine adjust tracking offset to enable/cause no forward/backward skipping/sticking.Hi Dan,
The Pierre Verany test CD has a 2.4 mm defect. There are also defects that come in doubles. These defects also obliterate the track so that the offset of the tracking servo can either push a skip backwards or forwards. Your choice!
Hi Chris.
Yes,the original Philips systems used 'wobble' 600Hz or so modulation of tracking coil current in order to derive correct average tracking.
The key to these Philips systems was the sheer mass of the swing arm assy.
A disc had to be really seriously damaged in order to cause audible mistracking.
The typical sled type pickups have very low lens mass, rendering them overly susceptible to large transient/peak tracking error signal values.
The very high effective mass of the Philips swing arm mechs constitutes a very effective LP tracking error signal filter.
Dan.
All Talk, All Theory And No Practical Experience eh Stuart....
The audio output artifacts are clearly audible in the case of typical consumer players.
Just take a proper look at typical consumer CDP board layouts and this is entirely to be expected, and is usual in practice.
Dan.
Take a typical CDP and wind up the T/F servo gains.
The audio output artifacts are clearly audible in the case of typical consumer players.
Just take a proper look at typical consumer CDP board layouts and this is entirely to be expected, and is usual in practice.
Dan.
So... you have no actual data. No real listening tests. Just repeating the assertion.
Yeah, yeah, yeah, that theory's been floated for years. Time to stop flapping gums and demonstrate that it's a real problem.
se
Hi Dan,
Both Philips lens assemblies and other ones are low mass. The swing arm is a high inertial moment type device that would average the tracking servo undulations out, but that little lens is flying back and forth with the servo. The actual course of the track is close to the average path including the 600 Hz signal. They average the amount of missing RF to correct for track position. So sled or radial arm, both lens assy's are low mass. Either one can be launched to its natural limits, same for focus too.
Its up to the service tech to control the gain for the servos, and hence susceptibility to large or peak tracking error events.
Hi Stuart,
Dan is correct to a degree considering ground contamination from over active servos. You tend to see this in less expensive players. Some coil assys have become so hot that they melt the dust cover for the servo coils. Servo oscillation can be another problem too. The end result is similar.
So the currents through the common ground return can upset various circuits depending on how the board was routed. However, if the servos are that busy, you are not getting clean audio, that's if you are getting any sound out at all! Better machines use a servo mute that kills servo action in these situations. Sometimes you might hear background noise in the audio when skipping entire tracks. That depends on the CD player of course! Players using separate servo / digital / analogue power supplies avoid this entire issue.
The equipment a technician sees on the bench consists of new players (sometimes just owner finger trouble), pro applications, restaurants and DJ units (worn out sometimes) and older machines needing TLC and parts. So my observations cover this range of products and issues. There are times when we see new machines that need change(s) in order to work properly. So we see engineering mistakes as well.
-Chris
Both Philips lens assemblies and other ones are low mass. The swing arm is a high inertial moment type device that would average the tracking servo undulations out, but that little lens is flying back and forth with the servo. The actual course of the track is close to the average path including the 600 Hz signal. They average the amount of missing RF to correct for track position. So sled or radial arm, both lens assy's are low mass. Either one can be launched to its natural limits, same for focus too.
Its up to the service tech to control the gain for the servos, and hence susceptibility to large or peak tracking error events.
Hi Stuart,
Dan is correct to a degree considering ground contamination from over active servos. You tend to see this in less expensive players. Some coil assys have become so hot that they melt the dust cover for the servo coils. Servo oscillation can be another problem too. The end result is similar.
So the currents through the common ground return can upset various circuits depending on how the board was routed. However, if the servos are that busy, you are not getting clean audio, that's if you are getting any sound out at all! Better machines use a servo mute that kills servo action in these situations. Sometimes you might hear background noise in the audio when skipping entire tracks. That depends on the CD player of course! Players using separate servo / digital / analogue power supplies avoid this entire issue.
The equipment a technician sees on the bench consists of new players (sometimes just owner finger trouble), pro applications, restaurants and DJ units (worn out sometimes) and older machines needing TLC and parts. So my observations cover this range of products and issues. There are times when we see new machines that need change(s) in order to work properly. So we see engineering mistakes as well.
-Chris
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Exactly, that's where you get skipping, dropouts, and refusal to play.
I'm sure, but I'm also sure that if you asserted that corrected read errors were audible, you'd have data- distortion, noise, or (heaven help us) an actual valid listening test.
Well, there is a tiny bit of truth here. It doesnt bother me at all if others know more than i do about medicine, cars or digital or what ever. I have not argued any technical issue one way or the other about CD but try to get broad output from people here....and it is fine so far. I ask a lot of questions because i dont take just one persons input as the law of the land. And, I get a fuller more complete view of the issues from a wider range of people. That is why I push over and over.... to see what else is out there.
It you like, it's a management technique applied here to elicit the widest range of views, ideas and understanding.
I get emails often outside this forum that the other person is afraid or intimated to reply here. I have sometimes encouraged them to go ahead and run the gauntlet. Otherwise, we have our own little party by our selves. Often a lot more interesting and informative.
I am only interested in any differences which can be found between the HD downloads and CD for play back. So sit back and learn. If you know it all then you have nothing more to learn. With the zillions of hits on this forum, there are a lot of people reading which do not participate and they are learning, also. learning about personalities, too. So far, I have not found a major cause for the difference but I'll keep asking questions... even dumb ones. I dont accept that there is no difference. If anyone wants to point to something else they know for sure is causing the difference... not speculation but measured and not theory only... lets hear it now. We are all ears......
THx-RNMarsh
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Perhaps if you deigned to do an actual well-controlled experiment, you might find out for sure rather than relying on a preconception.
Hi Stuart,
Well, absolutely! Besides, you well know I will only ever claim what I thought I saw!
Hi Richard,
Your methods are doing exactly what they are designed to do. I didn't expect such a turn out on this subject. For me, everything is either fact, fiction or I haven't got a clue! But then I'll say so.
As far as the silent thousands who hit the site in the background - yes! That is common for all web sites. I hope people can learn from what goes on in these pages.
-Chris
Well, absolutely! Besides, you well know I will only ever claim what I thought I saw!
Hi Richard,
Your methods are doing exactly what they are designed to do. I didn't expect such a turn out on this subject. For me, everything is either fact, fiction or I haven't got a clue! But then I'll say so.
As far as the silent thousands who hit the site in the background - yes! That is common for all web sites. I hope people can learn from what goes on in these pages.
-Chris
Richard:
Go used - I think the days of great electronics AND great mechanics in one box are long gone.
I don't think anyone makes really good transports like they used to.
I bought a used Sony CDP-X779ES because I wanted the best disc transport I could find and it was a steal of a deal. and i got a spare laser.
If I had the time, I could replace the circuitry after the receiver with "better" digital filters, DACs, I-V, etc. but having a great transport eased the vast bulk of the pains for me.
Chris:
Thanks for the background. It IS a nice transport and is my last CD player, unless someone drops an Accuphase that uses the same transport at my door.
mlloyd1
Go used - I think the days of great electronics AND great mechanics in one box are long gone.
I don't think anyone makes really good transports like they used to.
I bought a used Sony CDP-X779ES because I wanted the best disc transport I could find and it was a steal of a deal. and i got a spare laser.
If I had the time, I could replace the circuitry after the receiver with "better" digital filters, DACs, I-V, etc. but having a great transport eased the vast bulk of the pains for me.
Chris:
Thanks for the background. It IS a nice transport and is my last CD player, unless someone drops an Accuphase that uses the same transport at my door.
mlloyd1
Hi Stuart,
Well, absolutely! Besides, you well know I will only ever claim what I thought I saw!
Hi Richard,
Your methods are doing exactly what they are designed to do. I didn't expect such a turn out on this subject. For me, everything is either fact, fiction or I haven't got a clue! But then I'll say so.
As far as the silent thousands who hit the site in the background - yes! That is common for all web sites. I hope people can learn from what goes on in these pages.
-Chris
I'm not making the claim that they're different. You are.
edit: the qualifier I left out- IF the master is the same between CD and so-called HD. They're often not and differences have nothing to do with the format.
Richard:
Go used - I think the days of great electronics AND great mechanics in one box are long gone.
I don't think anyone makes really good transports like they used to.
I bought a used Sony CDP-X779ES because I wanted the best disc transport I could find and it was a steal of a deal. and i got a spare laser.
If I had the time, I could replace the circuitry after the receiver with "better" digital filters, DACs, I-V, etc. but having a great transport eased the vast bulk of the pains for me.
Chris:
Thanks for the background. It IS a nice transport and is my last CD player, unless someone drops an Accuphase that uses the same transport at my door.
mlloyd1
What kind of digital output(s) does it have/ can I go out to an external DAC?
THx-RNMarsh
Seems much, much much more sensible to build up a simple computer system with an off-site DAC than to sweat getting a good CDP. Offload all the data extraction and error correction efforts to the media transfer phase (CDP -> EAC -> HDD/SSD). The latter are also easy to make multiple backup copies.
Added bonus is you have your entire library readily available.
All the rest of this seems like a lot of hand wringing. (Shocking!)
Added bonus is you have your entire library readily available.
All the rest of this seems like a lot of hand wringing. (Shocking!)
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