Philips/Sony designed a system that doesn't require a perfectly controlled speed or scanning velocity. Where is the gain in adding mass or better control when it will not improve how the data is read from the disc?
Let us test it. Momentary slow down the disc rotation during playback and see what happens.
Anyone expecting a pitch change?
Let us test it. Momentary slow down the disc rotation during playback and see what happens.
Anyone expecting a pitch change?
No pitch change, no.
A more stable/sturdier (and maybe heavier) construction will be able to better control the unwanted movements of a plastic disc that's more or less out of shape.
Don't forget to make the mechanical contraption discussed in this thread light absorbant around the perimeter of the disc so we can stop using the green paint.
A more stable/sturdier (and maybe heavier) construction will be able to better control the unwanted movements of a plastic disc that's more or less out of shape.
Don't forget to make the mechanical contraption discussed in this thread light absorbant around the perimeter of the disc so we can stop using the green paint.
Hi jasse,
High mass is anything over a normal disc table and clamping system and over the mass of a normal CD disc.
There is no vibration caused by a spinning disc unless there is something wrong (read broken) with the motor or clamping system.
The very best transport will combine a magnetic clamp system with a good motor and a head on a linear track. I do favor the linear motor for sled motion.
I don't know how many of you actually have experience being professionally trained and practicing CD repair, but those folks would understand clearly that claiming the CD vibrates is simply not something that happens in normal operation. You guys are trying to fix a problem that quite frankly does not exist. The read operation does not impart any variable pressure onto the surface of the disc. Simple. There is nothing to cause a CD to vibrate in any normal acceptable situation.
-Chris
Please don't put words into my mouth. Not once have I ever suggested the cheap motors were okay. My best transport is the one used in the Nakamichi OMS-5 / 7. Not a cheap motor at all.
High mass is anything over a normal disc table and clamping system and over the mass of a normal CD disc.
There is no vibration caused by a spinning disc unless there is something wrong (read broken) with the motor or clamping system.
The very best transport will combine a magnetic clamp system with a good motor and a head on a linear track. I do favor the linear motor for sled motion.
I don't know how many of you actually have experience being professionally trained and practicing CD repair, but those folks would understand clearly that claiming the CD vibrates is simply not something that happens in normal operation. You guys are trying to fix a problem that quite frankly does not exist. The read operation does not impart any variable pressure onto the surface of the disc. Simple. There is nothing to cause a CD to vibrate in any normal acceptable situation.
-Chris
Hi Mark,
Denon made some CD players that had variable pitch. Pretty cool idea. They shifted the reference clock to the speed control part of the system.
Hi jasse,
<------ smiley for you Mark!
Honestly speaking, CDs do not vibrate, and if they are warped, the clamping force to flatten them is well beyond what would be used to clamp a CD. Remember that the reading surface must remain free of obstructions. Therefore all you really have is a nice cover for the disc. The only way to create force across the disc is to apply force that causes the disc to "dish". I for one would never want that!
Stable platter systems do not apply force or extra clamping power on the CD. It is only a flywheel, that's all. A useless flywheel at that!
Come on guys, give some thought to how you think this can work. How can you stabilize anything clamped only in the center (like all systems do)? The rest may or may not be in contact with the CD.
-Chris
No. I would expect the servos to go nuts! A heavier mass would take longer to get back into sync, so you would most definitely hear something followed by silence.
Denon made some CD players that had variable pitch. Pretty cool idea. They shifted the reference clock to the speed control part of the system.
Hi jasse,
I don't know where you are buying your CDs, but you had better start shopping elsewhere!!
<------ smiley for you Mark!Honestly speaking, CDs do not vibrate, and if they are warped, the clamping force to flatten them is well beyond what would be used to clamp a CD. Remember that the reading surface must remain free of obstructions. Therefore all you really have is a nice cover for the disc. The only way to create force across the disc is to apply force that causes the disc to "dish". I for one would never want that!
Stable platter systems do not apply force or extra clamping power on the CD. It is only a flywheel, that's all. A useless flywheel at that!
Come on guys, give some thought to how you think this can work. How can you stabilize anything clamped only in the center (like all systems do)? The rest may or may not be in contact with the CD.
-Chris
Hi mlloyd,
I think it is a brushed motor, but it is a substantial thing. The casing is thick (steel but looks) and milled on the top surface. The shaft is considerably larger than any normal CD disc motor, on par with the brush-less types. I have only heard of one that went bad due to bearings. It is a custom job by Kyrocea (I think, spelling?) and was only in that mechanism. Alpage used a similar motor in the same mechanism.
So far I haven't replaced a disc motor in any Nakamichi OMS-5 / 7 machine under warranty or otherwise. It ran very smoothly.
As far as motors go, I haven't got any complaints with the brushless motors at all. They all seemed to be good except for the one in the Denon DCD-1700. That one appeared to have bad sleeve bearings. Thinking back, I would be more suspicious of the clamper (or flapper). Earlier machines used a pressure flapper to chuck the disc firmly in place, but those always wore out long before even a Mabuchi motor.
Considering the cost and ease of replacement, I can't say much against the Mabuchi motors either. There were several other brands that did even more poorly. Later Chinese copies were so much worse that the Mabuchi motors looked downright reliable - and they were for several years. Cheap? Sure, but the other motors would sell between $100 to $250. That is expensive, so the Mabuchi was a bargain since it lasted as long as several far more expensive motors. I'm talking brushed designs.
Even Yamaha with a much more substantial motor had bearing problems. The feed and disc motor were the same with a different length shaft. It took three tries to get that right. Mind you, when they finally did get it right - it was a very good motor.
The main problem you might run into is the simple fact that all the better motors were larger in every dimension. The shafts were also larger in diameter which created a larger bearing surface (and lower wear). The overall length of the motor itself would be at least three times that of the Mabuchi.
The best way to make any motor last is to refrain from using the "shuffle" or "random" button (= die motor!). That and making sure there weren't any "stabilizing rings" or mats on the disc. I'm actually surprised that no-one drilled a series of equidistant holes around the outside edge of CDs. They could charge a lot for the "relief and damping of vibrations" or some such. They did just about everything else to the discs.
-Chris
I think it is a brushed motor, but it is a substantial thing. The casing is thick (steel but looks) and milled on the top surface. The shaft is considerably larger than any normal CD disc motor, on par with the brush-less types. I have only heard of one that went bad due to bearings. It is a custom job by Kyrocea (I think, spelling?) and was only in that mechanism. Alpage used a similar motor in the same mechanism.
So far I haven't replaced a disc motor in any Nakamichi OMS-5 / 7 machine under warranty or otherwise. It ran very smoothly.
As far as motors go, I haven't got any complaints with the brushless motors at all. They all seemed to be good except for the one in the Denon DCD-1700. That one appeared to have bad sleeve bearings. Thinking back, I would be more suspicious of the clamper (or flapper). Earlier machines used a pressure flapper to chuck the disc firmly in place, but those always wore out long before even a Mabuchi motor.
Considering the cost and ease of replacement, I can't say much against the Mabuchi motors either. There were several other brands that did even more poorly. Later Chinese copies were so much worse that the Mabuchi motors looked downright reliable - and they were for several years. Cheap? Sure, but the other motors would sell between $100 to $250. That is expensive, so the Mabuchi was a bargain since it lasted as long as several far more expensive motors. I'm talking brushed designs.
Even Yamaha with a much more substantial motor had bearing problems. The feed and disc motor were the same with a different length shaft. It took three tries to get that right. Mind you, when they finally did get it right - it was a very good motor.
The main problem you might run into is the simple fact that all the better motors were larger in every dimension. The shafts were also larger in diameter which created a larger bearing surface (and lower wear). The overall length of the motor itself would be at least three times that of the Mabuchi.
The best way to make any motor last is to refrain from using the "shuffle" or "random" button (= die motor!). That and making sure there weren't any "stabilizing rings" or mats on the disc. I'm actually surprised that no-one drilled a series of equidistant holes around the outside edge of CDs. They could charge a lot for the "relief and damping of vibrations" or some such. They did just about everything else to the discs.
-Chris
chris;
thanks. i've had some nice onkyo integra series machines for a VERY long time. they have what i consider to be good transports, except the mabuchi spindle motors wear out and have to be replaced sooner than I would like/expect. i was hoping with Salar opening this thread, some useful alternative spindle motors would surface.
The bottom line is it sounds like mabuchi is the lesser of other evils ...
mlloyd1
thanks. i've had some nice onkyo integra series machines for a VERY long time. they have what i consider to be good transports, except the mabuchi spindle motors wear out and have to be replaced sooner than I would like/expect. i was hoping with Salar opening this thread, some useful alternative spindle motors would surface.
The bottom line is it sounds like mabuchi is the lesser of other evils ...
mlloyd1
of course i don't mind you asking.
i don't keep real records, but it looks like every 5 to 8 years.
my trigger is suddenly significantly increased skipping on discs i play a lot.
and i'm not heavy handed on the "Skip" buttons, but i probably was 15 years ago.
while i'm here, if the service manual doesn't specify platter height and I suspect that somebody mucked around on the machine before i got it, what's a good way to "correctly" optimize height for a onkyo dx706 (or similar machine)?
mlloyd1
i don't keep real records, but it looks like every 5 to 8 years.
my trigger is suddenly significantly increased skipping on discs i play a lot.
and i'm not heavy handed on the "Skip" buttons, but i probably was 15 years ago.
while i'm here, if the service manual doesn't specify platter height and I suspect that somebody mucked around on the machine before i got it, what's a good way to "correctly" optimize height for a onkyo dx706 (or similar machine)?
mlloyd1
Hi mlloyd1,
Okay, you're getting the average expected life from those motors.
Does the manual mention anything about the focus servo offset? Some machines use a 0 value while others may specify 100 ~ 200 mV DC on the focus test point. What head does it use, as that will determine the height of the disc table from the top of the head.
I'm afraid I didn't service that many Onkyo CD players, so I'm going on generalities only. You have the advantage because you have the service manual to refer to.
-Chris
Okay, you're getting the average expected life from those motors.
Does the manual mention anything about the focus servo offset? Some machines use a 0 value while others may specify 100 ~ 200 mV DC on the focus test point. What head does it use, as that will determine the height of the disc table from the top of the head.
I'm afraid I didn't service that many Onkyo CD players, so I'm going on generalities only. You have the advantage because you have the service manual to refer to.
-Chris
hi chris,
head in these is spu3011 (early production i think) and spu3013 (later production; spu3013 is in mine).
a few snips from the service manual. check your PM for more ...
thanks,
mlloyd1
head in these is spu3011 (early production i think) and spu3013 (later production; spu3013 is in mine).
a few snips from the service manual. check your PM for more ...
thanks,
mlloyd1
Attachments
Hi mlloyd1,
Check the value of R103. Measure the voltage drop and calculate the laser diode current. On the head there should be a printed three digit number, or on the flexible PCB that connects to the head. The measured value should be within 10% of the number printed on the head (which has one decimal place that is not shown).
We are making sure the head is healthy before getting involved in an alignment of a bad head.
The easy way to do this is to find another machine with the same head and measure the distance between the top of the laser head and the top surface of the table. Failing that, there is another method.
Follow all the alignment steps in order. This places the machine in a known state that the manual assumes you are at. If you find your offsets where the manual says they should be, you can relax and just use it. Pay attention to the focus offset DC value in normal play mode. One thing that can happen is that the CD player fails to read the TOC after you have adjusted the focus offset. That means that the table height is wrong for certain. The gain setting should be where you found them to be. Using a good quality, clean disc will do for that test disc.
For gains, set the gain control where the low frequency wave forms settle down and before the high frequency noise becomes larger. Do this for both tracking and focus gain. Hopefully you do not have to correct the diffraction grating. That is pretty a fiddly adjustment. A special tool is required to adjust that, so you are off the hook.
Let us know how this goes for you. With careful adjustment, the player will normally operate much better than when it came out of the box. The alignment done at the factory isn't that great.
Good luck! -Chris
On page 24 there is a troubleshooting flow chart with some useful measurement points. Look at the "S" curve (focus search waveform). I would guess that your focus lock should occur near the center point.
Check the value of R103. Measure the voltage drop and calculate the laser diode current. On the head there should be a printed three digit number, or on the flexible PCB that connects to the head. The measured value should be within 10% of the number printed on the head (which has one decimal place that is not shown).
We are making sure the head is healthy before getting involved in an alignment of a bad head.
The easy way to do this is to find another machine with the same head and measure the distance between the top of the laser head and the top surface of the table. Failing that, there is another method.
Follow all the alignment steps in order. This places the machine in a known state that the manual assumes you are at. If you find your offsets where the manual says they should be, you can relax and just use it. Pay attention to the focus offset DC value in normal play mode. One thing that can happen is that the CD player fails to read the TOC after you have adjusted the focus offset. That means that the table height is wrong for certain. The gain setting should be where you found them to be. Using a good quality, clean disc will do for that test disc.
For gains, set the gain control where the low frequency wave forms settle down and before the high frequency noise becomes larger. Do this for both tracking and focus gain. Hopefully you do not have to correct the diffraction grating. That is pretty a fiddly adjustment. A special tool is required to adjust that, so you are off the hook.
Let us know how this goes for you. With careful adjustment, the player will normally operate much better than when it came out of the box. The alignment done at the factory isn't that great.
Good luck! -Chris
On page 24 there is a troubleshooting flow chart with some useful measurement points. Look at the "S" curve (focus search waveform). I would guess that your focus lock should occur near the center point.
Nothing Wrong with green LEDs! Better than blue in the tray...
HDrives are a good example yes.. They have no motor spindle and he sealed enclosure and air flow control, air pressure control is a major part of the design.
Can we find a better kind of motor, like an HD drive? What is the feasibility of creating a mech chassis shape and draw/accompanying enclosure to control airflow to aid stability (if it can help) ?
I've been having a look at different CD players I have and am pleased to announce that the vibration I recall seeing, the blurred edge of the CD I mentioned doesn't really happen. Sorry for asserting that it does!
I do have a problem with a sony 555 not reading and yhe clamp never engages properly so there's s little eccentricity. May or may not be why it doesn't play..
However I still think a better player will be one which helps play old, non-perfect CDs as we live in the real world where we don't go replacing out of print albums with non-available new discs every time.
A strong clamp with a very very slight dish to the spindle could tension the surface and make it uniform. Much lije Mietner's 80's record player design (no platter) .
But, hey, that can be thought about after the basics are done.
Top loaders mean there is much less compromise in mech design in my opinion - everything can be fixed and doesnt have to move to accomodate draws etc
On another note, can anyone say why the CDM0 and CDM1 use a heavy brass flywheel as part of their solid design? Was it removed in later designs as cost cutting by using standard, drop-in motors?
Sorry for asserting that it does!I do have a problem with a sony 555 not reading and yhe clamp never engages properly so there's s little eccentricity. May or may not be why it doesn't play..
However I still think a better player will be one which helps play old, non-perfect CDs as we live in the real world where we don't go replacing out of print albums with non-available new discs every time.
A strong clamp with a very very slight dish to the spindle could tension the surface and make it uniform. Much lije Mietner's 80's record player design (no platter) .
But, hey, that can be thought about after the basics are done.
Top loaders mean there is much less compromise in mech design in my opinion - everything can be fixed and doesnt have to move to accomodate draws etc
On another note, can anyone say why the CDM0 and CDM1 use a heavy brass flywheel as part of their solid design? Was it removed in later designs as cost cutting by using standard, drop-in motors?
Sadly that's where you hit the problem with your argument.. Whether you are correct or not in terms of the difference mass makes to getting best results.
Inertia is not a problem in any sense. So your arguement is open to be... argued against. A cd itself has too much inertia if the motor isn't powerful enough for even that.
All that's important is the power or torque you have to change the speed. As mass increases, the required power to move it in the same way has to increase by a power of 2. Impulse is the term. If the ratio between the mass and the torque of the motor is correct, the servo wont see a difference.
What about gyroscopic effect? Speed and mass both play a part, and as the speeds are fixed by redbook, only mass can increase gyroscopic effect for a more stable rotation of the CD. More gyroscopic effect will also provide a more solid connection between the rest of the mech and the CD surface (or platter if one is used), and therefore improve isolation from outside.
Some physics things there not covered by "it's not a record player".
I'd suggest both low mass and higher mass are valid solutions to playing CD. The low mass one has cost advantages, many fold! And always cheaper to come up with electrical or processing solutions over mechanical ones.
Still, what is best for the best sound is a different set of priorities and questionable magnitudes.
An trying to write this on my phone with half the screen yaken up by the keyboard and the viewable part skipping about all over the place.. sorry for anything garbled! Need to get my Blackberry Passport pressed in to use woth a real keyboard!
Hi NATDBERG,
-Chris
Not really. Poor bearings are more noticeable with low rotating mass. Low rotating mass will extend the life of thrust bearings, and making the motor more substantial would make it a rarely replaced part. Nothing wrong with that.
Pull out your physics text books and have a read. I'm not going to bother with the rest of the arguments. Why you want to fight inertia, I'll never know, but it is your right.
-Chris
Lets apply some CD technology to vinyl. We have the problem of absolute pitch, pitch variations per rotation and pitch at different diameters. These are caused by the player and the media. All cant be removed by mechanical improvements only.
Lets say we could playback the output through a device (a FIFO buffer) that can output a (delayed) pitch perfect signal. To complete the player we add a feedback loop to the motor so that the device is never empty or full. We have now removed the necessity for a fixed rotational speed and replaced it with a pitch controlled speed. Lower mass translates in a better feedback system and a smaller motor with less pitch correction.
Lets say we could playback the output through a device (a FIFO buffer) that can output a (delayed) pitch perfect signal. To complete the player we add a feedback loop to the motor so that the device is never empty or full. We have now removed the necessity for a fixed rotational speed and replaced it with a pitch controlled speed. Lower mass translates in a better feedback system and a smaller motor with less pitch correction.
You didn't read my post fully - I'm not bothered about it for a CD mech (I only talked about platters in terms of making sure a CD was flat, not for the sake of mass), only about a physics point.
You will find all the equations you need in those physics books to show that with the right torque on the motor, the servo won't notice the difference between high torque and high mass compared to low torque and low mass. All you have to do is get the response times for the speed change needed and work backwards.
How so? Smaller motor requirements, yes. But why is a smaller motor with low mass better than a big, powerful motor with an increased mass?
As I pointed out earlier, the brass flywheel on the CDM0 and CDM1 mechs seem to go against the idea that adding mass is intrinsically bad. Compare the mass of that with the tiniest masses of boombox mechs. CDM0 and CDM1 play redbook perfectly well .