Provided that the servo output stage & platter motor can handle it, I can say from experience that higher *centered & balanced* platter mass very significantly improves jitter performance & hence sound. Until someone shows me an absolutely *perfect* clock/PLL system, I will maintain my dedication to high mass platter systems. This is why I particularly love my Pioneer CLD-95(with coax out added, fed straight from spdif output chip with one series 75ohm resistor & pure silver coax to jack) as a transport. Never heard a better transport. Since it's a laserdisc/CD player, it has a high current servo and a 2 pound brushless/coreless hall motor. So it kicks the *** out of every transport I have ever a/b'd against it, despite having no upgrades at all to enhance transport performance, other than the coax digital install. Even beats the great Museatex CDD, a cdm1-mkii based unit with Meitner's brilliant C-Lock clocking circuit, which is the only transport ever to come close to the CLD95.
As far as the variable speed, cd's being CLV format, the speed changes are gradual(unless the cd or platter is eccentric), so the only consideration to make about adding mass to a platter is whether the servo & motor can handle starting the thing spinning without overheating. The one shortcoming of Pioneer's stable platter cd players is they use the same feeble little brush motor used on normal players(except in the PD-75 & PD-S95), so they develop excess carbon build-up on the commutators prematurely. This is also true of all of the Teac/Esoteric VRDS stable-platter knock-off models I have yet seen, including the Teac transport used in the Krell KAV series players.
I would certainly not attempt to add platter mass to any Philips CDM-12-series-based player, since the motor is pitifully weak & the driving servo is pathetic.
As far as the variable speed, cd's being CLV format, the speed changes are gradual(unless the cd or platter is eccentric), so the only consideration to make about adding mass to a platter is whether the servo & motor can handle starting the thing spinning without overheating. The one shortcoming of Pioneer's stable platter cd players is they use the same feeble little brush motor used on normal players(except in the PD-75 & PD-S95), so they develop excess carbon build-up on the commutators prematurely. This is also true of all of the Teac/Esoteric VRDS stable-platter knock-off models I have yet seen, including the Teac transport used in the Krell KAV series players.
I would certainly not attempt to add platter mass to any Philips CDM-12-series-based player, since the motor is pitifully weak & the driving servo is pathetic.
Phn, so, do you think all transports sound the same?
I think, with mass produced consumer electronics, there is definitely scope for modifying and improvements (I work in the consumer electronics industry and I know that cost cutting and profit is way more important than build quality to the manufacturer).
As I have said before, adding inertia will probably NOT help, but increasing the clamping force (by adding mass) should reduce mechanical oscillations in the CD itself - which will help the reading of the disc. Improving the electrical environment for the decoder and servo circuitry will help more, and general mechanical damping of the chassis and transport (if possible) will help.
I have mechanically modified a Marantz CD63, as described above, and cleaned up the supplies to the decoder and servo circuitry, and it improved the sound of the player, and improved its ability to read poorly kept discs. So, I believe, from my own observations there are gains in this. Because of this, I have learnt how important the transport and its environment is.
Do you disagree with all of the above?
The CDM modules are well designed, but they are still mass produced, cost reduced, consumer devices.
This is just a thought….. No measurement, no testing nothing.
A servo controlling speed (data velocity/rate) would if I understand correctly continuously hunt up and down to “tune” in to the perfect speed and keep hunting, continuously adjusting. The power supply feeding this is continuously being pulled on positive and negative sides alternating as the servo hunts up and down and is thus modulated this way.
Adding central mass to the spindle may do the following: the rotational mass will perhaps be increased to the point where the servo system ends up mainly slowing the speed down, being not strong enough to speed it up while “hunting”. What I mean is it is only fighting the inertia to slow the disc down…The draw on the servo PSU is thus more continuous and only on one polarity of the PSU, the modulation is thus less erratic and as a result has less impact on sonics.
How the servo circuits handle this in the long run is a of course an interesting question.
Just a thought
A servo controlling speed (data velocity/rate) would if I understand correctly continuously hunt up and down to “tune” in to the perfect speed and keep hunting, continuously adjusting. The power supply feeding this is continuously being pulled on positive and negative sides alternating as the servo hunts up and down and is thus modulated this way.
Adding central mass to the spindle may do the following: the rotational mass will perhaps be increased to the point where the servo system ends up mainly slowing the speed down, being not strong enough to speed it up while “hunting”. What I mean is it is only fighting the inertia to slow the disc down…The draw on the servo PSU is thus more continuous and only on one polarity of the PSU, the modulation is thus less erratic and as a result has less impact on sonics.
How the servo circuits handle this in the long run is a of course an interesting question.
Just a thought
tubenut said:
Hunting implies noticable speed changes. The inertia of the standard system is such that this does not happen !! The speed changes, once the disk is up to speed, are very small.
No !
Increasing the mass slightly may have an effect. After a certain point, the effect is to prevent start up as the motor cannot overcome the inertia.
Andy
awpagan said:
ERR ?
I have just read ( and re-read ) the section in my manual for my cdp (Kenwood DP-1100SG) and I will have to re-read it again !
If I read it correctly, data from 108 frames is deinterleaved to give 1 audio frame.
Wow and flutter (jitter) in the system is dealt with by the PLL and the use of a storage buffer of 5 frames ie while the data input rate may vary, the data output is constant (clocked by the system clock)
So increasing system inertia will have little effect on data rate.
Andy
I don't know if this is right but doesn't the cd spin with different frequencies while it is being read? I mean from beginning to end?
If this is so then the situation is entirely different from turntables. There you are interested in a high (torque of) inertia because you want the frequency to be the same. If the rotating frequenzy is constantly changed during the reading process a high (torque of) inertia produces a negative outcome of what was intended since it makes the cd doesn't want to change the rotating frequency.
If this is so then the situation is entirely different from turntables. There you are interested in a high (torque of) inertia because you want the frequency to be the same. If the rotating frequenzy is constantly changed during the reading process a high (torque of) inertia produces a negative outcome of what was intended since it makes the cd doesn't want to change the rotating frequency.
poynton said:
What decoder is it using?
I've been reading the pdf for the saa7210 and 7310.
once i understand these (might take a while)
Phil
"according to my datasheet:
pin 29 PD/OC - Phase Detector output/Oscilator Control input.
pin 30 Iref - Current reference
pin 31 FB - feedback"
they are ref to the PLL
allan
I was looking for an external memory that was used for buffering
Page 1 SAA7310 pdf
Bidirectional data bus to external RAM ( 16K x 4 bits ) with 64 frame FIFO capacity
external ram in uProcessor
at lest in the CD850!
Has anyone filtered or clocked the microprocessor and found audible improvements?
allan
Page 1 SAA7310 pdf
Bidirectional data bus to external RAM ( 16K x 4 bits ) with 64 frame FIFO capacity
external ram in uProcessor
at lest in the CD850!
Has anyone filtered or clocked the microprocessor and found audible improvements?
allan
Hi Allan,
I'm a bit confused, so bear with me.
I thought you were implying that pins 29,30 and 31 could be used to detect the second error condition - which threw me a bit.
The only error output I can find is EFAB - which I think is a rarely used pin that might actually be regarded as part of the I2S bus (I could well be wrong on that - so don't quote me).
Why do want to find the RAM bus? What are you trying to do?
Sorry if I'm being ignorant.
I'm sure Simon and Brent have tried seperating out the power for the microprocessor in the huge CD63 mods thread ;-)
Cheers,
Phil
I'm a bit confused, so bear with me.
I thought you were implying that pins 29,30 and 31 could be used to detect the second error condition - which threw me a bit.
The only error output I can find is EFAB - which I think is a rarely used pin that might actually be regarded as part of the I2S bus (I could well be wrong on that - so don't quote me).
Why do want to find the RAM bus? What are you trying to do?
Sorry if I'm being ignorant.
I'm sure Simon and Brent have tried seperating out the power for the microprocessor in the huge CD63 mods thread ;-)
Cheers,
Phil
philpoole said:
As long as the transport does what it's supposed to do--read without errors and the FiFo and buffer aren't broken--I cannot see how it can make a difference.
Exactly what is mechanical timing errors? Seriously, what is this thing people call "mechanical jitter"?
I googled "mechanical jitter" just for the hell of it. (http://www.google.com/search?hl=en&safe=off&q=CD+"mechanical+jitter"&btnG=Search) I got 263 hits. The first one was this thread! The following 2 were to the Burmester site. Anti-science, anti-enlightenment, anti-education magazines like Stereophile and Stereo Times scored high. But the majority were various audio forums, I think. I didn't actually count them. And I only checked the 50 first hits. Regardless of the numbers, all I got were pathetic sycophants and scumsucking liars.
I do not rule out that two transports can sound different. But the idea of "mechanical jitter" (whatever it is) is as ludicrous as "high-end digital cables." (Actually, "high-end digital cables" is a correct definition. "High-end" means the high-end of the price range, as in a high-end piece of furniture.) Only the most scrupulous bottom-feeders, like Burmester, Audioquest and Transparent, would try to sell you those things.
The thing about "mechanical jitter" is that any manufacturer, if scrupulous and dishonest enough, can claim "zero mechanical jitter." To say your CD player/transport has "zero mechanical jitter" implies that other CD players/transports have "mechanical jitter." If enough scrupulous and dishonest manufacturers make that claim, the honest manufacturers might be forced to follow. Then the scumsucking liars have won. Well, the scumsucking liars always win. That's the history of mankind. Lies are always more convenient than the truth. Nobody devices inconvenient lies. That would forfeit the purpose of lying.
I did somethink like Pam did with CDM2: Upper side of Laserarm/spidlemotor assembly is packed in 1 mm rubbersheet. Underside is lead glued on. I had to stretch the metal springs somewhay for the extra weight. The clamp is totally filled with woodglue/sand mixture and painted black.
The foam in the springs did became sticky in time, i made new foam dampers.
Good mechanisms get more details out of the CD (Teac VRDS?)
The foam in the springs did became sticky in time, i made new foam dampers.
Good mechanisms get more details out of the CD (Teac VRDS?)
phn said:
To decide whether 2 transports sound the same or differ, it is necessary to exclude some variables ie level the playing field.
To most people, transports refer to the mechanism, servo controls and electronics to the point of giving a usable audio / digital output. Since manufacturers use differing chipsets etc., there are going to be obvious differences. The only way to decide if a VRDS or a CDM-1 or CDM12 is better would be to use the same chipset on the same board with an adapter, changing only the mechanism. (a project, anyone ??)
I agree that "mechanical jitter" should not occur - assuming that the manufacturer does not take too many liberties with the design and manufacturing processes and produce a really bad system.
tubee said:
Impossible !
Good mechanisms reduce read errors and subsequent audible effects.
Well designed electronics reduce interference with the audio etc..
Andy
One cannot rule out that a transport with higher inertia can have less read errors. But in this case it has to be designed like that from the beginning. Doing this to a given drive is asking for trouble.
Apart from that the higher mass does also have to be manufactured with higher precision - otherwise the contrary of what is inteneded will happen.
Regards
Charles
Apart from that the higher mass does also have to be manufactured with higher precision - otherwise the contrary of what is inteneded will happen.
Regards
Charles
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