Jitter Induced By Servo's? - Guido Tent

[Fin]

Hi everyone

I found these comments by Guido Tent in some other threads and would like to address this issue in my CDP. Does anyone have any advice or additional comments on how to minimise these effects?

Other problems can be taken away by removing the crosstalk to that same supply. For that reason it often helps to seperately supply all servo's (actuator, radial, focus and spindle) in the player, as they induce huge LF currents (Hz - kHz range) in the (often poorly designed) groundplanes.

carry out jitter measurements, I expect to see low frequency disturbance due to the servo's (focus, radial and tracking) in the jitter spectrum

What is the best way to achieve this?

1. Provide separate regulated supplies from the original transformer, for each servo?

OR

2. Use a separate transformer for the servo section?

OR

3. Use a separate transformer and power supplies for the sensitive stuff (DAC, analogue stage....) and leave the servos to be powered by the original transformer - with separated supplies?

OR

Something else??????

 

[Zombie]

Hello!
I will make small 317-based regulators for the analogue and digital suply of the servo chip and see what happens.
Maybe even see what can be done with the motor drive supply etc.
Not a superreg, but quite cheap and easy to make, also used by Martin Clark on the clockmod site...
I am a bit reluctant to throw in the fixed coax at this point as they would make it difficult to disassemble the player.

Cheers,
T

 

[Elso Kwak]

Hi everyone

I found these comments by Guido Tent in some other threads and would like to address this issue in my CDP. Does anyone have any advice or additional comments on how to minimise these effects?
What is the best way to achieve this?
1. Provide separate regulated supplies from the original transformer, for each servo?
OR
2. Use a separate transformer for the servo section?
OR
3. Use a separate transformer and power supplies for the sensitive stuff (DAC, analogue stage....) and leave the servos to be powered by the original transformer - with separated supplies?
OR
Something else??????

Hi,
As an experiment I provided a separate transformer for the servo's in my Sony CDPX33ES. Initially I imagined I heard more bass but later when double checking I heard no difference at all.
What does help is improving the clock supply.
Providing crucial chips (decoder, DAC, digital filter) in the CDP with its own dedicated regulator may help also.

 

[Zombie]

Hello Elso!
But if the "crap" has already entered the laser signal? Can cleaning up further down the chain help?

 

[capslock]

Who cares about crap on the laser signal? You need to keep the master clock close to the DAC and feed both clock and DAC from a very clean supply. The rest does not matter then.

 

[Rotellian]

I dont think 'crap' on the laser signal is the issue here. The servos are usually supplied via the CD players main digital supply. The issue is the servos causing unwanted extra noise on the power supply for other parts of the circuitry. Hence the requirement for a seperate supply.

 

[Fin]

Thanks to everyone for getting involved.

For those who haven't noticed, there are some interesting comments related to this discussion, but specific to the CD63, in the following thread:

Marantz CD63 noise source?

 

[Fin]

What next?????

OK, so lets assume we all take care of the basics:

• Good clock with clean, low noise power supply
• Clean supply for DAC
• Clean supply for decoder
• Clean supply for digital filter

Where do we go from here?

We could add seperate regulated supplies for each IC.
Will this help prevent the servo's introducing noise in the supplies and groundplane?
It should help reduce noise to those chips.

I think we also need to look closely at the supplies and grounding of the servo's themselves.
How can we best isolate this section from the rest of the circuitry?
Do we also need to look at isolating each servo from the others?

 

[Fin]

Hi Rotellian

Have you tried anything wrt this issue?

I think Dr. H (Ryan) suggested the transformer idea - like Elso tried - a while ago. Did you try it?

 

[Fin]

More comments

I found some more relevent comments on this subject in the following thread:-

CD Transport Experience

Originally posted by Guido Tent
The jitter (even the pit jitter) at the RF is very important. It all starts there. Depending on concept and implementation and quality of (re)clock circuitry (and rest of driove, induced jitter by servo's is a known one....), a certain jitter will remain at the SPDIF output or DAC chips.

That is what you actually listen to....