CD PRO 2 - The making of a high end CD Transport

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Hi,
The intention of removing the onboard DAC has been mentioned a couple of times on this interesting thread. Even the thread starter anounced it, as I remember.

To the ones that did this mod, did the sound improved?

I guess it will, because some sheet (maybe decoder) says the chip can't feed both I2S signals, to the onboard DAC (AKM in my case) and to the I2S out. The onboard DAC outputs noise when my separate NOS DAC is connected, even when OFF. :eek: while it is clean when the NOS DAC is disconnected.

I didn't realized this until now. Maybe the onboard DAC is detrimental to the outboard DAC, even if unused...

I'll try it and see.

Cheers,
M
 
FibCouple said:
Hi Void

I was contemplating building a new transport built on possibly CDPro2LF and your comments have just come in the nick of time to maybe re-evaluate the situation for me.

Do you feel CDPro2 is a huge leap over CDM12, say VAM1202 etc and what would be your preferred choice for a transport? Obviously, most people here have made transports with CDPro but I couldn't find any direct comparison with older pickups from Phillips. So it is very enlighening to read your comments on the subject, as until now the only proof of improvements has come from data published by phillips themselves.

Maybe I should stick to older players with CDM9 , which was my original plan.

Many thanks for yor input.

Regards
FibC


I think the CD PRO mechanism isn't a huge leap over a CDM12 or a VAM1202, and the circuit board of the CD PRO is a big disadvantage. The circuit board is the limiting factor. We needed a board that can be modified properly, so the CD PRO was not an option for us. Modifying a simple 1-layer circuit board (with a cheap mechanism) gave us far better quality. We used a cheap Sanyo mechanism because of the better laser.

Try to avoid magnetic pucks, the rotating magnetic field seriously influences the tiny coils in the laser (focus and tracking errors, which means more corrections which increase jitter that can't be removed). Also any mechanical unbalance adds vibrations (increases jitter).
Just do a simple experiment and be shocked: play without puck, f.i. use a piece of paper to clamp the CD, it has to be perfectly balanced otherwise it sounds bad. A heavy puck is not an option, you'll get more unwanted vibrations. Because of the needle bearing of the motor it needs to be as light as possible.
It might be interesting to look at the mechanisms used in portable CD players.

About the old CDM's, these are interesting but I don't know if you can reach a high level. I've collected about 20 old players with various swing arm mechanisms, standard they don't sound good, I think the circuit boards and power supplies need to be modified. I suspect the magnetism of the swing arm is a problem too.
 
Hi Void,

Try to avoid magnetic pucks, the rotating magnetic field seriously influences the tiny coils in the laser (focus and tracking errors, which means more corrections which increase jitter that can't be removed). Also any mechanical unbalance adds vibrations (increases jitter).

I think you are totally right here. By coincidence I was listening to a CD that has a thight fit to the center piece so I could make fast and easy ABAB comparisons, with/without the magnetic clamp: without, the sound is denser; bass is fat and highs sound sweeter, velvety; all the audio spectrum has a warmer presentation, with more weigth. With magnetic piece the sound is crisper, hence appears more detailed, but I miss the sense of "integration" between sounds. It sounds more "artificial", lighter...

I'm trouble, I want to get rid of the magnetic piece. Maybe with a mechanism similar to standard CDP, with a supporting wheel and a lever mechanism??
I'll see what you mean by portable CDP...

Many thanks for the tip :)

Regards,
M
 
Well, I have here a clamping mechanism from a portable CDP. Much clever I must say, with these small steell balls.
From the "exploded " diagram of the transport I see that the disc supporting piece can be removed...anyone done that? :xeye: I don't dare to make "major surgery ".
Unfortunatelly, there is no measure on the "axis" width to see if the replacing piece (portable CDP) will fit there.

The alternative would be to lessen the clamping magnet's weight to the minimum necessary to have a good clamping and avoid part of the unwanted effect. "Sanding" maybe...

BTW, I removed the onboard DAC (AKM 4984). Don't know if AES output improved but I2S seems better now... cleaner, I would say.

Thanks,
M
 
If you look at the pic, you will notice that the main PCB and mechanism are attached to metal plate with standoffs.

The wooden board goes on top, attached to bottom plate with 6 standoffs (3 per side).

There are additional blocks on each side, attached to wooden board, which seem to act as footing, supporting the wooden board and CDP assembly hanging suspended from it.
 

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Thanks Peter

Could this be enough for vibration dampening?

My guess is that the mechanism top is snug fit into a rectangular oppening in the wood with some foamy rubber filler.

Second option is to try your brass/copper frame, but as per posted images some details are missed.
 
It seems like too much dampening is not best approach. My copper frame pictured few pages back, while providing solid imaging and nice bass/midrange, was sort of missing in highs and air extention could certainly be better. If anything, I would suggest for CD-Pro a frame as pictured here:

An externally hosted image should be here but it was not working when we last tested it.


It is directly based on a lead frame used in ML31.5 transport. The frame rests on 4 springs, the mechanism itself is installed using supplied rubber grommets and springs, all mounted in special brackets attached to frame:

An externally hosted image should be here but it was not working when we last tested it.


I've built that frame years ago, when copper was still reasonably cheap, now I would think twice what material to use ;)
 
Hmmm. This is a nice piece of work indeed but I had in mind a compact and low profile transport due to WAF. So I´ll focus in others examples like your version 2 or polish Lektor.

Chances for a Shigaclone depends on some parts group buy or surpluss offers.

Thanks for replies.

JC
 
Really good looking!

I have a question for Peter (talking about magnetic pucks):

I made my non-magnetic (bolt and nut type) clamp, finally from a polymer material, using a machine tool. It works OK but I am a bit tired about manually screwing the nut...
How much do your non-magnetic and non "screw-on" big puck weight?

I could easily do one with bronze.

Thanks.
M
 
maxlorenz said:
Really good looking!

I have a question for Peter (talking about magnetic pucks):

I made my non-magnetic (bolt and nut type) clamp, finally from a polymer material, using a machine tool. It works OK but I am a bit tired about manually screwing the nut...
How much do your non-magnetic and non "screw-on" big puck weight?

I could easily do one with bronze.

Thanks.
M

Roberto provides drawing of a simple non magnetic aluminium clamp

http://www.diyaudio.com/forums/showthread.php?s=&threadid=73089&highlight=

Cheers
 
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