Need schematic for a Cambridge Audio CD3 cd Player

pilli

Member
2006-08-15 9:46 pm
...a very incomplete answer:

If you have the CD3, the output section is quite easy to trace from the PCB. If you don't have it, I'll look for a "cheesepaper" on which I did it some time ago.

Concerning the digital section, you get some hints here:
http://www.diyaudio.com/forums/showthread.php?postid=980307#post980307

The way I understand it (sorry, it is not very precise, but I am quite a beginner...) is something like this:

Up to the SAA7220 it is pretty much the usual Philips architecture. The 7220 performs 4x oversampling.
After that, some shift registers "move things around" so that there are 4 copies of a samples, each one delayed differently and each converted by one of the four TDA1541s. This corresponds to another 4x oversampling, for a total of 16x.

The four DACs are then "superposed" together before the output stage; they just go through a resistor to the same point (this is in the big DAC PCB, not the TDA1541 "daughter-boards").

Thanks to the high oversampling and high current, the output stage can be passive and very simple.

Was forgetting: I/V is the usual OpAmp (5534), one for each channel of each DAC (this is in the TDA1541 "daughter-boards").


Hope this helps "a little bit" (pun?)


It's a player that I really love. Quirky transport, but the DAC gives this large dynamic precise sound.


Cheers,
pilli.


_
 

gaetan8888

Member
2007-04-08 5:11 pm
Hello

I did try to find a CD3 on Ebay at afordable cost but there is none.

Since I know that it was a very nice sounding cd player and since I have few TDA1541A , I would like to do a DAC using the digital section and especially the shift registers part of the CD3, and I would do a I-V convertion and low pass filter tube output.

I know the thread "Building the ultimate NOS DAC using the TDA1541A" but I found the schematic post by ecdesigns to be hard to understand and I would only use 4x TDA1541A chips, so I would find easyer to use a simplified version like the CD3 digital section and the shift registers part, but not the 4x oversampling.

Thank you

Gaetan
 
Gaetan,

I have somewhere a faulty CD3 and I might be able to sketch a circuit for the part that goes to the 4 dac chips but I am not experienced at this.

By the way I was thinking of doing the "Building the ultimate NOS DAC using the TDA1541A" circuit until that thread got out of control.

Now the interesting part is that this CD3 was hit by a power surge and the power supply was damaged so can I buy the power supply board off you oshifis?

I am hoping the rest of the machine is ok but in any case I am I still happy to sketch the circuit.

Regards, sp
 
Hi Gaetan,

I will try to find the bones of this player. Unfortunately I got it before internet existed and after unsuccessful attempts at contacting the maunafacturer I threw out the faulty parts but I definitely have the pcb with the 4 dacs on it.

Please give me about 1 week but a reminder is ok.

sp
 
Hello stoolpigeon

Will you try to fix this CD3 ?

If not, can you sell me the pcboard allone, and mail it to me ?

If yes, it would easyer for me, send me a private message by the Email button, to tell me the price and so we can also exchange address and decide how we would do it.

Thank a lot

Gaetan (Canada)
 

pilli

Member
2006-08-15 9:46 pm
Cambridge CD2/CD3 output stage

...OK, I found it in a drawer.

Sorry for the "low-fi scan" (a picture actually), I don't have time to draw it better right now. And I do not guarantee that the diagram is 100% accurate...

(Above the diagram is a piece of the DAC card of a Cambridge CD2, same structure as the CD3, just implemented much worse...)


Gaetan, in you previous post you say "...only use 4x TDA1541A chips, so I would find easyer to use a simplified version like the CD3 digital section and the shift registers part, but not the 4x oversampling".
I'm not sure I understand you completely, but I think that the very simple output filter of the CD3 (is that a first order?) only works with 16x oversampling. If you have "less" oversampling, you may have to start the lowpass much lower, so a steeper filter.


If it doesn't come earlier from someone else, I may find the time to trace the shift-registers part for you. Can't promise, though...


Bye,
pilli


Edit 1: I noticed that the output resistor value is not marked: it's a 100K.
Edit 2: Saw your latest post that came while I was typing; if you buy the DAC card, I don't need to trace it, right...?

_:)
 

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pilli

Member
2006-08-15 9:46 pm
gaetan8888 said:
Hello Pilli
Ps; I presume that your drawing are the section after the shift registers part of the CD3 ?


Yes, long after.
This is the output stage, when the signal is analog.

The whole chain is
CDM --> SAA7210 --> SAA7220 --> Shift-regs --> DACS --> I/V --> Out filter

The diagram is from DAC onwards, and it is just one channel.
Notice that "Shift-regs" splits into four parallel streams (per channel), so there are four DACs and I/Vs (per channel, the TDA1541 is stereo). The four streams join again after I/V, and the out filter is just one.



...er, this is for an integrated player.
A DAC would have an SPDIF receiver or something, feeding I2S to the SAA7220.


Bye.


_
 
Hello oshifis

I'm interest in your CD3 Dac board, is it include the shift registers part ?

For the PSU, maby stoolpigeon will take it.

I've try to send you an email at the address from your web page, I will try again. If you don't have my email send me one by the email button on my post.

Bye

Gaetan
 
Hi Gaetan and oshifis,

I am keeping the CD3 and am definitely interested in the PS board. I am also interested in the DAC board but Gaetan you can decide if you want it because it would just be a spare for me.

First thing is to find the parts, take some photos and see if we are all talking about the same thing. As mentioned earlier give me about a week because I will surely have time over the Easter break.

Regards, sp

By the way this is a fabulous sounding player!!!!!!

I have a Revox B226 with a crown dac and there is no comparison.