Hi ppl.
Just got myself a CD40 in great condition (with a nice TDA1541A in it), except for the tray loading gear wheel (like usually...). But cheap replacement part is already on its way (thanks, epos!). Now I'm in the process of modding the CDP. (yes, I do have the schematics)
I want to replace the output stage (so to have a better opamp, not too much passive filtering, and no unnecessary components) and build a better regulated supply board for this.
I also started to "recap" the whole board (at least the 'lytics, as they are 16 years old by now...) and want to add a few decoupling caps or change them.
Of course, it'll get new gold plated RCA outputs aswell as some kind of metal shield around the boards of the output stage and it's PSU so to reduce HF interference from the digital circuits.
And last but not least, I will change it to NOS mode.
For now those are all the mods I plan to do. But I am open to every good suggestion, as long as it seems possible (and worthwhile) for me to realize them. I mean, I don't want to do overkill, you see... and I am no EE... lol
I've already done a little search on this forum and also on others, and found some good ideas, but still decided to open a new thread, because I couldn't find answers for everything. So, for a start, here comes the schematic of my planned output stage and it's PSU. I kept the same design as in the original schematic, simply excluding passive filters and unnecessary stuff (like the deemp. circuit). If you see any mistakes in it (hopefully not :rotfl: ) or anything that could be improved easily, please tell me
About the NOS, I found a little schematic explaining it, what they do is:
they connect WSAB, CLAB and DAAB directly to TDA1541. Now I am wondering if it's better to cut off the leads of the SAA7220, or to cut the traces on the PCB...
They also describe a Mute mod, so that without the muting transistors, one won't run into trouble with clicks and pops:
connect pin 23 (MUSB) of SAA7220 to pin 11 (MUTE) of SAA7210. The thing is, I have SAA7310 in my player... schematic says pin 18 is called MUTE (with trace over the word, as to say it's inverting). I suppose it'll work just like the SAA7210, no? Any experience with that?
Any other change recommended for NOS?
Read somewhere about changing the way the clock signal goes... but for now I don't want to build a new clock for it (would be the best, I suppose, but difficult to do), so I think the best is to leave things like they are, right?
In regards of replacing the 14 decoupling caps of TDA1541, is it worth to increase the size, to, let's say, 220nF?
Also, I was wondering if I should implement a simple RC lowpass filter in the last opamp stage... to filter out any rest of HF noise... keeping in mind that I want to do NOS mod... I know I can't get rid of harmonics (as that's the goal with the Digital Filter...), but that's ok... just thinking I'd like to avoid injecting HF noise to my amp
And finally, to simplify things for everyone, what I'm not going to do (too much hassle for too less a difference, and too much cost in a CDP that's not that good afterall...):
I am not going to replace the power supplies of the whole CD player (although I would do a few tweaks to them, if you have any suggestions. They are nothing fancy, but aren't bad either).
I am not going to make any physical alterations to the player (change the case, make it a top loader, change the transport's mounting, clamping or whatso on), because I think it's quite ok as it is...
And I am not going to do any "crazy" stuff like glueing hundreds of cork or whatever strange materials all over the player, or fitting any real "boutique" componentes, etc, I think you see what I mean
.
Thanks in advance.
P.S.: if anyone needs the schematics, f.ex. of the PSU of the player, so to suggest mods, I'll post them here. I also can send the whole PDF per e-mail (it's of CD50, which is almost the same as CD40).
10th March 2011, 06:34 PM
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