Modding a Marantz CD40

[joydivision]

Ok, so I just finished the project.
Player sounds great so far. NOS mode is working now aswell (the problem is an error I did in the schematic: CLK signal for NOS mode has to be taken from 7310 (CLAB) and not from after 7220 like in my schematic... will correct post corrected schematic one day when I have time lol...

So, I now can switch between OS and NOS and back on the fly while playing, with no interruptions, nothing. Funny thing though is, that the sound seems pretty much the same
Important (and for me not easy to explain) is that it does have a different amplitude: 1.86V in OS, and 2.09V in NOS. So at first listening it does appear slightly different, but then it probably comes down to difference in amplitudes... I have to find a way of equaling the amplitude after the player, so I can do direct A-B comparison...

Anyway, for now I'm happy with the results, works fine, sounds great and looks ok


Ronnie,
I've only done the analog output, as I don't have any external DAC at home. But if you want, you can implement it, CD50 schematics shows how.
As for the mods, feel free to start with what I've done and described here in the topic. Or go all along your own way
If well done, in the end you'll be rewarded with a much better sounding player. At least here it happened

Just don't believe what some people say about NOS, because after hearing and comparing for myself, the difference seems to be very little. And I highly suspect: for worse... only explanation that some people judge their CD player better sounding after doing the very simple NOS mod (without changing anything else) could be proved by a theory I've heard: in OS mode, due to higher frequency, it's more jitter sensitive, so without a new good master clock, simply putting it to NOS mode might improve the sound, as there would be less jitter. I don't know if that's for real, but could be the explanation.
Now, as soon as we upgrade all the rest (new clock, output stage, etc), OS mode will most probably sound better, just like in the measurements: it has less staircase artifacts in the waveform...
But don't believe the other extreme side, either: NOS doesn't sound bad... actually as I said, it's very hard to hear the difference... it only looks worse on the scope, then probably all the "staircase things" get "anti-aliased" by the preamp and amp and finally speakers and our ear, the same happening to HF images of the sampling frequency, etc... but sure, you need at least a low pass filter in the output stage, so not to put at risk your amp (there are amps who react badly to HF).
So, good luck with the mods
Give me your email adress, and I'll send you the CD50 pdf.

Here come some pics of the finished player:

[sondguy]

Nice job & looks really good~ Don't you think the sound might get better after a little breakin time? Tkx for pics. Email schematics to me at: hillwolf61@yahoo.com Best regards Ronnie

[eta_beta_60]

The e-mail address is ritsacch@tin.it.
Thank you for the manual.
Regards.

[joydivision]

OK, just sent out the manual to you guys.

Ronnie: yes, perfectly possible. Although I've yet to hear a case where you can really distinguish the difference between "not-broken-in" and "broken-in"
But until any evidence against it, yes I do believe every _analog_ new electronic components have to "break in" to get to their full potential. What I do think though, based on experience, is that the difference has to be quite small. Otherwise I'd have noticed it more obviously.

Anyway, today just compared extensively my modded Marantz in O.S. mode to a classic Technics CDP with MASH DAC I have (and have known as quite good sounding. It's modified aswell, but only in the output stage. No new clock.). The Marantz wins, although with a small margin only consisting - and that's very interesting, probably being caused by the nice, jitter reduced, Kwak Clock - in better sound image and higher resolution. For all the rest they sound almost identical. But that little difference is enough to make it more pleasant and musical to listen to the Marantz than to the Technics.

Regarding comparison with my special Playstation CDP, I still have to do a few more tests. But the last conclusion I took was that the Playstation still sounds a little better than the Marantz. Have to check it again. The main problem is that output level in O.S. mode is little inferior to that of the playstation cdp... same thing is valid for the comparison between OS and NOS modes in the player... but I gonna find a way and then report about my conclusions.

So, good luck to you guys with your own experiments! Be sure to report back here, it'd be interesting for me aswell.

[robo]

it need so much modify?...
hi,joydivision, can you send me an copy of CD50 manual?Thanks a lot
eai-kevin@163.com.

[philpoole]

hi joydivision,
Glad to see you've been busy!
It think the hole OS vs NOS argument is fascinating - especially how people can have such strong opinions. I'm glad you tried both.
I first of all started off building a NOS DAC, mainly because it would be simpler (mainly because its dealing with lower frequencies), and less sensitive to jitter even though I was feeding it from something like a Kwak Clock.
I think that, and the fact that it can be used unfiltered, appeals to a lot of people. It does have a poor treble response (its really obvious if you have a test CD and oscilloscope - shocking in fact), but I feel that characterises the sound that appeals to some. A very 'laid back' 'analogue' sound perhaps. I found (especially when moving to OS and noticing the difference) NOS, due the lack of treble, seems to have a relative pronouced bass response that I really liked. But I don;t think it was a particularly truthful reproduction.
I was very pleased with the results of NOS, but wanted to try OS.
OS gets a bad rap (by the NOS fans) because, I think, it is trickier to implement, and requires more thought in circuit layout, and because the oversampler chip (especially the SAA7220) can pollute the power rails (hence the suggestion of using a seperate regulator - did you do that mod?) and introduce jitter into the I2S signal.
However, having tried both (alas I can't swap over on the fly yet), I was surprised by 4x OS. The relative reduction in bass was noticeable, but this was sacrificed in return for a far better frequency response and dynamics.
I think they're both different, and I can see how some prefer each other.
But I do prefer OS.

Also, I think the IV stage and filter can affect this. I doubt my anti imaging filter is optimum for instance - in relation to the SAA7220 and I want to go back and rework it some day. And I'm still working on a discrete IV stage, which should help.

Nice work!
Cheers,
Phil

[tvicol]

Originally posted by joydivision
[B]Ok, so I just finished the project.
Player sounds great so far. NOS mode is working now aswell (the problem is an error I did in the schematic: CLK signal for NOS mode has to be taken from 7310 (CLAB) and not from after 7220 like in my schematic... will correct post corrected schematic one day when I have time lol...

So, I now can switch between OS and NOS and back on the fly while playing, with no interruptions, nothing. Funny thing though is, that the sound seems pretty much the same
Important (and for me not easy to explain) is that it does have a different amplitude: 1.86V in OS, and 2.09V in NOS. So at first listening it does appear slightly different, but then it probably comes down to difference in amplitudes... I have to find a way of equaling the amplitude after the player, so I can do direct A-B comparison...

...

joydivision,

Nice work !

I have moded several players now. Marantz CD40 and 50 are a good choice in this regard.
There is still lot of room for improvement especially at servo part. That TCA0372xx Motorola chips can have a better supply etc.
Have a look also on laser supply. A lot of "digital" garbage is coming from there.

I have a question.
In OS mode, do you know how an interpolated sample is calculated. How many master clock circles are necessary to recover a C1 error and how many for each interpolated sample ?

Regards,
Tibi

[joydivision]

Robo:
Just sent the manual to you.
I wouldn't say "much" to what I did I mean, I didn't change the whole digital power supply, for example, or even the trafo for a toroid, like some people do, etc... you can do much more mods... the question remaining then, is if it's worth the "trouble"...

Phil:
What you said about OS and NOS, is a very concise resumée , I'd only add to it, that NOS also has its troubles, and they are not that small: the "stair-case" artifacts generated by the sampling frequency... yes, a normal analog active filter behind the I/V stage solves most severe problems, but leaves always a rest of "modulation", unless it's really complex multi-pole, but then you lose sound quality and phase linearity.
Anyway, not only high frequency loss is the consequence... not that you'd hear much of it, but well, it clearly is there... I can't say how tricky it is to get OS right, as I didn't do the mods sequencially in my player, but what I suppose is that you need a clock upgrade like I did, in order to have good OS sound, because it's more jitter sensitive. Probably I'd find NOS better sounding if I hadn't do the clock upgrade to my player... but like it is, suprisingly they really sound very similar... even the high frequency loss of NOS isn't very perceptible, probably due to the very nature of most music: it seldomly reaches out to over 15 khz... finally I do prefer OS also, if not only for the fact that while in A/B comparison sounding at least as good, I get a "theoretically" cleaner signal

What I find strange though, is the difference of level: 1.86V for OS, and 2.09V for NOS?? I can't see how that happens... would be much better for comparing A/B if they had the same amplitude... maybe the 7220 reduces the amplitude while filtering in digital domain? Anyone knows that?

Sure that the I/V stage and filter do a lot to the sound... I wouldn't be suprised if a really well designed discrete I/V stage would outperform a standard opamp design... and even in opamp version, there is the choice between VFB (which I used) and CFB (some recommended it to me, others say it's worse... gotta try it one day!).

Regarding mods of the digital supplies, I haven't done anything there, except for better decoupling and exchanging all the caps for new ones. That would be something to try in the future: better regulator ICs (I have got to like one very special: the LT1963, it has ultra-low noise output...), seperate supplies, etc... one day when I have time

About improving the servo section, don't think it's worth, at least with the CD40. Unless you mean doing it to avoid induction of digital noise to the rest of the circuit. Because the CD40, thanks to the CDM4, reads very well and quickly, almost every CD I through at it... much different than the old Technics (has a Sanyo laser unit) I have, it refuses to read some CDs, and I even had to do a complete readjustment to get it working acceptably again with normal CD-Rs (actually it's not that hard: find out where the Pot's are, mark there original position, put a good commercial CD in it, and start adjusting them, always looking to improvement of reading and tracking, etc... then repeat the process with a CD-R. Many a player that seems "laser dead" can be brought back to normal operation like this.)

Tibi:
can't answer your question. I am a little confused, though: what does OS mode have to do with error recovery? I thought that was done in a completely different IC (the 7310, if I'm not in error), so it should be exactly the same process, regardless of having the rest of the circuit in OS or NOS, no?

[joydivision]

As I announced before, here goes the corrected schematic of the NOS/OS switching circuit. It had one error in NOS mode: clock was taken from behind 7220, but it has to be taken from 7310

[philpoole]

One of the biggest changes I heard in my TDA1541A DAC was when I replaced the 78/9xx regulators with LM3x7 regulation followed by a further TL431 regulation stage. Regulation, I think, makes a huge difference!
I also feel regulation, and power rail seperation for other parts of the player contribute greatly as well. So I can understand why seperating the power supply for the servo is important.
The CDM 4 is a great transport isn't it? I use a CDM9 these days, but there are discs that I reckon my old CDM4 would've read better.

I prefer OS, as I do think the treble elements in the signal, especially things like percussion, and also soundstage have are more detail.