Philips CD951 A DAC7 (TDA1547) vs TDA1541A R1 vs SM5872 story - diyAudio
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Old 14th November 2009, 07:32 PM   #1
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Default Philips CD951 A DAC7 (TDA1547) vs TDA1541A R1 vs SM5872 story

Hello there,

I've been given a Philips CD951, CDM9/65 mech and TDA1547. (Thanks again Jan).
The mech is hold as a good one (it plays CDR-W wich is nice), the TDA1547, with its decoder and filter on separated ICs, is great on paper and specs, sounded nice in some good stuff.

My aim, wich will tell how much and how I'll go, is to compare it to my soon to be rebuilt Marantz CD-53 (check the huge thread about Marantz CD-63 mods) and a Xmas gift wich will be a familly unused Marantz CD-40 with a CDM4 and TDA1541A R1 DAC.
I need only one good player, will try to get the best from these 3 guys and get away the 2 loosers to my ears. And the CD951 can do a good transport seems, even if right now an integrated CDP is all I want.

As for now, virgin CD951 but some years old (caps dead?), it's heavier than my CD-53, bigger (nice headroom for adding stuff), at first I tought the front panel was plastic but no, Philips made the aluminium front looks like plastic...
Inside, it's like they applied the Special Edition treatment from Marantz to the CD950: Cerafine aoround opamps and DAC. The caps on other ICs are so small... they deserve to leak in peace. Opamps are JRC bugs. The top lid is a bit dempened and the TX humms... bad news. And last thing they've discarded the 2 lines dot display from 940 for a single line one under the large screen.

The sound, compared to my CD-53 (state of the CD-53 right now, smoothing caps @ opamp PSU, PFM Flea clock on clean test-board, Servo reclocked from /2 Flea, Regulated drivers and Rubycon ZLH caps around digital ICs, analog stage still factory but 6.8F MKP and removed transistors).
Stock CD-53 is warm but dull (boomy in fact) and in the right now state more open and clearer than the Philips but the main point is the lack of the half down (again, compared to the CD-53 as modded now) the lack of bass and mids. Or too bright if you want, with maybe clearer highs than the CD-53.
But it's a bit unfair as it still features cheap lytics as DC blocking caps, tiny decoupling caps and such nasty things.


First step, I can free the standard sound with LM4562 or OPA2132, fit 470/35 or 220/50 Rubycon ZLH at ICs but the DAC (or the DAC?), try to use bigger standard caps (from the CD-53 removal) in the PS and bypass here and there with 1 MKS, maybe 4x MBR1100TR schottky left and MKP caps for the output. It should already sing more.


And then we'll go for real work (unless I really don't like the cheap mods I'll try tomorrow),
I want to:
Spy what have been done on the best DAC7 products, guys with Deltec DACs please open the lid (mister MC? )

avoid opamps -if simple solution is possible- even the internal TDA1547 ones,
use of the Ray's DOS dedicated to the CD-63, have already been done by a member,
or http://digilander.libero.it/paeng/a__tda1547_tweak.htm
but having in mind the technical point of view from another great dutch boy "The internal opamps buffer the switched cap network (...) but with the TDA1547, the opamp can be bypassed, because the connections are made outside the IC. It's a good thing, because the internal opamps are crap. But now that the SC network is 'exposed' to the outside world, you have to be careful not to load it too much, or distortion will be unavoidable."

build some dedicated "not so" noisy regulated PS,
like that "sixpack": Fikustransport also great about the wood plinth.

fit a clock, a Flea or an AudioGD one (the AudioGD may go with a discarded player),

the right and definitive choice of caps on PCB (SEPC & BlackGates?) with no overkill values but efficient ones,

the ability to use it as very good transport...

And last but not least... I'm a bit lazy for ready and understanding, but I will so please... help me!

Matthieu
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Old 15th November 2009, 11:09 AM   #2
Markuzz is offline Markuzz  Netherlands
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Default Great!

Hi Matthieu,

I'll be watching this thread closely as I am currently in the middle of a personal modding battle between a Philips CD951 and a Marantz CD50.

So far I've added os-cons (from Fikus' modding list) to the digital part of the CD951, that makes the player sound good, shocking in fact.

For the CD50 I've only weighted the chassis and put it to NOS (with correct mute) playback.

I am falling more and more in love with the DAC7 sound compared to the good old TDA1541A. The mids are really amazing after the os-con change (it needs some time to burn in though) and the music is really alive already.

The CD50 is just okay at the moment, a lot better than stock but not superduper yet.

Next up is paralleling the decoupling caps on the DAC chips and do the reverse weightening and os-cons so the comparison becomes better. After that, individual PSU's to the digital consumers. By then, they should be unbeatable, and obviously I am curious in the sound difference.

I've put the mods as Fikus has made to both players in a nice Word document. If you're interested in those, PM me.

Cheers,

Mark.
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Old 15th November 2009, 11:11 AM   #3
Markuzz is offline Markuzz  Netherlands
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Default PSU Philps

Forgot to mention that I replaced all the PSU caps in the Philips too as they were as dead as yours I guess.....
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Old 15th November 2009, 11:17 AM   #4
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Hi Markuzz,
welcome aboard

I'll open a thread for the CD-40 anyway... keep you informed.
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Old 15th November 2009, 12:21 PM   #5
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Too late to edit...
I'm fitting all what I have left in, no matter what it is
Wonder if low ESR caps everywhere is really needed, e.g. smooting caps? And do bypass capacitor at rectifiers still needed with the schottky? I'll leave them right now anyway. They fit bypass caps everywhere!

Right now until a better solution I plan to use the internal op amp config, I mean the parts wich are out of the DAC now for them, use a single outside opamp there and then the same Discrete Output Stage as in the CD-63.

But that's later anyway...

Matthieu
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Old 15th November 2009, 03:19 PM   #6
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Any help welcome...
Yesterday in test purpose I've tuned it on for hours but had the opportunity to listen to it later. It was warm, but when pressed play aid a couple of time error. Some more press and it was OK. I thought it was an RC problem as it was another one... but in fact that was stupid as it worked fine sometimes and with the Marantz.

But today, after opamp changed and many caps changed for bigger (that's all) it refuse to turn the disc, it spins backward en a bit normal but "error" or "loading" messages. I've checked the flex ribbbon a couple of times without success.

I don't know where to check and I'm not familiar at all with the pcb, a bit lost.
Maybe bigger caps can harm there??? Sounds strange anyway...

Matthieu
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Old 15th November 2009, 03:26 PM   #7
Markuzz is offline Markuzz  Netherlands
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Quote:
Originally Posted by Malefoda View Post
Any help welcome...
Yesterday in test purpose I've tuned it on for hours but had the opportunity to listen to it later. It was warm, but when pressed play aid a couple of time error. Some more press and it was OK. I thought it was an RC problem as it was another one... but in fact that was stupid as it worked fine sometimes and with the Marantz.

But today, after opamp changed and many caps changed for bigger (that's all) it refuse to turn the disc, it spins backward en a bit normal but "error" or "loading" messages. I've checked the flex ribbbon a couple of times without success.

I don't know where to check and I'm not familiar at all with the pcb, a bit lost.
Maybe bigger caps can harm there??? Sounds strange anyway...

Matthieu
Bigger caps shouldn't hurt, as long as you stay in the 2x or 3x range...... Maybe you shorted something with some solder?
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Old 15th November 2009, 03:29 PM   #8
Markuzz is offline Markuzz  Netherlands
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Default Opamps

Hi Matthieu,

What opamps did you use (and in what player)? :-)

Cheers,

Mark.
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Old 15th November 2009, 03:39 PM   #9
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Oh sorry it'll be only for the CD951!
It's LM4562 right now. I'm going to check again for short or dry joint...
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Old 15th November 2009, 05:35 PM   #10
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Fixed!
Stupid at iron... I've seen a small cap at 2107... 2.2µF not for supply, changed it for a 470/35 back to 2.2 it works just fine! Will change this to film.
Now I'll have an ear but with cheap non polar lytics at dc blocking (and MKS to bypass them, won't be worst...).

Thank for support Mark
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