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Old 31st May 2012, 06:31 PM   #1
wheijke is offline wheijke  Netherlands
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Default TDA1541/A board to do mods

While doing mods to various TDA1541 based Philips and Marantz players I really dislike to desolder the SMD decoupling caps from under the TDA1541 but It is even more of a hassle to install new (MKP) caps..
So I was thinking why not use a proper board to do this so caps can be nicely aligned like in the more expensive TDA1541 based players. The chip would be moved to the new board and only a few wired connections need to be made from where the dac was to the new board.
My question, anybody know of a readily available board? At first I am not interested in NOS mods.
I have looked for such a board but could not find it anywhere and I might make something myself out of a standard board.

Thanks,
Wouter
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Last edited by wheijke; 28th August 2012 at 12:33 PM.
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Old 1st June 2012, 04:44 AM   #2
amc184 is offline amc184  New Zealand
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I don't know of any PCBs that do that without having a bunch of other functions (and hence being large). Another option you may want to consider is PPS capacitors. These are good quality film capacitors that are available in SMT packages and can be installed neatly in place of the original ceramics. Check out Cornell Dubilier's FCP series and Panasonic's ECHU series.
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Old 1st June 2012, 08:11 PM   #3
wheijke is offline wheijke  Netherlands
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Thanks for the reply, like your blog!
Wouter
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Old 1st June 2012, 08:25 PM   #4
wheijke is offline wheijke  Netherlands
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Im doing a board myself, first time thing.. it is not finished, have to so some things and then go over everything to check if i made no mistakes.
Also the boards you find online are complete DAC solutions which I don't want.. so who knows if this one turns out fine I might have real PCB made.

Wouter

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Last edited by wheijke; 1st June 2012 at 08:32 PM.
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Old 1st June 2012, 08:56 PM   #5
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Quote:
Originally Posted by amc184 View Post
I don't know of any PCBs that do that without having a bunch of other functions (and hence being large). Another option you may want to consider is PPS capacitors. These are good quality film capacitors that are available in SMT packages and can be installed neatly in place of the original ceramics. Check out Cornell Dubilier's FCP series and Panasonic's ECHU series.
How would these be better than the original ceramic caps, please?

Ian
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Old 2nd June 2012, 02:42 AM   #6
amc184 is offline amc184  New Zealand
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@PlasticIsGood: PPS film will outperform ceramic dielectric in a number of parameters that are important. The capacitors that Wouter is changing are fairly important, and do have a substantial impact on sound quality. For the particulars on why these PPS film capacitors are better, I'd reccomend the capacitor related articles in Walt Jung's archive. PPS film isn't mentioned in the articles, as they've only recently been commercialised, but I think their performance is somewhere close to polypropylene or polycarbonate.

It's also worth noting that Philips shared that view. While the cheaper players all used ceramics to decouple the active dividers, the higher performance players used film capacitors (such as the CD880).

@wheijke: It's pretty hard to check a PCA over just from a picture. One possible issue I see is grounding. How many ground returns to the main PCB are you going to use? Combining all the grounds on one return is a very bad idea.
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Old 2nd June 2012, 10:25 AM   #7
wheijke is offline wheijke  Netherlands
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I studied the player that i'm intending this board for and both analog and digital share the same ground, or do you suggest that even in that case I should add multiple ground wires to the main PCB?
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Old 2nd June 2012, 06:04 PM   #8
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@PlasticIsGood: PPS film will outperform ceramic dielectric in a number of parameters that are important. The capacitors that Wouter is changing are fairly important, and do have a substantial impact on sound quality. For the particulars on why these PPS film capacitors are better, I'd reccomend the capacitor related articles in Walt Jung's archive. PPS film isn't mentioned in the articles, as they've only recently been commercialised, but I think their performance is somewhere close to polypropylene or polycarbonate.

It's also worth noting that Philips shared that view. While the cheaper players all used ceramics to decouple the active dividers, the higher performance players used film capacitors (such as the CD880).
Some did, some didn't. It could be that, having doggedly refused for many years to pander to audiophiliacs, they finally got cynical. Or it could be that they suddenly saw the light. Or maybe the change is only significant for S1 or S2 chips.

The articles you cite appear to make no mention of either type of capacitor in question. How the tests apply to audio is not clear either...in fact how they apply to anything other than the tests themselves is not explained.

The reason I asked is because I have several examples of Philips, Marantz, Sony, Arcam, Rotel and Aiwa machines with TDA1541/A. Some of the Marantz machines are stuffed with Cerafines and huge "audio grade" Elnas, and yet they still stick to the Philips original standard SMDs for the DAC decoupling pins. Sony use leaded ceramic discs in the M75 and M95, although they use film caps in the gorgeous 337ESD. Aiwa use leaded ceramic beads, by the looks. Rotel use film like Sony...100n mylar I would guess. Arcam went their own way and seem to have started a mad craze.

Nowhere have I seen any data, or even reasoned argument, for what improvement results from using film caps in this application. All I see is a blanket assumption that ceramic caps are bad, as if they were all the same, and all bad in all situations. And I read many tiresome accounts of how film caps make everything sound great.

The only clearly documented tests of capacitor quality I have seen were published by Cyril Bateman, but I can't remember where. He measured distortion at 1V and 1kHz down to a level of -120dB. From memory, results were much as might be expected, with ceramic discs worst at somewhere around -50dB. Biased polar electrolytics were much lower but still considerably higher than plastic films. Films other than polypropylene where bunched together around -100dB AFAIR, together with non-polar, unbiased polar, and back-to-back polar electros.

Best of all were polypropylene and C0G smd ceramics, both of which tested the limitations of the equipment, around -120dB.

Poorly manufactured caps of any type can be very poor indeed.

This seriously undermines the most common assumption about ceramics.

There are of course many other parameters one might point a finger at, which is why I'm wondering. I guess the main one would be ESR (or Q or tan delta), but looking at datasheets I see this varies widely within each category of cap as much as between categories, so selecting by type seems dubious.

My policy at the moment is to change leaded ceramics for mylar film, but to leave the smd ceramics well alone. This has the advantage of being very easy. I suspect the changes will merely change the distortion mix rather than the total, at least for the plain vanilla DACs. So many other improvements can be made of demonstrable value, even though they aren't very sexy.

I would like to be persuaded otherwise; after all, plastic is good. Perhaps there are some good arguments and data somewhere, lost in the noise.

Finally, there is the issue of authenticity. If I wanted the most accurate and clear CD player, I wouldn't be looking for a TDA chip, which seems renowned for its musicality as much as for its performance statistics. It has a place in the history of music, and it was what it was in the context of a particular setting. I can see the point of emulating great players by applying their technology to some lesser machines. I can't see the point of new variations. I can't see how that can be high fidelity.

Laudably DIY though...

Ian
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Old 2nd June 2012, 11:25 PM   #9
amc184 is offline amc184  New Zealand
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@PlasticIsGood: Both articles do mention ceramic capacitors, but only in passing, as the author writes them off as unsuitable fairly early in the test. I do think these articles use test methodologies that are relevant.

While I agree that certain types of ceramic are quite good (C0G and NP0), I doubt that's what Philips used. They're much more expensive than X7R types, by about an order of magnitude, in the capacitance values used. I don't think that Philips was ever one to pander to anyone, but Marantz and Arcam, sure. Marantz probably used Cerafines and the like because they could do that without a PCB change.

I do agree with a lot of what you're saying though. Not all ceramics are the same, and neither are all films. PPS film is supposed to be similar to polypropylene, but more compact with lower voltage and heat tolerance.

Quote:
Finally, there is the issue of authenticity. If I wanted the most accurate and clear CD player, I wouldn't be looking for a TDA chip ...
Agreed. The most tragic is the the people who wax lyrical about the old Philips players, then you ask them what they've compared it to. Half the time it's something like "It sounds heaps better than the 3CD changer in my boom box". Don't forget the TDA1547 though, they could be quite good.

@wheijke:

I'd still replace the SMT caps on the players PCB, rather than adding another PCB. If you want to use the add-on PCB, I'd use three or four, from each separate ground to the main PCB.
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Old 3rd June 2012, 01:56 AM   #10
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One possibility I considered is to bridge over the SMT caps and stand the DAC up on axial MKT stilts. Sounds easy but my skill with a soldering iron might render the process irreversible. I'm more tempted to try it now, thanks amc184. CD40 looks a likely candidate.
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