TDA1541A decoupling capacitors value - diyAudio
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Old 15th July 2005, 09:16 AM   #1
Zoran is offline Zoran  Serbia
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Default TDA1541A decoupling capacitors value

I have some questions if You dont mind.
related to decoupling capacitors of the TDA1541A...
*
1. What value and type You can recomend for those caps?
Because different values of caps existing from 0.1uF...
*
2. Are the caps has to be of same values for all decoupling pins?
*
3. In case of paralleling DAC chips, will You preffer, each chip to be decoupled by separate set of caps,
or merging the all decopling pins and aplly decoupling with one set of caps,
where value of single capacitor has to be multiplyed by number of DACs?
*
Thank You very much in advance...
Zoran
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Old 15th July 2005, 05:14 PM   #2
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I tried many types and one of the best so far are orange Philips MKT caps.

I observed I prefer higher values of these caps. I think I liked 1uF the most , but can't get my favourite orange Philips of this value any more so I'm using 0,56 now.
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Old 15th July 2005, 07:41 PM   #3
Zoran is offline Zoran  Serbia
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Thanks zigibajt
what about
Q2
Q3
?
in case of paralleling the DAC chips
are the pins decoupling pins connected respectably
together and then linked to the decoupling capacitor,
or every dac chip has to be decoupled by own set of caps?
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Old 16th July 2005, 04:51 AM   #4
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Every dac chip has to be decoupled by own set of caps, all the same values. I use orange 0,1uF Philips MKT caps, but 1uF sound best, as zygibajt noted.
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Old 16th July 2005, 02:35 PM   #5
Zoran is offline Zoran  Serbia
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Thanks for reply...
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Old 10th October 2006, 09:10 AM   #6
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Hi All,

Thought I'd reheat this, as I've been perplexed by this...

Basically, if you follow the TDA1541A datasheet, it suggests 0.1uF for these decoupling caps. Not understanding exactly what these caps are for (I thought they could provide some kind of specific timing for the DEM circuit so the value is perhaps crucial), it is interesting to see other people use, I think I've seen up to 3uF, for some of these caps. AND, only some of them (I think for the most significant bits).
Are these just decoupling capacitors like any other? Is there too big a value (because if they were just decoupling capacitors, why not make them all 100uF and be done with it?)?
Which pins service the most signficant bits?

And also, why do some, sometimes, change the Cosc to 680pF?

Basically, is there any theory behind doing any this? And if so, where can it be found?

Cheers,
Phil
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Old 10th October 2006, 10:29 AM   #7
PetrL is offline PetrL  Czech Republic
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As for single chip: I use 2uF MKT for MSB pins 13 & 18. Higher value is definitely needed, the sound is *much* more lively and authoritative. Don't know why... In my setup going even higher brought no further improvement. 0.1 uF MKP for the rest, no need to increase. I tried 0.47 uF MKT here, but the sound went somehow raw. Not completely bad by itself, but once I heard the smoothness of actual solution, there is no other way.

The only "theory" I can serve is that datasheet solutions tend to impress by economy (small caps). Sound can't be printed.
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Old 10th October 2006, 11:28 AM   #8
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Hi PetrL,

Thanks for the reply.
Thinking about it, I guess it could be related to the fact that switching the MSB provides the biggest output change, and hence a bigger decoupling cap can help with this?

Good to hear it made a difference for you.

I like the economy theory, I guess some procurement departments would be concerned over the extra 17-odd capacitors needed for the implementation, so making them smaller values may help tip the balance.

Cheers,
Phil
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Old 10th October 2006, 03:09 PM   #9
PetrL is offline PetrL  Czech Republic
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Phil,

In the datasheet of tda1540 there is some functional diagram and explanation of the switching. Several values of caps should be used. Plain nightmare for a production engineer, I guess. The 1541 is probably similar.

The increased MSB cap has certain downside depending on the output stage. My diy DAC is modified one of www.tnt-audio.com The highs became sharp and unbearable, which I solved by LP filter caps parallel to i/v resistors (after some experimets with filtering at the end of output stage).
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Old 10th October 2006, 11:29 PM   #10
Kip is offline Kip  United States
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Hi PetrL,
I am using Thomas' DAC ver.3 and purchased a TDA1541A/S2 chip and a CS8412 from him also. I am considering selling the ver.3 dac and building the TNT design.

Can you share your modified TNT schematic with me? I can build off schematics, but can't design. I would rather use a solid state I/V stage and that is one of the reasons why I like the TNT design. I have read some comments that TNT's I/V could be better.

I value TNT's comments. I purchased a Karan integrated amp because of their review of it.
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