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Old 12th August 2012, 02:11 PM   #11
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Right then....so many options. I think the easiest option would be to buy the kit on eBay and experiment with changing the TDA1543 for others. But is the DIR9001 receiver chip OK?
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Old 12th August 2012, 02:12 PM   #12
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Quote:
Originally Posted by BertDB View Post
Check out the website of Doede Douma.
Yep I agree his website is a very valuable resource. He so far is the only one I think who has shown how distortion gets better when more 1543 chips are stacked.

Cooling is the big issue when stacking up 1543s, especially so when running at higher supplies. I wanted to build DACs with extreme numbers of chips (my highest so far is 40) so I abandoned 1543 because it consumes 300mW compared to TDA1545A which is a super-cool dude at a mere 15mW.

<edit> DIR9001 is fine - NOS DACs are the least jitter-sensitive DACs and this chip's jitter is OK IME.
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Old 12th August 2012, 02:14 PM   #13
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Thanks again. I think I'll buy it and play around with it

When stacking these chips, is it a simple case of pin to pin, or is there anything else needed like caps across the supply legs? like on the TNT audio link I posted a few posts ago.
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Old 12th August 2012, 04:58 PM   #14
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I am thinking of powering the DAC from my Gainclone PSU, using the +25v and 0 rail, feeding a 12 volt regulator inside the DAC enclosure. What kind of current draw would be expected from the DAC at 12 volts if I were to use the eBay DAC with 4 x TDA1545A?
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Old 12th August 2012, 05:14 PM   #15
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When stacking 1543 its pin-pin but keep pin7s isolated. In fact that rule applies to all the DACs in this 8pin family in my experience. Caps on the supply legs I haven't found too critical on 1543, much more so on 1387 because its CMOS and gulps current down on clock transitions.

The CMOS DACs take next to no current - one TDA1543 is about equivalent in current draw to 20 TDA1545s or 10 TDA1387s. A DIR9001 is 10-20mA I think so total is comfortably below 50mA - the other chip on that board is a CMOS logic (74HC00 I think) which takes almost nothing. Oh there's an optical Toslink receiver - I don't know how much that takes because I removed mine in a bid to keep power supply noise as low as possible.
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Old 12th August 2012, 06:23 PM   #16
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You say that that the 7 pins should be isolated, but in the drawings I found on TNT audio, these are all linked together! What do you mean by 'isolated'?
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Old 12th August 2012, 07:40 PM   #17
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Also, on the PCB I asked about at the start of the thread, the DAC chip is a TDA1543, can a 1545 be simply inserted instead (the pinouts look the same), or are there any other modifications needed?

Thanks again for all the help
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Old 12th August 2012, 08:13 PM   #18
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I just read the datasheets and I can't see a whole lot of difference between the 1543 and 1545, but a couple of other threads here on diyaudio.com say that they are not a direct replacement! Is it something to do with the voltage supply to the chip. I notice on the schematic for the eBay DAC, that the supply to the 1543 is 3.3v via the 317 chip.
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Old 12th August 2012, 09:21 PM   #19
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I'm even more confused now....... I've been reading about different DAC chips here:

EIAJ to I2S converter and vice versa

I also read that the TDA1545 differs from the TDA1545A!

I really want to implement a stack of 1545 chips because of the low current draw and low temperature, but need a bit of help please.

Thanks again
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Old 12th August 2012, 11:19 PM   #20
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Wow - so many questions!

Firstly about pin7 on the 1543 - its a voltage output. I don't connect voltage sources in parallel (the tolerance is 2.1 - 2.3V) - rather connect a resistor to each one individually, or leave them all floating and use an external current source. I make no assurances about the guys over on TNT Audio

Secondly, only 1545A can be found nowadays. The original 1545 was I2S input but seems not to be around anywhere. So no, 1545A isn't a direct plug in (1387 is I2S though - one advantage for using this). 1545A also has different output current and different (read lower) output compliance limits so does require some redesign for a 1543 socket. Also note it won't work above 6V.

A supplly of 3.3V to a 1543? Can't think of the advantage of going so low - most people seem to prefer to run above the 5V recommended to get more output compliance range.

Finally I suspect the 1545A can be driven by one of the formats available from the DIR9001 though I've not tried it myself. I coaxed a CS841X into the right (EIAJ) outputs without much difficulty.

Have I covered everything? If not, get back to me...
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