TDA 1543 x 4 schematic question - diyAudio
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Old 2nd October 2013, 08:36 PM   #1
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Default TDA 1543 x 4 schematic question

Hey guys, i want to build a DAC based on this schematic : https://dl.dropboxusercontent.com/u/...43parallel.gif . I am at my very early steps in DIY audio, and i have some questions regarding the schematic:
1. Is TR1 a trimpot of 1k? if yes why does it`s output shorted with the other pin?
2. All the resistors without value unit are in ohms? The caps i assume they are in nF since they are not polarized(CX is not polarized and is in nF)
3. Is the power input AC or DC? i have red that it is suposed to be 12vac, but the +/- signs tell me its dc...a bit of confusion here.
4. What voltage should the caps be rated at?(i have some 25v caps for c1,c2,c3,c4,c5, and 5v for most of the others).
5. I have made this schematic in Eagle Cad: https://dl.dropboxusercontent.com/u/...%20tda1543.png and i was wondering if it is alright because i want to print it. (schematic in .sch file type: https://dl.dropboxusercontent.com/u/45794359/dac.sch)

p.s. the input x1 is toslink but i don`t have that library in Eagle so i just put 2 pins.

I would really appreciate your help, and if you have any tips regarding the layout on the boards(like what parts need to be close to what)
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Old 3rd October 2013, 09:35 AM   #2
DF96 is offline DF96  England
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Tr1 is being used as a variable resistor. It doesn't have an 'output'.

Yes, resistors are ohms where no 'k' is used. Caps probably pF where no multiplier specified.

Power input is DC. Cap rating depends on the applied voltage. C13 needs to handle whatever DC supply voltage you use. The rest may need to take 5-8V, depending on how you adjust Tr1.

The 680 output resistors look too big. See my website. The exact value depends on the supply voltage (adjusted by Tr1) but I would expect something like 390.

To lay out a circuit like this you need to think about where the currents go. Your best bet is to study other TDA1543 PCBs (and hope they got it right). Mixed-signal design is not easy!
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Old 3rd October 2013, 03:18 PM   #3
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If you are using a toslink connector that will require a voltage (circa 3v)
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Old 1st November 2013, 09:10 PM   #4
uSonic is offline uSonic  Lithuania
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Hello, I have paralleling related question too. I have paralleled 2x TDA1543, ouput resistors are 470om and Vref resistor is 400om. Supply voltage is 6.45v.
Question is: when I am messuring DC between ground and one of outputs, it gives me different reads per output. One of ouputs shows 2.3v, another shows 3.6v. Shouldn't DC offset supose to be same on both outputs?
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Old 1st November 2013, 11:37 PM   #5
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Do you have the chip connected to a digital source? Its possible on power up that the DAC's left and right channels contain random data which would explain the large difference you're seeing.
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Old 2nd November 2013, 06:32 AM   #6
uSonic is offline uSonic  Lithuania
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Yes, dac is connected to pcm2706 and actually it plays music well. I just adjusted Vref value to do not get clipping.
As I understand from your responce there shouldnt be such different. I will double check that but data flows to dac only only when music is not. While it is silent it, it shows straight line in oscillo. I was checking Data pin.
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Old 2nd November 2013, 09:12 AM   #7
uSonic is offline uSonic  Lithuania
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I fixed it while still cannot explain what was wrong. Somehow it appeared to be related which chip is on top. I have messured offset per single chip and it was ok (~1mv diff between channels). Then I triend two different variation which chip is on top, and in one of configuration offset was ok, in another was not (as described above). Only explanation which comes to me is that it has something to do with legs connection to slot or legs resistance, otherwise, I have no ideas how it is possible.
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Old 4th November 2013, 12:28 AM   #8
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Makes me wonder if something strange happens by connecting pin7s together - they're voltage sources so in theory should not be put in parallel. You could try connecting one resistor per pin7 (820R each one).
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Old 5th November 2013, 06:26 PM   #9
uSonic is offline uSonic  Lithuania
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Probably that is right, but Vref adjust both outputs, it not supose to make difference between left and right output. Also, never saw dedicated resistors in tda1543 schemes.
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