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Old 13th March 2006, 11:11 PM   #1
lasso is offline lasso  Sweden
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Default TDA1543 problems

Hi,

Long time reader, first time poster.

Like so many others here, I've put together a TDA1543 DAC to venture into the DIY DAC world. For starters, I've intended to keep the circuit roughly according to the datasheets of the respective components.

But the problem I have now is that the DAC sounds good only at low volume and distorts badly when the samples reach a certain level. (Tested with a SlimDevices SqueezeBox, which has a digital volume control.)

See eg http://my.opera.com/lasso/homes/albu...osc440Hz_1.png . Links to more pictures below.

More details:

The main components:

* TORX173 optical jack (TTL out)
* CS8414 receiver
* TDA1543
* 7805 regulators

The CS8414 is surface mounted on an adapter.

I started with only one regulator for all components. (While searching for errors I added a separate 7805 for the TDA1543, but to no avail.)

Missing from the schematics are 100 nF on each of the V+/V- pairs on the CS8414.

At first I thought that I might have fried the CS8414 or that the TDA1543 might have been defect, but I've tried exchanging them and I still get exactly the same behaviour.

I've also tried adding more capacitance to V+ and V- of the TDA1543, but it didn't change anything.

Schematics, images of the prototype board and screenshots of the recordings are here:
http://my.opera.com/lasso/albums/show.dml?id=45429 .

Could the oscillation-like spikes be caused by digital switching? If so, how easiest to remedy that?

I'm aware that digital circuits should be given special care, but I also would like to keep the circuit as simple as possible while breadboarding. Hence no abundance of regulators, ferrite beads and so on.

But apparently the circuit is a little too simplistic and/or plain wrong. :-) Either in the design, or that the layout is done in such a way so that this problem is caused.

Does anyone have any ideas or suggestions? Do I need to provide more information, and if so, what?

Any help would be truly appreciated!
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Old 13th March 2006, 11:49 PM   #2
EC8010 is offline EC8010  United Kingdom
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The traditional waveform for testing a DAC is a ramp. Nevertheless, your picture shows that the initial problem is something to do with the MSB as the waveform changes polarity from + to -. After that, for some reason, the next most significant bit seem to get its knickers in a twist (technical term). The 1543 is a current DAC and it looks as though it's not seeing a proper load. I'd be looking very hard at soldered joints into the I to V convertor.

A photograph is always helpful.
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Old 14th March 2006, 12:20 AM   #3
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I notice the dac chip seems to have been painted over. Are you sure it is a TDA1543 and not a TDA1543A or a TDA1545A, as at first glance everything else seems okay.
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Old 14th March 2006, 12:24 AM   #4
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Mode is set wrong. Need to do something with pins 13 and 16
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Old 14th March 2006, 10:06 PM   #5
lasso is offline lasso  Sweden
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Thank you for all your comments. I follow up below.

Quote:
EC8010: The traditional waveform for testing a DAC is a ramp. Nevertheless, your picture shows that the initial problem is something to do with the MSB as the waveform changes polarity from + to -. After that, for some reason, the next most significant bit seem to get its knickers in a twist (technical term). The 1543 is a current DAC and it looks as though it's not seeing a proper load. I'd be looking very hard at soldered joints into the I to V convertor.
Waveform: I've taken some new measurements using a 440 Hz sawtooth (dunno if that would be the traditional form, but audacity could generate it . The result was pretty interesting, the DAC doesn't seem to be outputting anything negative:

http://my.opera.com/lasso/homes/albu...40_tda1543.png

Just to make sure that my measurements weren't totally off, I also took the output straight from the SqueezeBox DAC. It shows a little ripple at the extremes, but is otherwise ok:

http://my.opera.com/lasso/homes/albu...squeezebox.png

About joints: I've doublechecked all the joints and reheated all of them. All of them seem to be good, but still the same results. (Or did I misunderstand you?)

Quote:
rfbrw: I notice the dac chip seems to have been painted over. Are you sure it is a TDA1543 and not a TDA1543A or a TDA1545A, as at first glance everything else seems okay.
I think this is because of the angle in the photo. The text is pretty clear from other angles. In real life the chips only have a kind of strange structure in the plastic, but it's not paint. I checked the whole tube of chips I have yesterday, and they look non-fake, at least to me.

But the thought that I had got TDA1543A has struck me... But then I'd assume that they wouldn't even work for low volumes, since the input format is totally different?

Quote:
scottnixon: Mode is set wrong. Need to do something with pins 13 and 16
The way I read the CS8414 datasheet, pins 13 and 16 seemed unrelated to mode selection. They only seem to control the status output on pins 2-6 and 27. Did you mean other pin numbers or have I read completely wrong?

I just did a quick test, setting pin 13 low and pin 16 high, which would indicate that I want to see only channel information and won't have a clock connected to pin 13. Same result as earlier.
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Old 14th March 2006, 10:15 PM   #6
EC8010 is offline EC8010  United Kingdom
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The 440Hz sawtooth waveform shown in your second graphic is a good test waveform. Assuming that the settings on your "oscilloscope" (soundcard?) are the same, the first graphic is a disaster. There's something seriously wrong and the DAC doesn't appear to be reading the data correctly at all.
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Old 15th March 2006, 05:30 AM   #7
lasso is offline lasso  Sweden
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Yep, the settings are the same, and yep, I'm using my soundcard for looking at the signal. It isn't too bad for superficially looking at an audio signal, but of course I stand no chance of analysing eg the digital data that goes into the dac. Maybe I'll get an oscilloscope one day...

I've now redone the whole I/V stage in a new position on the protoboard, and triplechecked all the connections on the CS8414 with the datasheet and my schematics. No difference schematics-wise, but still the same (bad) result.

I did an image search for TDA1543, and most of them have a printed line on them between pin 1 and 8, approximately. Eg:

http://www.kyohritsu.com/CATALOG/SEM...TO/tda1543.jpg .

However, my chips lack the line:

http://my.opera.com/lasso/homes/albu.../tda1543_1.jpg
http://my.opera.com/lasso/homes/albu.../tda1543_2.jpg

Can't say if it means anything. I'll try to get hold of a TDA1543 from another source to try with. (I already have CS8414 from two different sources, and they both act the same.)
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Old 15th March 2006, 07:47 AM   #8
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The TDA1543s look strange to me... Too lazy to check the schematic........
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Old 15th March 2006, 01:20 PM   #9
ash_dac is offline ash_dac  United Kingdom
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Quote:
Originally posted by Elso Kwak
The TDA1543s look strange to me... Too lazy to check the schematic........
They look like someone has been at them with sandpaper (see top right tda1543 for example).

Where did you source them from ?

(maybe sourced from old cd players, and damaged during removal )
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Old 15th March 2006, 02:35 PM   #10
guytou is offline guytou  France
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..."But the thought that I had got TDA1543A has struck me... But then I'd assume that they wouldn't even work for low volumes, since the input format is totally different"

when you feed a 16 bit DAC with a 18 bits stream ,,you get the same behaviour your DAC present .
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