TDA1543 test results using SpectraLab. - diyAudio
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Old 22nd June 2004, 02:17 AM   #1
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Default TDA1543 test results using SpectraLab.

I did some tests on my TDA1543 nos DAC and was kind of disappointed with the results: THD .13% for 1.2kHz tone track The same track played on the Panasonic dvd player was producing .03% of THD.

The I/V is passive using 2 4.7uF non-polar BG caps(super-e) and Rikens 3.3k resistors. I removed the 50k resistors for now, they should make no difference on the THD, I think.

Attached are 2 graphs showing the 1.2kHz and white noise.
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File Type: jpg whitenoise.jpg (88.5 KB, 358 views)
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Old 22nd June 2004, 02:24 AM   #2
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Another image uploaded:
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File Type: jpg 1.2khz.jpg (95.0 KB, 299 views)
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Old 22nd June 2004, 04:01 AM   #3
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Will do testing with 5V supply for TDA1543 tomorrow. According to the datasheet, it should bring the THD down a little bit.
The datasheet says the THD is 0.01-0.03%, why mine is so huge????

how does it sound with a 5V supply, just curious?
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Old 22nd June 2004, 04:14 AM   #4
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You migh try to put a trimpot for Rref and see if you can bring distortion figure down.

I have to admit that the Riken value I'm using might not be optimal, but only one available in that range.
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Old 22nd June 2004, 04:16 AM   #5
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Default Check & adjust

VREF (pin 7)...
it can make a world of difference.

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Old 22nd June 2004, 12:00 PM   #6
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I have been too lazy or scared to measure mine but I
can definitely hear artifacts when doing a 20-20 sweep with a
test cd.
Funny though, it is still enjoyable to listen to.
I guess I must have cloth ears or the coloration the distortion adds is not as bothersome as expected....Unless that is what is
causing my perceived HF [minor] issues ..Hmmm.



Setmenu
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Old 22nd June 2004, 03:20 PM   #7
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Quote:
Originally posted by Peter Daniel
You migh try to put a trimpot for Rref and see if you can bring distortion figure down.

I have to admit that the Riken value I'm using might not be optimal, but only one available in that range.

I've always used a trimpot for Rfef to adjust to different loads when swapping resistors. It's much more convenient than guessing which resistor I'd need to solder to bias the loads and so on... Replacing the trimpot with a resistor wouldn't affect the THD, I hope, it's something else, that may be tweaked for best value.

I don't understand, how come the datasheet shows the low THD for TDA1543 and in the real world application, it's 10 times more? It is caused by a passive I/V vs active one using amps? Too much load on the analog output of the chip? Using prototype PCB without proper grounding? Bad power supply/regulators(I use the battery board and tried the 24v regulated one, it's all the same with both)? What did I miss....?

What are the values for THD and NOise from other folks on the forum? I remember Doede's ones only: THD=.08% for 1kHz, which is still pretty big

About the i/v resistors...
I used the 1.8k before for about 2 weeks and it sounded ok, but a bit quiet and lacked bass. I put back 3.3k resistors and the sound is more dynamic and punchier, I like it this way better. I will start experimenting with an active opamp i/v stage soon, but this combo would settle for my passive one. Maybe 2.7k is a better choice, but it's almost near 3.3k anyway.

How does the TDA1543 sound with 5V anyway? I cannot test it right now but a bit curious...
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Old 22nd June 2004, 10:10 PM   #8
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Hi,

IMHO any R2R DAC does not like voltage on its output.

Passive I/V always has voltage...

But also with op amp conversion it is mediocre ( what a nice word ) technically.

I had a computer CD rom drive with 1543, with -60dB signal the distortion on spectrum analyzer looked like Armageddon .

It is comparable to TDA1540 which is 14bit.

But some folks here say it is th best !

Rich harmoniics ...


Bernhard
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Old 23rd June 2004, 02:58 AM   #9
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Changed/added a couple of things on my DAC and the THD is now 0.017% with SNR at 75dB. Better than my dvd player for sure!!! And way to go for any portable use too, I think No doubt that other chips(nos dacs) may give better performance, but what other chips can be used for portable setups?

Peter Daniel was right about AN8xxx regulators. Not only do they sound better, but make a big difference in improving the specs too . Other things including output bias and fine tuning the VREF are also bring some distortion down.

Bernard, the non-oversampling harmonics are really rich and not ARTIFICIAL... give it a try some day with proper implementation.

Here's the new results from SpectraLab for 1kHz:
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File Type: jpg 1khz.jpg (67.7 KB, 343 views)
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Old 23rd June 2004, 07:10 AM   #10
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Quote:
Originally posted by IpsilonSound

Bernard, the non-oversampling harmonics are really rich and not ARTIFICIAL... give it a try some day with proper implementation.
That's what I say.
I liked it but still prefer absence of harmonics.
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