2x TDA1541. noise quesion - diyAudio
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Old 1st May 2010, 08:53 AM   #1
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Default 2x TDA1541. noise quesion

Hi, I received a 2 X tda1541a OS & NOS (with switch) DAC yesterday. It uses this board

DAC DIR9001+TDA1541A 2.0B parallel output OS/NOS - eBay (item 220594292877 end time May-02-10 14:23:55 PDT)

but with an added HDAM module instead of the opamp, and an USB connector.
Still trying it out, but it's quite apparent already that it is quite noisy when there are some quiet music. The noise is kind of a noisy shadow to the signal and "moves" with the music.
Is it likely it is coming from the analog output stage, or before the 1541? It happens both in OS and NOS mode. The output stage has 4-5 transistors before the HDAM.
I'm going to make a "lampizator" output stage later, but want tot look into this noise first. Any ideas?
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Old 2nd May 2010, 12:00 PM   #2
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Quote:
Originally Posted by Nick122147 View Post
,
The noise is kind of a noisy shadow to the signal and "moves" with the music.
Is it likely it is coming from the analog output stage, or before the 1541? It happens both in OS and NOS mode. The output stage has 4-5 transistors before the HDAM.
any input on what kind of noise this is would be appreaciated. Is this from the analog outputstage ? The dac chip itself? I'm not very familiar with dac design (yet), so I'm pretty basic in where to begin.
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Old 3rd May 2010, 09:11 AM   #3
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Are you sure about the wiring of your dac? Cause I haven't read alot of complaints about excessive noise on this dac chip.

Can you post a diagram on how you wired the dac, including the power supply and grounding.?
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Old 4th May 2010, 07:21 PM   #4
Joris is offline Joris  Netherlands
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Are the TDA's getting extremey hot?
There might be a power supply problem, or the DACs are broken due to static
discharge. You could try removing one TDA and listen then, also try the other.

Best regards
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Old 4th May 2010, 08:32 PM   #5
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I don't see any filtreing in the schematics. It can be intermodulation with the HF...
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Old 5th May 2010, 07:02 AM   #6
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Quote:
Originally Posted by marchel View Post
Are you sure about the wiring of your dac? Cause I haven't read alot of complaints about excessive noise on this dac chip.

Can you post a diagram on how you wired the dac, including the power supply and grounding.?
Hi. Do you mean how the transformers and input signal is connected? The PCB was already made.
There is also a USB input module which has some connection cable to a switch on the front. Can that kind of cable make inteference to the digital input signal? Those cables are quite close to each other.

Quote:
Are the TDA's getting extremey hot?
There might be a power supply problem, or the DACs are broken due to static
discharge. You could try removing one TDA and listen then, also try the other.

Best regards
Thanks, I will try that when I back home next week.

Quote:
I don't see any filtreing in the schematics. It can be intermodulation with the HF...
You mean filtering of the ouput signal of the DAC? Is that necessary?
There was another page of schematic of powersupplypart that I didn't upload, maybe I missed something important.

Thanks all for input. As I had to leave for a trip, I cannot try anything until next week.
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Old 14th May 2010, 11:29 AM   #7
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Quote:
Originally Posted by Joris View Post
Are the TDA's getting extremey hot?
There might be a power supply problem, or the DACs are broken due to static
discharge. You could try removing one TDA and listen then, also try the other.

Best regards
Hi,
I tried removing one. When only the left one is playing the noise is very loud. Only right one is better, but not noiseless. Tried putting the right one in left ones place, but no difference.
What does this tell me?
I want to try with an opamp in place of the HDAM module to see if that makes any difference, but I don't have one at hand here.
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Old 14th May 2010, 12:17 PM   #8
Joris is offline Joris  Netherlands
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Hi Nick,

When you tried the right one in the left socket, was the noise lesser or worse than the original left chip?
If the noise was the same as with the original left, you may have some problems in your circuit, otherwise I think you've got some nasty fakes of these chips, and yes, they are around Sometimes they remark totally different chips and sell them as DAC, not very kind of the Chinese people.

Can you post me a picture of the chips? It likely that it is noticable when a chip is fake... I hope I'm able to help you further then

Best regards
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Old 14th May 2010, 12:44 PM   #9
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Joris,
the noise didn't change with the right chip in the left one's place. I can post a pic later, but the chips looks used and old, so I would be very supriced if they were fake.
So it might be some problems with the circuit then. That sounds complicated ..
I was planning to try a tube outputstage. That would be interesting to see how if the noise changes. But it woulndt if the noise is made in the digital part.

Thanks!
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Old 14th May 2010, 05:00 PM   #10
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Here are some pictures:

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one tda1541
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the other 1541
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