static-like noise on raindrop_hui TDA1541a kit - diyAudio
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Old 22nd January 2012, 10:24 AM   #1
niek024 is offline niek024  Netherlands
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Join Date: Jan 2012
Location: Nijmegen
Default static-like noise on raindrop_hui TDA1541a kit

Hi, I'm new to this forum!

I obtained a Raindrop_Hui TDA1541 1.0U DAC recently. The DAC sounds absolutely wonderful. There is one problem, however:

When the source connected to the DAC starts transmitting signal, there is a loud static noise. It sounds to me like a capacitor is discharging through the sound-processing part of the board. It's a loud high-pitched static-like noise (a bit similar to the sound of a dirty potentiometer), that quickly fades away after about 1 second.

I tried to narrow down the cause of the noise, and have found the following:
- it occurs with different sources (computer, cd-player) and on both the coaxial and the optical input.
- in non-oversampling mode, the noise seems to occurs only on the right channel, in oversampling mode, the noise occurs on both the left and the right channel.
- the PCB is connected to the ground shared with the other audio appliances via the RCA connectors and the coaxial input.

I have a pictures of the board and a sample of the noise in a zip-file on my dropbox-server, here:
http://dl.dropbox.com/u/825616/dac.zip (13,5MB)

Two other things i tried after i took the pictures:
-Just to be sure, I have removed the loop in the AC-wires, after I took the pictures, and placed them in a straight curve. That did not resolve the issues either.
-I connected the white and green wires to the other pair (M-5V) of terminals on the control board. Makes no difference.

I'm very glad with the musical qualities of the board, it's just the noise that spoils the fun. (also i'm afraid it will damage my tweeters...)

I'm quite handy with a soldering iron and can do minor repairs, but my electronic skills are just lacking in this case...

Mr Hui does not respond to the trouble-shooting info he asked me for, so i'm in need of some other expertise.
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Old 23rd January 2012, 05:43 AM   #2
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Default DAC noise

Hi Niek024, OK, I don't have that DAC however have chased similar issues. I can tell you that a defective input receiver (in my case) a CS8416 will make a wide band static noise if bad. I realize you have the Wolfson part. So my question is did you build it or was it assembled by the seller? If sold to you this way I'd probably want my hard earned cash back. OK, on my DAC. CS8416, CS8421, CS4398. I replaced the CS8416 and that got rid of the hash. However that wasn't the total fix. After much head scratching I found grounding issues around my DAC. The ultimate fix and the symptom was as you described. Noise in the right channel that died away, static sound under the music. My SRC was in the wrong mode in my case "bypass". It was necessary to remove the resistor that was tied high and tie that pin low. On my TDA1541A DAC I experienced some hash noises using an experimental NPC digital filters with glue logic. I suspect that the clock speed is to fast or off frequency. That one I'm still working on. If you have the equipment I'd check your system clock first. It may be that the clock is recovered from your Wolfson input receiver or you may have a master clock. I'm not sure on your DAC. TDA1541A usually runs off 11.2896 Mhz and have clock dividers. Maybe someone will see your request for help and have your actual DAC. In the mean time it wouldn't hurt to check a datasheet for the input receiver. An incorrect part installed there can give you a lot of grief. Good Luck, Dave
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Old 23rd January 2012, 08:03 AM   #3
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+1
….the problem is most likely related to input receiver chip – it is either faulty, or you may have a short between pin 5 and 4, or 5 and 6. For some reason, the input receiver cannot obtain the correct input signal lock. Check the receiver’ datasheet and make sure the actual mode of operation is selected accordingly on that DAC board. Check if the DIP switch is installed the right way around….

You may want to take the photo of the underside as well – so that we can have a look…

The MP3 sound also reminded me on 1541 not being able to see correct negative analog power supply rail !!!

Boky
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Old 23rd January 2012, 10:43 AM   #4
niek024 is offline niek024  Netherlands
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Join Date: Jan 2012
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thanks for your input!

I have attached 3 pictures of the underside of the boards, as requested.
Let me try to respond to the other given suggestions.

Torchwood421:
- i got the board fully assembled, via Ebay. I wanted to give the seller a good chance to rectify the fault on the board, hoping it would be something simple. No luck with that strategy, so far, though And as the guy no longer responds, i didn't expect to get any money back. But i might check for Ebay-warranty...
- i don't hear noise during playing, only at the start of the signal.
- not sure what to do with the SRC-suggestion about the tying of the pins, and if it would work in my case, as i'm not totally sure what it means... Could you elaborate?
- according to the datasheet, and the actual '12:000 MHz'-part on the board, i suspect there's a separate clock. I have no means to check if it works correctly, but music sounds good after the noise fades away.

Extreme_Boky:
- the input receiver is a WM8805. I could not spot a short between any of the pins. There's a detailed picture attached. I someone would check my findings, i'd be very grateful.
- there's one block of 4 dipswitches on the board, for switching between OS and NOS mode. If have the SAA7220-chip removed for NOS-mode, with the switches in the specified position. If i move the 4 switches over, there's no sound at all, so i guess the switches are installed correctly.
- about the negative power rail: how could i check for that fault?

I hope this answers the questions.
Attached Images
File Type: jpg _DNG8010.jpg (718.9 KB, 150 views)
File Type: jpg _DNG8012.jpg (518.3 KB, 143 views)
File Type: jpg _DNG8014.jpg (542.7 KB, 140 views)
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Old 23rd January 2012, 11:06 AM   #5
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They are in the "spring festival" - nothing works there till 01.28, not even DHL. They probably don't even read emails - I had experience with something like that recently. That's unbelivable for somebody in US or EU.
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Old 23rd January 2012, 11:32 AM   #6
niek024 is offline niek024  Netherlands
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Quote:
Originally Posted by SoNic_real_one View Post
They are in the "spring festival" - nothing works there till 01.28, not even DHL. They probably don't even read emails - I had experience with something like that recently. That's unbelivable for somebody in US or EU.
Interesting. That could account for some delay in his (her?) response. My last mails were on january 10th and 16th, though. The latter one being a kind reminder...

In the mean time, i'd still be welcoming any help in troubleshooting...
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Old 23rd January 2012, 12:40 PM   #7
Magsy is offline Magsy  United Kingdom
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To be be fair it is Chinese New Year and most of these guys are 1000's miles from home (countryside); it is the only chance they have to go home so everything is shut for 1-2 weeks. Often they only see their children once per year at this time.

CNY was yesterday/today, so you should really of had a response to the first email but you never know..
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Old 24th January 2012, 04:16 AM   #8
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Wink Dac noise

Hi niek024, Yes, it is Chinese New Year and not much will happen there for probably a good week. I know that because my wife is in Nanning China right now visiting family. I have not heard from her for a few days. I suspect that you have a bad input receiver as mentioned. An input receiver runs in 1 of 2 modes. Master or slave. In master mode it recovers the clock in the SPDIF data stream. In slave mode there is usually some sort of reclocking and if you have that you should find a crystal oscillator of some sort. I couldn't tell from the bottom view that you posted however I suspect it is in "master mode". So I doubt it reclocks. SRC is a sample rate convertor and it is unlikely that a TDA1541A DAC would have one. I mentioned it in the off chance that maybe there was something extra special about that DAC. SRC's are used to reclock the recovered SPDIF data stream to a higher sample rate. The DAC I mentioned is running 192 Khz for all data rates coming in. Do you have USB input by chance? If you do and that is noise free then that would still suggest that the Wolfson input receiver chip is bad or some issue around the chip. Solder splash etc. The problem with the Chinese DAC's is one they are super cheap. Sometimes parts values are incorrect. That is why I suggested downloading the Datasheet for the input receiver. Usually they copy the datasheet exactly errors and all. Having said that I do have a Chinese DAC here and works OK. It's a very cheap platform for modifying. Anyway be patient. I'm sure Hui will get back to you.
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Old 24th January 2012, 04:59 AM   #9
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ok, I see.... the receiver chip is located on the solder-side. So, the chip in question is most likely 26C32 or similar to "square" / condition the S/PDIF signal train before it hits the receiver chip. Check with the multimeter that there are NO shorts between pin 5 and 4, and between 5 and 6 - from the photos you posted originally -> it looks like there might be!

1541 pin 15 should be sitting at between -16 to -14 V DC. Check with multimeter as well.

If you don’t know what I’m talking about….. send the DAC back for repair.

Good luck!
Boky
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Old 24th January 2012, 09:26 PM   #10
niek024 is offline niek024  Netherlands
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Join Date: Jan 2012
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Quote:
Originally Posted by Torchwood421 View Post
Do you have USB input by chance? If you do and that is noise free then that would still suggest that the Wolfson input receiver chip is bad or some issue around the chip.
i will try that later. My Linux-installation doesn't seem to recognize the USB-part of the DAC-board. So i will have to check with my Windows XP partition, tomorrow.

Quote:
Originally Posted by Extreme_Boky
Check with multimeter as well.
I did the measurements Boky suggested. There is no short between pin 5&6 en 4&5 of the Wolfson 8805. The resistance is not infinate, though. Should it be?

Pin 15 of the TDA1541A measures at -14.9V, within specs. That's good news, i guess!

Quote:
send the DAC back for repair
I was actually hoping to avoid another encounter with the dutch DHL-guys...

Thanks for all your advice and knowledge so far!
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