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Wednesday, May 13, 2020

Edifier S350DB high pitch noise defect

I bought these speakers for all the good opinions in the internet and it seems like there are many units with a manufacturing defect that involves a high pitch noise. Symptoms are:

- High pitch noise independent of speaker volume
- Only happens in Bluetooth, PC and AUX modes.
- Temperature dependent. As the unit warms up (after 10 min), the noise gets lower but never disappears. The colder the room, the worst.

I captured this picture with a spectrum analyser app:

You can see, it detected a peak around 4.4 kHz. This peak starts with higher frequency and amplitude when the unit is cold. As it warms up, it rolls down until maybe 1 or 2 kHz.


I investigated the problem. The sound amplification electronics are in the subwoofer box. It seemed like there was a problem with a switching power supply that steps down 20V from the main PSU to 5V for other parts of the circuitry. This noisy supply is controlled by a AOZ1210 IC. If one blows or apply heat to this IC, the noise frequency changes very noticeably.

I observed with an oscilloscope the supply output but no noise was being injected. This made me think, the noise wasn't being produced at the output but could be inductively coupled to other part of the PCB.

After this I decided to return the speakers, since, this was a manufacturer problem, not mine.

The replacement

The replacement speakers luckily worked fine. There was no noise at all.

As for the serial numbers, this new unit was manufactured actually before the defective one.

Defective unit SN: 441405044429
New unit SN: 441405042325

I try to visually inspect the PCBs of both units but couldn't notice any differences. The PCB revision was the exact same one, so no layout changes. The codes written in the AOZ1210 package were also the same ones.

The defective:

The new:


(The IC and the supply circuitry are located in the bottom right corner, next to the antenna).

The remote
Just as a remark, in my first unit the remote needed to be pointed exactly to the receiver in the speaker. It was very tricky but now I feel it's better. (BTW, the battery was more than OK).

Bottom line

I couldn't really tell what was the reason of the problem. but if you are in the same situation as I was, return them.

13 comments:

  1. Thank you for your blog post and great information about this issue. I received a set of Edifier S350DB speakers last week from Amazon and I've been really pleased with their performance. I am using them with a PC, I already have an excellent HiFi system and so they had some unfair competition when comparing. They really do live up to the online hype, which makes a nice change.

    I have not experienced the high pitch noise with Bluetooth or RCA connections. I plan to connect a different PC to it soon and will be using the optical link. I thought I would try a Google Chromecast Audio with its optical link last night and that's when I first experienced the high pitched noise. Then the google search began and I found your post.

    I like your idea of using a spectrum analyser app to inspect the frequency of the noise. I tried it myself and I found it to be 7.1-7.2kHz. My serial number is 441406531502 and so newer than your copies. I wonder if using an external DAC will help as in my case the amplifier doesn't seem to be the noise source.

    I will request a replacement set from Amazon and see if it makes any difference. Good to hear that your second set solved your problem, is that still the case?

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    Replies
    1. Hi James,
      To be honest, when I discovered this problem was a thing, I really wanted to ask for a refund instead of a replacement, but couldn't find any product that matched this one in terms of features and price.
      I think your problem is different. In my case, the noise was 100% shut when I changed the input to digital or coax. You seem to experience the opposite, which is very strange.
      The noise was temperature dependent. On a cold day, it could definitely reach 7 kHz when the speakers were just turned on.Then, the pitch ramp down noticeably in a matter of seconds as the set warmed up.
      I definitely recommend getting a replacement if, like me, can't find an alternative that suits your needs. For me they still work fine but I can't be 100% confident now.

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    2. Thanks for your reply Pedro. I too was considering whether to ditch the solution. I briefly considered creating a system from separate DAC, amp, speakers... but I agree that the features and price of the Edifiers are perfect and hard to match. I tried connecting my Arcam CD player via optical and I had the same issue. I also connected it via RCA (using internal DAC) and then A-B switched between the two. The internal DAC of the Arcam CD player was much better. I've concluded that I'm probably not missing out on much with the Edifier's DAC. Instead I am going to try a Topping E30 DAC and see how that performs.

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  2. 466003064362 same issue retruning it

    ReplyDelete
  3. Had these speakers for few days. Didn't notice anything wrong for the first couple of days but then now this high pitched whine started to appear. I'm trying to figure out what changed in the past day or so.

    ReplyDelete
    Replies
    1. Could be the temperature of the room. In a very warm room the frequency drops significantly.

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  4. I have 'almost' the same exact issue, the only difference being that my pitch starts around 6Khz, and then goes *upwards* to peak at around 10Khz. Very ear-piercing if you let them idle, and will definitely give me a headache.

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    Replies
    1. Wow, that's another variant. What a pity... On paper this set is ideal. It'll be interesting if you can share your serial number. Good luck with the return.

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  5. Same issue here, mine starts at 44KHz on Advanced Spectrum Analyzer App. I can see the peak drop off when the speakers are powered down. Someone will say that the human ear is only sensitive to 20KHZ, good point but this is clearly audible. The only input that doesn't produce this noise is the Coax input. A to D Converter is in the mail.

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  6. Looks like a similar problem. If the noise starts at 44kHz you definitely can't be able to hear it so I think there's something wrong with the app or with the measurement. But yes, that dropping pitch is a clear sign. It'd be cool if you can post your SN. Good luck with the replacement.

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  7. Pedro, I think the post above yours meant 4.4kHz, Spectrum Analyzer app has an upper limit of 20kHz.
    I contacted customer support through their web page. I sent a recording and Spectral plots with power off, then a couple with power on. The manufacturer sent out a replacement after their support manager agreed the system was faulty. I now have (2) systems. I plan on installing a linier supply to replace the AOZ1210 switching buc-converter.

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    Replies
    1. I'm glad you got a replacement, that's great. Definitely the way to go if you're so lucky to have the defective unit with you is to try to fix it. But first double check with something like a lab power supply that the problem is the one I point. If you eventually do it, you can send me some pictures and I'll post them if you like. Regards.

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