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Meanwell EPP-200-27 whining/hissing
Meanwell EPP-200-27 whining/hissing
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Old 16th April 2018, 01:54 PM   #11
matt_garman is offline matt_garman  United States
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Meanwell EPP-200-27 whining/hissing
While I wait to hear back from Meanwell, I have a bad feeling this may be a "feature" of the EPP series: I have another one of these PSUs, the 24 volt version (EPP-200-24). I just tested my LED on its fan header, same result: whining/hissing. I can of course put the power on LED on the main output. But it does take away from what I thought was a near perfect match for the amp (small size, high efficiency, PFC, not expensive).
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Old 16th April 2018, 03:47 PM   #12
radtech is offline radtech  United States
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Could you just connect where the existing power-on LED is?
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Old 19th April 2018, 05:30 PM   #13
bperboy is offline bperboy  United States
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It's pretty typical for power supply vendors to have a sort of "burst mode" operation at light load, in order to meet power efficiency regulations. This burst mode operation can result in effective audible switching frequencies, resulting in the types of hiss you're hearing. If you were to load down the power supply to probably 15-20% of rated output, the noise should go away.

Off-the-shelf power supplies typically have some drawbacks like this that aren't terribly desirable for audio applications.
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Old 20th April 2018, 05:10 PM   #14
matt_garman is offline matt_garman  United States
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Meanwell EPP-200-27 whining/hissing
Quote:
Originally Posted by radtech View Post
Could you just connect where the existing power-on LED is?
If I can solder cleanly, I might do this. Otherwise, I'll just go with the main power output.


Quote:
Originally Posted by bperboy View Post
It's pretty typical for power supply vendors to have a sort of "burst mode" operation at light load, in order to meet power efficiency regulations. This burst mode operation can result in effective audible switching frequencies, resulting in the types of hiss you're hearing. If you were to load down the power supply to probably 15-20% of rated output, the noise should go away.
I think you're on to something here. Meanwell got back to me, one of things that was said was, "there is a chance the whining noise caused by low loading on the main output."

I'm using an AC meter (Kill-a-Watt) to see how much AC power I'm drawing: 4 to 5 watts / 20 to 21 volt-amps. For a 200W power supply, I think this counts as low or light loading. The amp could theoretically max out the power supply. But for my purposes, I'm certain I'll never get anywhere near that. My speakers are reasonably efficient (87 dB IIRC), and my typical listening levels are well below 90 dB (according to a free SPL app on my phone). Not precise measurements by any means, but I'm certain my actual power needs are generally in the single-digit range.
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Old 20th April 2018, 05:18 PM   #15
bperboy is offline bperboy  United States
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Quote:
Originally Posted by matt_garman View Post
I'm using an AC meter (Kill-a-Watt) to see how much AC power I'm drawing: 4 to 5 watts / 20 to 21 volt-amps. For a 200W power supply, I think this counts as low or light loading.
In fact, that 4-5W is what is being drawn from the AC supply. This doesn't include the efficiency of the MeanWell supply itself at light load, which won't be terribly high. So probably from the output of the MeanWell, you may only be drawing 2-3W.

For audio applications, disabling light load bursting, ensuring high electrical current capability, but not necessarily thermal capability are desirable traits of power supplies. Since audio is "crest-y", the power supply doesn't need to provide sinusoidal output power forever, so if it's a little under-designed in that regards, that's acceptable.

Any off-the-shelf AC-DC power supply isn't likely going to have these characteristics, since they're designed to be used with just about any electronic application.
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Old 20th April 2018, 05:39 PM   #16
gholl is offline gholl  United Kingdom
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It's not unusual for converters to be designed for standard* operation from 10% of maximum load upwards. Standard* means continuous conduction of the output inductor and fairly steady pulse width modulation. Below 10% loading the PWM will vary according to the load and input voltage, with the control loop behaving in an, ideally, predictable manner. The manner in this case is probably a fast hiccup or lower frequency of operation. You have probably got it into an acoustically noisy region. The solution might be just to add a little dummy load. Personally I only use off-the-shelf SMPSU's for class A amplifiers.
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Old 28th April 2018, 09:52 PM   #17
matt_garman is offline matt_garman  United States
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Meanwell EPP-200-27 whining/hissing
A Meanwell engineer got back to me on this, and confirmed what many of you are saying: it simply hisses at very low loads. Here is what the engineer wrote to me:

Quote:
I have done some test about it. Once there is a 0.3A load, then I can only hear the noise when Iím really close to the power supply. When the loading is above 0.7A, Iím not able to hear the noise any more. Therefore, I would recommend to add a 40 ohm/ 20W power resistor or just use two smaller power supplies instead.
Thanks everyone for your help and feedback.
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Old 30th April 2018, 04:16 AM   #18
forestsgump is offline forestsgump
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Quote:
Originally Posted by matt_garman View Post
A Meanwell engineer got back to me on this, and confirmed what many of you are saying: it simply hisses at very low loads. Here is what the engineer wrote to me:



Thanks everyone for your help and feedback.
So does it also mean my Meanwell LR150-36 is also as per design? when it is connected to a Class-D for nearfield listening, this Meanwell produce whinning, cld be a couple-of-meter distance.
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Old 30th April 2018, 06:33 PM   #19
gholl is offline gholl  United Kingdom
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Quote:
Originally Posted by forestsgump View Post
So does it also mean my Meanwell LR150-36 is also as per design? when it is connected to a Class-D for nearfield listening, this Meanwell produce whinning, cld be a couple-of-meter distance.
Can you hear the PSU? If YES, add a dummy load resistor until the noise goes away. If NO, there's no problem.
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Old 3rd May 2018, 12:29 AM   #20
forestsgump is offline forestsgump
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Yes, cld hear the PSU, so add a dummy load resister to drain 10% full-load?

Is there any real concern if operate the whinning PSU very low load for long term, likely to cause failure?
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