wierd ticking/clicking sound from switching power supply - diyAudio
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Old 26th September 2014, 08:49 PM   #1
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Default wierd ticking/clicking sound from switching power supply

I have several identical dual rail switching power supplies for audio (amplifier) use. I hooked one of these up to a class-D amp today and when I powered it up there was immediately a faint rapid (e.g. 10Hz) ticking/clicking sound, almost sounding like faint arcing (but I don't think that is the cause). I can barely hear it from several feet away in a quiet room. The noise seems to stay at the same in frequency and intensity no matter whether the amplifier is idle or under various levels of power. After a few hours of operation there is no change.

When I disconnect the amplifier from the power supply and fire up just the PS, the ticking noise is gone. If I then put my ear right up to the PS I can hear a faint sound, almost like a whirring sound like when a little DC motor is powered from too low a voltage (not that there are any motors present, it's just recalls a similar sound).

Since I have several identical PS units, I switched out one for the other and it made the same exact noise as the first one.

Should I be concerned with these kind of noises, or is this something that a switching PS may make, and is nothing to worry about.
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Old 26th September 2014, 08:55 PM   #2
rayma is online now rayma  United States
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Quote:
Originally Posted by CharlieLaub View Post
I have several identical dual rail switching power supplies for audio (amplifier) use. I hooked one of these up to a class-D amp today and when I powered it up there was immediately a faint rapid (e.g. 10Hz) ticking/clicking sound, almost sounding like faint arcing (but I don't think that is the cause). I can barely hear it from several feet away in a quiet room. The noise seems to stay at the same in frequency and intensity no matter whether the amplifier is idle or under various levels of power. After a few hours of operation there is no change.

When I disconnect the amplifier from the power supply and fire up just the PS, the ticking noise is gone. If I then put my ear right up to the PS I can hear a faint sound, almost like a whirring sound like when a little DC motor is powered from too low a voltage (not that there are any motors present, it's just recalls a similar sound).

Since I have several identical PS units, I switched out one for the other and it made the same exact noise as the first one.

Should I be concerned with these kind of noises, or is this something that a switching PS may make, and is nothing to worry about.
Maybe the current limit is being triggered. Try a lighter load, say a resistor drawing half the current or so.
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Old 26th September 2014, 09:01 PM   #3
Vasquo is offline Vasquo  United States
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probably the inductor making the audible noise.

http://www.researchgate.net/publicat...9cba4541000000

some make a "frying bacon" sound.

could also be caused by this.
Magnetostriction - Wikipedia, the free encyclopedia
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Old 26th September 2014, 10:05 PM   #4
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Originally Posted by rayma View Post
Maybe the current limit is being triggered. Try a lighter load, say a resistor drawing half the current or so.
Not likely. It doesn't match the symptoms.
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Old 27th September 2014, 01:34 AM   #5
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I disconnected the power amp again, and have the power supply powered up and sitting there to do some more checking... heat sink is much cooler and there are no noises.

This got me to thinking... this is a Chinese copy of the IRAUDAMP7S (LJM 15Dx2). When I was running the amp for about an hour at low power the heatsinks on both the amp and PS got moderately warm. I could hold my finger on them no problem (checked if they were at 0V first!) but I wonder if the amp is oscillating and this is drawing and wasting power from the PS and in the amp's output devices. Just after powering down the amp, I could not find a really "hot" part on it, e.g. the output inductors on the amp were not any hotter than the heat sink. Also, I tried another amp board, the single channel version (L15) and the PS was making the same ticking noise with that one as well.

The amp will draw some idle power and is not all that efficient at lower output power, but some have reported that the heat sink of a similar amp barely gets warm when in use. Maybe oscillation would explain the PS noises, too...
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Last edited by CharlieLaub; 27th September 2014 at 01:45 AM.
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Old 27th September 2014, 04:35 AM   #6
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I checked out the amplifier board a little more carefully. I noticed that both oscillation frequency adjustment potentiometers have been omitted from the board and the wiper hole is shorted to one of the holes for the 2k pot. My guess is that this was done to save $1 in parts. The amp works, but the oscillation frequency is probably way too high. I have four stereo boards with this problem, so I will have to purchase the pots and install them myself. Then I will check everything out again.

Now I just need to figure out how to set/adjust the pots...
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Old 27th September 2014, 04:48 AM   #7
Vasquo is offline Vasquo  United States
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In a switching PSU, the audible noise is usually caused by the inductors "vibrating". When I rolled my own DC-DC converter, some inductors emit more, and some less audible noise. -- depends on quality and construction of the inductor. Switching frequency also affects the frequency of the audible noise you'll hear coming from the inductors.
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Old 27th September 2014, 04:56 AM   #8
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I understand about vibration/noise, but why is the noise I hear not like a "tone"? It's more like "ticking" or very light "popping".
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Old 27th September 2014, 05:08 AM   #9
Vasquo is offline Vasquo  United States
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From my experience, the noise can be all over the board... from a steady high-pitched whine, to a low-pitched whine, some have "frying bacon" random noise, and some intermittent. -- Shielded SMD inductors seem to emit the least amount of audible noise.
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Old 27th September 2014, 05:09 AM   #10
Vasquo is offline Vasquo  United States
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check out this article
Troubleshoot A Flyback Supply That Generates Audible Noise | Power content from Electronic Design
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