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.
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.
probably the inductor making the audible noise.
http://www.researchgate.net/publica...ode_converters/links/0c960529df9cba4541000000
some make a "frying bacon" sound.
could also be caused by this.
Magnetostriction - Wikipedia, the free encyclopedia
http://www.researchgate.net/publica...ode_converters/links/0c960529df9cba4541000000
some make a "frying bacon" sound.
could also be caused by this.
Magnetostriction - Wikipedia, the free encyclopedia
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...
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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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...
Now I just need to figure out how to set/adjust the pots...
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.
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".
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.
I would not try to replace noise emitting components like MLCCs, inductors or even the transformer by less noisy ones.
Because they indicate that something is wrong with the smps.
Very often you will find this low frequency noise as excessive ripple in the output voltage.
High pitched noise often indicates instable loop compensation and is referred to a subharmonic oscillation.
Noise at low load conditions may be due to "burst-mode", i.e. cycle-skipping often implemented in modern smps to reduce standby power.
A ticking noise often occurs in situations where the primary controller unit is not supplied by the transformer after start-up.
This may be considered "hiccup-mode". Check auxiliary supply with an oscilloscope for stability.
Because they indicate that something is wrong with the smps.
Very often you will find this low frequency noise as excessive ripple in the output voltage.
High pitched noise often indicates instable loop compensation and is referred to a subharmonic oscillation.
Noise at low load conditions may be due to "burst-mode", i.e. cycle-skipping often implemented in modern smps to reduce standby power.
A ticking noise often occurs in situations where the primary controller unit is not supplied by the transformer after start-up.
This may be considered "hiccup-mode". Check auxiliary supply with an oscilloscope for stability.
The noise is independent of load. There really is no perceptible "high pitched noise". Here is the latest from this ongoing saga...
Previously I had a CD player (variable outputs) feeding audio to a couple of class-D amps that I connected to the PS. I could hear the PS making the "ticking/clicking" sound but that was it.
Today I connected a miniDSP "kit" board (not in an enclosure) to the very same amps with some twisted pair interconnects (no shielding, just a twisted pair). When I used this setup for audio play back the "ticking" was now in the audio itself. Almost like a slow "motorboating" kind of sound. This seems to be caused by RF emissions from the PS much like if there were sparking or something going on (I doubt that's the case here).
This is very deflating. I bought a bunch (at least 10) of these power supplies from Ebay. They are Abletec model ALP-400-5301. A datasheet can be found here: Abletec ALP0400 series datasheet. On paper they are perfect for audio use, and are intended for it. Surprise! There is something wrong with them 🙁 🙁 🙁 well at least the two I have tried so far from my "stock".
Since I have so many of them, if there is anything I can do to fix or remedy this problem I would really like to know how to proceed...
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Previously I had a CD player (variable outputs) feeding audio to a couple of class-D amps that I connected to the PS. I could hear the PS making the "ticking/clicking" sound but that was it.
Today I connected a miniDSP "kit" board (not in an enclosure) to the very same amps with some twisted pair interconnects (no shielding, just a twisted pair). When I used this setup for audio play back the "ticking" was now in the audio itself. Almost like a slow "motorboating" kind of sound. This seems to be caused by RF emissions from the PS much like if there were sparking or something going on (I doubt that's the case here).
This is very deflating. I bought a bunch (at least 10) of these power supplies from Ebay. They are Abletec model ALP-400-5301. A datasheet can be found here: Abletec ALP0400 series datasheet. On paper they are perfect for audio use, and are intended for it. Surprise! There is something wrong with them 🙁 🙁 🙁 well at least the two I have tried so far from my "stock".
Since I have so many of them, if there is anything I can do to fix or remedy this problem I would really like to know how to proceed...
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As I mentioned before, check the auxiliary supply of the primary side controller circuit - feeding the smps by an isolating transformer.
Have a look at the DC output voltage with an oscilloscope to monitor low frequency voltage ripple.
Have a look at the DC output voltage with an oscilloscope to monitor low frequency voltage ripple.
some aux power chips like the nxp TEA17xx series have a green standby mode of low rate firing the flyback. if you load the aux suply this rate should go up.
Unfortunately this is not something that I can do. This is a commercial supply and I don't have a schematic.
OK, now this is something that I could try. So I could for instance just throw a resistive load on the AUX supply and try to draw maybe half its rated output to see if that changes the behavior of the main outputs?
On another forum I got some suggestions to put the PS in a metal box (shielding) and to use output filtering (ferrite beads, cap bank, or LC decoupling). Any thoughts on those approaches to this problem?
Well I might have solved the issue - thanks to Basreflex for the suggestion. I threw a couple of dummy load resistors on the AUX supply (outputs) from the supply and fired up the PS+amp combination with the miniDSP that was picking up all the RF spray.
Now the PS is silent! No audible noises, and no RF either. Wow, what a relief. I guess the PS doesn't like it when there is no load on the AUX supplies for whatever reason and the resulting behavior propagates over to the main supplies.
I will do some more extended testing and then report back with a final. This could turn out to be a really good day!!!
Now the PS is silent! No audible noises, and no RF either. Wow, what a relief. I guess the PS doesn't like it when there is no load on the AUX supplies for whatever reason and the resulting behavior propagates over to the main supplies.
I will do some more extended testing and then report back with a final. This could turn out to be a really good day!!!
Congratulations, some switching supplies do indeed need a minimum load by design.
Thank you very much for posting your findings (thanks also to Basreflex for the suggestion)! This seems to resolve a similar issue I had with an SMPS for my poweramp.
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