I have done a fair amount of design work with switch-mode power circuits. Nearly all low power regulators operate at frequencies that are well beyond the audio range. Despite this, it is possible for these circuits to emit sounds that we can hear. This usually happens when the circuit is not operating contentiously. One reason might be a design defect that allows the voltage control (or perhaps current control) loop to be unstable. Another possible reason, is that some modern-switch mode regulator devices change their mode of operation when operated at low output current. That is, they go into a mode where they operated in a series of burst of normal (high frequency switching) operation. This is done to make the regulator more efficient when operating at low current and to save power.
In both cases, there is a possibility that increasing the load current would cause the sound to disappear, as Ed Fochler suggested. The best image of the net6501 I can find does not allow me to read device part numbers. If anyone knows which device is creating the noise, is it possible to read a part number on it? I know from experience, that identifying the source of noise can be difficult. One way is to use a small microphone as a probe to find the source. Another possibility is to somehow couple a hose to your ear and use the other end as a probe. The most likely source is one of the inductors. Gavrik Peterson On Sun, Jan 24, 2016 at 4:55 PM, ED Fochler <[email protected]> wrote: > Soekris boards use at least one DC to DC transformer. These are notorious > for creating whine, even when they are spec’d in such a way that audible > whine would seem impossible. they also react differently under load. The > only one I can find listed is for the pci slot, so you may want to try > adding load to that (insert a card) and see if that changes or eliminates > the whine. > > Otherwise, you’re in sound dampening territory. High pitch whines are > easy to squelch if you can locate them. I can’t hear anything from my > boards, so I can’t help you in a more practical a manner. > > ED. > > > > > > On 2016, Jan 21, at 12:05 PM, Muffinman <[email protected]> wrote: > > > > Hello, > > > > My NET6501 runs quite well except for a very annoying high-pitched tone > > originating from the board (sometimes). Since I intend to use this > > computer in my hifi setup, well, it's a bit problematic. > > > > I've got an external 12v power supply some distance away from the board, > > so that isn't creating the noise. In addition, I've tried two different > > 12v power supplies, both with the same effect. I don't see a relation > > with CPU load (though the processor has an easy job anyways), or any > > relation at all. Sometimes the tone is there, gets more intense, and > > then it's gone to a low level (or perhaps gone). > > > > Has anyone got experience with this (annoying) feature. Also important: > > does anyone have a (possible) solution? > > > > Kind regards, Maarten > > _______________________________________________ > > Soekris-tech mailing list > > [email protected] > > http://lists.soekris.com/mailman/listinfo/soekris-tech > > _______________________________________________ > Soekris-tech mailing list > [email protected] > http://lists.soekris.com/mailman/listinfo/soekris-tech >
_______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
