Riden RD6006P faint hissing sound - Page 1
Forum section: electronics / testgear

author: TechSplendid
author_rank: Newbie
timestamp: November 26, 2022, 11:54:40 am
content: Hello all,Hope everyone is well.I received my new Riden RD6006P today and I immediately notice that it makes a faint hissing sound when I turn on the voltage output. As soon as I increase the output voltage, the noise becomes less and above 35 volts, the noise is gone.Does anyone know if this is normal? Or is this a malfunction of the buck regulator?Thanks in advance for your help

author: Martin72
author_rank: Super Contributor
timestamp: November 26, 2022, 12:39:54 pm
content: Hi and welcome,Did you noticed this without load?If yes try the same with a "little" load on the output...

author: TechSplendid
author_rank: Newbie
timestamp: November 26, 2022, 12:59:33 pm
content: yes the hissing sound is also with a load connected. The sound is very soft, but I doubt if this is normal. Have not experienced this before. The seller says (of course) that this is normal.

author: Martin72
author_rank: Super Contributor
timestamp: November 26, 2022, 05:41:14 pm
content: Is this a complete supply (you have only plug it to mains) or do you "feed" it with an extra dc-supply?If last, which kind of...linear or switched..What the sound concerns, "normally" it vanished when enough current flows (load on), if not there are several possibilities, beginning with simply design fail, ending with some kind of interaction with the supply.Did you wath the output with scope?

author: TechSplendid
author_rank: Newbie
timestamp: November 26, 2022, 06:08:42 pm
content: I just tested with a bigger load (1amp). The bigger the load, the less the noise becomes. is this normal?

author: TechSplendid
author_rank: Newbie
timestamp: November 26, 2022, 06:13:00 pm
content: It is a complete riden rd6006p set with psu connected to mains. Unfortunately I don't have an oscilloscope to make further measurements. the only thing i know now is that noise gets less when i increase the voltage or have connected a bigger load to it

author: Martin72
author_rank: Super Contributor
timestamp: November 26, 2022, 09:25:21 pm
content: Hi,The noise comes from coils, their windings are swinging in a frequency you can hear when in idle mode or too less output current are delivered.It´s not nice behaviour but probably not a fault, it depends on the design of the switching supply circuit.I got a switching supply from mean well which "sings" when not enough load are present, maybe tomorrow I can make some measures on it.Do you could make pics from your supply, ideally from the inside too ?

author: Martin72
author_rank: Super Contributor
timestamp: November 26, 2022, 10:03:00 pm
content: I´ve found several measures I made on the meanwell output.Background:In another forum a user heard annyoing noise from his speakers, record it with a app, was something about 900hz..1khz.He used the meanwell supply for an switching audio amp.This supply was so cheap that I´ve decided to buy it just for measuring..And indeed, I could hear the noise too, coming out of my speakers (where also a switiching class d amp is working) and from somewhere on the supply pcb.Connected scope to the output of the supply, for measuring ripple and output current flowing into the amp.And shoot...ripple got a frequency of 914hz, current also.Then measuring with resistor load, the more current flows, the less you´ve heard a sound, the less the amplitude of the ripple and the ripple frequency increase to a not hearable range.The used meanwell is designed to deliver full current all the time for industrial purposes, not for audio ones..I actually guess the noise you hear is coming from the mains switching supply.

author: mawyatt
author_rank: Super Contributor
timestamp: November 26, 2022, 10:13:23 pm
content: Beware of faint "Hissing Sounds" they often can be traced to:1) A lit stick of dynamite2) A pissed off Rattlesnake3) A pissed off SpouseWe've had experience with the later two, the last is by far the worstBTW 1) and/or 2) might be related to 3)Best,

author: TechSplendid
author_rank: Newbie
timestamp: November 27, 2022, 01:04:26 pm
content: Here a few pictures. The noise seems to be coming from the buck regulator and not the psu itself. But if I understand you correctly, this is normal and not bad?

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 27, 2022, 02:26:32 pm
content: Electrolytics connected backwards sometimes do that before exploding.Just joking (It would have already blown apart)Some switched PSUs run in burst/skip mode when the load is small.Than means: Switching few pulses, stopping, switching again and soon.As you increase the load, it eventually starts continuous regulation, where every single PWM cycle puts some energy.The modulating frequency is within the audible spectrum, that's why you hear the hissing.To me it pretty clear seeing the waveforms. Nothing to worry about, unless that PSU was not suppossed to to that.https://www.analog.com/en/technical-articles/when-pulses-are-omitted-in-switch-mode-power-supplies.html

author: adeuring
author_rank: Contributor
timestamp: November 28, 2022, 06:22:31 pm
content: A bit off-topic but anyway: The acoustic noise generated by inductances and capacitors can even be used to extract a private RSA key by observing the acoustic "noise patterns" during the decryption of RSA encrypted messages:http://www.cs.tau.ac.il/~tromer/acoustic/