Hi *!
One of the AMP2s that I'm using produces annoyingly loud mechanical whistling noise. Should I be concerned? It's very high-pitched and thus easily shielded, but I wonder whether this mechanical stress will affect reliability?
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HiFiBerry team Hi,
without having this here in the lab, it's hard to say if this is normal. What speakers do you have connected and at what volume do you play music?
Best regards,
Daniel -
nettings I'm measuring with a Behringer ECM 8000 into an RME Micstasy with 30dB gain. The mic is positioned like this:
https://luchtbeweging.nl/download/HifiBerry%20AMP2%20measurement%20setup.jpg
Here is a spectrum. The green line is the baseline room/measurement chain noise with the AMP2 disconnected from power.
The blue line is the noise spectrum with the AMP2 running. The red line is the difference of blue and green.
https://luchtbeweging.nl/download/HifiBerry%20AMP2%20whistle.png -
nettings The speakers are connected, but nothing is playing. This AMP2 hasn't seen much action, about two hours of very moderate level in total since I unpacked them. They displayed the whistling behaviour from the very beginning.
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HiFiBerry team Hi,
unfortunately this doesn't really help to figure out what's going on. We would need to check this here and see where this comes from.
Also the open question is still what speakers are connected and what volume the Amp2 is running at.Best regards,
Daniel -
nettings Speakers are two cheap Sonys with a rated impedance of 4 Ohms. The AMP2 is playing digital zeros at full mixer settings. The mixer settings do not make any difference in the whistling noise.
It's hard to pinpoint precisely, but I'm 90% sure it originates from the little coil in the top left corner. -
nettings As mentioned elsewhere, this AMP2 will set any connected RPi into a boot loop, where a few system services come up ok, and then it reboots spontaneously. The misbehaviour occured with three different Meanwell power supplies (the ones you recommend), so I guess the root cause is the power regulator on the board. Maybe the coil is the culprit, maybe it was just getting thrashed about by some fault earlier... If you're interested, I can send it to you for a post-mortem, or run specific tests here if you tell me which ones..
(Note to casual readers: I'm using _loads_ of AMP+ and AMP2 boards, and my experience has generally been very good, except for one AMP+ with the clicking issues, and now this AMP2, all others continue to work flawlessly. Whenever I had complaints, the support from HifiBerry was quick, competent and helpful.)
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HiFiBerry team I'll create a ticket for this.
Best regards,
Daniel
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