I will try a AC filter if I can find one at a decent price.
Earlier this year I bought a new Denon AVR-X1700H. I was happy with it, but after a month I noticed it produced a humm when I turn it on. It's only noticeable when the room is near silent, but it's really annoying when you notice it.
After investigation, it's coming from inside the device, I guess from a coil or transformer. I disconnected all sources and all speakers and it's only coming from inside the enclosure. It's silent when on standby mode (red led) and can be heard as soon as I turn it on (green led).
Spectrogram of the noise:
https://imgur.com/a/oaBrRhK first click is the first relay when the device is turned on, the 200Hz humm is here. Then comes the second relay. Then I turn the device off, both relays are clicking again and then the 200Hz humm is gone.
sound file:
http://sndup.net/ns947
I contacted my local dealer after sale service describing them in details the problem. they were not responsive. after a second email they accepted I send it back for service. (after telling me there would be fee is my claim is bogus). I quickly received the device back without any explanations about what was done. Only a List of replacement part serial numbers, they apparently replaced the main transformer.
Unfortunately, once plugged in, the problem was still the same. I contacted the service again, and I was told the noise they detected was "within the normal range" and "that this hum comes from the customer's network (ripple control pulse)."
None of my other sound devices are making this kind of noise at home. I tried to connect the AVR to another socket in another room, same result. I even tried to disconnect all the electrical devices in my flat (even the fridge, the dishwasher, the cooker and the internet box) and I still have the same result.
Could someone tell me, by the files I uploaded above, If I'm extremely sensitive or if there's indeed something wrong with my device ?
After further reading about filters I ended as the same conclusion as you. I first thought the L2 was removing high frequencies, but it is in fact an LC filter to remove bass more efficiently.
That's my question, how do I get rid of the crossover. In my limited understanding of electronics, the c3 capacitor will do nothing if terminals 11 and 12 are open. I'm not sure though.
I have this old pair of Technics SB-3130, they are three way speakers. Both of the super tweeters are dead (infinite resistance) and I’m not sure if this impact the range of frequency feeded to the tweeter. Given the schematic diagram, if I remove the super tweeter, should I modify something to have all the high frequencied on the tweeter?
At home my PCs have CIFS/SMB shared folders, it's handy and simple to use. However I can't find an Android app capable of browsing these shares.
There's Android Samba client and CIFS Document provider on F-droid but both require to know the exact IP and path, you can not just browse the network like on a PC.