Fishman Loudbox amplifier rattle sound on bass notes

Question edited for clarity and Capitalization.

Contact them direct and ask where their closest service centre is. Rechargeable items only last so many charge cycles.

Loudbox Mini Charge - Fishman

https://www.fishman.com > portfolio > loudbox-mini-c...
Rechargeable Battery Power (up to 18 hours); 60 Watts; 2 channels: Instrument & Microphone; Digital Reverb & Chorus; Bluetooth® 4.0 Connectivity.

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Assuming there isn't an instrument plugged into it when it's humming, it will be time to have it recapped,

http://www.fishman.com/product/loudbox-mini

Fishman iis you best bet http://www.fishman.com

You can download the user manuals, they do have a block diagram, but the scan is pretty bad.

It may end up the person looking at it is going to need to rely upon their general knowledge.

My own suggestion is to pull the chassis out so you can work on it while powering it. And then work your way through the amp with either a signal source plugged in at the input, and with high impedance headphones with test lead ends, go through each audio stage carefully. until the fault is isolated. If it is not caps or the rectifiers in the power supply, faulty ground connections to chassis or faceplate, a faulty 4558 is most probable. The headphone approach is the fastest way to address this last one. If a different series of preamp chip is used, a good source for the IC datasheets in general is Digikey http://www.digikey.com and parts too.

I have seen defective XLR cables so check it with an ohmmeter. It is possible the mic input preamp has been damaged. If that is the case, the unit will have to be repaired.

I don't understand your question. The "Aux in" is just that an input that goes to the power amp. Please note that the Fishman Loudbox does NOT have a headphone jack so don't be disappointed as there plain isn't a headphone jack on this unit. I would recommend that you get a small headphone amplifier for the purpose... or even go to a thrift store and get an old stereo system that has a headphone jack and use that.

Does it make the noises at higher gains with nothing plugged in? If not, check your guitar cables and connectors.

http://www.fishman.com/files/loudbox_100_user_guide.pdf

 

Hope this helps!

It is a poor ground but it is not necessarily in your amp.
If it is only buzzing when you have a guitar or other piece of equipment connected try a new lead cable.
If it buzzes all of the time......remove the cover at the rear of the amp and remove control panel.
Inspect the feed line to the input. If it is loose or broken....repair or take to have repaired.

That is happening because your grounds went bad. Without grounds, then the amp will produce a buzzing sound. I would replace the input wire, that is probably the problem