Hum from S1 Pro when A/C power is connected


Bose product name  S1 Pro




Firmware Version ?

(1.0.7, 4.8.1, 1.7.0, etc.)

App Version

(4.1.1, 13.0.2, etc.)

What devices were you using that were affected and what version are they on

(Samsung Galaxy S9 on Android 11, iPhone X on iOS14, etc.)

Detailed description of the issue and steps to reproduce

My S1 pro has a hum in both of the input channels when connected to an acoustic-electric guitar with a 1/4" cable.  The hum increases as you turn up the volume.  The hum goes away when I touch either of the cable plugs, ie: when I ground it. There is no hum and the S1 operates normally when the unit is running on the battery and the A/C power cord is not connected. I tried moving the S1 to various locations and plugging it in to different A/C outlets. The problem seems to be related to using A/C power or the power cord itself.  OK otherwise.


What environment do you experience the issue in?

Any environment


When did you start to experience the issue? Did it work correctly previously?

This unit worked perfectly up until about a week ago when I noticed the hum problem. Have used this unit a lot in various locations and for a lot of different situations with no problems at all for well over a year. 


Any troubleshooting steps you took

Contacted Bose support and was walked through diagnostic procedures with the rep I spoke with. That included trying different cables, switching to a different guitar, trying both of the input channels.  All of that did not change the issue.  Then, a day later, to try and avoid shipping this unit back to Bose for service, I moved the S1 to a different location in my home and tested all of it again, but this time, I tried using the S1 just on battery and the hum disappeared.



Hi GlenMc!

Welcome to the Bose forum, I'm sorry to hear you're having this problem with the S1 Pro. 

When you connect the S1 Pro system to power, would you plug straight into a wall outlet or into a power strip? 

Having too many high-powered electrical devices (e.g. mixers, FX units) plugged into the same circuit can create ground loops, which can cause humming or buzzing. If you're using such equipment in your setup, I recommend connecting them to another circuit.

To avoid interference, I'd recommend keep audio and power cables at least 8 inches apart, crossing them at right angles if necessary.

Hope this helps!

Thanks for the suggestions!  I tried connecting this S1 Pro to various A/C outlets in my home. The hum is the same regardless of which outlets I plug into.  My latest test this weekend was to use an outlet on our kitchen bar, which has nothing else plugged into it and is away from everything other than a TV monitor and microwave oven, neither are within 8 feet of the outlet.  And, I got the same hum in my music studio (lots of gear and cables around!) and in a bedroom where there is nothing electronic for 20'.  The only thing left to do, I think, would be to take the S1 to some other location away from my home and try it there in a few outlets. If there is still a hum, I have to conclude that it is not because of interference or something odd in the electrical system at my home.  Ideas?

Hi GlenMc,

Thank you for trying these steps, I think that would be the next step. If you try the S1 Pro in a completely different space and the hum persists, I'd recommend contacting the Bose Pro support team directly for further on-call troubleshooting.

Having exhausted my own troubleshooting based on everything I could find, including your advice, this unit was shipped to the Bose repair center in Indiana using the shipping label and instructions provided by Bose support.  I'm hoping to get back my S1 soon because I use it often, and I sincerely hope that it comes back without the annoying hum!

Hi GlenMc.  I came across this thread while searching for answers to the same problem.  I never noticed a hum before as I use the S1 on battery power.  Did you get the issue resolved by sending the unit to Bose support?


Thanks Jim