Connecting just the Pa900 and the Bose into a different surge protector connected to a different power outlet was suggested by Sweetwater tech to be sure to eliminate any grounding issue. As the video showed, that's exactly what I did.

Roland, at least in the past, always used a floating ground system, which would preclude a ground fault conflict.

Graham, if I were faced with this, the very first thing I would do is unplug everything, everything from every connection. The only thing that would be plugged into the surge protector would be the Bose. Then turn the most on, turn the volume to the 12 O'clock position and connect your RCA wires to the Bose and nothing else. Now, I looked at those wires you are using and they appeared to be unshielded, but there is no way I can tell by looking at the vids.

Next, plug the keyboard into the power strip, turn on the keyboard, and if there is no hum, turn the volume all the way down on the Bose, connect the keyboard using those RCA cables, then turn the volume of the Bose back up to the 12-O'clock position and see if there is a hum. If there is, turn everything off, then try using fully shielded individual RCA cables. The cables you are using appear to be adapter type, but again, I can't tell from the vids. The hum almost sounds as if there is an open connection of sorts, but I would have to check them out using a multi-meter.

Keep in mind that even when other devices that are plugged into the surge strip are turned off, they are still connected through the ground connection of the strip. And, some surge protectors produce their own problems with the type of protective circuitry. You can also try using just a power strip without a surge protector to see if the same problem persists.

This is all just guesswork on my part, Graham, and I hope you can get this ironed out. Or you can slip down to Marathon Key after the first of the year, bring your gear and join in on a jam session at the marina, which will give me a first hand look at the connections and possibly solve the problem. Even if I cannot, the Keys are always a fun place to visit during the dead of winter.

All the best,

Gary

Try using a 3 to 2 prong adapter where you plug the power strip into the wall outlet. It sounds like a ground loop problem. Berringer has a ground destroyer you use in line with speaker

Hi Gary, what cables did you use when you did your test? I'll happily buy similar ones if you can point me in the right direction.

On the video you will see me use both fully shielded unbalanced TS cables with TS to RCA adaptors, and also the best quality TS to RCA cable I could find http://smile.amazon.com/gp/product/B004N...arch_detailpage

When I did the 1/8 inch input test on the video I used exactly the cable you advised.

Go to You-Tube Type Bose speaker humming. some video tutorials

That cable is fine, it is shielded.

Graham, I make all of my own cables, all are shielded and very heavy duty. I used to purchase Hosa and Monster cables, both of which are relatively high quality, but not great. I found that I got much better results by constructing my own cables of much heavier gauge wire and soldering all my connections. Most commercial cables are crimped connections, which eventually fail due to corrosion or mere break at the crimp.

Good luck,

Gary

I just finished doing a search for the most likely culprits, and because you are using the RCA plug input, there is a possibility there is an impedance mismatch, which could also cause this type of problem. I don't know what the output impedance of your keyboard is, so you may have to contact the manufacturer to get the information. Then I would check with Bose customer support to determine the input impedance specs for the L1 Compact's RCA connection.

All the best,

Gary

Solution: get TWO Bose Compacts and run a cable to each one. Then you'll have stereo.

YEP! And, I have one for sale that was only used twice, then put back in the box so I would have a spare. Now that I'm retiring the first of October, it's up for sale - $700 plus shipping.

All the best,

Gary