Hum when using external speaker port on 6300

Paul Lourd · July 2021

Odd problem with a JBL control 2p.

Getting nice solid hum when connected to Flex external speaker port. Even with volume at zero on flex.

Plug same cable into my phone or other audio source, no hum. Speaker is good. Tried two cables, with ferrites etc. no difference.

Plugged headphones into external speaker jack, no hum.

Took same cable that was plugged into JBL and plugged it into Bose Companions, which I use for my PC. literally one foot from the JBL. No hum.

Mystified.

W1ip

KD0RC · July 2021

Hi Paul, this is likely a ground loop. You can buy little ground loop breakers on Amazon for $10 or less. They are just an audio transformer to break the ground connection while allowing the audio signal to pass.

VE7ATJ_Don · July 2021

Paul, do you have another speaker you can plug into the 6300 as a final test of whether it's the speaker or the 6300? I understand, you've plugged the JBL into other sources and it works fine, which would likely eliminate it as the problem, but one last test would be another speaker plugged into the 6300.

Also, do you get the hum if you plug headphones into the front panel jack on the 6300?

Pat_W5WTH · July 2021

FWIW, I have this issue as well and never fully understood it. I use headphones 99.9% of the time and they do not have the hum issue so I haven't worried about it much.

That said, the solution for me was to use a battery operated speaker when I want an external speaker. This, of course, is an awful solution if you need a speaker all the time and you operated longer than the speaker battery capacity limits.

I really am perplexed about what it is with the Flex design that causes so many to get the hum.

WX7Y · July 2021

This is a Ground loop as Len commented, If your "a do it yourselfer" you can try installing in the Speaker cable a couple 10Uf Electrolytic capacitor, If it changes the pitch of the audio to much you can try a smaller or larger capacitor value maybe 1Uf to about 100Uf Electrolytic capacitor to get the audio Pitch the way you want it, the Idea is to break the Ground loop and still keep the audio passing to the Speaker, You may only need to install a capacitor in the Ground side of the cable.

A covenant place to do this is in the Speaker case which is where the factory should have done this in the Speaker design.

DaveC · July 2021

You may also try plugging the speaker Wall Wart into a different outlet or, if possible, reverse the plug in the socket.

Some wall outlets are wired incorrectly, which can create a grounding problem.

Patrick · July 2021

Audio isolation transformers available from Amazon, easy fix for ground loops.

Paul Lourd · July 2021

Why is it a ground loop for one speaker and not another? Both speakers wall warts are plugged into the same power **** (which is not wired incorrectly). Thanks all for the suggestions. I think its something funky with the internals of the JBL

Paul Lourd · July 2021

OK, I may have caused my own issue by using the "balanced" input on the JBL. I took a cable that breaks out the stereo 1/8" from the Flex to two RCA (red/white) and plugged one of those into the JBL input. Hum gone. THanks.

Hum when using external speaker port on 6300

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