#1
Considering how I want to get another amp soon with a line out port, I'd like to know how to solve an issue with my Roland Cube 20X's line out port.

I can plug in my guitar to the amp/with my pedals in front of it, and through the amp's combo speaker it sounds fine.

But, using the line out port causes problems. When I connect the line out port to a direct box which goes to a powered PA system, I get hum. When I connect the line out port to a usb-powered headphone set (1/8 male with a 1/4 male adapter to port, the usb to a computer) there is hum. However, if I connect the line out port to a non-powered headphone set (1/8 male with the 1/4 male adapter), I don't get any hum.

This leads me to believe that the cause of this issue is a ground loop, which I am fairly ignorant to understand. I use this direct box: http://www.musiciansfriend.com/pro-audio/behringer-ultra-g-gi100-di#productDetail which has a "ground lift" function. Will that solve my issue?

Also, I use an outlet that is relatively close to the amps of the PA system, so they might be coming from the same source with the same "ground potential". I know that one way of fixing the loop is by using the same outlet, but using those outlets didn't seem to solve the issue. Without the Cube, I also use that outlet to power my pedals, and I don't get any hum.

I also saw that you could use a 3-prong to 2-prong adapter, but I saw that wasn't advised. The Roland 20X Cube also only has a 2-prong power cord, so maybe it doesn't have ground or something? I unno.

help.
Last edited by Will Lane at Dec 23, 2014,
#2
I got an EHX 22 caliber (power amp in a pedal) as a backup to run cabs. Since the 22 cal. is only 2-prong, there is always hum. Plugging it into a power surge strip helps with that for me, that might be a start. The 3-prong adapter, why is that not advised?


EDIT: Yeah I was reading it backwards, a 3-to-2 prong adapter wouldn't do much in this situation.
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Last edited by Funk Monk at Dec 23, 2014,
#3
Quote by Funk Monk
I got an EHX 22 caliber (power amp in a pedal) as a backup to run cabs. Since the 22 cal. is only 2-prong, there is always hum. Plugging it into a power surge strip helps with that for me, that might be a start. The 3-prong adapter, why is that not advised?


I'm not entirely sure. I think because the ground from the 3-prong male is sent to an open screw mount on the adapter. And considering how the Cube doesn't have a 3-prong cord, I'm not sure what that adapter could do.
#4
Ah, I see. I thought they had 2-to-3 prong adapter, to add a ground, but I guess not. Must be something I don't understand about electricity lol. I would try a good power strip, it worked for me.
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#5
I tried it earlier today with the mentioned PA system and direct box. Didn't seem to give me too much of an issue with the GL100's ground lift and speaker sim activated.

I still don't think the issue is really solved, because without the speaker sim, the hum is noticeable. But I can work with it.