Zoom B3 Loud Hum When Using USB into PC and Output to Amp Instead of Headphones

pbass74

pbass74

Sep 19, 2015
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Sunland, CA
#1
I've only been a member for a short time, and Talkbass is starting to cut into my practice time. So much great information in one place! Thanks to all the members for contributing.

I have a new Zoom B3 which I'm having a great time with. (Gift from my sweet wife.) When I connect it to my PC and use headphones for practice it works great and tweaking the patches from the desktop is much easier than bending down to the floor.

However, when I unplug the headphones and plug into my amp, all I get is a loud hum like a grounding buzz. I've tried different instruments and different amps with the same results. I'm starting to wonder if the B3 is made to be used that way?
 
#2
There was a Reset involved with the fix for this IIRC. Check manual to do reset(Page 31?). I hope that's it. My memory ain't what it used to be.
 
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#3
Sounds like you've got a ground loop (mains outlet -> pc -> USB cable -> Zoom -> amp -> mains outlet). You need to break the ground path. The best way to do it in your situation is on the signal cable from Zoom - amp. Stick a passive DI in there & lift the ground. There are specific products that do this on a more consumer level. Ebtech springs to mind, but i'm sure there are cheaper alternatives. You could even build your own if you've got mad skillz.
 
#4
IME USB connections always cause some hum. I've never seen hum of the level you describe, but there's always some of it. Looking for 3rd-party isolating solutions seems to indicate that these are really hard to make - I've only found devices capable of doing USB-1 speeds and even these are pretty expensive - so I guess this gives us a hint why many devices suffer from this.

My "solution" is to forgo USB when I need the quality. If you only use it for controlling settings (which seems like you do) - this is usually not very problematic. If you use it to record - it's a tougher problem.
 
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