When I plug in my active acoustic Ibanez guitar with an active Fishman pickup I get a loud hum… I assume it’s a ground hum, because it goes away as soon as I touch the foot switches.
My quad cortex is plugged into Neumann speakers via XLR that should ground the unit.
I only experience this hum with this acoustic guitar, my other instruments have no hum.
But this acoustic guitar has no hum when I plug it into my audio interface, a mixing desk or an amp.
On an electric guitar, your bridge, strings and pots are connected to ground but the strngs are sometimes not grounded on an acoustic. If your electric is plugged in and you don’t touch any metal parts, is the hum there? Have you checked the ground lift setting on your QC?
Hey Pete, thank you for your thoughts! This is really helpful.
Yes, I have checked the ground lift - it doesn’t make any difference.
My electric guitars do not hum. But now I’ve tried several acoustic guitars with a battery and they all cause this hum…
I have even felt electricity on the foot switches!!!
This makes me wonder: I was going to purchase a battery pack and play the quad cortex with a battery powered amp. It’s probably not going to work with my acoustic, is it?..
Do you have any other sort of ideas on how to solve this annoying ground humming problem?
I might just send the unit back otherwise…upset about this flawed design.
Very odd. I haven’t had an issue with any of my electrics (active or passive) or my Taylor 814B (with active K&K pickup). If your cord has a metal barrel on the plugs, does the noise go away when you touch the plug? I can’t imagine how you could feel any tingle from touching the footswitches as the power supply output is only 12 volts with very limited current capabilities. Could it be related to something you have the QC connected to? Is your speaker or amp well grounded? Do you still have noise with only headphones connected?
I need to apologise and give an update:
I don’t really know why, but the issue has disappeared…no more hum when plugged into my Neumann speakers.
But still, if my quad cortex is not grounded via XLR or USB, I get a ground hum.
This is the case with my active acoustic instruments playing with headphones or a battery powered amp…
When I touch the jack and my guitar strings, the hum goes away. If I connect the metal tailpiece with a metal piece with the jack output the ground hum also goes away.
Toggling the ground lift on the quad Cortex or the phase invert on my instrument doesn’t make a difference.
Question to everyone:
What would you recommend in my case?
I have done some research and found three options:
Someone came up with this grounding solution for hx stomp:
What would you do if there is no possibility to plug this into a grounded electric power strip?
Say, you have a mobile setup (quad cortex powered by a battery used with a battery powered amp on a stage without electricity - no power strip to plug it into).
Could you use a similar solution like the one of the link but with a crocodile clamp? But what would could you use to ground it on?
By the way, there’s a hidden feature to reduce hum in the Quad Cortex:
Option 2: grounding acoustic guitar
Ideas for grounding acoustic guitar with a grounding plate:
Idea for grounding acoustic guitar with a grounding bridge:
Someone also commented that installing string ferrules or a tailpiece that you connect to the jack could be easier. Connecting the tailpiece to the jack definitely works on my bouzouki.
If I understand it correctly, the instruments use my body to ground everything in this case.
Is this something I need to worry about in any way?
Option 3: going wireless
There’s a setup idea here.
In theory, no physical cable should also mean no grounding issues, right?
Maybe that’s the easiest way to go?
What do you think and what would you recommend?
I don’t think that a hum buster cable would solve the problem as a ground loop doesn’t seem to be the issue. If it were, you’d have hum with all instruments. If you don’t want to use one of the solutions for grounding your QC, it seems that grounding the strings on your acoustic would be the next best answer. Although the grounding means shown in the vid would work, it would require a lot of work and might alter the tone of your guitar. I think a simpler solution would be to make a thin grounding plate to mount under the bridge. It would have six holes for the strings to pass through. The string ball ends would contact the grounded plate once the bridge pins are installed. You would want to make the grounding plate as thin and small as possible as not to add mass to the top. If your guitar uses a rear-pass-through bridge (like an Ovation), the grounding plate idea wouldn’t work. Just one of many possibilities.
