Hum with Humbuster III


My stereo consists of Atoll preamp and amplifier.

When amplifier working without any inputs - there is no hum. When preamp is connected - there is mechanical hum in amp and preamp+some low noise only in the right speaker. Both of them connected with Humbuster III and Powergrip.

Can anyone tell me - what is wrong and what I can do ?

Thank you for help :slight_smile:

Hi Igor,

Thanks for reaching out to us and sorry to hear that you are having this issue.

Our best recommendation would be for you to follow this tutorial to see if you can source the hum:

If you cannot solve the issue then please reach out to us at and we’ll be happy to assist.


  • Jeremy

Thank you, Jeremy.

Followed the tutorial of three steps and there were answers NO to step 1 and 2. and YES to step 3.
I have no TV connected, so need to use some ground isolator, but it is not suitable for using with power cables in my country. And the price is very high - about 100 euros with delivery…when I already spend much money for Humbuster and Powergrip to avoid the hum. Well…think I must simple accept that noise.

Anyway - Humbuster is a good at least for making sound definitely better :slight_smile:

Sorry to hear you can’t get rid of the hum Igor. I know how annoying they can be.

Anyway, a belated welcome to the forum!

Hi Igor,

A yes to Step 3 means that you very likely have a ground hum.

“If steps 1 and 2 were “no”, but removing all inputs eliminates the hum, it is likely you have what is called a ground loop.”

Although it is not recommended you can try lifting the ground pin to one of your items like the Preamplifier as a test.

If the hum completely stops then clearly there is a difference in ground potential between your two items.

The tutorial recommends trying the Humex ground line filter:

If you continue to have this issue then please reach out to us directly at and we’ll be happy to assist directly.

Thanks in advance,

  • Jeremy

Thank you stevem2 and Jeremy :slight_smile: