Blackstar Fly 3 amp

I had one of these bought for me for Christmas. I have just purchased a power lead to plug into the electric instead of using batteries, I'll save them for when I play away.
I have only been playing for just about a year now so know nothing of these amp things. I wanted one to project my voice really as I can only sing quietly I don't have a loud voice.
Anyway, when I plug the amp into the power socket I get a consistent throbbing sound and I don't know why. I have removed the batteries and placed the amp somewhere away from other electric appliances but I still get this sound.
I have been in touch with Blackstar but apart from getting a response in the first place they seem to have dried up on my question now.
Any of you more experienced guys know why I am getting this problem?

That is a ground-loop hum, most likely. Is the plug that goes into the wall a 3-prong or a 2-prong? If it's only a 2-prong, are the blades that go into the outlet the same size? If they are the same size, try unplugging it and flipping the plug before plugging that back in. If the prongs are not the same size, there's not much you can do to reverse the blades at the wall. Does the power cord that goes from the brick to the wall unplug from the brick? Can that plug be reversed? If so, try that. If not then you may have to invest in a ground-loop-isolator. There are different sorts but you can investigate them online and I hope that someone will chime in with something specific to recommend.

In the meantime, buy some rechargeable batteries so you're not constantly throwing things in the landfill and use the amp only on battery power.

Thanks dhbailey......
If I knew how to attach a sound file on here I could include one for you all to hear.

Does the amp hum without the instrument plugged in?
Dhbaily is correct about grounding, but it may also be in your instrument.
I have a bass that hums when the amp is plugged in, but fine when running off battery.
It is the only instrument that hums with the amp.

That almost always indicates that the wiring is not properly grounded in your home. That could easily be fixed inexpensively by an electrician at the main electric panel.

Are you using the manufacturer's recommended power supply, 6.5v at 1.5A?

If not, chances are that your power supply is either not capable of providing sufficient power to drive the amp properly and/or isn't regulated to the voltage required by the amplifier.

I had similar problems with my mini amp using a variety of apparently adequate power supplies, it was only when I acquired a properly regulated device that my problems went away.

I have that amp and have no issues with a hum. Being in UK, I'm not sure of the plug configuration (2 or 3), but the US version has a 3 prong with a ground. If you are using a generic 2 prong floor pedal wall wart power supply, that could be the problem as indicated above. If not then I would try a different location, another house or business and see if you still have a problem. If it goes away, it most likely is the house grounding.

I recently bought that amp and was really surprising how nice it sounds, especially with the extension speaker.

John

Hopefully, you'll discover that the hum does not occur in other locations. If so, you might want to try one of these when you are home;

https://www.amazon.com/dp/B0002D017M/ref=cm_sw_r_oth_api_CqoNybYTDYP4W

Research amp EMI on YouTube.

Thanks for all your replies and suggestions. I shall investigate them all.