T-15 Hum

This forum is for talking about all kinds of Peavey electric and acoustic guitars.
Post Reply
Steve.Maxson
New Member
Posts: 5
Joined: Tue Mar 28, 2023 2:16 pm

T-15 Hum

Post by Steve.Maxson » Tue Mar 28, 2023 2:30 pm

Newcomer question: I just purchased an ‘82 T-15 with the super ferrite pickups. The hum from the guitar is pretty significant. Also, with the pickup selector in the middle position the pickups are NOT “noise cancelling”. Is this normal? Any recommendations to reduce the hum?

Thanks.

Tele-Driver
Member
Posts: 25
Joined: Sun Oct 09, 2022 1:57 pm

Re: T-15 Hum

Post by Tele-Driver » Wed Mar 29, 2023 5:02 pm

Hi, first did you or should I say can you try a different amp. Also make sure you do not have an electrical source nearby causing the hum such as a halogen light . Those PU are very pron to electrical interference. Change the guitar cable if you are not running in a peddle board, if you are, run direct to amp without the board in between.
If it still hums you may need to check the internal wiring for a bad ground. One other thing if when you touch the strings, bridge, or pickup housing ad the noise get better most likely it is a ground issue, a cold solder or broken ground. Check the input were the cable goes in also.
Let us know what you find out.
Cheers

Steve.Maxson
New Member
Posts: 5
Joined: Tue Mar 28, 2023 2:16 pm

Re: T-15 Hum

Post by Steve.Maxson » Wed Mar 29, 2023 10:45 pm

Thanks Tele-Driver for the suggestions. I tried a different cable and that did not help. Then I tried my other electric guitars and they were also producing hum. :( I tried moving around the room and noticed the hum was loudest near our printer. That is new to the room where I am practicing. (Home office.). The noise does get much, much better when I touch the strings or control knobs so I will eventually check the internal grounding. I also found something else that helps and others might find interesting. My amp is a Vox TV8 tube amp. It has built-in attenuation so it can run at 5 watt, 1 watt or 0.1 watt. I was using the 0.1 watt setting with the guitar volume cranked up to 8-10. If I switch the amp to 5 watt and lower the volume on the guitar, the hum lowers to a much more acceptable level. However, putting the selector in the middle position is Not hum cancelling. Was not a design feature on the T-15?

Regards, Steve

User avatar
dak
Member
Posts: 428
Joined: Fri Dec 24, 2021 7:20 am
Location: Germany

Re: T-15 Hum

Post by dak » Thu Mar 30, 2023 8:58 am

There's two ways to pick up hum: electric field and magnetic field. Guitars are high impedance and thus good at picking up electric fields. But the pickups are also good at picking up magnetic fields. Humbuckers work by using two pickups in reverse configuration with regard to uniform magnetic fields (fields originating from a larger distance). Also by being high-gain which helps drowning out electric field hum.

A noise-cancelling setting for single pickups sort of emulates the process for cancelling magnetic fields but tends to (anti-)parallel the coils instead of putting them in series, so the gain isn't really higher, and electric field hum remains unimpressed.

What can be the sources for electric hum? #1 is insufficient grounding. If you have an AC voltmeter, check the voltage between neutral and ground in your socket: that should be a fraction of a Volt at most. Then unplug the amp from the mains and check the resistance between the ground pin of the amp and the shield of a cable plugged into the amp's input (one at a time). That should be stable and very near to zero ohms.

Then check that the same holds for the strings or at least the main metal parts of the guitar.

Of course the first thing to check at all is your hum level when no guitar is plugged into the amp (preferably when the input is short-circuited but the Peavey amps I know actually do short-circuit unused inputs with a socket switch). You cannot get significantly better than that...

Steve.Maxson
New Member
Posts: 5
Joined: Tue Mar 28, 2023 2:16 pm

Re: T-15 Hum

Post by Steve.Maxson » Thu Mar 30, 2023 5:43 pm

Thanks dak, I will look into your suggestions.

Regards, Steve

Steve.Maxson
New Member
Posts: 5
Joined: Tue Mar 28, 2023 2:16 pm

Re: T-15 Hum

Post by Steve.Maxson » Sat Apr 08, 2023 3:37 pm

Dak, I finally got around to testing. If I am doing things correctly I might have a ground issue in the guitar. I will eventually open it up and check if everything looks correct.

Does anyone have a hack to temporarily fix the gnd issue without taking off the pickguard, maybe a wire from the metal bridge to the washer on the input jack?

Thanks, Steve

Post Reply