60 cycle hum

[radec52]

I just purchased a Fender Bassman 150 and have noticed a slight 60 cycle hum sound that you can hear from the amplifier. It is very much like the sound you hear when flourescent lights make when you turn them on. Admittedly, I am sitting on the floor only a couple of feet away from the amp when I hear it. Is this normal or is it something to be concerned about? Thanks!

 

[Joe Nerve]

I believe it's the bass, not the amp. If it's the amp, then I also believe there's something wrong with it. Also, some basses (pickups) have it, some don't. That's why they make humbuckers. I personally can't handle any noise from my pickups, but some people don't mind at all.

People are going to want to know what kind of bass you've got.

 

[radec52]

I have a Fender Highway 1 Jazz Bass. Actually you hear the sound even when the bass is not plugged in. It is not loud but you definitely know it is gone when you turn the power off. The sound does not come from the speaker, but from inside the amplifier. Thanks again.

 

[billfitzmaurice]

Some hum is normal, but enough to be obtrusive usually indicates that your tubes aren't properly biased or the filter caps are weak.

 

[Matthijs]

Are you talking about hum as heard through the speaker or the amp humming itself? If so it can be the trafo humming.

 

[dulouz]

I once test drove a Fender Bassman 250 head and 410 cabinet and found a similar problem. When I turned towards the amp to adjust it I was overwhelmed with 60 cycle hum. I called Fender Tech. Support and this was their response "It is normal for such a high gain amp to cause interference with the pickups. You just can't get within three feet of it."

Funny, the Ampeg SVT classic I tried wich has twice the power, didn't make near as much noise when I practically laid my bass right on top of the amp. For as much as Fender amps cost you would think they would isolate their power supplies better.

 

[radec52]

The hum is from the amp only. It is not all that noticeable and sounds like an electric train transformer when you turn it on. I've only had it for 2 days and I just want to be sure that the sound is "normal".

 

[billfitzmaurice]

For as much as Fender amps cost you would think they would isolate their power supplies better.

It's not a matter of isolation. The source of that particular type of hum is the electromagnetic field generated by the power transformer, received by the electromagnetic pickups. It can be minimized by transformer orientation, by using a toroid transformer, or by using twenty odd pounds of mu-metal shielding, but it can't be eliminated.

When I turned towards the amp to adjust it I was overwhelmed with 60 cycle hum.

I went to the doctor, told him my arm hurts when I do that, he said don't do that.

 

[yamaha]

Make sure the amp is well grounded. Try it in different plugs in the house, and even maybee at someone else's. I once had to manually groung the ground pin, because the electricity where i used to live was only 2 wires thru out the house, and made a metal rod, hammered it in the ground, and ran a wire to the ground pin of the power cable. The hum alsost completely dissapeared. This was with a passive P-J.

 

[Jeff F]

I have not found a review on TB for this amp. I am thinking my Fender Standard Jazz would sound good thru it.

Thanks

 

[Luke73]

What you probably have is either the transformer laminations humming due to poor transformer construction, or a metal plate (perhaps part of the amp's chassis) in close proximity to the transformer humming in sympathy with the electromagnetic field generated by the transformer.

Google "transformer hum" and spend about twenty minutes reading, and you'll be well versed on the subject.

It's a very common phenomenon in electronics goods with a power transformer.

 

[radec52]

Thanks to all for the information. I have concluded that the slight hum is not an issue or any type of defect. Sitting cross-legged with my bass playing 2 feet from the speaker in my living room is not really a fair situation to judge the performance of the amp. I like the Bassman 150 quite a lot. It is solidly built, not too heavy and is a good match for my current requirements: Practice at home, play at church and in moderate volume situations. It offers great tone and a lot of EQ ability for a fair price. The music store where I bought it is 15 minutes from home and I feel good about supporting the local, independant dealer. Thanks again.

 

[Jeff F]

Thanks. Sounds like your situations are similar to mine.