Amp buzz only on certain amps

[Perfessor]

I really like my Aria TAB 66 bass, but it has a directional EMI buzz when I use either my Carvin amp or an Ampeg amp. It does not do this when I run the bass through a Markbass, Hartke or Aguilar bass amp. Why would the buzz only happen on Carvin and Ampeg amps?

[WRGKMC]

Bass and Guitar Amps contain a preamp and power amp in the same head.

Heads can have different sensitivity and gain levels in the preamp section.

They can also have varying amounts of shielding depending on how the chassis is designed.

The chassis acts as a Faraday cage (and so does the guitar cord shield right up to the pickups themselves)

 

Since this bass looks like it has Humbuckers, its unlikely the pickups are generating the hum.

If I were to guess its a budget guitar cord that has 70% shielding or less.

 

Because the Carvin and Ampeg "Do" pick up the hum its likely those amps have more sensitive preamps

which are amplifying the noise coming from the crappy guitar cord.

 

Its "not" because those amps are defective, and the other amps that fail to amplify it are better.

 

Different preamps can be more sensitive to amplifying noise, and some amps have preamps designed to block noise.

In the process they may rob some signal frequency in the process. Bass amps don't produce allot of treble either.

The Ampeg I have does extend up quite high and If I have a noisy signal going in it is heard more easily.

Some bass amps also have limiters and Gates which can block noise when no notes are being played.

 

Simple fix is use a good cable and see if the problem is fixed.

You may have a badd string ground on the bass so try a different bass as well.

[Perfessor]

It does it on all my basses to various degrees. I have changed cables many times and even tried a Monster cable with the same results. Yep, I'm going with a lack of shielding. Maybe that's one reason the Carvin amp is so light.