Amp buzz, or bass?

[steimlem]

I've got a classic vibe 60s p bass that buzzes through my at home ampeg amp (worse with tone turned up) . When I touch the strings or knobs the buzzing stops. This sounds like a case of bad shielding on the bass, yeh? However..when I plug the same bass into my interface/computer setup in the same room, there is 0 buzz. This makes me now think the issue is with the amp?

Any troubleshooting ideas of how to figure this out or theories as to why this happens? If it were the bass, i would think it would have the same issue with my interface setup but it doesn't. If it were the amp, i would think it would have the same issue with my other bass but it doesn't.

 

[dreamadream99]

Because Buzz can come from many stages in your signal chain, you have to systematically eliminate each step in the chain one at a time, until you isolate the culprit.

1. Try a different bass. If the buzz goes away, it’s the bass. If it does not go away it is not the bass.
2. Try a different cord. If the buzz goes away, it’s the cord. If it does not go away it is not the cord.
3. Try a different amp. If the buzz goes away it’s the amp. If it does not go away it is not the amp.
4. Slowly turn 360°. If the buzzing changes, it is a grounding issue in the bass, cord, home, or amp.

 

[dreamadream99]

When I touch the strings or knobs the buzzing stops

This sounds like a grounding issue in your home. Unplug the amp from its current outlet, and plug it into the outlet your computer interface uses, and test the rig there. There is a good chance the buzzing will stop, because you are on a different circuit.

 

[steimlem]

This sounds like a grounding issue in your home. Unplug the amp from its current outlet, and plug it into the outlet your computer interface uses, and test the rig there. There is a good chance the buzzing will stop, because you are on a different circuit.

they're in the same room so i assumed same circuit, but i tried same outlet to be safe just now. no improvement.

however, the pad feature on my amp seems to greatly reduce the hum. with the pad engaged and volume knob raised to compensate similar levels, the hum noise is greatly reduced. this has me leaning towards issue with the amp more now. no issue with my 2nd bass through this amp regardless of settings. but that one is active and has much hotter output (related?)

 

[agedhorse]

Ok, before we start guessing about a solution, let's think this through to see if we can determine what exactly is happening first. There's plenty of time for guessing later, after identifying the cause and a real solution.

1. The buzzing stops when you touch the strings... this almost positively indicates that it has nothing to do with the amp and the power or ground (though a bad ground can make the symptoms worst it's not part of the root cause).

2. When saying it doesn't make this noise when using your interface, that's not all that important because we don't know if the input impedance or ground reference structure of the interface is the same as the amp (and it is probably quite different).

The very first thing to try is a small jumper wire between the bridge of the bass and the sleeve of the output jack (or plug when the cable is plugged into the bass). If the noise goes away, it points to a missing or damaged bond wire between the bridge and the output grounding structure of the bass. Depending on the bass, there may be multiple points within the bass that are bonded to the bridge and cavity shielding.

 

[agedhorse]

they're in the same room so i assumed same circuit, but i tried same outlet to be safe just now. no improvement.

however, the pad feature on my amp seems to greatly reduce the hum. with the pad engaged and volume knob raised to compensate similar levels, the hum noise is greatly reduced. this has me leaning towards issue with the amp more now. no issue with my 2nd bass through this amp regardless of settings. but that one is active and has much hotter output (related?)

I think you are chasing up the wrong tree here.

 

[grizzly59]

Do you have fluorescent lights in the room? Try on/offing stuff like that.

 

[steimlem]

I think you are chasing up the wrong tree here.

well it works so i'll do it for now

Do you have fluorescent lights in the room? Try on/offing stuff like that.

tried turning lights monitors off etc, no help or change. don't think this would be it since i have no noise plugged into my interface/monitor speakers, only my amp.

thanks for the ideas people, but still not really sure what the cause is.

 

[steimlem]

Ok, before we start guessing about a solution, let's think this through to see if we can determine what exactly is happening first. There's plenty of time for guessing later, after identifying the cause and a real solution.

1. The buzzing stops when you touch the strings... this almost positively indicates that it has nothing to do with the amp and the power or ground (though a bad ground can make the symptoms worst it's not part of the root cause).

2. When saying it doesn't make this noise when using your interface, that's not all that important because we don't know if the input impedance or ground reference structure of the interface is the same as the amp (and it is probably quite different).

The very first thing to try is a small jumper wire between the bridge of the bass and the sleeve of the output jack (or plug when the cable is plugged into the bass). If the noise goes away, it points to a missing or damaged bond wire between the bridge and the output grounding structure of the bass. Depending on the bass, there may be multiple points within the bass that are bonded to the bridge and cavity shielding.

sorry didn't see this message at first. i'll definitely consider and try your idea at the end of the message. my interface has a hi z instrument input that i use and same cable as with my amp. if the interface is dead silent with the bass, but the amp isn't.. it makes me believe the amp is lackluster/having issues. but i understand what you're saying about the bass as well and will try this. it seems these 2 pieces of gear do not get along whatever the reason..but the pad engaged does reduce the level to negligible .

 

[Dave TB Killer]

Seems like a ground issue on the bass. Bridge suspect.

 

[steimlem]

Seems like a ground issue on the bass. Bridge suspect.

i'm inclined to agree this is the top suspect, or top 2 at least. but can you tell me why it would have an issue with the amp, but not my interface/speakers in the same outlet ? that's the part that doesn't make sense to me.

 

[Dave TB Killer]

i'm inclined to agree this is the top suspect, or top 2 at least. but can you tell me why it would have an issue with the amp, but not my interface/speakers in the same outlet ? that's the part that doesn't make sense to me.

The amp has a lot more power than an interface.

 

[agedhorse]

sorry didn't see this message at first. i'll definitely consider and try your idea at the end of the message. my interface has a hi z instrument input that i use and same cable as with my amp. if the interface is dead silent with the bass, but the amp isn't.. it makes me believe the amp is lackluster/having issues. but i understand what you're saying about the bass as well and will try this. it seems these 2 pieces of gear do not get along whatever the reason..but the pad engaged does reduce the level to negligible .

It may be that the input impedance may be much lower than the amp (common), or that the interface's input may be TRS balanced and the noise may in fact be common mode to the tip and everything else. There are some peculiar input circuits used in interfaces to help with noise in the digital interfacing domain, sometimes they might have a positive effect even if it's unintentional for how you are using it.

 

[steimlem]

The amp has a lot more power than an interface.

maybe i'm just not savvy enough to understand your point but in my scenario the approximate volumes are set to the same on both . loud audible hum on amp, dead silent on interface/monitor speakers. unless you're saying the larger electricity amount provided to the amp itself is having an effect?

It may be that the input impedance may be much lower than the amp (common), or that the interface's input may be TRS balanced and the noise may in fact be common mode to the tip and everything else. There are some peculiar input circuits used in interfaces to help with noise in the digital interfacing domain, sometimes they might have a positive effect even if it's unintentional for how you are using it.

thanks for the info. this would explain my scenario if true. so most likely my bass is the cause for the noise, and something in the interface is "cleaning it up" while the amp is not. as opposed to the amp causing noise to be added to the bass

 

[Dave TB Killer]

maybe i'm just not savvy enough to understand your point but in my scenario the approximate volumes are set to the same on both . loud audible hum on amp, dead silent on interface/monitor speakers. unless you're saying the larger electricity amount provided to the amp itself is having an effect?




thanks for the info. this would explain my scenario if true. so most likely my bass is the cause for the noise, and something in the interface is "cleaning it up" while the amp is not.

Your amp is going to have a lot more preamp gain than an interface. Thus any ground issue onboard the Bass is going to be much more apparent. If you plug your Bass into the amp, turn the Bass volume to full and the amps preamp to 1 and the master to 5 it will still have the ground noise but just not as present. Reverse this to preamp to almost full and master to a minimum and the ground noise will be very loud. If this is what is happening with a split single P style pickup, there is some fault in the wiring.

 

[agedhorse]

Try the jumper wire, it's an easy and non-invasive troubleshooting step that can avert screwing around with a lot of other things (potentially creating new problems).

 

[steimlem]

Your amp is going to have a lot more preamp gain than an interface. Thus any ground issue onboard the Bass is going to be much more apparent. If you plug your Bass into the amp, turn the Bass volume to full and the amps preamp to 1 and the master to 5 it will still have the ground noise but just not as present. Reverse this to preamp to almost full and master to a minimum and the ground noise will be very loud. If this is what is happening with a split single P style pickup, there is some fault in the wiring.

still not sure i'm following. i do understand how gain staging works. i have my bass turned to max and the amp turned to about 2 or so for practicing indoors at a reasonable volume. i set the input on my interface (and output) in such a way to get the same volume level without clipping. interface is dead silent, amp is buzzing. i can also turn the interface preamp and output much louder than the amp while still staying silent.

unless you're saying the amp's built in preamp is automatically set to much much higher levels internally, and the volume knob acts more as an attenuator to this or something along those lines? i did say earlier that engaging the built in pad button of my amp (and increasing the volume knob to compensate same volume levels) does reduce the noise significantly. i found that interesting. i mostly record bass/songs and have less understanding of amps in general.

Try the jumper wire, it's an easy and non-invasive troubleshooting step that can avert screwing around with a lot of other things (potentially creating new problems).

yes i will try this. i'm betting this will end up proving the results you suspected but will update any interesting findings

 

[villegastx]

Because Buzz can come from many stages in your signal chain, you have to systematically eliminate each step in the chain one at a time, until you isolate the culprit.

1. Try a different bass. If the buzz goes away, it’s the bass. If it does not go away it is not the bass.
2. Try a different cord. If the buzz goes away, it’s the cord. If it does not go away it is not the cord.
3. Try a different amp. If the buzz goes away it’s the amp. If it does not go away it is not the amp.
4. Slowly turn 360°. If the buzzing changes, it is a grounding issue in the bass, cord, home, or amp.

5. Try to take down your nearest 5G cellphone tower. If the buzz goes away, it’s the 5G. If it does not go...

 

[butterfingers1]

I had the exact same problem last year. Moving the electrical cord around would fix it. It would come back if it had been moved again.

The cord snakes through a drum kit and is plugged into one of those multi-plug surge protectors.

Plugging other live cords farther from amp cord in the same surge protector also fixes this problem.

The electrical cord seems to interact with metallic drum stands and other live cords plugged near it. I tried another cord, same thing.

 

[teleharmonium]

unless you're saying the amp's built in preamp is automatically set to much much higher levels internally, and the volume knob acts more as an attenuator to this or something along those lines? i did say earlier that engaging the built in pad button of my amp (and increasing the volume knob to compensate same volume levels) does reduce the noise significantly. i found that interesting.

Agedhorse said it pretty clearly in post 13. There's a lot more to connecting analog audio signals than gain staging. Lack of noise in an interface doesn't tell you much because the interface input impedance and grounding reference are (or at least can be) so different compared to the amp.