Bass Has Weird Noise Issue

[JBoogy]

I just bought a bass, new to me. Second owner. It is a Warrior Messenger Bass (1 of 2 prototypes).Love the bass, the playability, the weight, the look, all good. BUT I noticed a weird subtle light hum that appeared whenever I took my hands off the strings. Or wasn't touching a metal surface. After looking on talkbass, it looked like it has been discussed a lot before and it is a shielding issue in the electronics cavity that causes that. So I take my bass to my local repair shop, Blues Angel in Pensacola. I have had tons of work done there before on other basses and amps, never been disappointed. They give it an electronics once over, said they added more shielding, checked all the grounds, etc. They can't find where it is happening. Thotherey keep it for several days and said they had two different technicians go over it, but they can't find the source. So they recommend a new preamp, that it must be the preamp (Aguilar pickup, Aguilar preamp in bass). So I buy a new Aguilar preamp, when it arrives I take it to the shop. Another week goes by, and they call and say it is all fixed, they can't get it to make that noise anymore, all good. I pick it up today and get it home, plug it in, same exact noise issue. My other bases don't have this issue on my amp or anything, so I am sure it is the bass and not my amp or other localized issue. This is the only bass I have that does this. BUT now I am not sure what to do. Any thoughts or advice? I am not handy and don't know anything about soldering or electronics, so fixing it myself is not possible.

 

[JBoogy]

Anyone have any ideas or suggestions??

 

[Bass Viking]

Hmmmm, I’m stumped. Did you test it at the repair shop after the preamp was installed or did you take them at their word?

 

[Bass Man Dan]

Just for giggles, take your amp to a different room or try a different outlet and also if you can swap your cable to the bass and see if that changes anything.

 

[Old Garage-Bander]

The hum is supposed to go away when you touch the strings or other grounded metal parts on the bass.

Your body is essentially an antenna for noise that can then be picked up by your pickups. This noise is often location related and depends on what other electrical or electronic devices are operating in the area. Perhaps your guitar shop has gone to some trouble to reduce their local noise sources.

When you touch the strings (ground the antenna) the noise goes away.
This is more prevalent in some basses than others.

Why replacing the preamp made a difference, I can't say. Especially if the preamp was working fine before. Perhaps in replacing it they also, inadvertently corrected a previously unseen wiring problem.

 

[JBoogy]

I didn’t try it at the shop, it would have been a pain and I trust them. I will try with a different cable and in a different room. But my other two basses don’t have that issue at all. No noise at all when hands off the strings, so really not understanding this one. I looked in the cavity and it looks like they shielded it really well, and the soldering and preamp installation looks super clean and nice. Really no idea what is creating the noise and why they didn’t hear it but I do at my house. I am going to experiment tonight with different plugs and rooms and cables to see. But because no other basses are doing it, I feel like 99% sure it has to be something with the warrior bass. I sent an email to Warrior, hoping they get in touch this week. Maybe they will have an idea of what is up.

 

[JBoogy]

The hum is supposed to go away when you touch the strings or other grounded metal parts on the bass.

Your body is essentially an antenna for noise that can then be picked up by your pickups. This noise is often location related and depends on what other electrical or electronic devices are operating in the area. Perhaps your guitar shop has gone to some trouble to reduce their local noise sources.

When you touch the strings (ground the antenna) the noise goes away.
This is more prevalent in some basses than others.

Why replacing the preamp made a difference, I can't say. Especially if the preamp was working fine before. Perhaps in replacing it they also, inadvertently corrected a previously unseen wiring problem.

It is my understanding with proper shielding, this interference/noise shouldn’t be audible. I suppose some people with just live with it, but it bothers me that my two cheap Ibanez basses are dead silent and my high-end warrior bass has an annoying (but subtle) noise if it isn’t being grounded by my hands to the strings. Just seems wrong to me. Lol

 

[Old Garage-Bander]

It is my understanding with proper shielding, this interference/noise shouldn’t be audible. I suppose some people with just live with it, but it bothers me that my two cheap Ibanez basses are dead silent and my high-end warrior bass has an annoying (but subtle) noise if it isn’t being grounded by my hands to the strings. Just seems wrong to me. Lol

Are your cheapies passives?

 

[JBoogy]

No both the Ibanez basses are active, with Bartolini preamp/eq. And dead quiet. The Warrior has an Aguilar music man style AG 4-M pickup and the Aguilar OB-1 2 band boost only preamp/eq. It has push/pull active/passive in the volume knob. The noise happens in active and passive mode. Ugh it sucks because I literally love everything about this bass except for this one issue lol

 

[Aloe]

some hum when not touching strings is pretty normal, the degree may vary (and proper shielding indeed helps to some degree). the most common way to mitigate it is with technique: just always touch the strings with left or right hand.

if you like how it sounds, just learn to work around this problem. if you don't really -- you might want swapping pickups/preamp for Bartolini and see if it will help.

 

[EagleMoon]

Here’s a thought. I had a Spector bass years ago that had a similar issue. I sent it to Spector to be worked on. They couldn’t find what the problem was with it so they sent it back to me. Turns out it was the strings. The bass had come with coated strings and they weren’t making contact magnetically with the bridge. So my suggestion would be to try changing the strings to another type and see if that helps.

 

[Lostgallifreyan]

I noticed a weird subtle light hum that appeared whenever I took my hands off the strings. Or wasn't touching a metal surface. After looking on talkbass, it looked like it has been discussed a lot before and it is a shielding issue in the electronics cavity that causes that.
.
.
.
...they added more shielding, checked all the grounds, etc. They can't find where it is happening.

You may not need to have much gear or electronics knowledge to verify this.

Have you got a cheap multimeter for checking fuses and cable continuity? If not, get one, they can be so cheap it's hard to justify not having one.

When strings pick up noise that vanishes if you touch them, it usually means you're either grounding them capacitatively, or resistively, so even if shielding is good, it has to be grounded properly so you don't have to do it through your body (which in some contexts can be truly dangerous!). I have seen a great result of modification on a bass done by someone who completely overlooked the quality of connection between a ground wire and the bridge!

Try checking for the resistance between the strings, the bridge, the largest bit of metal on your output jack socket, and see if they all measure well below 1 ohm. If some bit of touchable metal is NOT connected to the main output jack shell by that low a resistance, you've probably found something someone else missed, and shouldn't have.

(Also, bear in mind that this is unlikely to be related to a hum loop, the description sound to me like electrostatically induced noise.)

EDIT: Check the ground of the signal cable for continuity too, and if there's any looseness in the bass audio jack fitting, check for grime. Anything that compromises this ground from bass to amp can cause this because you might now be the best route to ground! This has safety implications too, so look deep... The trick is to try to find whether two contacting surfaces that both seem fine with other gear, are NOT fine when they act together specifically. This is a common problem. It can be hard (or impossible) to replicate by experts too, if they don't have the entire system to test it. If you explore this carefully you may solve it even without expert knowledge. Just note what you tried if it gets hard to remember.

 

[DrBnz]

Agree, since your other instruments work just fine, I'm still thinking its a bad ground and "you" are acting as the ground. But a multi-meter should lead you in the right direction. One end on a ground point, just touch the other end on various metal parts and note the readings. If I didn't have a meter, I'd just use an external wire attached to a ground (output jack) and touch the other end to various metal parts and note when the hum stops.
Once all logical things are exhausted, I'd pull the pickups and check the backside of the P/U for lost/missing washers/screws stuck to the magnet.

 

[mikewalker]

A small amount of hum with no string ground is 100% NORMAL, even with humbuckers... we live in a world which is CHOCK FULL of electromagnetic fields

 

[Ghastly]

I feel your pain. I have a great Guild acoustic bass guitar that I love playing, but I can't use it for any gigs because it buzzes pretty bad when plugged in, no matter what I do. It has a Piezo electric pickup, btw. None of my other basses do this, with the same amp/gear/location. I've taken it to a luthier who couldn't isolate the problem. So I only play it when I want to sit around and noodle, quiet and unplugged.

 

[mikewalker]

PS: if you absolutely must have 'no hum with hands off the strings" - then the best you can probably do ( aside from maybe buying an Alembic Series II) is to invest in EMG active pickups ( no string ground). They are not infallibly perfect hum free in all situations, either - and in fact it seems to me that their 'low-impedance coils thru differential op-amp' strategy has worse noise resisting performance now than when I started using them back in the late 70s! Although that may have a little to do with the increased ambient EMI...

 

[BlueTalon]

A couple questions come to mind. What sort of strings are you using? And what style of bridge? Shielding/grounding is basic and effective (assuming it's done right and everything is grounded), but can be complicated when using tapewound strings or mono bridges. If you are using uncoated rounds or flats and a one-piece bridge (multiple saddles on a single base), then something else is going on. Ideally, with a multimeter, you should be able to read zero ohms between the outside of the jack and any of the tuners.

Another idea -- do you have a wireless unit? Or know of anyone who has a wireless unit that you might be able to borrow? I'd be interested to know if you still get that hum when not physically connected to your amp.

 

[Lostgallifreyan]

A small amount of hum with no string ground is 100% NORMAL, even with humbuckers... we live in a world which is CHOCK FULL of electromagnetic fields

Indeed. My bass will protest if I walk near my active monitors while carrying it, though in this case it's magnetic (from toroidal transformers), not electrostatic. Not a lot will shield that (maybe 'mumetal'), but it's easy to avoid by distances greater than 2 feet or so.

RF is where separating electric and magnetic fields is hard, but if RF were a cause, there'd probably be some very complex subtle patterns in the noise, not just hum or buzz. I have a Casio projector that emits ludicrously high RF noise even in standby, but it falls off strongly at three feet away. I avoid triac or thyristor based lamp dimmers because those do it too.

I noticed in your other post, a mention of differential op-amp rejection. Nice idea. If it fails in newer designs it may be that someone picked a less precise common mode rejection spec, so an upgrade op-amp might fix it. I suspect most times this is best solved passively though, it probably costs less. Less to go wrong too. I have rarely seen electronics in a guitar that weren't ingeniously reduced to the lowest and cheapest parts count. The one time a 'boutique' bit of electronics was in a guitar I saw, I suspect it worked less well than the original.

Which reminds me: if noise ever arises, mixing parts to modify a guitar or bass might be a partial cause, if the original was designed as a single system. I doubt the maker had modularity in mind.

 

[Lostgallifreyan]

I feel your pain. I have a great Guild acoustic bass guitar that I love playing, but I can't use it for any gigs because it buzzes pretty bad when plugged in, no matter what I do. It has a Piezo electric pickup, btw...

VERY high resistance output I think, from a piezo source. Relatively high output too maybe, so could be good SNR. If you use a circuit similar to those used for condensor mics or active electric field antennas, very close to the pickup, you might tame it by good local grounding and low output resistance presented to the amp. If it already has this, I don't know what to suggest.

 

[No Compute]

How about an ungrounded metallic pickup cover (I didn’t see the type of bass or pickups mentioned)? Check for continuity between the cover(s) and the jack. Shielding the cavity only helps what is inside the cavity…