Amp Buzz At Church/Ok At Home

dkterry · #1 04-21-2010, 03:05 PM

I have a 4X10 bass cabinet and an Eden Roadrunner bass head. When I use this rig at home I have no issue with buzz or interference but as soon as I take it to church I get buzz and on really bad days I will get a radio station or two coming through. One thing I realized was I wasnt using a speaker cable to connect from my head to the speaker cabinet, I was using an instrument cable and someone at American Musical Supply said that changing to the speaker cable would help eliminate the humm/rf interference, is that true? My bass instrument cable is a very nice Mogami cable. My bass is a 2yr old Elrick Platinum 6 string and the electronic cavity is well shielded. I picked up a very good quality speaker cable and I will give it a shot this Sunday at church. If this doesnt solve the problem, is there something else that I can try to get rid of the hum/rf interference that I am getting? Any help would be welcomed! Thanks!

dkterry

Calaverasgrande · #2 04-21-2010, 03:10 PM

I would question the guitar lead before I would quesiton the speaker lead. the bass preamp does more amplification in terms of db and is more likely to pick up RF interference. I have never seen an amp get RF interference from a shielded cable instead of a speaker cable. They just sound cruddy that way.

uhdinator · #3 04-21-2010, 03:11 PM

could be bad ground/electrical issue at church. Old buildings have old wiring that may not be properly grounded.

are you sending a direct output on the bass amp to a mixer as well.
that can cause ground loop hum as well and most amps have a ground lift switch for this. if that is causing it the only way around it is mic the speaker instead of the direct out.

K-Frog · #4 04-21-2010, 03:11 PM

The church may have grounding issues, such as we have at our church. I run an ungrounded adapter(3 prong to 2 prong) on my amp power cable to eliminate the ground hum

Calaverasgrande · #5 04-21-2010, 03:23 PM

Oh, yeah, forgot to mention. My gigbag has one of those 3 prong "christmass tree" outlet testers. I use it when I play unfamiliar stages to see what the sitch is.
Check the available outlets at your church. Sometimes there is one good outlet, and several with bad wiring. Maybe the congregation has an electrician or two?

dkterry · #6 04-21-2010, 03:46 PM

I've tried using the 3 prong to 2 prong adapter and I still get the buzz/rf interference. I dont use any direct outs from my amp head to a board/mixer of any sort just a 1/4" out of the amp to a 1/4" input of the speaker cabinet. I'm thinking it is an electrical issue at the church. I noticed that the keyboard player's amp buzzes a lot also and he is plugged into a different outlet on the other side of the church. I havent heard any radio stations out of his amp as of yet! LOL!

bigntasty · #7 04-21-2010, 03:50 PM

Quote:

Originally Posted by K-Frog

The church may have grounding issues, such as we have at our church. I run an ungrounded adapter(3 prong to 2 prong) on my amp power cable to eliminate the ground hum

+1 on the grounding issue. Had the same problem at ours, and I used the same solution.

Pilot172 · #8 04-21-2010, 04:01 PM

Sounds like a ground loop.

bertbassplayer · #9 04-21-2010, 04:03 PM

Sounds like a grounding problem, another possible problem is if there are any fluorescent lights or CRTs around as well, they will cause a lot of noise.

MNAirHead · #10 04-21-2010, 04:18 PM

Test..

Can you run a long thick (extention cord to an other part of the church) as a test?

Many times the sanctuary is the part of the church with worst electrical.. additions, kitchens, bathrooms etc are commonly better.

WingKL · #11 04-21-2010, 04:37 PM

Running without a properly grounded power cable is generally not a good idea. If your amp develops a power short to your amp chassis, you will get electrocuted. There are better ways to handle noise problems. If the amp is not making noise with no cable plugged into it input, that means the noise is coming from whats being plugged it. Single coil pickups can and will buzz but that can be mitigated by shielding and running both neck and bridge pickup so that they hum cancel.. Cheap instrument cables with broken or insufficient shielding will cause noise. If you have AC powered effects, ground loops can happen. If you have a DI out that has a ground lift, that's safe to use.

leehoop · #12 04-21-2010, 04:51 PM

improper ground in church wiring.

dkterry · #13 04-21-2010, 07:33 PM

Quote:

Originally Posted by MNAirHead

Test..

Can you run a long thick (extention cord to an other part of the church) as a test?

Many times the sanctuary is the part of the church with worst electrical.. additions, kitchens, bathrooms etc are commonly better.

I can move my rig to another part of the church (band/choir room) to test and see if I encounter the same problem. I will do that this weekend. Thanks!

dkterry · #14 04-21-2010, 07:38 PM

Quote:

Originally Posted by WingKL

Running without a properly grounded power cable is generally not a good idea. If your amp develops a power short to your amp chassis, you will get electrocuted. There are better ways to handle noise problems. If the amp is not making noise with no cable plugged into it input, that means the noise is coming from whats being plugged it. Single coil pickups can and will buzz but that can be mitigated by shielding and running both neck and bridge pickup so that they hum cancel.. Cheap instrument cables with broken or insufficient shielding will cause noise. If you have AC powered effects, ground loops can happen. If you have a DI out that has a ground lift, that's safe to use.

I will check to see if the amp has the buzz/rf interference without my bass plugged in. If it doesnt then I will check the instrument chord that I'm using. The pre-amp cavity looks like it is shielded quite well seeing that the bass is only 2yrs old. I hope to get to the bottom of this real soon because the noise is very annoying to me.

testing1two · #15 04-21-2010, 07:54 PM

I would suspect the church has some cheap lighting dimmers for the house lights, stage lights, or both (I've seen/heard it a hundred times). Dimmers without sufficient RFI filtering actually cause the building's wiring to act like a broadcast antenna for RFI and your rig picks it up and amplifies it. See if the noise increases when you dim the lights or goes away if you shut them off entirely.

Calaverasgrande · #16 04-22-2010, 12:02 AM

If its a dimmer issue that canbe xpensive to solve. The cost of the noiseless rheostats isn't much less than puttin in another circuit entirely!

Petebass · #17 04-22-2010, 07:39 AM

Some good advice here already. Definitely use a speaker cable for speakers. It has nothing to do with your hum problem but it'll save you some possible amp damage.

Do you by any change have any power cables running along side your instrument cable at church? That can cause hums because the magnetic field generated by the electricity in the power cable can be strong enough to penetrate the shielding in the instrument cable.

If none of this helps, buy (or make if you're handy) an "isolation transformer" based hum eliminator. You simply put in the signal chain, usually the signal to the input of your amp, and the principle of "Galvanic isolation" goes to work to eliminate the hum.

Some DI's have isolation transformers built in. Even a cheap Behringer HD400 will do the trick. I made one from bits I bought from Jaycar (our version of Radio shack) for about half the price of the behringer. I leave in it my gig bag and pull it out whenever I get to a venue that's humming.

KJung · #18 04-22-2010, 07:59 AM

My best guess is that Jesus doesn't love you. Stay out of church, and you should be fine

dkterry · #19 04-22-2010, 08:59 AM

A lot of good advice. I really appreciate all the feedback. I will start with simple and least costly fixes and go from there. I will let you all know what I find to work. If all else fails i will just stay at home and stop playing at church...haha...just kidding!

MX21 · #20 04-22-2010, 10:19 AM

We had the same issue in a big theater. Guitarist's amp was buzzing/humming really badly. It was the lights. We had the lighting guy turn down the lights one by one and on one particular light bank the buzzing went away. So the problem was with the dimmer pack. We just had to play without that particular bank of lights.

MX