hum active electronics ?

[FRANK]

Hum I have a bass Guitar and was reading about wire ing a capacitor and a resistor inline with the bridge ground to eliminate noise when I put my finger on the volume pot it goes away when I let go its back ?anyone also notice when I pick up static electricity that I get a little pop through the amp when I touch the potentiometer ?

[Ned Knepp]

Paul,
I don't know much about electronics in instruments but I do know a bit about electronics in general. The "pop" makes me think that you have a bad ground somewhere. I assume from what you said that the pickup isn't a "humbucker" style pickup, so it could be that you become the circuit ground when you touch the pot .

Ned

[Len Biglin]

Hi Paul , this is a common problem , you will notice that most electric guitars get quieter if you touch a grounded part like the jack or the strings. You have grounded your body and it's assosciated noise . Now if you are not touching the strings and you grab the vol. pot. , you are touching a poor ground through the pot shaft and it will crackle as you turn it . Easiest cure is to add plastic knobs , or hang on to the strings with your left hand .The bridge or tailpiece is normally grounded through a hidden wire , and the reason for replacing this with a resistor and cap. is to reduce risk of electrocution in the event of a major wiring problem in amp or P.A. EMG actually ask that you remove this connection if using their pickups , its gonna be so quiet anyway ! Hope that clears up the hoodoo with noises . Len

[FRANK]

yea but len isn't this a cheap fix shouldn't I be looking for a loose ground wire or loose pots?

[Rick Hoey]

Single coil pickups are always noisey, that's one reason humbuckers were invented, to buck the hum by using two reversed coils to negate the hum. If the bass has a humbucker in it then I would suspect a bad connection or circuit, bad solder joint etc. The amplifier and cord you use can also add noise. You could try a different cord and amp to eliminate that possiblilty. Some times the problem can be added to by badly grounded house wiring. If the bass has a single coil pickup then there is nothing to buck the hum. Many people try to shield these instruments with conductive paint or foil and shielded wiring and that can reduce but not totally eliminate the problem. There are many websites about guitar wiring and shielding. With Fender style single coil guitars there is often just so much you can do. Luck to you. And thanks for not using caps. Rick

[FRANK]

yes Rick the Guitar is shielded with two single coils the customers complaint is that it has started making more noise .and he was getting shocked when touching the tuners or strings or Knobs anything connected to the bridge Ground so when he was standing there I did it nothing.He would do it and a pop would come out the AMP just after he left I picked up some static off the floor moon walking and pop sure enough a pop through the AMP My concern is it could be the chip since it is Active I have dealt with this before but here is signal. Where when I had a bad chip no signal it is easily replaced . Here in this situation it plays so it cant be fully blown, the reason I bring up the chip is I heard from an old AMP Tech who says when soldiering use a Iron with a Ground if not you start to burn out the Chip? its been worked on in the past so I opened up the cavity cover found two exposed wires leaning up against the aluminum shielding ? I fixed that buy shielding them but still getting a lot of noise when the volume is up.thanks Rick H

[Rick Hoey]

Paul, could you tell me the make and model of the instrument? Is this an active bass? Are the pickups active or is there a seperate pre-amp wired into the bass control cavity with a battery? If it's a passive bass I suggest the problem is in the amp.

[FRANK]

Wash Burn BB-6 is the model active with a gang plug for computer chip Made in Indonesia two soap bar pickups

[Rob Mercure]

I've been doing electronics repairs for almost 35 years now and if your customer is getting shocked it means that the amplifier he is using isn't properly grounded - this isn't a problem with the instruments. The problem might not be the amp but the outlet where he plugs in as folks commonly replace an ungrounded outlet with a grounding one when the old one dies and just leave the grouding connection open. Anyone who played in the 70s and before when grounded outlets were scarce remembers holding a guitar in hand and getting your lips whacked when you touched them to a microphone with a potential between the amp and the PA amp.


Rob

[Tom Krebs]

Some active pickups are internally shielded and do not require a bridge/string ground.

[Russell Vance]

Len Biglen is on the money here (all things being normal otherwize) - you can spend a lot of time chasing this problem and getting all sorts of voodoo quasi science from the web. Static build up is a nuisance and if you wear shoes with insulated soles or cat fur jumpers, play on synthetic carpets or have a plastic type finish on your guitar and live in a dry climate it is worse......chuck in a bit of corrosion/dirt in the earth path of your guitar and amp (the older the worse the earth issues), not to mention dirty grid power and you have a whole bunch of things which can mess up your day. Use plastic knobs, as a starter and don't fiddle with your pickup poles either as some of them are noisy critters also.

But, the one that almost bought me to tears was a guy who played in church and said the cold weather affected the noise level in his single coil guitar (a custom build I did for him) drastically - after checking and doing everything I knew and using a power conditioner with another guitar to no avail....the penny dropped. When it got cold the underfloor heating coils turned on and set up the mother of all inductance circuits. Life became humbucking in that church.

[stevenrosburg]

Just fyi, you can also get metal knobs with plastic inserts. As for church hum, boy am I with you on that. I have dual humbuckers AND foil shielding and it's still not enough for my church's stage.

Static build-up is one thing (clicks and pops when you touch it), but if the customer is getting shocked it's probably a grounding problem with the amp. I have a Parker P30 (Strat copy) with a perloid pickguard and that thing made all kinds of noise when I rested my finger on the pickup screw or rubbed it back & forth on the pickguard while arpeggiating. I insulated the entire cavity and pickguard with copper foil, and that knocked it right out. I would suggest getting your multi-meter out and testing the bridge against each of the pots, pickups and output jack to make sure you don't have a floating ground somewhere. If there is continuity between all metal parts, then the answer definitely lies with the amp.

[Ron Frazier]

The old Fender amps had a two pronge cord that pluged in the wall .. We never knew what a ground wire was. Try unpluging the cord from the wall and inserting the other way. If the amp has a polority switch just click it and it will do the same. If the micropone and the amp are not grounded and you touch the mike with your lip it is a dead short and I have heard of some one getting killed with this.

As you all know all the new cords have a wide poug and a small one so you can get the polority the same.

Ron