AC Buzz sucks.

[Kiwiburger]

Frustrating day. I have an AC buzz problem that has stumped all experts so far. The best electrician, recommended by the best serious audiophile hifi shop in our city is stumped. He's referred me to some electrical guru who might have a clue.

 

Today we fired up an expensive custom wound 5kVA transformer that can do symmetrical power. Buzz.

 

I'm running out of ideas (and i've removed all the usual suspects). Consider this scenario: concrete standalone 3 room bunker. Any hum bucking guitar into a Pignose battery amp. No serious hum or buzz - no worries. I can walk around the room, holding the guitar up to various AC powered objects, light, clocks etc - and you have to get really close to pick up any hum.

 

Same with a little Fender battery amp, which has way more gain and can easily feedback. Some hiss, but no hum or buzz to worry about.

 

As soon as I plug in an AC adapter - nasty buzz (rich harmonics of 50Hz).

 

Any guitar amp or processor I use - e.g. POD or Univalve or whatever: loud stinking buzz. Most of it goes away if I securely wire myself to 'ground'. Although most adapters these days are two prong and don't have a 'ground' as such - ground and neutral are supposed to be the same 0 Volts.

 

I did an interesting experiment today. I took a speaker I didn't mind blowing up, and wired it to an AC plug - neutral and ground. I plug this into the wall, and get a loud fruity buzz. It's stronger in some rooms in my house, and absent in my garage and workshop. Wierd.

 

But that would seem to be irrelevant, because we tried this transformer today. Total isolation, floating ground. Straight run of wire to my POD. Loud freaking hum. I give up.

 

The buzz is coming through the guitar and/or cable. But ONLY for anything AC powered. Logically, you would think that if EMI or RFI existed in the room, the exact same guitar and cable would present the exact same buzz to any amp, whether AC or DC. But there is no buzz through a battery amp; a helluva buzz through anything remotely AC powered. That's just fkng obtuse.

 

Time to call in the witch doctor.

 

Maybe I need to rip everything out and go 12 volt, solar powered all the way. But that means I can't use my favorite AC powered stuff. Maybe I need a pure sine inverter. Maybe I need to shield my AC wires in grounded conduit. Maybe I need to build a faraday cage in my room.

 

Whatever the hell it is, i'm determined to have the quietest guitar room in the world. But I seem to be located in the Bermuda Triangle or somewhere just as whack.

 

Bugger.

[BrainChild]

Some random thoughts;

 

Most AC adapters are the cheapest DC converters possible. You might try getting a nice DC power supply that actually has some built in filtering.

 

Maybe convert your guitar to be low impedance with balanced cables.

 

Get an oscilloscope and hunt the culprit down.

 

Try a hum eliminator box that iso's the guitar signal.

 

Maybe New Zealand isn't well earthed. Drive a big stake deep into your back yard and get a good ground happening.

[The Chinese]

Kiwi, I've beeen watching your threads on this with interest...

 

Let me review a couple of things so I can make sure I've got it right....

 

A) your Power is 240v Single phase from the street.

 

B) You have measured your Neutral line to have Current/Voltage on it

 

C) You do NOT have a Solid ground because of the Dry Environment

 

D) Your New Transformer is Providing Symmetrical Power i.e. 120v/120v on each leg Plus Ground.

 

Refresh me if anny of this is wrong.

 

Try and post a schematic of the wiring of the Tranny if you can, I'd like to see what's going on there.

 

A Faraday cage is only going to help you if you have a ton of Fields nearby....Are yo uin the City? It sounds like you're away from the typical city noise sources...Is there an electrical tower nearby?

 

How about Light Dimmers? Have you replaced these or shut them off?

 

Peace,

 

-Todd A.

[Kiwiburger]

Thanks BrainChild and Todd - your experience is very much appreciated. I'll try to answer your questions:

 

 

 

Most AC adapters are the cheapest DC converters possible. You might try getting a nice DC power supply that actually has some built in filtering.

Will probably do that when i've sorted this problem out. This is a bog standard PodXT that is perfect in the shop. Used in studios everywhere. I'm only using it because it's quieter and better than any tube amp - but I want to buy and use tube amps.

 

 

Maybe convert your guitar to be low impedance with balanced cables.

How I wish all guitars were lo-z balanced, like microphones. How I wish. Currently, I only use humbuckers - but I want to go back to single coil strats. I have no problem with battery amps - and I could make the ultimate battery amp, but maybe I want the sound of an AC15 or a Champ ... I shouldn't have to do this.

 

 

Get an oscilloscope and hunt the culprit down.

That will probably happen soon. But it will only give a picture of AC buzz. I've already used my own spectrum analysis. We have 50Hz AC - and 50Hz and 100Hz are not very prominant. The peaks are around (from memory) 150Hz, 250Hz, 350Hz, etc, etc. Seemed wierd to me - I would have expected a descending series at every 50Hz.

 

 

Try a hum eliminator box that iso's the guitar signal.

Good idea - any suggestions?

 

 

Maybe New Zealand isn't well earthed. Drive a big stake deep into your back yard and get a good ground happening.

That was my first reason for hiring this audio-oriented electrician. He puts in ground spikes for audiophiles, but the first thing he found is that my wiring and phase is perfect. For reasons given below, we have ruled out ground issues.

 

 

 

 

A) your Power is 240v Single phase from the street.

Yes. Good strong voltage, there is a transformer in our street.

 

 

B) You have measured your Neutral line to have Current/Voltage on it

At any AC socket in my house or studio, I can plug an 8" 8 ohm speaker into the Neutral and Ground, and get a good healthy buzz. Some sockets are far louder than others. My garage and workshop seem immune - but maybe that's just oxidised contacts - they don't get much use. I think this is a good example of ground loops - there is plenty of current to drive that speaker. But - for reasons below, we have ruled out ground loops as the source of this buzz. (Although I find it interesting that this ground loop buzz has the same timbre ...

 

 

C) You do NOT have a Solid ground because of the Dry Environment

We get a bit of rain - and my electrician doesn't think he can improve the ground at my studio end. Maybe he's wrong - but this guy puts in ground stakes for hifi buffs, and I have almost begged him to do this, and he doesn't see the need.

 

 

D) Your New Transformer is Providing Symmetrical Power i.e. 120v/120v on each leg Plus Ground. Try and post a schematic of the wiring of the Tranny if you can, I'd like to see what's going on there.

 

Yes - it's a very simple primary and centre-tapped secondary. 240VAC goes in, 120v/120v on each leg Plus Ground comes out. The schematic is printed on the top - it's that simple. We haven't wired this in permanently yet (no point until we solve this problem).

 

 

 

A Faraday cage is only going to help you if you have a ton of Fields nearby....Are yo uin the City? It sounds like you're away from the typical city noise sources...Is there an electrical tower nearby? How about Light Dimmers? Have you replaced these or shut them off?

I'm in a quiet suburb - lots of land, nothing obvious in the neighborhood. I have no worries with my high gain battery amps - I can induce hum by placing my guitar pickup right up to an AC transformer, but I can always move away and have silence (except for normal hiss and guitar feedback).

 

I hate light dimmers, and there are none in the studio. I use energy saver lights, and I know they can cause I little hum. But this 'buzz' is several orders of magnitude greater. I turn off the lights, and it makes no difference.

 

Our house has a nasty dimmer that I intend to remove soon when we renovate that room. I can hear the effect of turning that on/off when I use a battery amp in the house. But turning this off doesn't stop the buzz.

 

My current theory: I don't think this buzz has any magnetic component at all. I don't think it involves current at all. I am thinking that this is a pure AC voltage, that propagates through copper wire, goes straight through an isolation transformer, and also through human bodies, but can't go through air. Does that sound possible? I've read all literature on guitar buzz I could find, and somebody mentioned the difference between electromagnetic and electrostatic fields. I can't understand how AC can be electrostatic, but this is what I think I must have.

 

Yesterday we connected two long wires from the transformer, to my Pod and amp. The Pod and amp are dead silent, with a high gain setting and NO gates. I hate gates. But as soon as a cable is connected, there is buzz. The guitar only makes a difference when the volume pots are right off, otherwise it buzzes. It was a Peavy Wolfgang with excellent humbuckers, but it could be any guitar or pickup at all.

 

I tested the EMI field around the transformer - which is a few feet. That hum is directional and obvious, and recognisable (more of a hum than a buzz). We were nowhere near this.

 

If it makes any difference - I know that when my powerboard is totally switched off, I can hold a battery amp with a very short cable near any AC wiring, and it buzzes. Also, any large metal object (like a mic stand, or digital piano) induces this same hum. That sounds like RFI to me. It seems to me that the copper wires are a carrier - like a radio antenna - and don't really need to be carrying current. But maybe i'm totally wrong.

 

It's got to be something basic and simple. Either that, or i've tapped into a zero-point energy source and i'm about to revolutionise the power industry.

[The Chinese]

At any AC socket in my house or studio, I can plug an 8" 8 ohm speaker into the Neutral and Ground, and get a good healthy buzz. Some sockets are far louder than others. My garage and workshop seem immune - but maybe that's just oxidised contacts - they don't get much use. I think this is a good example of ground loops - there is plenty of current to drive that speaker. But - for reasons below, we have ruled out ground loops as the source of this buzz. (Although I find it interesting that this ground loop buzz has the same timbre ...

 

 

If you're doing this, then you have current in your ground. AFAIK there is no other situation that causes this.

 

As for a Grounding Stake, Just Water it!!!! Seriously. A good Friend of mine was telling me about a studio that they had buzz and they just went outside and watered the sstake when things got too noisy..

 

I would be very surprised if your problem was Static. Electro Magnetic makes much more sense. Somewhere in your room your pickups are picking up a field that your amplifiers are multiplying. *OR* your Guitar is poorly Grounded. Forget about the battery powered amps for a second, I think they're a poor benchmark in this case (IMO). Are your pickups shielded and properly wired/Grounded? If your Guitar is Stock, then the answer to that questino in absolutely NOT. I put Copper tape all over my Guitars, and then Ground it all back to the star Point. This works WONDERS....

 

 

Also, I would recommend shutting your entire house OFF for testing. see what happens when the ONLY thing on Is your Amp and Guitar. Then start firing up circuits....

 

Alos, Get a Volt/Ohm Meter. A Hek of a lot safer than wiring a speaker to electrical loads...plus this will reduce speculation.

 

Lastly, if you are spending money, I do know an excellent Tech in New Zealand. I can['t remember his hame, but I can get it for you if you wish (I worked with him in Thailand troubleshooting the power issues we were having there...)

 

 

-Todd A.

[Kiwiburger]

Thanks Todd, I would love the name of that tech. Good suggestion to water my ground - will find out where it is (hopefully not under the asphalt driveway we put in).

 

I know that better shielded guitars would help. But my thinking is that I want to totally remove the source of the EMI, so that even badly shielded guitars can be used. I want to use a bog standard strat, with a bog standard Univalve if the whim takes me. I want clients to be able to use their own guitars. I want to use Woody pickups in acoustics with a high gain amp. I want my clients to be able to use their own guitars.

 

If the problem is simply the guitar, then why is it practically silent through a pignose? Why did it not buzz in the guitar shop? Because of these issues, I never buy a guitar that buzzes in the guitar shop.

 

How can EMI not be directional? This is totally non-directional.

 

I bought the Pod because it seemed buzz-free in the shop - with fluro's everywhere.

 

My studio wiring couldn't be any simpler. 3 rooms, a single outlet in each room, a dedicated wire for each one back to the fuse box.

 

My transformer used as an isolation transformer should have killed any ground loops, and the Pod adapter doesn't have a ground pin anyway.

 

I let you know if I ever solve it - even if it takes 12 Volt solar power.

[BrainChild]

I don't know whether the Ebtech's work well for guitar level signals but you could ask.

 

http://www.ebtechaudio.com/index.html

 

One guy said it works between his Les Paul and Sansamp so maybe worth trying.

 

http://www.musiciansfriend.com/srs7/search/detail/base_id/36853/src=00631

 

http://www.onlinerock.com/mf_store/guitar/h/Hum_Eliminators/

 

You may want to turn off your energy saving lights. If these have scr's in them to half wave the power then they will send spikes up the power line. A transformer will usually clean this but not always. We have had to buy special Corcom filters to clean the power lines in our equipment to meet CE requirements in Europe because our machines were sending noise back up the power lines. They come in various filtering capabilities to remove different types of noise.

 

http://www.cor.com/

[Kiwiburger]

Thanks Brainchild - i'll check them out.

 

I've been aware that energy saver lights are mini fluroescents, and cause some hum. I frequently turn them off just to make sure they aren't the culprit, and it makes no difference. I would rip them out in a heartbeat if I thought it would make a damn difference. In the meantime - 9 x 11 watts (99W) is giving me the same candle power as 9 x 60W incandescents (540W) which is kinder on my power bill.

 

I'm fairly sure that an oscilloscope is going to find that I have an extremely distorted AC waveform coming into my property, and if the electric company doesn't fix it i'm going to have to go to sinewave inverters.

 

Once this major buzz has gone, I expect i'll be able to hear all the normal hums and buzzes that normal studio's hear.

 

I can record acoustic instruments (usually all balanced gear) in total silence. It's just when I use unbalanced stuff, all hell breaks loose. I can't even record DI through anything. Not at the quality I want - I'm sure some people would just apply a gate and forget about it. I've heard albums with gobs of hum on the guitars, and I just hate it.

 

I find it hard to believe that a simple concrete box can be such a hostile EMI environment, compared to music shops and anywhere else. And I still find it strange that battery amps are immune.

[Guest Anonymous]

Kiwiburger,

 

It appears the problem is hum being trapped between the two AC legs and not being dissipated to the ground connection. If you can turn off one of the 120 volt legs by flipping a breaker, turn off each one in turn and see if it helps. If you can't turn one of the legs off due both legs being activated with a master breaker, turn off the master breaker and disconnect each of the legs in turn and see if that helps. Tightening all of the connections, especially the grounds at all of the breaker points could help also.

[Kiwiburger]

I'm not sure what you mean by 'legs'. This is single phase New Zealand 240 volts 50Hz AC. It comes into my property on two wires and a seperate common ground wire.

 

Todd - I suspect my grounding rod for the house is covered in ashpalt and non-accessible now. The studio doesn't have it's own one, which is why I hired this electrician, but he doesn't want to put one in if it doesn't solve anything. My temporary one only seems to make matters worse, so I'm not sure it's a grounding issue.

 

I've just had another expert come and have a look, and he was very nice and knowledgeable, but he has refered me to another retired professor guy because it's stumped him.

 

We are starting to think that it might be ground currents on my property. I have a concrete floor with steel reinforcing that wasn't earthed by design. The closer my guitar gets to the floor, the louder the buzz. But only which AC powered amps/mixers/pods.

 

This AC {censored} seems to defy logic. It's a complex mixture of electromagnetic and electrostatic and RF fields and all sorts of wierd {censored} that nobody really understands. One moment my body appears to be acting as a ground, the next it appears to be acting as an antenna. Improving the actual ground with a ground rod seems to make things worse - which suprises me.

 

I'm considering building an enclosed steel room within a room and electrically grounding that.