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Old 15th November 2003, 08:03 AM   #1
AlvinB is offline AlvinB  United States
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Default Help - Extreme Guitar Problem (noise related)

Hey all,

I've been having a severe electrical hum on my guitars since May and no one can seem to help diagnose/fix it. I've been posting to forums and had several 'experts' up to my pad to help but everyone leaves scratching their heads. I have a feeling it's very simple but I'm not sure how to pinpoint the problem.

To make what has become a very long story short, here are the details in point form:

- moved to a new apartment in May only about 0.5 miles from our old place.

- small recording rig: 2 guitars, Yamaha Motif keyboard, PC's, 1 external rack that contains Echo Layla sound card, Rocktron Prophesy and Drawmer Front-End One.

- all gear was functioning exemplary at the old location.

- at the new location the guitars have a terrible broadband noise. ON an RTA there is a definite 60 Hz spike, with harmonics all the way through the audible range.

- most notable is the single coils on the strat. Although the humbucker is actually noisy enough to be unusable. Pickup Positions 2 and 4 (middle out of phase combo) are almost acceptable with a noise gate.

- the keyboard actually registers noise around -65db. Assumed it is picked up through the line-out instrument cable.

- the guitar has one null point where it clears up (again not enough to be usable with high gain). The axis is such that the power supply to the building is directly in line with the narrow of the body. On that axis (180 degrees from the supply) is a newspaper printer that may be operating interfering communications devices.

- the rest of the system is wired balance and has an acceptable noise floor, but still maintains the 60Hz spike (not directly audible but measurable).

- old apartment built in 1960s, had what I would consider old wiring, 100 units.

- new apartment even older but the outlets have been replaced. 7 units. Each outlet is grounded to the panel via conduit. Approx 0.9V RMS measured between neutral to ground. Powerline transformer feeds 7 buildings about the same size.

In terms of diagnostics, here is some of what has been done to date - with no measurable change. All results are measured against the guitar performance and not the RTA.

- tested all outlet wiring.

- Removed all gear from rack and moved just the preamps to another location in the apartment. Plugged into headphones, disconnected all other appliances from circuit in the house.

- shielded guitar a la instructions from Stew Mac - copper shielding of both single coils and cavity (strat only).

- plugged into two different UPS devices

- plugged into two different isolation transformers

- tuned radio to a noisy weak station. (690 AM). Incredibly noisy until immediately past the transformer at the end of the block, at which point it is crystal clear (for a distant station anyway).

- Power company has had TV and RFI, EMI, and Power Quality divisions here several times but no one can find a problem (none of them seem to be able to replicate the radio problem). Measurements have seemed to fall within their 'Normal' parameters. However, TV and RFI were unable to do a broadband frequency analysis. Power quality couldn't measure anything other than 60Hz.

- Gear has been moved across town and performed well again indicating no damage has been done due to the move.

Hopefully that gives you an idea of what I'm battling. I'm currently back in school studying music and electronics and it's killing me to not be able to use my gear! If any of you have any further avenues to explore, or recommendations please let me know. Likewise a knowledgable professional in Los Angeles would be welcome!
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Old 19th November 2003, 03:16 PM   #2
mgreene is offline mgreene  United States
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Default Your Noise

Hate to ask a dumb question but do you have fluorescent lights?
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Old 19th November 2003, 03:36 PM   #3
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Are there any RF equipment (xmitters) near by? I had an instance where they installed a HBO repeater near by and someways AC hum rode in on the RF (evedently) Cured it by replacing the front end op-amps with jfet types, but your situation is more complicated (although could be caused by the same mechanism)
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Old 20th November 2003, 01:44 AM   #4
AlvinB is offline AlvinB  United States
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No floursecent lights on in our place but there are old circular flourescents in the carport. They shouldn't be a problem as power to them is controlled by a timer - and the noise is constant whether they are on or off. Also, a handheld radio test doesn't offer any noise difference close to the flourescents.

Could be a transmitter but nothing is apparent to the eye. We are in a residential area but there is a newspaper printer very close, about 250 feet. I could picture them sending but no need for sending. We are not on the same supply transformer as them.

At wit's end. I was testing my bass in my drawmer pre today and noticed another computer-like sound on the line, even when the computers were unplugged. Of course that is only audible when the bass is off-axis and the other broadband noise is at minimum. I can see lights dimming and hear those changes on the guitar as appliances are switched in and out of the circuit.
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Old 20th November 2003, 01:43 PM   #5
mgreene is offline mgreene  United States
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You say its an apartment - is it possible that someone else on the same circuit box is running some sort device 24hrs a day that is polluting the line (say maybe something on the order of a fish tank)?

I think that every one has experienced intermittent noise when someone in your house/condo/apartment runs a power tool or possibly a defective electrical device of some sort.

Probably not practical, but could you dummy up a seperate fuse box that is not bringing the noice from the common box to every receptical in your apartment?
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Old 22nd November 2003, 02:11 PM   #6
mbroker is offline mbroker  United States
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I sent the link to this thread to a very good friend of mine who has had significant experiences in bands, recording studios (he co-owned a 128 track studio at one point) and the printing/graphic arts industries. To paraphrase his response, the problem is that you are living next to a printing company (he said something about a "6-colour Heidelberg"). Their presses are causing all the RF hash you describe. The only real fix is to move. Sorry.
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Old 23rd November 2003, 09:59 PM   #7
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I can't tell you the complete answer, BUT you should find someone to try to 'sniff' out the interference with some test equipment. The RF techs may be looking in the wrong part of the spectrum. I have a Strat myself, I understand.
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Old 23rd November 2003, 10:39 PM   #8
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You must disconnect from wall all machines and start listen only with the combo. If problem will be in this " basical case " too, use insulating transformer and step by step connect all machines and watch when it comes. You must use " elimination method " - try any guitar, any combo etc. - I mean, that problem may be in three cases : damaged combo, near printer or " grouded anthena " connectin ( if is there ).
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Old 24th November 2003, 02:25 AM   #9
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izzit possible to use a DI box and use balanced line stuff instead?? would probably cure the problem...unless the noise pickup is from the guitar innards itself...
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Old 24th November 2003, 04:46 AM   #10
sangram is offline sangram  India
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It sucks not to be able to play without huge background noise. Sorry.

That said, have you access to a line conditioning unit (fancy name for an RF filter)? You might try one of those to shield some of the electrical noise in the power line. Will not help very much, but still worth a shot. An isolation transformer will pass the noise through the core, may lose some of the higher frequencyies, but will be effectively passing all the noise in the guitar band (upto 3-6 KHz) so will be ineffective.

The second thing that helps is to completely shield your guitar. I had a similar problem where I was when I bought my electric gear (subsequent locations had better power conditions) and I used aluminium foil to completely shield the innards - the pickup cavity and the spring cavity. It made a world of difference. In the case of Strat type guitars it's easier, as there is a pickguard which you can remove and mask with copper tape, and ground it to make a nice large shield. You can also convert your gear to balanced input/output, which will help a lot.

Last of all, change your cables. I realised that street-retailed cable is junk, and started making my own. My noise levels cut down tremendously, and on stage there was no background buzz at all, and this without using a noise gate. I just buy samples of all wire available, and keep testing till I know which has the best shielding.

Again, your only real solution may be to move, as that makes the biggest difference.

Edit: Sorry, I see now you've tried shiedling the guitar. My mistake.
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