High Gain Noise

[niqstu]

Hola, I recently moved to a new house and my guitar makes much more noise now. The noise, the best I can describe, is a pulse of pinkish white noise at 7.83Hz with a 50% duty cycle. With the noise gate off and strings muted, if I rotate while holding the guitar in the playing position the noise is roughly -15dB to -70dB from 12 o'clock to 9 o'clock respectively. (9 o'clock being guitar perpendicular to the face of the amplifier)

The same noise can be found (on a different amp) when I lift the stylus of my turntable. I assume it is the resonant frequency of earth (shumann frequencies). Is there anything I can do cancel this noise or am I 'geographically screwed'?

Thanks?

[Mike Sulzer]

From Wikipedia, Schumann Resonances:

The Schumann resonance electric field amplitude (~300 microvolts per meter) is much smaller than the static fair-weather electric field (~150 V/m) in the atmosphere. Similarly, the amplitude of the Schumann resonance magnetic field (~1 picotesla) is many orders of magnitude smaller than the Earth magnetic field (~30-50 microteslas)[16] . Therefore, special receivers and antennas are needed to detect and record Schumann resonances. The electric component is commonly measured with a ball antenna, suggested by Ogawa et al., in 1966,[17] connected to a high-impedance amplifier. The magnetic induction coils typically consist of tens- to hundreds-of-thousands of turns of wire wound around a core of very high magnetic permeability.

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Not likely you are detecting them. Any way, Schumann resonances are a extremely low frequency electromagnetic radiation, not a pulse of pink noise.

Maybe there is some interference getting onto your power line.

Hola, I recently moved to a new house and my guitar makes much more noise now. The noise, the best I can describe, is a pulse of pinkish white noise at 7.83Hz with a 50% duty cycle. With the noise gate off and strings muted, if I rotate while holding the guitar in the playing position the noise is roughly -15dB to -70dB from 12 o'clock to 9 o'clock respectively. (9 o'clock being guitar perpendicular to the face of the amplifier)

The same noise can be found (on a different amp) when I lift the stylus of my turntable. I assume it is the resonant frequency of earth (shumann frequencies). Is there anything I can do cancel this noise or am I 'geographically screwed'?

Thanks?

[niqstu]

Thanks for the input. Most first responses (posted on scientific forums) are to powerline problems. But I have run the amp/guitar off of a generator and had the same noise. It has also been in a Faraday cage so you can eliminate electric fields.

If a power frequency was involved would it not be 60Hz (usa)? 60Hz is not a multiple of 7.83Hz. And why, if it were a ground problem, would it rise and fall depending on what position the guitar is in?

If I have a 7.83Hz signal being sensed by the guitar I certainly would not hear 7.83Hz. But I do hear chirping, pinkish white noise, possible harmonics of this frequency with a 50% duty at 7.83Hz (measured).

Quote from above: "The magnetic induction coils typically consist of tens- to hundreds-of-thousands of turns of wire wound around a core of very high magnetic permeability." --Sounds like a guitar pickup to me.

Here is my interpretation of the earths resonant frequencies: the Earth/sun magnetic field is the 'DC' component while the Schuman frequencies are the 'AC' component that rides on the 'DC'. Everything resonates, bigger things more slowly. According to Wiki, the resonance is cause by random lightning strikes around the world at a rate of 50/second.

What is the 'AC' component of a string/pickup (in microTeslas)?

[niqstu]

From Wikipedia, Schumann Resonances:


Not likely you are detecting them. Any way, Schumann resonances are a extremely low frequency electromagnetic radiation, not a pulse of pink noise.

Pulsed chirp-like pink noise is what my speaker says, extreme low MAGNETIC freqency with audible harmonics is what the pickup senses. Don't confuse electric fields (space between two charges) with magnetic fields (space between magnetic flux lines).

How can it be then, that my noise problem is directly related to 7.83Hz?

[Mike Sulzer]

Pickups get interference from both electric and magnetic fields. Shielding should get rid of the electric. Opposing coils (humbucker) should reduce the magnetic. I would get a cheap four wire humbucker, check that the resistance on both coils is about the same and then check to see if you get a lot less interference pickup with it wired as a humbucker than as a single coil. That should demonstrate that it is magnetic.
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The Schumann resonances have to do with propagation in the spherical waveguide made by the surface of the earth and the lower edge of the ionosphere. This has nothing directly to do with the solar magnetic field or the earth's magnetosphere.

A magnetic detector uses 10s to 100s of thousands of turns and probably a lot of magnetic material in the core; a pickup has no more than about 10,000 turns and very little magnetic material in its core. The detector needs all that to detect the 7.83 Hz; harmonics high enough to hear are much weaker. It is hard to believe that you are detecting that.

Of course, the fanciful explanation is that your next door neighbor is hosting a Schuman resonance detector that broadcasts its signal back to the base station using high power rf.

[niqstu]

Pickups get interference from both electric and magnetic fields. Shielding should get rid of the electric.

The guitar is well shielded, and I even put it in a large aluminum box and wrapped aluminum foil around the cable with a star ground connected at wall plug/generator; any of my guitars, single coil, humbucker or bass (combo) senses the same interference.

Forget I mentioned Shumann...

the facts:

Audible pulsing chirp-like pinkish white noise
pulse period = 7.83Hz (measured, was +/-0.05Hz over 20s or so)
Magnitude dependent on 3-D position
Shielded from electric fields
Isolated from ground in two tests, iso x-frmr and honda generator.

the objective:

no noise

[tedmich]

if its position sensitive my vote is for magnetic coupling, either through an old fluorescent lighting ballast or some other transformer. Does a line filter on the amp help any? Maybe a bad electrical ground on the house; check for safety's sake.

[Mike Sulzer]

When you were running it off the generator, did you try turning off all the breakers in the house box?

[David Schwab]

In one of the bands I play in, we rehearse in the drummer's basement, where he also has a Mac running ProTools complete with mixer, control surface etc. And a small PA for vocals. So there is a lot of gear down there.

All my basses exhibit this high pitched whine/chirp that sounds similar to what you are describing. The guitarist also gets the same noise from his rig. One of his guitars is a Strat, so obviously that picks up the most noise, but the humbuckers get it too. Both of my basses have humbuckers.

So it seems it's either something coming through the power lines, or otherwise being emitted by something.

[Steve Conner]

You're probably picking up the mind control rays from my Tesla coil.
OBEY!

Or, on a more mundane level, did you put your cell phone on top of the amp?

Not only does it have a radio transmitter that can break through your amp, but cell phones, as well as computers, have DC-DC converters inside with little coils that radiate magnetic crap.

The current in these coils is modulated by whatever the computer CPU happens to be doing, and can vary at an audible rate. My Macbook will make chirping noises through my guitar pickups, and my old Nokia phone makes some crazy ticking, bleeping and blatting noises if I hold it right against a pickup.

Many laptops and handheld info-toys also have a Wi-fi transmitter inside that can break through just like a cellphone does.

[David Schwab]

One way I test my pickups is to sit at the computer and see what noise I pick up. Besides the G4 Mac and CRT monitor (yes, time for a new Mac), I have a Roland Digital mixer sitting on a low table next to my chair, and that produces a lot of noise.

Things are quiet enough unless I move the bass very close to either the mixer or CRT. That's why I was so surprised by the amount of noise in the rehearsal space. I also played in a bar a couple of weeks ago that had very noisy power. Every guitar with humbuckers was humming up a storm.

[jrfrond]

Great technical info guys. Now, the story:

We are enveloped in a world of noise-producing EMI/RFI shit! You want some real noise, come down to our shop in midtown NYC around mid-afternoon.

Houses are not much different. Flourescent lights, TV's, computers, refrigeration, blower motors, etc. ad nauseum.

Then, we take electric guitars, with high-impedance antennae (pickups) mounted, plug them into high-gain amps, amplify the signal a couple of hundred times, and expect them to be quiet???

Seriously, that is a lot to ask of a high-impedance/high-gain circuit, even with humbuckers. Oh, you ARE talking about humbuckers, aren't you?

Have fun chasing that ghost. As a fellow tech and player, I can tell you that you can try all of the high-tech tricks like Faraday cages and isolation-transformers, and spout Schumann noise equations until you are blue in the face, and you will probably STILL have to live with the quirky noise. Not trying to be a wise-ass, this is just a reality check..... been there/done that.

[Steve Conner]

We are enveloped in a world of noise-producing EMI/RFI shit!

Amen brother!

Sometimes it's not worth even trying to track down those bizarre noises. I have a ham radio license, and I recently tried to set up a HF rig in my apartment. Even if I switched off all the other equipment in my own house, my neighbours' computers and electronic toys made reception on the HF bands pretty much impossible. I gave up.

Guitars are much less sensitive, but they still pick up plenty of crap. A friend was telling me that when he ran a home studio, he was always troubled by his pickups picking up buzz from the computer monitor. His solution was to get EMG pickups. I had the same problem, but I decided to keep my pickups and get a LCD monitor.

[jrfrond]

Amen brother!

Sometimes it's not worth even trying to track down those bizarre noises. I have a ham radio license, and I recently tried to set up a HF rig in my apartment. Even if I switched off all the other equipment in my own house, my neighbours' computers and electronic toys made reception on the HF bands pretty much impossible. I gave up.

Guitars are much less sensitive, but they still pick up plenty of crap. A friend was telling me that when he ran a home studio, he was always troubled by his pickups picking up buzz from the computer monitor. His solution was to get EMG pickups. I had the same problem, but I decided to keep my pickups and get a LCD monitor.

Thank God for LCD TV's and monitors. Talk about making a racket!!! You can be on the other side of a wall from a CRT monitor with a guitar, and still hear harmonics and transients from the horizontal oscillator leaking through. BIG noise generators!

I don't know about the UK and the rest of the world, but electronic equipment in the USA must conform to FCC Part 15 specs. Read up on this here:

Title 47 CFR Part 15 - Wikipedia, the free encyclopedia

My guess is that other countries have regulations in place as well.

This is only the tip of the iceberg. If by some chance you are in a known high RF area (as I am in NYC), you can kiss your noise floor goodbye.

Oh, another source of noise I failed to mention: triac-controlled light dimmers and speed controls.

[David Schwab]

Oh, another source of noise I failed to mention: triac-controlled light dimmers and speed controls.

The WORST!