Noise when I'm not grounded?

[exztinct01]

I built a fuzz face using PNP silicon transistors in positive ground configuration. I understand that fuzz pedals are really noisy and I'm using a telecaster copy with two single coils.
Now, I noticed that when I'm touching the strings and feet's on the floor, there's one kind of noise that's being reduced (don't know what that noise is). Now when I remove my hands on the metals of the guitar, or lift my feet up, that noise amplifies.
What should I do?

[PRR]

Feet on floor?

Your amp is not grounded. This is bad.

Finger on strings... strings should be grounded in the guitar's wiring.

You never get rid of the magnetic hum, unless you play in the woods on battery. But these steps should eliminate electrostatic hum/buzz.

[exztinct01]

we only use two prong wiring here, so we actually don't connect our electronic devices to the "real" ground. It's always floating. Is there any other solution?

[GibsonGM]

we only use two prong wiring here, so we actually don't connect our electronic devices to the "real" ground. It's always floating. Is there any other solution?

Where are you, Stephen?  And is "here" your whole country, or just your house?

[R.G.]

Preceeding replies are correct, including the question from GibsonGM.

Does your amp have a three-prong AC line cord end, or only a two-prong?

What's happening is that the AC line itself in most countries/places has one of the AC power lines ("neutral") attached to earth ground back in the wiring of the building, and the other power line swinging above and below it. Early two-wire amps connected the amplifier chassis (and signal ground, which is then connected to YOU by the signal cables) to the "neutral" AC power wire with a big capacitor. This prevented some ugliness, like picking up radio stations, but introduced the issue that the amplifier has more hum with the amplifier power cord plugged in one way round than the other.

If it hums more when you touch the strings and less when you touch them, YOU are "grounding" the hum voltage on the chassis. In this case, try flipping the AC power cord plug 180 degrees in the wall plug. It ought to get less. Not zero, but less.

It's possible to make an amp much, much quieter by using a three-wire AC cord grounding system if your AC mains setup allows you to use it. The third wire is connected to the chassis and signal grounds, and drains off the power-line-frequency leakage that is making your hum.

[pappasmurfsharem]

Preceeding replies are correct, including the question from GibsonGM.

Does your amp have a three-prong AC line cord end, or only a two-prong?

What's happening is that the AC line itself in most countries/places has one of the AC power lines ("neutral") attached to earth ground back in the wiring of the building, and the other power line swinging above and below it. Early two-wire amps connected the amplifier chassis (and signal ground, which is then connected to YOU by the signal cables) to the "neutral" AC power wire with a big capacitor. This prevented some ugliness, like picking up radio stations, but introduced the issue that the amplifier has more hum with the amplifier power cord plugged in one way round than the other.

If it hums more when you touch the strings and less when you touch them, YOU are "grounding" the hum voltage on the chassis. In this case, try flipping the AC power cord plug 180 degrees in the wall plug. It ought to get less. Not zero, but less.

It's possible to make an amp much, much quieter by using a three-wire AC cord grounding system if your AC mains setup allows you to use it. The third wire is connected to the chassis and signal grounds, and drains off the power-line-frequency leakage that is making your hum.

If his house doesn't have that 3prong , could he run a wire from the chassis to earth?

[R.G.]

If his house doesn't have that 3prong , could he run a wire from the chassis to earth?

Yes - but...

Hard-wiring metal things you're going to touch to earth when the power lines are not themselves hard-wired to earth reference in some way is a prescription for getting electrocuted in some unusual but possible scenarios. It might be a useful technique if he had, for instance, a studio in one room that he set up for the process and modified all the equipment to be hard wired, etc. It's a positive danger when you play with YOUR chassis grounded and some other equipment, like PA (microphone...) or other guitars not hard-wired ground. There can easily be leakage from the other equipment through no fault of yours, but you have made a solid, low-resistance ground from your sweaty hand through the strings and cord to the amp chassis, and now if you hold that and touch the unground other stuff, you're -  um, toast.   

Guitarists have died this way, no fooling. That's why the question of "my microphone shocks me when I play" was encountered so often a few years ago.

It's better in countries where third wire grounding has been set up and in use for some decades because the older equipment has slowly been discarded or in the case of guitar amps changed over to third-wire ground.

This whole issue is also tied to the "death cap" line reverse switch, which connects a high-voltage cap from the chassis to one of the two AC lines and lets you "reverse" the line by flipping the switch. This kind of works, but if the cap shorts and you flip it the wrong way, you're tied to the hot side of the AC line through the strings and you now get shocked touching anything that is solidly grounded.

This is a complex issue that was solved with a sledge hammer in the USA by the national electical code: new buildings are *required* to have three-wire outlets, and although it's not required by law, all new equipment that passes safety standards by UL, IEC, CSA, etc.  that have only two wires have to pass more stringent insulation standards to ensure that any single fault in the equipment doesn't let it become live to the AC line.

It's a problem with boutique amps, too, because clever boy geniuses (genii?) may make good amps by tinkering, but they may not understand safe wiring. I've peered into the back of boutique amps at guitar shows, shuddered, and just had to walk away.

[PRR]

> Where are you, Stephen?

Location is in his Profile (click his name).

"Philippines"

I suspect the Philippines' long geography and history allows many local variations. Most sites suggest A and B plugs, US-like 2-blade and 3-blade/pin connectors (however fed 220V instead of 120V!). One site suggests Schuko can also be found. (Not stated if this is grounding Schuko.)

The 3-pin forms allow for apparently proper amplifier anti-buzz grounding. (But as in my old kitchen, the electrician can wire the wall outlets more wrong than right.)

Connection to "earth" (dirt) is just wrong, and may be unsafe.

The real issue:

"All" utility power systems are connected to dirt somewhere. The main reason is to absorb lightning strikes. A second reason is to limit the maximum voltage which a person standing on ground may be exposed to.

Assume 120V AC power.

So inside a room with electric power, everything is exposed to electric fields from both power wire. One is generally near-"zero" (ground), the other is generally 120V away from ground. The average is 60V, AC, a low audio tone. (In a 220V land it would be 110V.) This voltage couples "through the air". You can't measure it with a volt meter. Most circuits "suck up" this coupling. However if even 1% of the 60V gets onto a wire, that is 0.6V. Guitar signals are about this size (usually smaller).

It helps a LOT to enclose sensitive audio points in metal. Chassis, shielded wire. It helps a lot more if that metal is "connected" to the low side of the room's power wiring, to drain the small coupled current away.

However with 2-pin plugs (old US or Schuko) it is not clear which side is "low".

And if you direct connect the chassis and shield to the high side, then touch dirt, concrete, plumbing, or other electrical devices, you get a full voltage shock, which has been lethal.

We actually do not need a great connection, only enough to drain small hum voltage. In the bad old days, US guitar amps connected a 0.05ufd cap to one side of the line. Done right, hum may be lower. Done wrong, you get a shock, but based on limited data this shock was not considered very fatal. (The real danger on "death-cap" amps is that the caps were under-rated, soon failed, often SHORT. Now you just sticking your finger in the hot hole.)

Without visiting the Philippines, I would suggest looking for 3-pin outlets. I would also look for "3 pin testers" in the hardware store. That U-hole might not really be connected to anything. Even the testers can be fooled.

If no 3-pin outlets are available, it gets tough. I have survived many "death cap" shocks but my luck will run out, so I would not advise that cheap trick.

[GibsonGM]

What about an isolation transformer?  Not perfect, but if one could determine their current needs, couldn't one be set up to provide at least SOME modicum of safety and/or isolation?

Altho, I guess any amp worth anything is drawing a lot more than 30mA, LOL....which certainly can be fatal.  Just thinking that you could gain:

1) knowledge about where the hot is going and
2) SOME limit to how much current you'll get at full voltage before sagging off, perhaps using this to the advantage of causing a fuse to blow before YOU take 100's of mA....


If the chassis can be determined to NOT ever be able to go hot thru any normal and reasonable activity, perhaps more insulation in the right places can make the thing safe?

[PRR]

> make the thing safe?

Notice the OP is asking about hum/buzz, NOT "safe".

With ambiguous electric outlets, there's no good answer.

[R.G.]

Believe it or not, I was actually trying to be brief, in spite of how long that ran.   

There is a deep well of stories and advice on how to get quiet and safe AC power. Studios go fairly nuts about this, and with good reason. Center tapped isolation transformers for "balanced power" were all the rage for a while, don't know if it still is.

A really ugly set of circumstances can get you when playing in venues that run from generators. Unless these are set up right and grounded properly, very strange circumstances can occur.

Back at the OP's question, it gets important to distinguish real hum (AC power line frequency) from power supply ripple (usually 2x power line frequency) from power line buzz, which is a higher pitched set of transients that happen to occur every power-line-time. Generally the buzz is RF.

[amptramp]

If you are running on a 115 VAC system, this is usually delivered as 115 - 0 - 115 where you have two phases with the centre tap grounded.  If you end up with your guitar amplifier coupled to the 115 on one side, the microphone amplifier may be coupled to the 115 VAC on the opposite side so you could get across 230 VAC.  That could be more than just a problem, that could be your final problem.

[exztinct01]

common electrical system here in the Philippines uses two prong (one hot and one neutral connected to earth via circuit breaker box).
And yes, only problem is we don't know which one of the outlet holes is hot, or which is not. I never really had much interest in electrical system until I started building electronic devices, which would be last year.
Anyway, we do have some three-prong here in our house, those outlets designed for use with air conditioners.
But, if I hardwire my chassis to signal ground, I don't think this will ever be safe when I use it away from home.

[Hatredman]

We had the same problem in Brazil, though now a new 3 prong plug model is being enforced by law. Many musicians died in Brazil because of that, including famous ones.

Guitarists here often carry cables with alligator clips in their guitar cases to connect the amp chassis to the mike stand. If it's not possible to do it, they connect the bridge of the guitar to their bellies and the hum is gone.

Enviado do olho da rua da amargura.

[R.G.]

There is a mod for guitars that may prevent electrocution. The bridge on most guitars is connected to the signal ground on the knobs and jack by a wire, to lessen hum. That's how you get "grounded" by the strings. The mod is to cut that wire and insert a resistor of about 220K, paralleled by a 0.01uF capacitor. The resistor ensures zero DC voltage on the strings, and the capacitor "grounds" you for RF purposes. But at power line frequencies, a 0.01uF cap has an impedance of 265K, so the cap/resistor combination lets through very little current. So you're "grounded" for the RF buzz, but not enough power line AC will flow to kill you.

... unless you happen to grab the mike stand and your guitar cord's metal/grounded plug at the same time. Still a better bet than the strings being solid grounded.

[exztinct01]

If there is no real grounding, is there any benefit of shielding?

[R.G.]

The intellectual water starts getting deeper here.   

Interference comes in magnetic field, electric field, and at higher frequencies, electromagnetic fields/radiation - radio. Grounding helps prevent two forms of this, electric field (that is, AC line leakage) and radio. Anything inside a completely surrounding, perfectly conducting box cannot have any external fields get in, so shielding by a Faraday cage (that's what this is) is very good, whether the cage is grounded or not.

But no cage/shield is perfect, so it helps at very low frequencies to ground the cage. At high frequencies, the cage needs to be either nearly seamless, no openings any bigger than 1/4 wavelength of the signal being excluded, or grounded through low inductance connections. Things just get different with different frequencies.

So yes, you still need to shield to cut down AC electrical field hum, and RF pickup; not getting an earth ground just means that the shielding is less effective than it would otherwise be.

As an aside, magnetic fields at low frequencies are very, very, very difficult to shield. Different animal altogether.

[exztinct01]

ahh, got it 
Honestly, my setup has so many different kinds of noises.
One is that which is lost when I become a path to ground, it's a noise (buzz) which is present even when my guitar's volume is turned down completely.
Another is which amplifies when I actually touch the string, it's a hiss I think but only present when my guitar's volume is up. I just don't remember if it's present only when my fuzz is on or not.
There's more but I can't identify them anymore.
I'll deal first with the first noise I mentioned. 

[PRR]

> Guitarists here often carry cables with alligator clips

If you are going to do that, put this:

> resistor of about 220K, paralleled by a 0.01uF capacitor

-in the cable.

A zero Ohm jumper can unleash infinite current, bad for you and the electronics.

A few hundred K of impedance, especially dropping at high frequencies (capacitor), will divert most voltages induced "through the air" (many hundred K ohms) and ear-obvious high harmonics, without passing too-dangerous current at power frequency (50Hz).

But I deny all responsibility for your death, or even nerve-damage.

[mac]

...But no cage/shield is perfect...

https://arxiv.org/pdf/1112.5495.pdf

Teacher is assuming that in a metal j = s.E
I did those experiments using cookware and my cell phone and pocket radio sounded. I had to put one cookware into another to block signals.
Never tried with a 1590...
Different materials, different penetration factors.

mac