17 May 2013

Accessories: How to troubleshoot noise in our rig


Noise is a bad beast for a musician. I am not talking about distortion, which we love, I am talking about that noise that seems to ruin our tone from time to time.

I've already know that the key to get rid of noise is a proper ground but, how in the heck can I know if my mains is ok?. How can I check which element is producing that noise, apart from disconnect everything and reconnect everything one at a time?.

I would like to compile here some external articles and videos that will help us to get rid of our noise. To be it was a good thing to discover some easy to use electrical tools to detect such an issues.
I hope this could help you to take control of your own issues.

I am not any kind of expert so, if you find something wrong here, please be kind and let me know it.

Mother Earth

As soon as you start searching information about electrical noise, GROUND (or EARTH) and SHIELDING immediately pop up in your face. Aren't they the same?. Anyway, what they are, at the end?.

Ground or Earth

While in USA this concept is known as Ground, in Europe is usually named Earth but, both concepts are equivalent and mean the same.

What is voltage?.

Voltage is the difference of potential electric energy between two spots in a circuit.
We must understand this: it's a DIFFERENCE and, that means that difference will be the same, whichever the REFERENCE value is.
So, if the expected voltage at spot B is 220V respect of spot A, it means that B - A = 220V and, it doesn't matter if A = 0V or A= 400V, the difference between both spots will be always 220V.

To better understand how it works, let's talk about a better known analogy: Potential Energy.
As soon as you lift any object to any height, that object accumulates potential energy. The higher you lift the object, the more potential energy it accumulates. This "sleeping" energy will be released as kinetic energy as soon as you release the object. The higher the object was lifted, the harder the object will impact the ground.

Voltage is analog to Potential Energy. The higher the difference between two spots in a circuit, the more available potential energy (that the electrical device has available to perform its tasks).

But, in the same way that we refer Height to a reference value (Sea Level, by example), we need a reference spot in electricity. This reference value is Ground (Earth), whichever the real voltage of Earth is.

Ground / Earth

So, how can any kind of device measure that reference value?.
The truth is that Ground or Earth is really that!.
All our (modern) home electrical installations have 3 wires: Live / Neutral and Ground and, all our modern cables / plugs should have same 3 prongs.

The ground wire of our whole home installation should be linked together and, it will end in a metallic rod or post that is inserted in ground so, that wire is in real contact with ground or Earth.

Ground is to electrical safety as Air Bag is to car's safety. Is our Air Bag for most of electrical dangers and, you should take it really seriously. By example, if your amp isn't properly ground and you accidentally touch its metallic frame, you could get a shock.

But ground is more than just an electrical safety trick, ground helps to "throw" to ground electrical noises.
No ground or bad ground equals to noise.

Noise Knight' Shield

What Shielding means?.

Apart of the noises that any device can introduce in the line by itself, this device can catch environmental noises as Radio Frecuency (RF) or Electro-Magnetic Interferences (EMI). We are all surrounded by electrical and magnetic fields everywhere and, some devices or electronics parts are more sensitive to those and can even amplify the loudness of such noises.
Our Noise Knight needs a shield to be protected against such a kind of interferences.

Faraday already discovered that that kind of noises were cought by any conductive surface and, that if you link that surface to ground, noise is being thrown to ground. So, the idea was to enclose any electronics component inside a metallic cage (named Faraday's cage) and, connect such a cage to ground.

You will often see electronics components enclosed in some metallic case that hidden the electronics inside, that case is there to shield the component and, as soon as you connect such a case to a good ground, any potential noise catch by such a case will be thrown to ground, leaving your signal clear.

We shield the guitar's electronic cavity to enclose all our electronics components inside a cage that will get rid of that kind of noises, as soon as we properly ground it. For that we need a true closed cage (walls and tap covered with some conductive surface and linked to ground).

The pot's case is a Faraday's case. The metallic foil inside cables, surrounding the signal conductor is a Faraday's cage. The shielded conductor that outputs our old humbuckers is a Faraday's cage. The Pickup's cover (soldered to the metallic plate that supports pickup components) is a Faraday's cage (and a good reason to use metallic covers in pickups).

All these elements help to control such a noise. Any hole there and, you can potentially start having noise issues (depending on the RF and EMI "contamination" of your environment).
We know that some fluorescent lights, mobiles, etc. introduce noises.

But we aware of this: you can have a perfect Faraday's cage but, if you don't connect it to ground, the noise will be not dampened to ground.

Ground Loops

Even if you have anything properly shielded and correctly grounded, you can still have noise due to Ground Loops.

What a ground loop is?.

A ground loop can happen every time you have a signal's ground connected to two devices that are ground in different plugs. By example, you route your guitar signal thru an ABY box to two amps and, each amp is being plugged to a different wall socket.
The ground in your signal's cable tries to choose between the two grounds provided by both amps, which compete for ground.
I bet (but I don't know it for sure) that noise comes because those two different ground spots haven't exactly the same voltage (reference value).

Ground Quality

Not, man, we are not talking here if ground is good for potatoes or rice.

As everything is being connected to ground and all noises are thrown to ground it is possible that some of the noises that our neighbor is throwing to ground can be induced in our own ground.
I think (but I don't know it for sure) that this could happen because the ground voltage can be different at each spot where you measure it.
Anyway, sometimes some engines connected to the electrical line where you and your neighbor are linked can induce engine noises in your home's main.
This can be named a bad ground and, can ruin all the effort you've put to properly shield and ground your gear.

I think that, even in your own home, this kind of situation can happen, what talks also about the bad quality of your ground network.

Weapons for our Noise Knight

Ok we can more or less understand what we discussed above and make our best to have it all controlled but, in case we did everything we could and we still have noise, how do we know what's wrong?.
And, once we identified what's wrong, how can we fix it?.

Let concentrate now in our guitarist hear, to get the picture.

We have a rod inserted in ground and, linked to a ground wire network that reaches our wall socket, ready to link our devices to such a ground.
We plug our amp in such a socket and, it's being ground (it's own ground network is being physically put in contact with our home ground rod).
We plug our guitar to such an amp and, all our guitar's ground network is connected to amp's ground network that is connected to our home ground.
If we insert pedals, same should happen with all them.
If we use AC/DC transformers to supply our pedals, those should follow same rules.

Ok. Theoretically, we have everything rightly shielded and grounded so... why do we still get noise there?.

Firstly, we should be clear that our rig generates it's own noise so, there is some noise types and levels that can be understood as "regular noise".

By example, pickup's coils are responsible for generating our signal but, they introduce their own floor noise.
Humbuckers were designed to remove such a noise and, they do it at a certain level. To effectively cancel the noise both coils of a humbucker should be exact clones. But, for sure, the floor noise of any humbucker is usually way lower than the floor noise in a true single coil pickup.

Amps are generating their own noise. Each electronic component can add its own noise. It's well known that carbon resistors are really noisy (but, they seem to provide the most musical signal in a tube amp!!!). It's also well known that tubes create their own noise (hisses, pops, cracks, ...). At the end, the amp with nothing plugged there could present some "regular operating noise". It can sound quiet while volume and gain controls are low but, it could be clearly heard when you rise any or both controls.

Since the signal level of our guitar is really weak, we are amplifying its level with the help of several gain stages. After each gain stage, the original signal level was raised and, together with the "good things", the floor noise level that was present before the gain stage is being raised in the same ratio.

Each pedal effect introduces its own noises also and, very specially, modulation or filter effects. Any gain pedal pushes up the existing floor noise.

So, we have to take into consideration all this and be conscious that our rig will have certain "regular operating floor noise", that will depend on the sum of all those noises and how much were they pushed up by our several gain stages.

Checking sockets

If you have not "regular operating floor noise" but higher noise than expected, it's a good thing to firstly check your sockets, where you plug your gear. And, we aren't talking just about wall sockets, we are also talking about the socket of any extension cable or extension sockets.

Sometimes, you buy some sockets extension rule apparently ready for Line / Neutral / Ground but then, they've didn't used a three-wires cables and that ground is just a fake!.

Sometimes, someone forgot to link that ground wire in your wall socket or, someone wired the three wires in a wrong way.

Fortunately, we have some Socket Testers. Relatively cheap devices that, once plugged in the socket we want to check, they inform us about any kind of issue with the help of three led lights.

This will help us to identify if our gear was plugged to a right wall socket, a right extension cable or rule of sockets, etc. Due to the electrical shock risk, it's is highly recommended to have it one ready at any time to check the sockets where you have to plug your rig (home, studio, gigs...).
Remember, a properly ground rig isn't just safe, it makes your sound better.

Check additional info section at the end.

Checking low voltages

There are some tools named Low Voltage Testers that help us to identify the presence of low voltage electricity in our rig. This helps to trace back which spot in our rig is the one that introduces noise in our signal (it can be just a mains cord over a guitar cable, inducing current).

Check additional info section at the end.

Each illness has it's own medicine

We already discussed most of the ways noise can be present in our rig. Some are easier to control by us, some are harder.

Start with source: our guitar

The best shielded you have your guitar, the best possibilities to get rid of environmental noises you will have.
A proper shielded guitar cavity can do very good things for you. Use conductive paint in wall and some metallic conductive-auto-adhesive foils to cover your pickguard or cavity's tap.

Don't forget that this Faraday's cage should be connected to your guitar's ground network.
If you have a pot lying over the shielded pickguard or shielded cavity and, the case of such a pot is linked to your jack's sleeve, don't worry, your Faraday's cage will ground (as soon as your amp is ground).

Remember that covered humbuckers will produce the lower floor noise of all pickup types. Maybe your guitar looks sexier without pickup covers and, maybe the sound is a bit duller with covers but, if noise is what worries you, this is just one more thing to take into account.

Any cable that runs outside your electronics cavity, by example, from pots to 3-way switch in Gibson's Les Paul or, from cavity to jack, should be a shielded conductor (solder signal to jack's tip and shield -that metallic jacket- to jack's sleeve), while inside the cavity, you don't need shielded wires (because they are protected by your Faraday's cage).

Remember that single coils will present a higher level of noise than any humbucker (covered or uncovered).
There are single coils that have a stacked dummy coil just to cancel hum but, as you already know this affects the tone.

Second step: our guitar cords

Many people thinks that cables make no difference and, if they do some, it's just a capacitance issue that can be solved with the help of a buffer.
In my previous entry What is a good guitar cable? I've already discussed about the differences between guitar cables and, what should be considered when choosing one or the other.

It's a fact that not all cables have same shielding ratio and quality and, some go microphonics. A cable is (know what?) a Faraday's cage also so, the better the shield the purest the signal.

Be sure your cables have no issues (sometimes, are broken in some part of their length introducing intermittent noises). Hit the cable with something (a screwdriver or whatever) to check if the sound is clearly audible in your amp, to check if your cable has microphonic issues.

Be sure your patch cords, that you use for your pedals, are also of quality and are free of issues.

Third step: our amp

With a low gain/volume level and no guitar plugged, the amp should present no noise when plugged to the wall socket, if ground is correct. When raising gain/volume controls the operational floor noise of the amp will be heard but, it should be a reasonable operational noise.

If you are using some extension cable to plug your amp, maybe your wall socket is correctly ground but your extension isn't so, check everything.

Forth step: our AC/DC transformers and Power Suppliers

To avoid having to substituting dying batteries in our pedals and, be in the situation where we loose our effect in the middle of a gig, we often use some Power Supply Unit to feed our pedal effects, what's nice.
But, not all those kind of transformers are made in the same way and some can be a source of noise.

By example, those power supply units can have a two-prongs plugs to connect them to electricity, while others will correctly use 3-prongs plugs. We've already discussed about ground issues a lot, right?.
Think that the ground of your guitar, pedals and amp are connected also to that... wait... no ground! of that power supply or transformer.

Also, some Power Suppliers will have a toroidal (or other) transformer inside that will physically de-couple your mains ground from the rest of grounds, what helps to filter some ground induced noises, while preserving a "virtual" (induced) link between both grounds.
Those, usually have isolated outputs, that have that "virtual" link between output sockets but that ensure that the issues in one socket (pedal effect) doesn't affect the rest of outputs.
A good example is this kind of Power Supply Unit is the Voodoo Lab Pedal Power 2 Plus, highly recommended.

Five step: a Noise Gate

If we still find that our floor noise is unacceptable, we have one of the most detested solutions for a guitarist: to use a Noise Gate in our pedal chain.

A Noise Gate works the opposite to a Compressor. You set up the threshold for the acceptable minimum signal level or maximum noise level and, whatever signal below that threshold will be pushed down to practically zero value. This gets rid of the noise, indeed, but often cuts the tail of our sound and, our softer parts are compromised, as well as our dynamics.

In my tests, there is just one single Noise Gate that works practically pefect: the ISP Decimator G-String. Even the regular ISP Decimator cannot work as good as the G-String version.

If you cannot solve your issues in other way, maybe this will help you but, consider that your dynamics and sound can be compromised.

Line issues

Until here, we were taking care of the noises that our rig can introduce but, there are other noises that can be introduced by the mains lines also.

As we saw, first is a good thing to check all sockets, for a proper installation and to be sure that they are grounded.
We can also check the low voltage issues with the help of that Low Voltage Tester with discussed above.
Then, what to do with other induced noises?.

This is the hardest part and the expensive one. In the worst case, we will need Filtering Units to filter the noise in our mains but, we can still test some cheaper options before.

There are cheap Power Conditioner units that help to protect our rig from mains anomalies and that include some filters (RF, EMI and others). A cheap unit is the Phonics 9000E, by example. The better the filters, the less the noise so, the expansive the unit (like the well established Furman's Power Conditioners line).

A Power / Voltage / Tension Regulator can help also here in several ways. Those devices are accepting a broad range of input voltages (by example from 120V to 260V for a 220V nominal line) but, delivering a barely constant voltage level (220 +/- x%).
This is actually one of my main issues, since I'm getting readings that go from 185V to 237V in just the space of a minute!.
A constant voltage will make your rig to sound in the way it was designed for and, will keep your components in the right voltage levels for which they were designed to operate.
Those units often include protection and filtering and, often, a ground-decoupling via some transformed. Everything together helps to "clean" your lines.

An UPS is some kind of Voltage Regulator with the additional help of use a battery in case of a mains failure, that will provide you of energy for a certain amount of time. Same comments as per Voltage Regulators apply here.

For any of those devices, you should check your power needs, calculating the maximum power that you will need for your complete rig: amp + pedals + power suppliers + whatever.

If your amp's mains plug operates at 220V and drains 3A, your amp can potentially consume 220V * 3A = 660W (maybe just to deliver 50W RMS at its output!).
If your pedal power supply operates at 220V and drains a maximum of 450mA it can potentially consume 220V * 0.450A =  99W.
So, sum up everything together to be sure you get the right device for your needs.

In some studios, were the quality of audio is of even higher importance, there are specific filter units that get rid of noises that occur at certain frequency ranges and, that cannot be solved with that "regular" equipment we discussed above. Those are out of any regular pocket, sure.

Additional Info

As I stated in the beginning, I am not expert in such a kind of things so, I wanted to share with you what some more knowledgeable people says about this topics.

All you wanted to know about guitar' shielding and grounding was clearly discussed by uOpt, a member of Seymour Duncan's forum, in this thread:

Catalog of Shields and Grounds in an Electric Guitar

I cannot add anything else!.

All we've already discussed about grounds, ground loops, socket and low voltage testers can be found (it's were I've learnt it from) in Taylor Guitar's Youtube videos.
These are PURE GOLD videos. Watch and hear them, your spent time will be rewarded!.

I highly hope all this information can help you to get rid of your noise, in the way it helped me.
At least, I am way clearer about what to check!.

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