MC208
New member
Hmm ok, so what is the solution to the hum caused by letting go of the strings? I know the setup in the instrument is correct. I was told the noise comes from high voltage power lines nearby.
TalismanRich
Well-known member
You can get noise through the air with a guitar. Fluorescent lights, digital equipment, transformers, light dimmers can all induce noise that is picked up by a guitar. I can move my guitar around the basement and get more or less noise. That's one reason humbuckers were invented! Single coils are more susceptible to picking up noise. When you touch the strings you can become a shield to some induced noise. Better shielding in the guitar can help a lot. Lots of high end guitars have shielding paint in the pickup and the pots/caps cavities. A shielded pickguard can help quiet a strat or tele. Shields should always be connected to ground.
In no case do you want to use yourself as the path to ground. If there is a poor ground setup in the amp, you can become the path for the electricity to travel. NOT GOOD!
I remember back in the late 60s/early 70s when there were no grounded plugs, just two wire nonpolarized plugs. Amps had capacitors on the power lines. These later were called "death caps" because if they failed, they could put mains level voltage on the ground line.
Many amps had a polarity switch, which would swap the power and ground lines. If your amp and your PA had them switched in opposite directions, and your mouth hit your mic while you held your guitar it could flat out light you up! It was worse than putting a fresh 9 volt battery to your tongue. My Guild Thunderbird amp has both a polarity switch and a "hum balance" which has a pot and capacitor. I learned to walk up to my mic and tap it with my finger.
In no case do you want to use yourself as the path to ground. If there is a poor ground setup in the amp, you can become the path for the electricity to travel. NOT GOOD!
I remember back in the late 60s/early 70s when there were no grounded plugs, just two wire nonpolarized plugs. Amps had capacitors on the power lines. These later were called "death caps" because if they failed, they could put mains level voltage on the ground line.
Many amps had a polarity switch, which would swap the power and ground lines. If your amp and your PA had them switched in opposite directions, and your mouth hit your mic while you held your guitar it could flat out light you up! It was worse than putting a fresh 9 volt battery to your tongue. My Guild Thunderbird amp has both a polarity switch and a "hum balance" which has a pot and capacitor. I learned to walk up to my mic and tap it with my finger.
E
ecc83
Well-known member
The fact is friend, guitars and their amplifiers have ALWAYS* been noisy Bs! The amps themselves were often not that well designed for low noise and as ' rock n roll' moved into ever more high gain, distorted sounds this got worse. But, noisy as a 100W amp was, once you hit the strings the headroom was SO immense that the "Signal to Noise Ratio" was in fact pretty good. The drummer had deafened everybody anyway!
The coming of home recording changed all that. That hissy, hummy monster was now a bloody nuisance! As Rich says, single coil pups don't help, all you can really do is orientate the guitar for minimum hum, also check it has cavity screening. Now you can buy an interface with a 100dBFS noise floor for the cost of a decent single malt we want the rest of the kit to be AS quiet. Power soaks can help as can noise gates post tracking.
*The likes of Chas Cristian and Les Paul had access to top amp techs of the day to make quiet amps. They were not in any case into 120dB SPLs nor distortion and Paul was a top engineer in his own right. I am gratified that I was involved in some small way with the development of guitar amps with decent S/N ratios. Say what you like about the "Blackstar Sound" the designs were quiet! I will state that the HT-5 has the best S/N figure of any guitar amp on the planet.
Dave.
Papanate
Well-known member
I have ISO transformers on my electrical feeds to my room - have for years - amps and just about everything are dead quiet - I used to use a similar system live and it work work very well - but I remember the days of my Hiwatts (which were relatively quiet) and pedals - thank god drummers are loud!
E
ecc83
Well-known member
ISO transformers? Do you mean balanced mains supplies? Probably not so bad when it is about 55V above earth but over here such gear constitutes a big hazard to service personnel who may not realized that even though a mains fuse has popped, one side it still at 115V ref earth.
In fact it is hard to find an isolating transformer here with a centre tapped 230V secondary. There is I understand special provision made for certain medical and scientific uses? You would have to go to a specialized (AKA expensive!) supplier for that.
We do have 110V tools for use on outdoor sites with 55-0-55v traffs, tap to earth.
Dave.
Papanate
Well-known member
I use Isolation transformers and Balance Power for the incoming power - it is a silent system completely insulated from any external noise, glitches , appliances etc….and my amps respond according - some of my older amps run at less than 120 - my Hiwatts run and sound best at 105 volts - so I have a few stepdown devices - when the amps get the correct voltage they perform smooth as silk -
rob aylestone
Moderator
That's interesting - virtually unheard of in the UK. Every house has their mains come in and then goes to the sockets and appliances - we don't use transformers in domestic properties.
MC208
New member
"I can move my guitar around the basement and get more or less noise"
Yes, same here! Unfortunately, the exact position that the guitarist needs to be, due to filming, in is where the noise occurs. The guitar is a hollow body archtop, and it does have a humbucker. We're not using an amp, we're going direct into the mixer's Hi-Z input. The only thing that has worked to help (not eliminate) the hum, is the wire in the sock trick...
Yes, same here! Unfortunately, the exact position that the guitarist needs to be, due to filming, in is where the noise occurs. The guitar is a hollow body archtop, and it does have a humbucker. We're not using an amp, we're going direct into the mixer's Hi-Z input. The only thing that has worked to help (not eliminate) the hum, is the wire in the sock trick...
Papanate
Well-known member
I just have it in my Studio Room - I had a 80amp service wired just to my room - straight from the breaker box.
TalismanRich
Well-known member
If the noise changes as you move around, electromagnetic interference is the root problem. You have two choices, eliminate the interference or shield the guitar. Move the guitar around until you find where the interference is coming from and address that. When the noise get loud, that's your clue!
MC208
New member
Yeah I guess we're stuck with the noise then, sucks!
R
RFR
Well-known member
You could always install EMG pickups. No string ground required and they are noiseless.
(not recommending or endorsing. Just another option)
E
ecc83
Well-known member
Well, hang on! How bad is it? Post a clip* of guitar at -20 dBFS average oriented for minimum hum then damp the stings for say 20 seconds. If your noise floor is better than -70dBFS I would say you are doing pretty well. If significantly worse than neg 70 then you need to investigate noise gates and post tracking software.
There are two ways mains noise gets into the guitar. The primary cause is electro-MAGNETIC coupling. Your pickups become in effect the secondary of a huge AC transformer! There is little you can do about that. Mic transformers can be completely enclosed in "mu metal" which can effect 30dB+ of hum reduction but of course, a totally enclosed git pup would pickup FA! No, humbuckers are the answer there.
A lesser, secondary effect is electro-STATIC coupling and can be virtually eliminated by screening the pup cavity NOT forgetting the back of the scratchpalte.
*An MP3 clip at the best rate 320kHz is the most useful form for me (.wav would be better but we can't have that)
Dave.
MC208
New member
I don't have a clip to post, but I believe the noise is around -40 on the meter. I do use a noise gate, but it's only helpful when the guitar isn't being played. The guitar is usually an archtop hollow body, with Kent Armstrong high quality humbucker pickup. I know the noise is interference because if we move him around, face another direction, it goes away. Problem is it's a video studio, and he kind of needs to be where he is, and oriented in the direction that he is, that just happens to be where the noise comes in.