EMI?? - noise disappears when touching strings

rickenbacker198

rickenbacker198

Active member
All my outlets / amps and guitars act the same .. noise when not touching the strings.

Anyone ever have an EMI issue in their house ?
I’m guessing that’s what this is….

We don’t have any dimmers, I know from experience they can be horrible for noise
I’ve killed everything in the house but the main panel and I still get noise.
No power station near us - buried lines - no local transformers.

Anyone ever have someone come out and look into an issue like this ?
 
rickenbacker198 said:
All my outlets / amps and guitars act the same .. noise when not touching the strings.

Anyone ever have an EMI issue in their house ?
I’m guessing that’s what this is….

We don’t have any dimmers, I know from experience they can be horrible for noise
I’ve killed everything in the house but the main panel and I still get noise.
No power station near us - buried lines - no local transformers.

Anyone ever have someone come out and look into an issue like this ?
Click to expand...
How old is the house?
 
What amp? I assume you are referring to a buzz when you stop playing with the volume up on your guitar? If it were me, I would check my amp's first preamp stages grid resistors. I had this issue and found my amp had a very low value grid resistor on the input stage. I upped it to 27k and added 10'ks on the next two stages. The buzz is gone. Buzz like this is hitting your first stage grid.
 
glip22 said:
What amp? I assume you are referring to a buzz when you stop playing with the volume up on your guitar? If it were me, I would check my amp's first preamp stages grid resistors. I had this issue and found my amp had a very low value grid resistor on the input stage. I upped it to 27k and added 10'ks on the next two stages. The buzz is gone. Buzz like this is hitting your first stage grid.
Click to expand...
I use 7.5k on every grid for RF stability. Commonly ignored and overlooked, it also adds some tube bias stability when they’re biased electrically hot.
 
Every amp does it.. really seems to be coming in through the pickups.,, but hopefully it’s the ground , that would be likely easier to deal with.
 
rickenbacker198 said:
Every amp does it.. really seems to be coming in through the pickups.,, but hopefully it’s the ground , that would be likely easier to deal with.
Click to expand...
Likely not ground, that is for things like lightening and safety. More likely a problem with the neutral in your home or a wiring issue…

Have you physically moved the amp and your guitar to a different room and outlet to see what happens?
 
glip22 said:
What amp? I assume you are referring to a buzz when you stop playing with the volume up on your guitar? If it were me, I would check my amp's first preamp stages grid resistors. I had this issue and found my amp had a very low value grid resistor on the input stage. I upped it to 27k and added 10'ks on the next two stages. The buzz is gone. Buzz like this is hitting your first stage grid.
Click to expand...

What value was in there before you upped it to 27K? I recently experimented with grid stoppers in my Bogner Helios. It normally doesn't have one on V1. Lots of radio coming in. So I tried 33K, 27K, 15K, 10K, 5K7, 2K7, and 1K2. I went as low as could before I heard radio show up again. 2K7 kinda worked. But I could hear radio with amp really cranked, so I went up to 5K7.
 
FourT6and2 said:
What value was in there before you upped it to 27K? I recently experimented with grid stoppers in my Bogner Helios. It normally doesn't have one on V1. Lots of radio coming in. So I tried 33K, 27K, 15K, 10K, 5K7, 2K7, and 1K2. I went as low as could before I heard radio show up again. 2K7 kinda worked. But I could hear radio with amp really cranked, so I went up to 5K7.
Click to expand...
It had a 6.8k. I think you lose highs going with higher values.
 
FourT6and2 said:
Yup, you do. The math says it shouldn't be audible, but I tried it and I could hear a difference so I went as low as I could.
Click to expand...
I agree 100% Also resistor type makes a difference. Carbon comps might be best but they add noise. I prefer to use old Carbon film like Piher if you can find them. I also feel each amp is different. When I stop playing and mute my strings I prefer the least amount of noise. I have to play around a little more with this amp and lower my first stage from 27 to 10K and see how it reacts to the input buzz on the grid.
 
FourT6and2 said:
Yup, you do. The math says it shouldn't be audible, but I tried it and I could hear a difference so I went as low as I could.
Click to expand...

I think on my 5152 I run a 10k.

On my 74 I run the stock 68k and I make up for it with little or no plate bypass caps. I have no problem setting it to cut my head off if I want to lol

The high end that I get from a smaller first stage grid stopper isn’t something I normally want that early in the stages.
 
glpg80 said:
Likely not ground, that is for things like lightening and safety. More likely a problem with the neutral in your home or a wiring issue…

Have you physically moved the amp and your guitar to a different room and outlet to see what happens
Click to expand...
I've tried most of the outlets in the house and tried shutting everything down - all breakers but the one the amp is plugged into off- even running to the outlet beside the panel - noise is still there.
 
glpg80 said:
I think on my 5152 I run a 10k.

On my 74 I run the stock 68k and I make up for it with little or no plate bypass caps. I have no problem setting it to cut my head off if I want to lol

The high end that I get from a smaller first stage grid stopper isn’t something I normally want that early in the stages.
Click to expand...

Well the amp I installed one on was intentionally designed without one. But it's just too damn noisy. So a normal value grid stopper did affect the feel/sound of the amp negatively, IMO. If I were building an amp from scratch, I would just shape the tone with a grid stopper in mind.
 
FourT6and2 said:
Well the amp I installed one on was intentionally designed without one. But it's just too damn noisy. So a normal value grid stopper did affect the feel/sound of the amp negatively, IMO. If I were building an amp from scratch, I would just shape the tone with a grid stopper in mind.
Click to expand...
That’s basically what I did, I voiced around a stock grid stopper on the front end. It makes such a drastic change in the amp that I personally couldn’t reduce my value now without an avalanche of changes I’d have to make further down the circuit to control Vpp amplitudes and voicing. Basically I’d recommend others pick a value you like earlier in the design and planning phase and stick with it.
 
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