Ground observation

[RVA]

I recently decided to try a cable instead of my Line 6 G30 wireless, which I have been using the last few years, mostly because the G30 is failing and I am not sure I will replace it. Here is what happened.

When using the cable, my LP Special would hum upon touching the strings & bridge, an obvious ground issue. However, I had not realized it before because the active wireless system suppressed it. I verified this by going back and forth and using different cables.

After re-soldering all my grounds, the Pure Tone output jack was all that was left to check, and touching the metal sleeve of the cable would suppress the hum. Swapping out the Pure Tone jack to a Switchcraft cleared the issue. I do no see anything obviously wrong with the Pure Tone, but I will do some testing later

 

[Inspector #20]

Never had a problem with the Pure Tones...

 

[RVA]

Never had a problem with the Pure Tones...

Me either. I will check it over

 

[RVA]

I cannot detect any shorts. I will re-install it on the next project and see what happens

 

[chilipeppermaniac]

Good Luck Ray

 

[syscokid]

I cannot detect any shorts. I will re-install it on the next project and see what happens

Vewy intewesting mystewy...

Do you have another Pure Tone jack to compare with the first PT jack?

 

[RVA]

Vewy intewesting mystewy...

Do you have another Pure Tone jack to compare with the first PT jack?

I do have a stash of them. My first approach was to replace it with something else because I wanted to clear the issue - after resoldering all my points I was getting desperate - the only thing after the jack was to check the bridge wire at the bridge. I even tested with three different cables to see if cable one end jack may be too wide or long for the Pure Tone, but there was no difference. With the switchcaft jack, all three cables worked without any hum

 

[RVA]

I also found it interesting that the wireless device could eliminate the ground issue. Good if you want a work around, but bad in that you may have a latent issue. Say you go to a gig and your batteries run out or the unit fails, so you attempt to plug in. That would be a bad time to discovery you have an issue. If anyone can give me an explanation of how the wireless does this, I would be interested to know.

 

[Kerry Brown]

Did you try a different amp?

 

[RVA]

Did you try a different amp?

The same amp (Kemper) was used each time. I tried to isolate my variables, and the issue came down to the output jack.

 

[Amp Mad Scientist]

I recently decided to try a cable instead of my Line 6 G30 wireless, which I have been using the last few years, mostly because the G30 is failing and I am not sure I will replace it. Here is what happened.

When using the cable, my LP Special would hum upon touching the strings & bridge, an obvious ground issue. However, I had not realized it before because the active wireless system suppressed it. I verified this by going back and forth and using different cables.

After re-soldering all my grounds, the Pure Tone output jack was all that was left to check, and touching the metal sleeve of the cable would suppress the hum. Swapping out the Pure Tone jack to a Switchcraft cleared the issue. I do no see anything obviously wrong with the Pure Tone, but I will do some testing later

This is caused by lack of shielding inside the guitar.
It's a really common issue, happens frequently.

If the guitar is properly shielded inside these type noises won't occur.
Using humbucking pickups is also recommended....

If you play on stages with lighting systems, or in bars with neon signs, you will especially benefit from shielding the inside of the guitar.

Of course with low gain / lower loudness levels it's not as much of a problem.
But in a high gain amp or louder stage levels (or recording) it becomes a major irritation.

The best guitar shielding is multiple layers. Shielding paint and metal foil.
But aluminum is not recommended.

 

[RVA]

This is caused by lack of shielding inside the guitar.
It's a really common issue, happens frequently.

If the guitar is properly shielded inside these type noises won't occur.
Using humbucking pickups is also recommended....

If you play on stages with lighting systems, or in bars with neon signs, you will especially benefit from shielding the inside of the guitar.

Of course with low gain / lower loudness levels it's not as much of a problem.
But in a high gain amp or louder stage levels (or recording) it becomes a major irritation.

The best guitar shielding is multiple layers. Shielding paint and metal foil.
But aluminum is not recommended.

Good info. However, I do not think that was the issue in this instance. Changing the jack made it go from loud hum when touching the strings (ground issue) to dead silent.

 

[Don O]

Ray, did you ohm meter the Jack you took out? Any high resistance (a whisker wire connection) would act as a path from ground to the input signal. Touching the strings would change their capacitance and introduce noise.

 

[RVA]

Ray, did you ohm meter the Jack you took out? Any high resistance (a whisker wire connection) would act as a path from ground to the input signal. Touching the strings would change their capacitance and introduce noise.

I did not use an ohm meter, I just checked for cross continuity. I will give that a try. What should I be looking for precisely?

 

[Don O]

A high ohm reading, maybe in the mega ohms. It obviously should be a dead open. So use the ohm meter in a high range setting.

 

[chilipeppermaniac]

Dono, I am getting the impression you may have had some experience in some electronical type field of endeavors.

 

[Don O]

Dono, I am getting the impression you may have had some experience in some electronical type field of endeavors.

I started soldering around age 6, 1962. Wrote my first FORTRAN software program in 1973. Built computers starting 1977. My entire career was in electronics Hardware, Software and Systems Engineering. Now its time for guitars and music

 

[chilipeppermaniac]

Dono, I SURE wish I met you before you left town. I was putting on and taking off training wheels at 6 circa 1970.

My Stepdad was a Systems designer for CSX railroad, but I sadly did not go any further than 1 Fortran class in Western Md College back around 1984 when I was 20. Do Loops and If thens is all I remember, other than arrays and getting stuck on one task where the program went through one time to pick something from the array, then when I had notation to go again, it would pick the same word from the array. I had trouble making it make random choices.

Electronics Hardware and Car Parts, and anything that makes a thing go whirr always fascinated me as long as it wasn't cheap or over engineered junk with planned obsolescence. Transistor radios and all the bits inside always blew my mind that anyone knew what all that stuff did.

 

[syscokid]

I do have a stash of them. My first approach was to replace it with something else because I wanted to clear the issue - after resoldering all my points I was getting desperate - the only thing after the jack was to check the bridge wire at the bridge. I even tested with three different cables to see if cable one end jack may be too wide or long for the Pure Tone, but there was no difference. With the switchcaft jack, all three cables worked without any hum

Since you have a stash of those Pure Tone jacks, I'm very curious if the other ones present the same issue. If the other ones work silently like the Switchcraft jack that you installed, then you know you've got a dud.

Are you sure the ground wire leading to the PT jack is perfectly fine? Did you wiggle the wire while the cable was connected to the guitar and plugged into the amp? The ground wire might have an internal break. This could easily lead to an intermittent symptoms of poor grounding.

No corrosion on the inside of the PT jack's ground sleeve?

You said "touching the metal sleeve of the cable would suppress the hum". Did you try to wiggle the cable without touching the metal sleeve?

 

[RVA]

Since you have a stash of those Pure Tone jacks, I'm very curious if the other ones present the same issue. If the other ones work silently like the Switchcraft jack that you installed, then you know you've got a dud.

Are you sure the ground wire leading to the PT jack is perfectly fine? Did you wiggle the wire while the cable was connected to the guitar and plugged into the amp? The ground wire might have an internal break. This could easily lead to an intermittent symptoms of poor grounding.

No corrosion on the inside of the PT jack's ground sleeve?

You said "touching the metal sleeve of the cable would suppress the hum". Did you try to wiggle the cable without touching the metal sleeve?

I do not think it was a poor wire connection issue. I never swaped out the ground wire. I did resolder the wire on the PT jack with no effect. I also touched all ground connections in the cavity at each pot to see if it would have an effect...nothing.

There was plenty of cable wiggling going on. I removed the jack from the port when testing to make sure the jack was not crushed in there so as to created unwanter contact. There was no change as I moved the guitar around with the freed jack, only when I touched the metal cable sleeve, and even then, the hum would dissipate over 1-2 seconds, not just stop.

Also, the hum was louder when my bare feet were touching the ground. If it was not so frustrating, it would have been more interesting!