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[Mike Sokol]

Short notice, but if any of you are within "spittin' distance" of Winchester, VA, I'm presenting a free 90-minute NoShockZone seminar at Shenandoah University beginning around 6:00 PM this evening in the Ruebush Hall 208 Choir Room. This seminar is being hosted by the SU student AES Chapter, and a number of the Washington DC senior AES members will be attending. Send me an email at [email protected] if you're coming by and I'll put your name on the guest list.

This 90 minute seminar will include live demonstrations on measuring and preventing ground loop hum, hot-ground shocks and RPBG testing, plus a preliminary discussion of my new Ground Loop Intermodulation Distortion (GLID) theory as to why some sound systems seem to have undefined (fuzzy) bass.

I'll post pictures tomorrow....

[John Roberts {JR}]

Short notice, but if any of you are within "spittin' distance" of Winchester, VA, I'm presenting a free 90-minute NoShockZone seminar at Shenandoah University beginning around 6:00 PM this evening in the Ruebush Hall 208 Choir Room. This seminar is being hosted by the SU student AES Chapter, and a number of the Washington DC senior AES members will be attending. Send me an email at [email protected] if you're coming by and I'll put your name on the guest list.

This 90 minute seminar will include live demonstrations on measuring and preventing ground loop hum, hot-ground shocks and RPBG testing, plus a preliminary discussion of my new Ground Loop Intermodulation Distortion (GLID) theory as to why some sound systems seem to have undefined (fuzzy) bass.

I'll post pictures tomorrow....

GLID... Oh boy... a new distortion. 

Are you talking about actual "loops" as in a one turn magnetic winding that intercepts the magnetic field present and converts that to voltage/current flowing in that one turn winding? "And" a section of this loop (winding) being one of the two conductors passing single ended audio between chassis?

 Professional audio interfaces should not be very susceptible to ground loops or ground potential differences. But a mainstream general audience may have less robust hifi interfaces in mind. At least if they have a ground loop they have two paths to ground. 

JR


 

[Mike Sokol]

GLID... Oh boy... a new distortion. 

Are you talking about actual "loops" as in a one turn magnetic winding that intercepts the magnetic field present and converts that to voltage/current flowing in that one turn winding? "And" a section of this loop (winding) being one of the two conductors passing single ended audio between chassis?

Not exactly. This GLID is basically the pin-1 problem that produces ground loop hum which is increased during heavy power transients. Imagine a sound system that is hum-free while idle, but as soon as you draw significant AC power due to the program audio (such as a kick drum or bass guitar) then a momentary 60-Hz hum appears which then mixes with the original audio and creates a sort of fuzzy bass. So the program audio can modulate the ground loop hum, even in balanced XLR connected systems.

Now, I've not created the experiment to gather empirical evidence of this, nor have I developed the live demonstration for a listening test. But I'm pretty sure it exists and can prove it in double-blind listening tests. Should be interesting... 

[John Roberts {JR}]

Pin 1 problem is pretty well known to product developers, and a circuit design flaw that mainly persists in older legacy products.

Proper handling of shield ground currents inside the product input section, and keeping audio signals well segregated from those shield currents maintains signal integrity.

There is still product out there with this problem but hopefully less of them every day...

JR

[Jerome Malsack]

I would like to jump in and say I managed to make the 200 mile trip out and back for the 90 minute lecture and we all had fun and learned much from the time spent.   

It was fun watching the guitar player when the guitar and player were floating with 120 volts on the ground.   Happy to see that he was able to walk away and still had a good hair dew! 

[Mike Sokol]

I would like to jump in and say I managed to make the 200 mile trip out and back for the 90 minute lecture and we all had fun and learned much from the time spent.   

It was fun watching the guitar player when the guitar and player were floating with 120 volts on the ground.   Happy to see that he was able to walk away and still had a good hair dew!

Like this?

and this?

[Mike Sokol]

I just taught a NoShockZone clinic at Austin Community College this afternoon. The teacher thought it should take 1 hour max, with maybe 30 minutes Q&A. But as we got halfway through my presentation the teacher announced he was cancelling the next class so we could expand the seminar time, and we spent 3 hours on sound system grounding, hums, buzzes, shocks, and electrocution. Good times....

[Jonathan Johnson]

Like this?

and this?

Mike's obituary will read "Mike was killed when he plugged his RPBG demonstration unit into an outlet he didn't know was an RPBG."

Nah, we all know he will test the outlet before he plugs ANYTHING in. Be safe out there, Mike, you're playing with fire. We all benefit from your experience, and none of us want that experience to include a fatal mistake.

[Mike Sokol]

Mike's obituary will read "Mike was killed when he plugged his RPBG demonstration unit into an outlet he didn't know was an RPBG."

Nah, we all know he will test the outlet before he plugs ANYTHING in. Be safe out there, Mike, you're playing with fire. We all benefit from your experience, and none of us want that experience to include a fatal mistake.

Not to worry since I do test every outlet before plugging in my demo unit, first with a NCVT to check for proper polarity and a possible hot ground, then with an Amprobe INSP-3 to check for line voltage and ground impedance. I also have a 100K resistor in series with the guitar demonstration just in case my test subject does something silly like grab a water pipe while holding the intentionally electrified guitar. And of course, I would never do this demonstration on grass or damp concrete. Too many things to go wrong.

I've thought about adding a basic AED component to this demonstration. Does anyone on this forum have a contact with an AED manufacturer?

[John Roberts {JR}]

I've thought about adding a basic AED component to this demonstration. Does anyone on this forum have a contact with an AED manufacturer?

Automated External defibrillator?

====
A GFCI in series with your rig might prevent even a suicidal test subject from being successful.

JR

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