ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 ... 5 6 [7] 8 9 ... 55   Go Down

Author Topic: brain storm an optimal human safety system for back line  (Read 96226 times)

Lyle Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1548
Re: brain storm an optimal human safety system for back line
« Reply #60 on: December 20, 2014, 07:04:26 pm »

It is an excellent exercise; an extra level of protection or a deeper understanding of the mechanisms of failure are very good things.

Logged

Scott Holtzman

  • Hero Member
  • *****
  • Online Online
  • Posts: 5271
  • Ghost AV - Avon Lake, OH
    • Ghost Audio Visual Systems, LLC
Re: brain storm an optimal human safety system for back line
« Reply #61 on: December 20, 2014, 10:03:22 pm »

I have been thinking about the question of how injecting a pulse train would detect.  there would need to be a pickup on the ground neutral.  Each fault would have a unique signature much like a radar.  the fault conditions would cause a radical change pattern.    A type of Monte Carlo analysis cpuld be employed to collect a large library of these returns.  Once the fault patterns are qualified you have a single ended non loading detector
Logged
Scott AKA "Skyking" Holtzman
River Delta Audio is now:

Ghost Audio Visual Solutions, LLC
Cleveland OH
www.ghostav.rocks

Jonathan Johnson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2972
  • Southwest Washington (state, not DC)
Re: brain storm an optimal human safety system for back line
« Reply #62 on: December 21, 2014, 02:22:47 am »

I am thinking of something for the musician to carry with him to protect himself from bad venues, not as a semi-permant fix for a venue.

I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

Like a GFCI, the signal line (positive, shield, and if equipped negative) would pass through a current transformer. Under normal conditions all current flowing through should cancel to zero. But in the event of a ground fault, there would be a imbalaced and therefore nonzero current. If the current exceeds a predetermined value, say 6 mA, the interrupter would open all the signal lines including ground/shield.

Could such a device be built in such a way that it would not sonically color the signal?

Such a device could be placed either in the path between the guitar and the amplifier, or between the microphone and the console.

By not being placed in the electrical power path, it would be easier to gain regulatory approval.
« Last Edit: December 21, 2014, 02:25:19 am by Jonathan Johnson »
Logged
Stop confusing the issue with facts and logic!

Scott Holtzman

  • Hero Member
  • *****
  • Online Online
  • Posts: 5271
  • Ghost AV - Avon Lake, OH
    • Ghost Audio Visual Systems, LLC
Re: brain storm an optimal human safety system for back line
« Reply #63 on: December 21, 2014, 02:51:00 am »

I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

Like a GFCI, the signal line (positive, shield, and if equipped negative) would pass through a current transformer. Under normal conditions all current flowing through should cancel to zero. But in the event of a ground fault, there would be a imbalaced and therefore nonzero current. If the current exceeds a predetermined value, say 6 mA, the interrupter would open all the signal lines including ground/shield.

Could such a device be built in such a way that it would not sonically color the signal?

Such a device could be placed either in the path between the guitar and the amplifier, or between the microphone and the console.

By not being placed in the electrical power path, it would be easier to gain regulatory approval.

This was also the theory of my digital scheme.  As it would measure current along with the waveform function on the pickup coil.  All of that data would form the sampled fingerprint.  Easier tuning in the digital domain that with analog components that are also subject to tolerance drift.

If the thing is too sensitive it will become a projectile at FOH.  Digital would allow much more granular false fault rejection processing.

Logged
Scott AKA "Skyking" Holtzman
River Delta Audio is now:

Ghost Audio Visual Solutions, LLC
Cleveland OH
www.ghostav.rocks

Lyle Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1548
Re: brain storm an optimal human safety system for back line
« Reply #64 on: December 21, 2014, 04:36:14 am »

People interact with systems powered from multiple sources and feeds all the time.  We aren't scared of picking up a telephone while using a computer or a kitchen appliance.  Existing electrical safety rules can work if they are followed.
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16284
  • Hickory, Mississippi, USA
    • Resotune
Re: brain storm an optimal human safety system for back line
« Reply #65 on: December 21, 2014, 09:52:02 am »

I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

Like a GFCI, the signal line (positive, shield, and if equipped negative) would pass through a current transformer. Under normal conditions all current flowing through should cancel to zero. But in the event of a ground fault, there would be a imbalaced and therefore nonzero current. If the current exceeds a predetermined value, say 6 mA, the interrupter would open all the signal lines including ground/shield.
Sounds like that should work,,, an external fault current would definitely imbalance the current transformer.
Quote
Could such a device be built in such a way that it would not sonically color the signal?
That I do not know? Guitar pick-ups (especially lead guitar) are relatively high impedance (tens of K ohm) so they would definitely need their own current transformer.
Quote
Such a device could be placed either in the path between the guitar and the amplifier, or between the microphone and the console.
I still lean toward dealing with this at the guitar end because there are multiple dragons to slay (bad stinger caps too).
Quote
By not being placed in the electrical power path, it would be easier to gain regulatory approval.

I have already talked with a friend who makes guitar pedals and there are other options for that signal path. He mentioned to me that some people have used input transformers for guitar amps (I never heard of that and worry about response). While I would not advocate adding input transformers in a guitar path, it seems to me an output transformer in a guitar pedal would be dealing with lower drive impedance and could float that ground path (ASSuming the guitar pedal is battery powered or using an ungrounded wall wart.)

Sensing for current in the single ground lead is a somewhat simpler task than detecting small current leakage from a pair of higher current conductors. 

That said interfering with the guitar signal path could offend the tone snobs and be an added expense most musicians don't feel necessary.  Protecting against legacy guitar amps seems easier to sell to a perhaps wealthier cliental.

JR
Logged
Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3351
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: brain storm an optimal human safety system for back line
« Reply #66 on: December 21, 2014, 11:35:47 am »

I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

This is exactly what I've been talking about earlier on this thread, using a pair of magnetic latching reed relays driven by a current transformer. These reed relays would be placed in the guitar signal path and open both the shield and signal lines if more than 6 mA of current went through the current transformer. Because it's a relay contact there should be no signal coloration issues. JR and I have been discussing if there's enough power from the current transformer to trip the latched relay open without a battery for power. JR says no, but I say maybe. More to study to see which one of us is correct. The beauty of opening up the guitar-to-amp signal line is that NEC wouldn't be in the middle of this, and I don't think that UL approval would be required either.
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16284
  • Hickory, Mississippi, USA
    • Resotune
Re: brain storm an optimal human safety system for back line
« Reply #67 on: December 27, 2014, 05:50:51 pm »

OK, first Merry Christmas to everybody...  I think I nailed it. I was thinking too hard looking for a complicated solution using relays and gadgets.... KISS.

The problem I am trying to protect against is a live energized ground, either in the guitar amp or the console power drop. Pulling a very old trick out of my kit bag, separate grounds can be bonded together using diodes. This way as long as the ground voltages are pretty close to each other, the diodes don't conduct and the two grounds appear isolated. BUT, if there is enough voltage difference between the grounds the diode(s) will conduct and presto, no dangerous ground potential.

So my new proposal is a small stage box with two XLR jacks one male and one female with 1,2,3 normalled between them. two 1/4" plugs wired tip to tip and sleeve to sleeve. The jack grounds are isolated from the stage box but connected to each other through back to back diodes (in fact I would use two diode bridges in series for 4x diode drops, or more than 2V before conduction).  An LED could be wired in parallel with the diodes so there would be some LED light should there be a hot ground, but only until a panel circuit breaker or GFCI trips.

In use the musician plugs in his mic and guitar using the mult- through jacks on the box, but these hard wired jacks will not affect his audio path, beyond an extra metal to metal jack contact. The grounds will remain happily floating unless there is more than 2V between the two safety grounds.  If one or the other ground is energized the diode shunt will conduct and take out the fuse, or breaker. or GFCI.

Back in the '80s I did some research and determined that diodes usually fail as a short circuit from over current, so all I need is diodes with enough thermal mass to not vaporize before the mains circuit breakers trip. Diode bridges, like used in power supplies work like a charm. 2 bridges will provide +/- 4 diodes drops so ground noise < 2V will be ignored. (If needed for horrible grounds more diodes could be used in series and this will still protect the meat puppets).

What cha think???  I like it...  No moving parts, and diodes are about the least active of all "active" devices...

JR 

PS: This should also protect against a rouge ungrounded guitar amp bonding it's chassis to the console ground. 

« Last Edit: December 27, 2014, 05:52:56 pm by John Roberts {JR} »
Logged
Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

Rick Earl

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 272
Re: brain storm an optimal human safety system for back line
« Reply #68 on: December 27, 2014, 06:17:50 pm »



In use the musician plugs in his mic and guitar using the mult- through jacks on the box, but these hard wired jacks will not affect his audio path, beyond an extra metal to metal jack contact. The grounds will remain happily floating unless there is more than 2V between the two safety grounds.  If one or the other ground is energized the diode shunt will conduct and take out the fuse, or breaker. or GFCI.


What cha think???  I like it...  No moving parts, and diodes are about the least active of all "active" devices...

JR 


Would all mics in the system need to be plugged into something like this?  I'm thinking of the sweaty guitar player leaning up against the sweaty singer with a hard wired mic in  hand,  or the bass  player, who may or may not have one.  I deal with a lot of young musicians with a lot of energy and into vintage gear.  I work real hard with them to pay attention to their gear and the venue, but there are still some scary places out there.

Thanks for working on this, it is beyond some of my skill set, but I've been following this thread to help me keep others safe.
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16284
  • Hickory, Mississippi, USA
    • Resotune
Re: brain storm an optimal human safety system for back line
« Reply #69 on: December 27, 2014, 06:28:00 pm »

Would all mics in the system need to be plugged into something like this?  I'm thinking of the sweaty guitar player leaning up against the sweaty singer with a hard wired mic in  hand,  or the bass  player, who may or may not have one.  I deal with a lot of young musicians with a lot of energy and into vintage gear.  I work real hard with them to pay attention to their gear and the venue, but there are still some scary places out there.

Thanks for working on this, it is beyond some of my skill set, but I've been following this thread to help me keep others safe.

No just one mic per stage/back line depending on what the fault is. If the console power drop is hot, that will trip when grounded. If the guitar amp or back line power drop is hot that too should take out the circuit. Of course to protect against individual old legacy killer guitar amps each amp needs to be diode bonded. However a stage box with two or three sets of 1/4" plugs could protect multiple guitar amps while we might need separate diode bridges so each guitar amp is floating for the first 2V relative to the other guitar amp ground.

BTW if your mic or guitar cable melts that is also an indication of a fault.  8) 8) But a mic/guitar cable should hang long enough to trip a breaker or GFCI.

JR
Logged
Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/
Pages: 1 ... 5 6 [7] 8 9 ... 55   Go Up
 


Page created in 0.026 seconds with 23 queries.