benb

Re: bill whitlock
« Reply #20 on: December 11, 2018, 02:10:33 PM »
By the way, last I spoke with Bill, a couple years ago, if I’m recalling correctly (and I very well may not be), he said he’s not sure how necessary the hoopla and trouble is to have 120 balanced on the secondary; sounded like he needed to do more testing there.
I think the biggest thing that makes it necessary is modern switching power supplies (the word 'switching' is redundant here) that have a filter block (needed to reduce RF emissions) at the power input, with three line-rated capacitors between the hot, neutral, AND ground connections.  The one between hot and ground puts a 60Hz current through the ground wire at a level that's a lot higher than it would be just from stray capacitance. Balanced 120V puts half the voltage from the (formerly) "hot" on that capacitor, and half the voltage with the opposite polarity on the (formerly) "neutral" capacitor between neutral and ground,  thus the currents (mostly) cancel out (depending on how close in value the two capacitors are).

Of course, older/classic  guitar amplifiers are different, and the "ground reverse" switch on them won't make much if any difference in hum on a balanced power line, as either way its ground/chassis is capacitively coupled to about 60V. Ironically, these "need" unbalanced power.

On the other hand, for best safety, their power connections should be rewired to modern standards.  Is this usually done with older guitar amplifiers?


JohnRoberts

Re: bill whitlock
« Reply #21 on: December 11, 2018, 02:17:42 PM »
I think the biggest thing that makes it necessary is modern switching power supplies (the word 'switching' is redundant here) that have a filter block (needed to reduce RF emissions) at the power input, with three line-rated capacitors between the hot, neutral, AND ground connections.  The one between hot and ground puts a 60Hz current through the ground wire at a level that's a lot higher than it would be just from stray capacitance. Balanced 120V puts half the voltage from the (formerly) "hot" on that capacitor, and half the voltage with the opposite polarity on the (formerly) "neutral" capacitor between neutral and ground,  thus the currents (mostly) cancel out (depending on how close in value the two capacitors are).

Of course, older/classic  guitar amplifiers are different, and the "ground reverse" switch on them won't make much if any difference in hum on a balanced power line, as either way its ground/chassis is capacitively coupled to about 60V. Ironically, these "need" unbalanced power.

On the other hand, for best safety, their power connections should be rewired to modern standards.  Is this usually done with older guitar amplifiers?
Death caps/stinger switches need to be removed and mains line cords rewired with chassis bonded to safety ground

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Recording Engineer

Re: bill whitlock
« Reply #22 on: December 11, 2018, 02:23:26 PM »
The studio owner has quite a collection of old guitar amps, so that is one thing that still needs to be looked over on an individual basis. We also have a bunch of dirty, unbalanced 120 power all throughout the studio as well.

JohnRoberts

Re: bill whitlock
« Reply #23 on: December 11, 2018, 02:47:46 PM »
The studio owner has quite a collection of old guitar amps, so that is one thing that still needs to be looked over on an individual basis. We also have a bunch of dirty, unbalanced 120 power all throughout the studio as well.
In case I am sounding like a broken record a GFCI protected outlet can prevent the death caps from actually killing anybody, while the 6 mA threshold can still be enough to sting you. 

They make GFCI protected outlet strips, but I worry that musicians would just plug around a tripped GFCI outlet strip, before taking the old soldier in for repair/rewiring.

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Recording Engineer

Re: bill whitlock
« Reply #24 on: December 11, 2018, 02:53:49 PM »
All outlets are GFCIs... Code around here now days.

pucho812

Re: bill whitlock
« Reply #25 on: December 12, 2018, 01:06:36 PM »
All outlets are GFCIs... Code around here now days.

Where?
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

Recording Engineer

Re: bill whitlock
« Reply #26 on: December 12, 2018, 01:46:28 PM »
Most everywhere, as it’s permitted as a garage.

JohnRoberts

Re: bill whitlock
« Reply #27 on: December 12, 2018, 01:48:08 PM »
Code for new buildings does not affect all legacy venues.

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

pucho812

Re: bill whitlock
« Reply #28 on: December 12, 2018, 02:06:39 PM »
Most everywhere, as it’s permitted as a garage.

hmmmm.  so how does that work exactly. My understanding of GFCI's is that the first outlet in the row is GFCI and the rest are not.  am I missing something here?
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

JohnRoberts

Re: bill whitlock
« Reply #29 on: December 12, 2018, 02:13:08 PM »
hmmmm.  so how does that work exactly. My understanding of GFCI's is that the first outlet in the row is GFCI and the rest are not.  am I missing something here?
GFCI outlets have a pass through so you can protect a couple outlets with one, but to protect an entire branch you need a GFCI breaker in the panel.

JR

[edit a less obvious issue the ground leakage is cumulative, so a few in series could be easier to trip, like in a studio full of legacy guitar amps.  ::)  [/edit]
« Last Edit: December 12, 2018, 06:43:06 PM by JohnRoberts »
Visit https://circularscience.com to hear what properly "cleared" drums sound like.


abbey road d enfer

Re: bill whitlock
« Reply #30 on: December 12, 2018, 02:39:44 PM »
On the other hand, for best safety, their power connections should be rewired to modern standards.  Is this usually done with older guitar amplifiers?
It should, but some folks are quite finicky about the correctness of their vintage gear. For them, I can only recommend a safety isolation transformer. The capacitance between primary and secondary is minimized (<120pF in Europe) and the secondary is floating, i.e. none of the wires is connected to neutral. The amp may hum, but it's very easy to provide an earth connection to the chassis.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

pucho812

Re: bill whitlock
« Reply #31 on: December 12, 2018, 06:33:33 PM »
GFCI outlets have a pass through so you can protect a couple outlets with one, but to protect an entire branch you need a GFCI breaker in the panel.

JR

thank you JR
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

Speedskater

Re: bill whitlock
« Reply #32 on: December 14, 2018, 07:49:48 PM »
I have not seen any new papers or blogs from Bill Whitlock is some time now. Will this pdf be posted anywhere?
Kevin

pucho812

Re: bill whitlock
« Reply #33 on: December 14, 2018, 08:27:19 PM »
I have not seen any new papers or blogs from Bill Whitlock is some time now. Will this pdf be posted anywhere?

Yes the moment I get it. Mr Whitlock is currently in the middle of a home move, when he gets unpacked, I'll have it
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


 

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