Body
Norm,
Even with GFI I don't agree with the unit being grounded for the same
reason as the Carlson lab iso transformer same as the alleged water
heater issue. Most of the new gear runs off a switching supply which is
buck converted to a bypolar +- 15 volts. Everything should be floated
and the mic cables for baptisms should only have terminals 2-3
connected. Many units use phantom power which is run off a voltage
divider of two 6.8k resistors between terminals 2-3 with the shield 1 as
the return. Most PA mics are dynamics so do not require phantom power
so no need for the shield to be connected. Even though phantom power is
very low current 48 volts DC it should also be blocked in the cable for
extra safety with a pair of capacitors.
Sounds like a product to market if not already out there. Safe baby
baptismal mic cables.
Most of the new gear is chip op amps and the whimpy 30v power supplies
are unlikely to have the juice to take someone out even in water so I
don't think the water heater claim is as unlikely as it first sounds. I
have a saying here at the studio that if there is not enough voltage to
kill you it probably sounds like shit. 48 volts is supposed to be the
minimal voltage to kill so the old discrete mixing op amps with the +-
24 volt supply are minimally acceptable in my book. Most of the mic
preamp stuff here runs off bipolar 600 volt supplies as it is class A
push pull balanced tube. The solid state pre's runs at about 120v dc.
Both tube and solid state have big current available too for the bass
frequencies.
Bass needs current. On most mixing boards plug in one channel it sounds
great then sixteen channels of mics and the bass starts to disappear
because there is not enough current. In the old days with the big
mixing consoles we used to piggy back extra power supplies for this
reason, often three of them were ordered form the mfg instead of one.
On 11/5/2018 3:07 AM, Norman Wootan [email protected] [EVGRAY] wrote:
>
>
> Please understand that in the US there are approximately 400,000
> Baptisms performed annually. In most cases there is water and an audio
> system involved. There are a lot of electrocutions that we never hear
> of as quoted here:
>
> This type of death happens annually. Therefore, sound operators should
> be aware of potential electrical hazards associated with sound
> reinforcement systems. We have a responsibility for producing quality
> sound but also doing so in a safe environment.
>
> /Disclaimer: "Please note this article is meant to discuss safety
> issues with baptismal amplification. In no way is it meant to claim
> cause of or accuse those involved in any negligence."/
>
> /See: https://www.behindthemixer.com/baptismal-amplification-and-safety//
>
> /I have heard of three such cases while living in Texas. The last was
> the Waco Pastor and I find the Court explanation rather lacking in
> that a damaged Calrod water heater was to blame. You cannot sue in
> Court if the Pastors' own amplifier was to blame so you search for a
> supposed responsible party. I don't know, I just read the news and
> form my own opinion!/
>
> /https://www.chron.com/news/houston-texas/article/Family-settles-lawsuit-in-electrocution-death-of-1881419.php
> /
>
>
> On 11/4/2018 12:21 PM, Mick [email protected] [EVGRAY] wrote:
>>
>>
>> Norm,
>>
>> I really hope that was an accident and not a prank, how awful!
>>
>> Assuming that was a class AB if push pull as most of the old tube
>> Push Pull PA amps were biased AB instead of solid class A due to heat
>> dissipation. Single ended up until the push pull current buffer
>> because this section requires a phase inverter tube to make it push pull.
>>
>> Unlikely it still worked with a shorted plate supply cap, probably
>> had not been tested in awhile or shorted at the moment.
>>
>> What a horrible spectacle for a baptism, hope the child was not harmed.
>>
>>
>> On 11/4/2018 5:50 AM, Norman Wootan [email protected] [EVGRAY] wrote:
>>>
>>>
>>> Mick! Your comment about some people dying from pranks! True
>>> Story! Back in the early 80s a pastor at a Duncanville Church
>>> (suburb of Dallas) was preforming a live Baptism at his church on a
>>> typical Sunday morning! His audio amp was the old vintage single
>>> end class A push-pull tube amp. As he descended into the Baptism
>>> pool in front of congregation and flipped on the hand held mic
>>> switch has was instantly fried by 450VDC plate voltage on chassis
>>> ground. Coroners report showed that an electrolytic cap in the HVDC
>>> plate power supply had gone to ground in effect energizing chassis
>>> at the 450VDC potential. All those vintage amps had the old two pin
>>> 120VAC plugs before the 3 pin safety grounds we now have.
>>>
>>> http://www.angelfire.com/electronic/funwithtubes/Amp-Power_Supply.html
>>>
>>> Having gone through DeVry Electronics back in 1953, I totally
>>> understood the lethality of such an event!
>>>
>>>
>>> On 11/3/2018 7:55 PM, Mick [email protected] [EVGRAY] wrote:
>>>>
>>>>
>>>> Norm,
>>>>
>>>> The interconnects used for home audio should be illegal for bad
>>>> sound, but even a properly designed mic cable with an XLR on each
>>>> end with a hot a cold and a shield one will notice only on female
>>>> side the shield connects to the chassis of the connector. It is a
>>>> single shield run on #1 to both sides though as the connections are
>>>> designed balanced for just the reason you mentioned.
>>>>
>>>> XLR's are the best connector for long run connections but I make my
>>>> own cable with silver plated aircraft cable with teflon insulation,
>>>> a pain to work with but sound is great.
>>>>
>>>> For short single ended runs the RCA end sucks and it should have
>>>> been BNC or the extra small microwave connectors that look like
>>>> mini BNC's If one removes the RCA connectors and replaces with BNC
>>>> and high quality aircraft cable and the rest of the gear is good
>>>> enough one will notice the difference. Networking cable Cat 5 or 6
>>>> can also sound great as speaker cable.
>>>>
>>>> The story gets worse though as the old tube guitar amp had a switch
>>>> that would toggle chassis ground between either connector on the
>>>> power connection for the purpose of preventing ground loops when
>>>> some live show venue had the outlets wired with hot and neutral
>>>> reversed. Well when that guitarist also happens to be a vocalist
>>>> and touched a mic stand with the ground switched wrong it was not
>>>> pretty if the shield was run to both chassis of the connectors.
>>>> This was an old soundman trick to get back at the rude ego asshole
>>>> guitar players using the special fully grounded mic cable. I am
>>>> sure some people died from this prank where 220 was used.
>>>>
>>>>
>>>> On 11/3/2018 4:46 PM, Norman Wootan [email protected] [EVGRAY] wrote:
>>>>>
>>>>>
>>>>> Mick! Just had to laugh at your remark about floating grounds in
>>>>> the recording studio! Ha! Ha! Way back when I was learning about
>>>>> fine audio, I ran a shielded line level audio cable to hook two
>>>>> sound systems together, about 100 ft run. When I turned on the
>>>>> systems and selected line in on the 2nd system, I had the
>>>>> prettiest motor boat you ever heard! Lol Yep! I had grounded
>>>>> both ends of a shielded cable and got a good example of a ground loop!
>>>>>
>>>>>
>>>>> On 11/3/2018 4:54 PM, Mick [email protected] [EVGRAY] wrote:
>>>>>>
>>>>>>
>>>>>> Norm,
>>>>>>
>>>>>> Thanks for that.
>>>>>>
>>>>>> I love Mr Calrsons lab, I could happily live there for quite
>>>>>> awhile with all that awesome vintage gear. I have seen isolation
>>>>>> transformers wired like that and it's so insane but I am used to
>>>>>> testing all the grounding points. When building a recording
>>>>>> studio we have to float all the grounds so they are single point
>>>>>> at the service panel and not looped anywhere else. Often they
>>>>>> are lifted at the outlet j-box due to the lack of control in a
>>>>>> prewired building. Ironically we also used to use autoformers
>>>>>> for all of the light dimmers to prevent noise, so we often
>>>>>> referred to the variacs as light dimmers.
>>>>>>
>>>>>> I still don't completely trust a scope on an isolation
>>>>>> transformer even if the ground is properly isolated/ lifted due
>>>>>> to the somewhat rare magnetic emp events we are talking about
>>>>>> like when I kicked off all my ground faults in the house through one.
>>>>>>
>>>>>>
>>>>>> On 11/3/2018 2:03 PM, Norman Wootan [email protected] [EVGRAY] wrote:
>>>>>>>
>>>>>>>
>>>>>>> Mick! Here is a helpful video regarding scopes and isolation
>>>>>>> transformers on the test bench!
>>>>>>>
>>>>>>> https://www.youtube.com/watch?v=XBsQ3sZ45Fk&feature=youtu.be
>>>>>>>
>>>>>>> https://www.youtube.com/watch?v=xaELqAo4kkQ
>>>>>>>
>>>>>>>
>>>>>>> On 11/3/2018 12:36 PM, Mick [email protected] [EVGRAY] wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Norm,
>>>>>>>>
>>>>>>>> Thanks for the nudge in the right direction. Now the process
>>>>>>>> demands repeating with a totally isolated battery source
>>>>>>>> configured the same way. Funny how I was concentrating on
>>>>>>>> isolating and connecting saturated inductive charge without the
>>>>>>>> first magnetic variable taken into account.
>>>>>>>>
>>>>>>>> I have had no problem creating the event with my grid power
>>>>>>>> source and even warned Sven that an isolation transformer will
>>>>>>>> not always protect his scope when messing around with this
>>>>>>>> energy. My scope probe sitting on a bench shot me in the leg
>>>>>>>> when I walked by when performing the experiments from my bench
>>>>>>>> supply. The bench supply has an isolation transformer of
>>>>>>>> sorts. Being it is torroidal there is more inter-winding
>>>>>>>> capacitive coupling and mutual inductance than with the proper
>>>>>>>> EI transformer though there is at least the electrostatic
>>>>>>>> shield and galvanic isolation.
>>>>>>>>
>>>>>>>> Thanks for that reference. the Brit guy was funny, although I'm
>>>>>>>> very familiar with iso transformers in audio work used for
>>>>>>>> galvanic isolation and balancing to eliminate common mode noise.
>>>>>>>>
>>>>>>>>
>>>>>>>> On 11/3/2018 4:42 AM, Norman Wootan [email protected] [EVGRAY] wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Mick! Your DUH reference is funny! To understand
>>>>>>>>> Isolation, best to study and understand the Isolation
>>>>>>>>> Transformer. The super high quality ones are built to
>>>>>>>>> eliminate noise and DC components that effect sensitive
>>>>>>>>> instruments like EEG and EKG instruments. This will give you
>>>>>>>>> an idea as to construction and purpose::
>>>>>>>>>
>>>>>>>>> https://en.m.wikipedia.org/wiki/Isolation_transformer
>>>>>>>>>
>>>>>>>>> A little tutorial as to how they work!
>>>>>>>>>
>>>>>>>>> https://www.youtube.com/watch?v=sfzy5IQMzyc&feature=youtu.be
>>>>>>>>>
>>>>>>>>> https://www.youtube.com/watch?v=14kPQif9P7c&feature=youtu.be
>>>>>>>>>
>>>>>>>>> https://toroid.com/Products/Medical-Isolation-Transformers
>>>>>>>>>
>>>>>>>>> The 230VAC, 5 HP locked rotor experiment was an example of
>>>>>>>>> electrically isolated electrical circuitry when mains
>>>>>>>>> contactor was opened since there was no neutral involve. There
>>>>>>>>> is magnetic and capacitive coup[ling only The dielectric
>>>>>>>>> insulation was not compromised therefore no electrical
>>>>>>>>> connection. The Chinese motor experiment was isolated,
>>>>>>>>> (electrically) when the reversing action was in transient.
>>>>>>>>> (Floating neutral) since there is a line neutral in the 120VAC
>>>>>>>>> input.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 11/2/2018 2:44 PM, Mick [email protected] [EVGRAY] wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Norm,
>>>>>>>>>>
>>>>>>>>>> Since you have performed mass research on this event would
>>>>>>>>>> you concur
>>>>>>>>>> with my long distance observation that the event is not only
>>>>>>>>>> due to
>>>>>>>>>> charge isolation but inclusive of a magnetic connection from
>>>>>>>>>> source in
>>>>>>>>>> addition to the saturated and lifted inductive load?
>>>>>>>>>>
>>>>>>>>>> Your bell buzzer and bell transformer acting as an isolation
>>>>>>>>>> transformer.
>>>>>>>>>>
>>>>>>>>>> Both motor experiments, the small Emerson type and the HVAC
>>>>>>>>>> unit with
>>>>>>>>>> only two hot's no neutral, must have been powered by an isolation
>>>>>>>>>> transformer of some type also such as the utility step down
>>>>>>>>>> for the
>>>>>>>>>> neighborhood or dedicated delta or wye for commercial or even
>>>>>>>>>> acted as
>>>>>>>>>> such from the dual windings of the HVAC motor.
>>>>>>>>>>
>>>>>>>>>> Have you reliably produced the NS from any type of isolated
>>>>>>>>>> battery
>>>>>>>>>> system, or in all such cases was there a magnetic connection
>>>>>>>>>> to an earth
>>>>>>>>>> bonding in another spot?
>>>>>>>>>>
>>>>>>>>>> My thoughts being one side of a transformer acting as a source is
>>>>>>>>>> grounded and the secondary side isolated so that the only
>>>>>>>>>> conceivable
>>>>>>>>>> ground bonding on the sink might be considered as magnetic
>>>>>>>>>> aside from
>>>>>>>>>> the bonded motor frame or what not producing the reconnection.
>>>>>>>>>>
>>>>>>>>>> I may be pissing up a rope notwithstanding the NS seems to be
>>>>>>>>>> predicated
>>>>>>>>>> on a B field connection somewhere in the source feed though
>>>>>>>>>> the neutral
>>>>>>>>>> is isolated electrically.
>>>>>>>>>>
>>>>>>>>>> Perhaps this is a simple "Duh" to you that you had already
>>>>>>>>>> figured out
>>>>>>>>>> assuming everyone else at least this smart. Either way it
>>>>>>>>>> does create
>>>>>>>>>> an interesting position in which to view 3 phase and
>>>>>>>>>> transformers with
>>>>>>>>>> an extra resonant winding.
>>>>>>>>>>
>>>>>>>>>> By the way, ironic your implication that the large medical
>>>>>>>>>> isolation
>>>>>>>>>> transformers create a heretofore unknown vector of extreme
>>>>>>>>>> danger.
>>>>>>>>>>
>>>>>>>>>> Mick
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
>