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running RCAs by power


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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: October 27, 2005 at 8:25 AM / IP Logged  

Dave, a magnetic field does not have to swing negative in order for it to collapse.  Indeed, if the current flow goes to zero, it collapses.  If the polarity swings negative, the field reverses polarity.  But "collapse" literally means it goes from some value to zero, and it will certainly do that in a DC circuit.  Faraday (and Maxwell) showed that anytime a magnetic field is moving in relation to a wire, an EMF is induced.  It does not matter the polarity.

The magnetic field change I am talking about is in the power cable for an amplifier, not in the signal cable.  This field change can be very radical as the amplifier draws more or less current, and this field is certainly more than sufficient to induce a voltage into adjacent wiring.

You are correct of course that the LARGEST contributors to EMI and other induction effects is more likely a noisy system (rippled DC, arcs and sparks in the alternator, other mechanical and magnetic devices, etc.) than from pure induction through magnetic field interaction.  But you cannot say it does not happen.  That was my only point: that it is certainly possible and in some cases very problematic.  Poorman's theory that it is a "misconception" is simply wrong.

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Tegpilot 
Copper - Posts: 93
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Posted: October 27, 2005 at 9:32 AM / IP Logged  
I'm already in the car on my way to ABC to pitch this one as a Reality TV Show. 
99 INTEGRA LS 4DR Forest Green.Alpine CDA9857 Deck. JBL 755.6 AMP, Kappa 50.7cs Front, Kappa 6x9's Rear, 4 JBL GTO804 subs
dwarren 
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Joined: December 03, 2004
Location: California, United States
Posted: October 27, 2005 at 9:36 AM / IP Logged  
Sounds...boring, but there could be some great "drama" especially from the Dave's.
Tegpilot 
Copper - Posts: 93
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Joined: July 11, 2005
Location: United States
Posted: October 27, 2005 at 9:48 AM / IP Logged  

Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos. 

Then we just see who cracks first.  "or proves the theory first"  

99 INTEGRA LS 4DR Forest Green.Alpine CDA9857 Deck. JBL 755.6 AMP, Kappa 50.7cs Front, Kappa 6x9's Rear, 4 JBL GTO804 subs
haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: October 27, 2005 at 10:28 AM / IP Logged  
Tegpilot wrote:
Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos.
'cept mine'd hafta be jerky... I'm on Atkins!
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Mad Scientists 
Silver - Posts: 380
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Joined: February 07, 2004
Location: United States
Posted: October 27, 2005 at 12:20 PM / IP Logged  

haemphyst wrote:
The changing of the magnetic field in the power cable is always a positive - sometimes a little more, sometimes a little less - but ALWAYS positive. There is never a SWING from positive THROUGH zero, to negative.
There is simply not enough change in magnetic field with MUSIC signals to produce the necessary magnetic fluctuations required to induce a voltage high enough to go to the effort of tearing apart the entire car to run power down one side, and the signal down the other. There ARE fluctuations, but they ARE always POSITIVE. There is NEVER a negative swing - required to cause a total collapse of the magnetic field, inducing the voltage on the secondary - in this case the positive signal wire contained in the RCA wire.

Looking specifically at "There is NEVER a negative swing - required to cause a total collapse of the magnetic field, inducing the voltage on the secondary"

explain how an ignition coil (which is nothing but a step-up transformer) works in this situation.. and why diodes are used on relay coil leads.

Jim

haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: October 27, 2005 at 3:16 PM / IP Logged  
Perhaps my statement translated to needing AC. While this is NOT true, a pulsed DC is a minimum. This is what is fed to the primary side of your ignition coil. ON, then OFF - the cycle of your ignition points (or in the case of most of today's cars, the solid state switching circuitry)... The OFF is when the spark occurs.
Diodes in relay coils are there to prevent the back EMF, produced when the field collapses, from feeding back into the driving circuitry. The diode is placed in opposite polarity of the driving voltage so it is "invisible" to the driving circuit.
When the field collapses, the back EMF produced is an opposite polarity of the voltage that produced the field to begin with. This is why the diode is placed the way it is... it will short the back EMF across the terminals of the relay coil, preventing the high voltage spike produced from being sent back into the driving circuitry.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: October 27, 2005 at 3:18 PM / IP Logged  
Tegpilot wrote:

Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos. 

Then we just see who cracks first.  "or proves the theory first"  

...and I think he's talking about us, DYohn... you ready? running RCAs by power - Page 3 -- posted image.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
tcss 
Silver - Posts: 1,623
Silver spacespace
Joined: June 07, 2004
Location: United States
Posted: October 27, 2005 at 3:43 PM / IP Logged  
WOOOOOOSSSSSSSSHHHHHHHH. ( The sound of most of that going over my head ) Deep stuff guys, I'm going to go bang my head on a dashboard.........
There is no such thing as free installation!
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: October 27, 2005 at 3:50 PM / IP Logged  
haemphyst wrote:
Tegpilot wrote:

Oh come, we'll give em each a glass room, Some wire, goggles, a big ol battery and a six month supply of Doritos. 

Then we just see who cracks first.  "or proves the theory first"  

...and I think he's talking about us, DYohn... you ready? running RCAs by power - Page 3 -- posted image.

I'd rather work with you than against you, my friend.  We could cook up some pretty good Frankenstein monsters if we wanted too.  I see large open frame plasma drivers.....  and plenty of Doritos and jerky...  running RCAs by power - Page 3 -- posted image.

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