[ARC5] Carbon cartridge replacement circuit

Fri Apr 28 11:43:08 EDT 2017

I have not been following this thread, However, I just about always look at
Mike's responsive as they are usually very informative. I think it may be
beneficial to review the operation of the S. G. Brown Magnetic amplifiers,
which sounds close to what Richard was describing. 73 - Mike 

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell, NJ, 07731

848-245-9115

From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Michael Hanz
Sent: Friday, April 28, 2017 11:28 AM
To: Brian; arc5 at mailman.qth.net; Richard Knoppow
Subject: Re: [ARC5] Carbon cartridge replacement circuit

I'm not gonna get in the middle of this debate, but it occurs to me that
there might be some semantic misunderstandings near the heart of it.  To try
and make sense of the two positions: 

Brian, can you imagine any sense in which the energy transfer function of a
carbon microphone transducer with a DC current flowing through it might be
greater than 1, making adjustments for the equivalent energy levels of input
acoustic energy and output electrical energy?   Richard, are you sure you
mean power amplifier, as opposed to voltage amplifier, or current amplifier?

Enquiring (or inquiring) minds might be interested in an ensuing
(respectful) discussion...

 - Mike  KC4TOS

On 4/28/2017 8:41 AM, Brian wrote:

Well Richard, 
I would have to say, once again, that you have an interesting slant on
electronics theory. From which electronics degree college did you graduate? 
What Class of amplifier do you think it is? A, B, C, D, G, H ??? 
Actually, there is no power output from a carbon microphone, except in terms
of self-heating. All the power comes from the power supply delivering
varying current in response to the mic element's changing resistance. Yes,
there is power going into the mic transformer's primary; but once again,
that comes from the power supply, not the mic element. 
There is no similarity to a vacuum tube, because there is no grid to control
current flow - in fact there is control at all, except in the shape of the
flares and wind buffering / filtering around the mic element, altering its
frequency and 3D response pattern. It is the drive that is all mechanical,
not the control. The nearest you could define it as is a transducer,
converting mechanical energy into changes in resistance. 
By your definition, you would have to claim that a water tap was an
amplifier - the mechanical action of operating its valve varies a powerful
stream of water. I wonder if this is a Class A, B, C, D ... amplifier? Maybe
a hydro-electric generator is an amplifier, turning the potential energy of
the head of water into the dynamic energy of electrical power? 
Wow, your last sentence that I have left here beggars belief - output power
of a valve is the variation in plate resistance?? So, P = delta R? Hmmm. 
73 de Brian, VK2GCE. 

On Friday, April 28, 2017 11:28 AM, Richard Knoppow said: 

    A carbon microphone is an amplifier because the power out is 
greater than the power in. The controlling force is the acoustic energy 
available to the diaphragm, the diaphragm in turn converts the acoustic 
energy to mechanical energy which moves one of the contacts with the 
resistance element. This in turn varies the voltage across the resistive 
element and varies the current applied to it. The input energy, as 
absorbed from the air, is a small fraction of a watt but the output can 
be very large depending on the dissipation of the carbon element.  The 
action is rather like a vacuum tube which also acts as a variable 
resistor. The input power to the grid is very small compared to the 
output power from the plate the variation being in the effective plate 
resistance. 
<snip> 
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