Re: arsclist Need Amp

["George Brock-Nannestad" <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

Kurt Nauck wrote

> I need an amplifier with 70v outputs to drive fifteen 8 ohm mono
> ceiling speakers in my new building. Speakers are configured in a
> star, and each one has it's own volume control.

----- to me it sounds as if they are all connected in parallel, but that 
each has a low-ohm variable resistor in series. This would mean 
that the sound pressure distribution may be changed, but probably 
that would not occur too often. However, a parallel connection 
would mean that the amplifier would look into a total load of ca 1/2 
ohm (impedance-wise it would be some more, except at 
resonances). Now, that would call for a high-current amplifier, not a 
high voltage one. I would rather have thought that perhaps car 
speakers with an amplifier per speaker and a simple 12 V power 
supply could do a better job. This way you would have to run 12 V 
and a signal lead to each speaker, but you would not have to use 
heavy gauge as when you distribute amplifier output to the heavy 
half-ohm load. And you would save the expensive low-ohm variable 
resistors.

High-voltage amplifiers are used in PA distribution over long 
distances and for driving the by now quite rare Philips 400 ohm 
loudspeakers (invented in the vacuum tube era when they could be 
a direct anode load and saving an output transformer).

Best regards,

George
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