RE: arsclist Need Amp

["Dave" <audio101@xxxxxxxxxxxxxx>]

70V amps are commonly used for music distribution these days, I design
hundreds of systems per year using 70v amps, BUT all speakers MUST have
a 70V to 8 ohm transformer on them. This keeps all speakers at the same
volume level if desired, or allows you to "tap" each speaker at a
particular setting. IE: lobby areas at say 1 watt and production areas
at 8 watts, all running off the same amplifier. This is a very common
type system and information can be found on may amplifier manufacturers
websites. www.qscaudio.com or www.crownaudio.com www.toa.com etc.




Dave Meyers
Overkill audio inc.

-----Original Message-----
From: owner-ARSCLIST@xxxxxxxxxxxxxxxxx
[mailto:owner-ARSCLIST@xxxxxxxxxxxxxxxxx] On Behalf Of George
Brock-Nannestad
Sent: Monday, August 05, 2002 2:43 AM
To: ARSCLIST@xxxxxxxxxxxxxxxx
Subject: Re: arsclist Need Amp

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
-
For subscription instructions, see the ARSC home page
http://www.arsc-audio.org/arsclist.html
Copyright of individual posting is owned by the author of the posting
and
permission to re-transmit or publish a post must be secured
from the author of the post.

-
For subscription instructions, see the ARSC home page
http://www.arsc-audio.org/arsclist.html
Copyright of individual posting is owned by the author of the posting and
permission to re-transmit or publish a post must be secured
from the author of the post.