[Boatanchors] Speech Amp

[J Forster]

Take a look here:

http://www.dvq.com/hifi/images/260a.pdf

AFAIK, 600 ohms is used for inputs, not outputs, and is typically
balanced.

A 70 V line means that the amp output is 70 V RMS at the amp's rated
output. The 70 V is usually stepped down at each speaker to voice coil
impedance. Typical transformers have taps for the desired wattage to the
speaker, so you can hook up a number of transformer/speaker combos. So
on a 10 W amp, you can hook up four 1 W and three 2 W speakers. The amp
looks a lot like a voltage source.

Since Power = V * V /R, if R=600 ohms and V=70 volts, there is only one
possible power output from the amp. (4900/600 = 8.1 W)

Nope, 600 ohm and 70 V are NOT the same.

-John

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Barrie Smith wrote:

>   It's my impression that the 70 volt output on a PA amp is 600 ohms.
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