Re: Help with Audio Amp

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From: Paul Harden (pharden@aoc.nrao.edu)
Date: Fri Feb 09 1996 - 12:04:05 EST


Smitty,
The LM386 is probably the best bet in that it is easy to implement
(almost sailor proof) and takes about a 1/3rd of the current of an
LM380. LM386 rated at 0.5W, sufficient to make a fair amount of
racket in a speaker for most applications; the LM380 is rated at
2W and IS a very sufficient audio amp, however, if you really need
some audio horsepower.

Many application circuits on both the LM380 and 386 show the volume
control, a 100-200 ohm pot, on the output of the amplifier feeding
the speaker. Best way to prevent motorboating, but it does mean
the IC is running full power and thus full current all the time.
If current drain is a consideration, then put the volume control on
the IC input to make current draw a function of the volume.

If it motorboats at high gains, let me know. I'll send you a couple
of hints on settling it down. The LM380 audio boards I lab tested
for the St. Louis club drew about 14mA at full throttle, but the
fidelity was excellent. Flat from DC to 400 KHz!

GL, Paul NA5N


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