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Old 9th October 2007, 04:11 PM   #1
gni is offline gni  United States
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Default Changing Output Resistors to Make Current Source Amplifier

I finally read some articles on the Nelson Pass website; but this is a
question about solid state amps.

There is talk of making a voltage source amplifier act like a current
source amplifier.

At one point the article states adding up to 47 ohms in series with
the output; in another it states adding 47 ohms in parallel with
the output.

Would adding this magnitude of resistance to the output of an
amplifer make it magically work like a current source amplifier?

Would it be better to increase the value of the 0.22 ohm resitors on the power transitors outputs?

Wouldn't reducing negative feedback also raise the output impedance
of the amplifier equally as well.
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Old 9th October 2007, 04:38 PM   #2
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Adding a series resistance is one possibility,
but most of your output power would then be going to the resistor.
all of a sudden your 500 watt amp is a 50 watt amp.

Changing internal resistors is possible (having the speaker in the feedback loop) is possible, but you change so much you'd want the amp designed for that application.
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Old 9th October 2007, 04:42 PM   #3
gni is offline gni  United States
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Just did some quick calcs. . . my rotel RB-850 has about 41V rails:
but can only produce about 50w into 8 ohms. . .but since the
impedance is higher, it would probably use all 41V into the 55 ohm
load. . .4.45w into the 8ohm load and 26.1w into the 47ohm with
745mA!
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