Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

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You're amazing...let's try this one more time

Posted by Commuteman (A) on August 25, 2004 at 09:55:31

In Reply to: I am sorry to say posted by Soundmind on August 25, 2004 at 04:54:19:

The point is heatng in the output devices, not the loudspeakers. The fact that you were the only person who misunderstood this, and now you point it out to me, is absolutely amazing.

As to the rest of the BS above....

For the purposes of JC's simple point, it's certainly close enough to say that the voltage across the output devices will be independent of load impedance. Remember that he was talking about heating at low output levels, so we can ignore power supply sag, and the output voltage is controlled by the feedback loop.

The current through the devices goes up by a factor of 3. So, to a reasonable aproximation, the power in the devices goes up by 3 (which is v.v.v. different from 9). Am I missing something?

One thing I agree on. You said:

tripling of the current will not necessarily result in the transistors generating exactly nine times as much heat.

Damn right. It will NEVER result in nine times the heat.

As you point out, there are many factors that will determine the actual temperature rise resulting from the TRIPLED dissipation. the design of the amp, the ambient temperature of the room, the incoming AC voltage, etc. etc. What bearing does that have on John's point?

You misunderstood the original post and you made a mistake. Happens all the time. Try admitting it.

See jensw's post for an example of how to do this....

Peter

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