Re: Measuring audio power ...

I
tp://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9508180&N=401

A bunch of those nice, aluminium clad, 50 Watt resistors from Farnell.
They're bolted to a chunk of extruded aluminium rectangular tube. There's
a fan on one end and a thermal switch on the other. When it gets hot, the
fan switches on and cools the assembly (and warms the workshop, on these
cold Winter mornings). I have a bloody big old switch, so I can choose 8
Ohms, 4 Ohms or 2 Ohms for testing. Additional to that, but less often
used, I have a 0.1uF and a 2uF cap to switch across the load to test for
stability. I also use, less frequently, a dummy load, like this one:

http://stereophile.com/reference/60/

Mine has impedance minima to around 3 Ohms and there are other
differences, but this one is pretty good. As PA has indicated, such a test
shows up many, otherwise exemplary, amplifiers as being rather bad at
operating into real loudspeakers. All monitored by a 'scope and a wideband
millivoltmeter. For a long time I used a real power meter, using an
analogue multiplier IC. It was nice and convenient.


--
Trevor Wilson
www.rageaudio.com.au


Hi Trevor

Yep, those are the exact same resistors as I am using, but in the 100 watt
flavour.

Yep same ones here:)

Heatsink the size of the Titanic with a matching fan bolted to the
end, but mine runs all the time. Has proved very useful for repair of high
power PA amps, where the owner complains of things like " cuts out half way
through the second set ". I can now leave the amp thrashing away into this
load, with the scope hung on the socket I've provided.

Arfa



--
Tony Sayer

.

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