measuring Input impedance of an Amplifier

pinkmouse

diyAudio Moderator Emeritus
2002-04-03 7:15 pm
Rotherham, England
I am planning to cobble together a cheap sub with bits and pieces I have lying around and could do with some advice.

I have built the box with no problems at all, and I had lying around an old 150w mono power amp built by a friend years ago to power it, but I need some help.

Because buget is a major factor, ( and I also like to play around), I would like to use a passive 2nd order line level crossover to run at about 80-90 Hz to drive the amp from the lfe output of my Arcam Alpha 10 Dave system.

But, as far as I can see, I need to know the input impedance of my power amp to properly calculate the component values in the crossover.

So, my question is this... Is there an easy way to measure input impedance using basic tools, such as a multimeter and pc based tone generator in the same way you can measure drivers, or do I need massive amounts of test gear?

And if that's too easy, any way to modify passive line level crossovers to give a sweepable crossover frequency for room tuning?

Anyone any Ideas?

Cheers

Al
 

pinkmouse

diyAudio Moderator Emeritus
2002-04-03 7:15 pm
Rotherham, England
Hi Per

Thanks for the tips, I'll give it a go this evening and see how get on.

Sorry about the resistance/impedance confusion, I had searched many pages whilst doing research, and I think my brain was overloaded! ( as a stage lighting tech, normally I use 3 phase power at several hundred amps, and this small stuff gets confusing!).

Cheers

Al

p.s.
Your site is great, and very informative, but it would not load in Explorer 5.1 on the Mac.