Re: Assisted Listening systems.

Duncan Wood wrote:

> You need a current drive amp, not a voltage drive amp as the induction of
> the loops significant, especially a multiturn one. Then you need to
> equalise for the steel in the room, it's got a nice resonant attenuation
> hump. Also the loop is obviously a big areial so the output drive needs to
> be stable & reject noise on it's output , which Quads aren't that good at
> , nice as they are otherwise.

To a first order appoximation a simple band limited differentiator will get
you at least much closer to workable with that old quad (Funny how everyone
who has had to hack a quick bodge on this uses a 405....). 
I didn't find the 405 to be that bad from an RF pickup perspective, but the
few ohms of series resistance and a few carefully placed caps probably had
something to do with that.

The steel thing takes a little more work (cheap parametric), and some fairly
serious compression/limiting really helps. 

Dan (Who has been blessed by a blown loop driver before the 'blue rinse'
free pensioners show)!
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