Don Pearce wrote:

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It seems the big advantage of loop systems is they are the cheapest option.


The real reason they became popular was because they function like a
transformer rather than a receiver/ transmitter. The field strength
within the loop is more or less constant wherever you stand, and
outside it the signal drops away rapidly. That lets you implement
virtually private circuits - for bank checkouts and the like.
And as you say, they are also really cheap to set up - just a moderately
powerful audio amp and you are done.



** Except when that "moderately powerful audio amp" objects to driving a copper wire loop. Even using 1 sq.mm wire involves a loop 220 metres long to achieve a safe resistance value of 4 ohms. I've seen a 2 ohm loop connected to one channel of a 2 x 300W amplifier to cover a private cinema - the amp did not last long.

Standard practice is to use a "constant current" amplifier and a signal limiter to prevent accidental overdriving of the amp. Band limiting the audio is a good idea too, from say 250Hz to 10kHz.

Oh yes, if a group using electric guitars wants to perform in the space, turn the loop amp of.


..... Phil