Induction Hearing Aid Loop Problems

We get contacted a few times a year from people who are getting audio feedback problems because their hearing aid induction loop is interacting with a guitar - this is the solution....

You need to check a few things (in the order to check/rectify)

Are you using a "real" induction loop amplifier? Some churches have pressed an audio amplifier into service for the loop. This is not acceptable and causes odd peaks in the signal on the loop, which can cause these problems.

Is the loop level turned up too high? If the signal on the loop is too high, there is obviously a much stronger coupling between the loop and the guitar. So firstly check with a loop signal strength meter that the loop is at the right level.

Are you using very long unbalanced leads on the guitar? By this I mean is the guitar lead longer than about 5 metres? If so, you *must* use a lot shorter leads, as the coupling will be happening here.

Are you using unbalanced leads from the band area to your mixer? Again, any/every long unbalanced lead *will* couple with the loop. Use balanced cables and a DI box instead - this is the only real solution with long cable runs in conjunction with an induction loop.

We just said it, but will say it again - short unbalanced leads are essential with an induction loop.

Is the ground good in the guitar? It is essential that there is a good connection on the ground part of the guitar and this must also make a good connection to the lead. Additionally, there must be a good ground connection from the amp to the ground in the wall. Look into this if the above issues do not solve your problems, as it is slightly difficult to check (you can use a multimeter between mains socket GROUND and the metal work on the guitar - be careful and do not electrocute yourself!). If this is the problem, you need to shield the electronics in the guitar better, and maybe consider using a humbucking pickup. This can be done by a good guitar shop. This is a last ditch solution, and is 99.99% not necessary if the above solutions are used. You can also consider using a much higher quality guitar lead before resorting to any permanent changes in the guitar.

One final tip is to place the instrument amplifier as CLOSE to the loop cable as possible, as there is a dip in the field strength at the wire. Might just make some difference...

We hope that this helps you solve this problem, but if you wish to contact us, we would be happy to discuss your particular problem with you.

Tim.