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.

Radio Microphones

We have just come back from a church who were having problems with their radio microphones - one did not appear to be working. It turned out that adjusting the settings on the back of the microphone fixed the problem, but we know that many churches do not understand the settings on the back of their radio microphone receiver, so here goes for an explanation...

There are generally two controls on the back of a radio microphone receiver - the first is called Gain or Volume and the second called Mute or Squelch. What do they do???

The gain control adjusts the output level from the radio microphone receiver, so that it can match the input of the mixer/amplifier which it is driving. This can be very useful as you will see...

The Problem : we found that the church had the level controls on the mixer set to around 1.5 out of 10 for the radio microphone channels. This meant that there was very little room for adjustment when there was a loud speaker using the radio microphone - even the slightest touch turned off the channel or worse still made it far too loud!

The Solution : by reducing the output level from the receiver, using the Gain control, we were then able to turn up the level on the mixer input. Carefully, we were able to set a nice sound level where the mixer control was half way, i.e. 5 out of 10. This therefore meant that the operator had lots of upward and downward movement to compensate for different speakers.

The Mute control sets a threshold where the receiver decides that incoming radio signals must be rubbish, or interference. When the radio signal level is below this threshold, the receiver automatically mutes its output. This is great for ensuring that you do not pick up transmissions from local taxi firms, airports and such like. However it has a downside...

The Problem : it appeared that one of the radio microphone receivers was not working - or that the transmitter had stopped transmitting. Whichever, it seemed that there was no radio signal and therefore no audio coming from the microphone.

The Solution : on closer investigation, we found that the Mute control had been turned up to maximum. This meant that the radio microphone was muting out (removing) all signals, including the valid signal from the radio microphone transmitter. This gave the impression that the system was not working. By simply reducing the mute level we made the receiver "work" again. However, it is worth listening to the system with the transmitter off for a while to make sure that you don't then start picking up the local disco again.....

Well, thats it for this time.

Tim.

***** Visit us online at www.ChurchPA.co.uk *****
***** Phone 0845 430 9486 *****

Our New Blogsite!

Hi everyone!

Finally we have got our own blog! We plan to discuss new developments in audio equipment, general topics for audio in churches, and also to keep on top of the questions that people ask us about the sound in their church.

So, thanks for taking the time to read this blog, and we look forward to adding great content over time.

Tim.

***** Visit us online at www.ChurchPA.co.uk *****
***** Phone 0845 430 9486 *****