iamp’s support team is here to help you achieve the best results with each installation. While some aspects of an installation are fairly straightforward, others can be more nuanced. Here are some of the most common questions we receive about gain structure, along with helpful suggestions for resolving them.

When Setting Gain Structure, Why Are Amplifiers the Last Element to be Adjusted?

Because you won’t know the strength of the signal your amplifier is going to receive until you set up all of the devices that precede it in the signal chain, it’s not advisable to adjust the amplifier first. Adjusting gain structure is best done in a methodical, linear fashion, starting from the beginning and working step-by-step to the end of the signal chain. Skipping steps will often lead to problems.

Setting up gain structure by adjusting the amplifiers first is like building a house by constructing the roof first and working your way down to the foundation.

What’s a Good Target for Minimum System Headroom?

That depends on the nature of the signals that will be passing through that system. If the signals have a very steady level (like highly compressed music), you can get away with perhaps as little as 6dB of headroom. However, if the signals are more “peaky” (like live, uncompressed microphones), you’ll need considerably more headroom to avoid clipping, perhaps as much as 18-24dB. For situations where you don’t know which types of signals will be passed through the system, or if it could be a mixture of all kinds of signals, it’s best to err on the side of having more headroom.

How Do I Maximize the Signal-to-Noise (SNR) Ratio of a Microphone?

One of the best methods of maximizing the SNR ratio of a microphone signal has nothing to do with any of the settings inside the DSP processor, or even in any of the other audio electronics in the system. The ideal way to maximize the SNR of a microphone is to physically locate the microphone as close as possible (within reason) to the person who is talking. The closer the mic is to the talker, the higher the SNR. For instance, let’s say that a gooseneck mic is installed on a conference table such that it is about 6 inches away from the talker, and that mic has a SNR of 50dB. Install the same mic as a ceiling mic that is 8 feet away from the talker, and you have reduced the SNR to 26dB.

Of course, once the sound gets into the mic and is converted into an electrical signal, using proper gain structure will continue to maximize the SNR of the signal. Many people overlook the fact that if you start out with a low SNR due to poor microphone placement, it generally can’t be corrected with audio processing.

Why Should I Use Meters When Setting Gain Structure?

You need meters to measure the signal level, otherwise you’re flying blind. Setting up gain structure without meters is like driving a car without a speedometer: you’d have an approximation of how fast you’re going, but you can’t know for sure (and you’d be more likely to get a speeding ticket).

What Are the Advantages of Using an Automatic Mixer?

Automatic mixers (or “automixers”) are great for audio systems that have several microphones. Using an automixer is like having a little robot friend who politely unmutes your microphone while you’re talking into it, and then mutes it when you stop talking. Robots aside, it’s good to minimize the number of open (i.e. unmuted) microphones in a room, for a number of reasons:

  • The more open microphones, the more room noise each microphone will pick up and send to the system. This will translate to increased noise (or “hiss”) in the system.
  • More open microphones make it easier for your system to go into feedback.
  • The more open microphones, the more reflections each microphone will pick up from sound bouncing around the room. Having a lot of open microphones will contribute to a “muddy” sounding room. That’s because every sound in the room – whether it is someone talking into a mic, or something being played out of the speakers – will bounce off of the walls in the room and get picked up by all of the microphones at slightly different times, resulting in a “smeared” sound.

By only unmuting microphones when they’re actually being used, you can avoid all of the above problems. While this can be done manually (i.e. having someone operate a mixing board, and manually push up the fader for your microphone as you start talking, and then pull the fader down when you’re done), it’s usually more effective, less expensive, and much cooler to have that figurative little robot friend do it automatically.

If My Signal Is Clipping, What’s The First Step to Troubleshoot This?

If the problem is as simple as the signal is clipping, you could start by turning down the input gain to correct it. Still having issues? Biamp’s Applications Engineers are always happy to help with any gain structure concerns. Give us a call.

I’ve Set Up My Gain Structure and Have Plenty of Headroom, but the Signal’s Too Low At the Back of the Room. What Should I Do?

Crank up the amplifier as high as it goes! Just kidding. If you try to correct the problem by turning up the overall level of the system, you’ll end up with a good level at the back of the room, but you’ll have signals that are way too loud in other parts of the room. When the signal is too low in certain areas of the room, but the level is good in other areas, the solution is to add more speakers. In this scenario, to get even coverage in all parts of the room, you’ll need to install more speakers that only cover the back of the room.

For additional information, check out the series of gain structure videos on Cornerstone, Biamp’s technical support knowledgebase.

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