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Setting Up Monitors – Board Unity Gain vs. Amplifier Output Gain

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Setting Up Monitors - Board Unity Gain vs. Amplifier Output Gain

Setting Up Monitors

Today’s post is regarding monitors.  At North Ridge Community Church, NRCC, we run our three separate monitor mixes from the front-of-house.  These monitor mixes are fed via the pre-fader aux sends, go through a graphic equalizer, are then amplified by a Crest Audio amplifier and then show up to our JBL floor wedges.

This is a very normal way to do monitor mixes and all is great, until… I discover how it is truly set up.

The Problem!

  • The amplifiers in the amp room are all turned up to full.
  • The output of the board aux sends are not full signal.  In fact, they don’t have enough signal to light up the -21dB light on my equalizer.
  • 100-105dB volume normally output by monitors.
  • AC hum present when the system is turned on.

Because the monitor amplifiers are turned up so loud, the aux send knobs are in the 9 o’clock to 11 o’clock range on our sound board.  While this doesn’t sound that bad, on the Allen & Heath ML4000 the unity gain (+0dB) for aux sends is at 3 o’clock and the knobs are a logarithmic potentiometer.  They act just as a normal fader does on the sound board, where there is more resolution in the higher areas of the fader.  Basically, if you move the aux send knob from 9 o’clock to 10 o’clock you would increase the volume by 10dB.  If you were to move the knob from the 2 o’clock to the 3 o’clock position you would increase the volume by 1-2dB.

Setting Up Monitors - Board Unity Gain vs. Amplifier Output Gain

Found at www.bigmuffpage.com is a perfect graphic for explaining the logarithmic taper of the potentiometers that are used in aux sends.

LOTS of NOISE!

The most noticeable problem with having such a low output from the board and the amps turned up high is that the noise level is very high. I have made a graphic below to show the how the the signal to noise ratio is resulting:

Setting Up Monitors - Board Unity Gain vs. Amplifier Output Gain

By having the board turned down and the amplifier turned up to full, you have made your signal to noise ratio very small. But, when changed to a full board output and to a lower gain on the output of the amplifier you will have a high signal to noise ratio giving you less noise in the monitor system and better clarity.

THE FIX

Turning the amplifiers down and turning the board feed up, you not only raise the signal to noise ratio, but you also have more resolution on the aux knob giving you an easier time mixing the monitors.  Additionally, when you do an AFL (after-fader listen solo) you don’t need to turn your headphones up to hear it.

After turning the amplifiers down and turning the board up I was able to keep the same overall volume with the monitors but now there is no audible noise in the room from the system being on.  So, if you find yourself having a hard time getting a consistent monitor mix or a noisy system, you might want to double check your amplifiers output gains to make sure they are receiving a unity gain signal.

3 Comments
  1. David says:

    In your YouTube channel,I noticed that all your amps where turned up during the amp room tour. Doesn’t this same principle apply???

    1. It would, but in this case the EAW system processor relies on the amps at full gain to correctly compensate the use of different output gain amps for the tri amped EAW KF650e’s.

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GET THE X32 ROUTING WORKSHEET FOR FREE!

I FOUND THAT OVER THE YEARS, HAVING MY ROUTING WRITTEN DOWN NOT ONLY MADE MY JOB EASIER BUT IT MADE ME FASTER AT MY JOB!

AS A THANK YOU FOR COMING TODAY, I WANT TO GIVE IT TO YOU!

Subscribe Me