Amplifier input attenuators (or volume controls)

A look at the "volume controls" (input attenuators) that are found on many amplifiers. This is a brief overview of what they actually do and how they are sometimes misused.

Whether they are called "volume controls" or "gain controls", or etc... it's important to know what they do and how integral their use is with your sound system.

It's been awhile since we posted a non-event video. We hope to have more videos soon covering equipment and how that equipment is used.

[isettech]

Proper use of the amplifier attenuators is as follows.
1 Set up your console for nominal levels all the way through. This is proper gain structure and is used in both a small club and in a large amphitheater. This provides some protection for the amplifier and speakers. With proper console setup, the maximum headroom is about 12 db. Most consoles provide a nominal output of +4 DBU. Most consoles clip at about +18 DBU, so there is no more after that.
Now set the amplifier attenuators for the maximum loud sound for the event. This can match the speaker rating, Venue DB limits, or safe hearing level for the event.
This allows the console to operate with the proper headroom, high signal level of +4 DBU to provide the maximum recommended signal for the noise level of the system. Yes this operates at the best S/N ratio for the cleanest sound with little chance of running out of headroom.
How not to operate the attenuators.
1 Turn them all the way up. This amplifies the noise floor. The console operates with the output very low to manage output levels. This provides poor S/N ratio, and allows the amplifier to be driven to clipping at maximum power, which may be more than 30 DB of headroom, resulting in blown speakers in a runaway feedback conditioin when a guitar is set on a monitor, or a mic is dropped, etc.
Most consoles are able to output between + and - 12 to 15 volt peaks before clipping. Your amp attenuation should never be turned up for sensitivity for a 1.2 volt signal. The console can provide up to 30 volts peak to peak. Check the specifications for your console. Industry standard is +4 DBU balanced signal. The extra gain is for when you use a home receiver, VCR, cassette deck, etc which operates on lower voltage and outputs -16 DBU as the nominal output. This includes consumer grade tablets, MP3 players, some DJ USB powered mixers, etc.The DJ's with RCA connections can use the extra gain. A pro board with the nominal +4DBU does not need the attenuator turned to the max ever.

[makstaz]

Thanks for this information I found it very helpful, keep up the good work .

[jasonhpratt]

That helped a lot !thank you so much 🙏

[LucasWasson]

Great video I would love more info on powered speakers. Should I be treating them the same and be running them wide open as you called it? Or just turn them up to what's loud enough?

[DhanjitMr]

Sir Show some demos. Thanks for the knowledge..

[travisgulley]

If the clip led on a power amplifier comes on when the volume on the mixing console is cranked up halfway will the speakers be just fine and not blow

[Dabbyreverb]

So i have issues with the whole sensitivity stuff, after setting up and having my gain structure in place from the mixer board, turning up my amps to the highest causes lots of feedback issues. Although i use a speaker management at 0db. What could be the solution. Thanks

[travisgulley]

Do some pro audio power amplifiers have a bass boost and or a loudness feature that you can turn on or off.

[travisgulley]

Will the clip indicator leds on a power amplifier still be able to come on if a compressor is hooked up to a power amplifier

[jessecoonen]

I have EV ETX boxes that are self powered. They have an input gain or attenuator and a master volume knob. I’ve been running the master wide open and keeping the input at unity. They’re 2000 watts peak power but still don’t seem very loud when they start to limit. Any thoughts?

[travisgulley]

Does turning up the volume on the mixing console cause the power amplifier to draw more current.

[travisgulley]

Do the low frequencies on the equalizer need to be turned up if you are using a power amplifier to power subwoofers

[travisgulley]

Does hooking up a graphic equalizer to a power amplifier effect how loud the speakers get.

[valentingheorghe]

Know the nominal level and the maximum output level of the mixer, which may be +18 dBU, +20 dBU or +24 dBU.
The clip level of the mixing console is, usually, marked at 6 dB over the last yellow/amber leds on the level meters.
If the mixer has a nominal level of +4 dBU (0 dB mark on the level meters) and a maximum output level of +20 dBU (+16 dB red led on the level meters), I have 16 dB of additional dynamic range above the nominal level.
I intend to use the maximum dynamic range of the mixer and to ensure the best signal to noise ratio in the system, before the signal is sent to the amplifier. Therefore, I set the channel input gain to hit the 0 dB mark on the meters, then I raise the channel fader or the master output fader fully up (+10 dB), to hit the last yellow/amber leds on the meters (+10 dB), just below the clip LEDs. This offers me 6 dB of headroom before clipping the mixer output.
On the amplifier side, set the input sensitivity switch to 1.4 V RMS to match the mixer's nominal level and adjust the sensitivity controls to -10 dB attenuation for rated continous power output. At this point, the continous power output of the amplifier is about 1 dB below its maximum power output.
The above procedure it is based on the assumption that the loudspeakers continous power rating are matched with the amplifier continous power rating.
If a compressor/limiter is used between the mixer and the amplifier, the mixer output level can be increased to its maximum level (+20 dBU) and the limiter threshold should be set at the point where it begins to catch the signal peaks, with an additional 3 dB of attenuation, for safety.
If the speakers continous power rating is lower than the amplifier continous power rating, lower the amplifier input sensitivity controls or the mixer master output level according to the power you need for the loudspeakers and allow for about 1 dB of headroom also for the speakers.

[travisgulley]

If a power amplifier has a 15 amp fuse on the back of the power amplifier and outputs way more than a 1000 watts rms does it have to be plugged directly into the wall outlet and not a power strip

[travisgulley]

Does the amperage of the fuse on the power amplifier determine how much rms power the power amplifier puts out.

[travisgulley]

Why do some power amplifiers say caution high voltage on the speaker terminals on the back of a power amplifier.

[travisgulley]

Is it safe to plug pro audio power amplifiers into a power strip or is it a fire hazard.

[Extremeadventuresandevents]

hi, bob. can you please recommend for me entry level industry standards wireless microphones that are tech rider friendly. thanks

[darrenchase]

I have the levels maxed out i have it connected to my avr pre outs