A common scenario . . .

You're setting up your sound system and it's time to connect up the amplifiers. Where do you turn the knob on the amp? Hmm . . . 12 o'clock looks good. Well, believe it or not, there is actually a correct position to turn that knob to and it can be calculated.

Enter GainSet . . .

GainSet is a computer program that does this calculation for you. Using information you provide about your system, GainSet will show you the gain setting for your amplifier that will provide the highest signal to noise ratio and the "hottest" signal you can achieve before your system clips.

GainSet is free and you can download it from our website. The only thing we ask in return is that you help us make GainSet better by submitting your equipment data to be included in a future version of GainSet.

To download GainSet, go to the download page. You may be asked to accept a security certificate. Go ahead and accept it. A little applet will run and determine which installer you need for your operating system. If you are using Windows you have the option of downloading GainSet with the latest Java Virtual Machine included. If you already have Java 1.4.1 or higher installed on your system then you can uncheck the option to include the VM. If you don't have Java installed or you are not sure, download the windows installer with the VM included.

After that, just follow the instructions in the installer and you'll be up and running in no time.

GainSet is simple to use and will provide accurate information as long you configure your system properly. The data in GainSet is calculated using the following assumptions about your system:

• You have properly set up the gain structure on your mixing console to allow the maximum signal to noise ratio possible for your program material.


• You have properly spec'd your power amplifiers relative to the power handling of your loudspeakers.

***If either of the above requirements are not met, GainSet may not give you accurate information***

When you start GainSet you will see four selectable menus and a graphic of a knob representing the gain knob on your amplifier.

Simply select the manufacturer of your mixing console from the top left list and select the model number from the list below that. Then select the manufacturer of your amplifier from the top right list and the amplifier model number from the list below that. The graphic of the knob will change to indicate the optimal gain setting for your amplifier.

It's that simple! Just turn the knob on your amplifier to the position indicated.

Remember, GainSet will tell you the optimal gain setting for the electronics. You may choose to waiver slightly from that if you are trying to balance an active loudspeaker stack or if your amplifier is too powerful for your loudspeakers. You're the designer. GainSet will tell you where to start. You can take it from there.

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What if my equipment isn't listed?

We have done our best to include equipment definitions for as many poplular mixing consoles and power amplifiers as possible. In some cases, we are still waiting to hear back from manufacturers with the specifications we need to include their equipment in GainSet. In the meantime:

If your mixing console isn't listed . . .

Dig out your manual and locate the spec for the maximum output level of your console outputs. The value should be in dBu. In GainSet select "Other" from the "Mixers" Manufacturer list and select the dBu level from the "Models" list. Then visit the Submit page on our website and e-mail us the manufacturer and model number of your console and the corresponding max output level. We will then add it to the GainSet database and include it in the next update.

If your amplifier isn't listed . . .

You're pretty much out of luck if your amplifier isn't listed. If you can locate the neccesary specs for your amplifier, you could do the calculation yourself. What you definetely need to do is locate the neccesary information and send it to us using the instructions on the Submit page. We will then include your amplifier in our next update.

Here is the info we need on your amplifier:

• The manufacturer and model number
• The maximum input level
• A picture of the gain knob and/or a desicription of how many detents or index markings on the knob and the level of attenuation that corresponds to each detent.

See the Submit page for more info.

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What if I have signal processing devices between my mixing console and my amplifier?

As you can see, GainSet in its current form is only configured to calculate gain structure for a system where the mixing console outputs are connected directly to the amplifier inputs. In most cases you will have signal processing devices between the mixing console and the amplifier. We chose to only include mixing consoles for the first release of GainSet because we felt it was more realistic for us to anticipate what sort of mixing consoles are being used rather than attempt to predict all the signal processing devices. That would be a never ending battle.

However, in the next major update to GainSet, we plan to include signal processing devices but we need the help of GainSet users to tell us what equipment we should include. For now, if you can find the max output level of the last processing device in your signal chain, you can enter that in GainSet using the "Other" option in the "Mixers" list. It is very important that you have properly set up the gain structure of all your processing devices relative to your mixing console in order for GainSet to give you accurate information. There is a tool called the ClipCop that can help you in that process.

When you find the max output level of your signal processing device, go to our Submit page and let us know the manufacturer, model, and max output level of your device and we will include it in the next release of GainSet.

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How does it work?

When used properly, the gain knob on a power amplifier is used to make the incoming line-level signal match the requirements of the input circuitry of the amplifier. GainSet simply takes the maximum input voltage level for the amplifier and subtracts the maximum output voltage of the mixing console. The result is usually a negative number representing the amount of attenuation in dBu needed to get the two signals to match. GainSet then calculates how far the knob needs to be turned to achieve the desired attenuation. Let's run through an example:

You have a Soundcraft K3 mixing console with a max output level of +26 dBu. You have a QSC PowerLight 1 amplifier with a max input level of +22 dBu. 22 - 26 = -4. So you need to turn your gain knob on the amplifier down 4 dB from full voltage gain in order to match the signals. If you select Soundcraft K3 from the "Mixers" menu and QSC from the amplifiers menu GainSet will show you the following knob position:

Here is a picture of the corresponding knob position on an actual QSC PL1:

Notice that the full voltage gain on this amplifier is 32 dB. The position GainSet calculated corresponds to the 28 dB position on the amplifier gain knob. 28 dB is 4 dB less than 32 which performs the required attenuation of -4 dB we previously determined.

Apple is making it increasingly difficult to develop new applications that will run in both OS X and OS 9. This is especially true for programs written in Java. Apple abandoned Java development on the classic Mac OS four years ago. Since GainSet uses some Java technology developed within the last couple years, we are having a hard time getting it to run in OS 9. So now is as good a time as any to make the switch to OS X. If anyone out there is familiar with the Java environment and would like to take a stab at getting GainSet to run in OS 9 we'd be happy to let you take a look at the source code.

The same electrical principles that make GainSet work are also applied to self-powered loudspeakers. In the next update, we plan to include self-powered loudspeakers but we need to know which ones to include. Follow the instructions on the Submit page to get your self-powered loudspeakers included in GainSet.

GainSet is brought to you by Jason Romney and Michel Marrano, former MFA graduates in Sound Design at the North Carolina School of the Arts. A couple years ago we were given an assignment in the form of a graduate research project to come up with a solution that will demystify power amplifier gain settings. GainSet is the result of that project.

To learn more about the Graduate Theatre Sound Design program at the North Carolina School of the Arts you can visit the school website or you can contact David Smith.

To learn more about Jason Romney you can visit his website at www.cd-romney.com.

If you would like to contact Michel Marrano you can contact her here.

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