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Amplifier Gain Setting – Introduction

Amplifier Gain Setting introduction

Have you ever said any of these things about amplifier gain setting?

  • I set it to halfway
  • It wasn’t even turned up all the way!
  • I didn’t even touch it
  • It’s supposed to be louder than that

Disclaimer: Before you get into this, please understand I do not know your individual skill level. This is a primer to a topic that brings in a lot of science, and the science is not going to be discussed in depth. This is skimming the surface. Got it? Good. Let’s go.

Why does this thing we call Setting Gains even matter? 

The purpose of an amplifier gain setting is to match the input range of the amplifier to the output voltage of the source unit.

Why? The thing we get to listen to by hitting Play starts as sound waves, which are changed into electricity, which eventually get changed from electricity(we will measure this as Volts) back to sound waves.

Back to gain setting. The source unit is the radio. Output from the radio goes to the input section of the amplifier. 

The output voltage swings up and down as we adjust the volume setting of the radio, and also as the program(music, talk radio, podcast, etc.) changes in loudness. 

We know the bottom of the range. That’s Volume at ‘0’ or when the music is paused. The top of the range can be assumed to be 3/4 of maximum. That’s for the output of the source unit

The input of the amplifier is also adjusted. When the gain setting is too low you’re going to run out of volume, or the bass won’t get as loud as you think it should. 

A Note About Loudness

Turning the gain knob to the right makes the sound louder. This is similar to the result of turning up the volume at the radio. We are doing different functions. The gain knob is not the volume setting of the amplifier.

gain knob on amplifier
Another label for amplifier gain setting might be ‘Level’.

Rob Haynes, Product Training Specialist at JL Audio in Miramar, FL, explains the four primary reasons we must have a repeatable and accurate method for amplifier gain setting. This might also be called the Input Sensitivity setting.

  1. Optimize performance from the amplifier without excessive clipping
  2. Reduce distortion
  3. Improve sound quality
  4. Avoid damaging the speakers

The following video gets right into some technical terms and it assumes you already have experience of successfully installing car audio amplifiers and the use of basic tools that are shown in the video. If you want free step-by-step guidance, and you’re on Facebook, now is the time to join our group Students of Mobile Audio.

Top 3 Gain Setting Methods (in no particular order)

  • By ear with music
  • By combining tone test tracks and a digital multimeter (set to measure volts).
  • Use tone test tracks and an oscilloscope

I’ve done it all three ways with success. Each method must include reference quality test tracks so you or a technician can go back at any given time and get things back in alignment. Turning the knob up halfway is not a method I will endorse. That’s guessing.

There have been many sources of reliable test tracks for audio systems over the years. One that came up as a free download is Focal Tools CD

Focal Tools CD
Focal Tools CD

Advanced amplifier gain setting

  • Balancing multiple amplifiers
  • What to consider in low power versus high power amplifiers
  • Clipping indicator lights and other in-built amplifier setting aids
  • How much clipping is too much?

Would you like to contribute your own amplifier gain setting article? Ask me how to be a guest author!

Barry Schanz
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Choose 2 Channels or 4 Channels – Speaker Amplifier Buying

Choose 2 Channels or 4 Channels

How do I choose 2 channels or 4 channels when I decide I need an amplifier for speakers?

When you’ve committed to upgrading your sound system this question might have been very sharp and clear in your mind.

Let’s dive into a real world example. This could happen if you talked with a sales person and they go to the effort of trying to understand your motives. Often there is a hidden complication or twist that comes from a difference of understanding what can be done.

Tip for Better Communication: Ask open-ended questions when you’re in discovery mode.

This is pulled from an online discussion. Jim is the inquisitive shopper.

Overhead drawing of car and 4 door speakers Kevin Hulsey

Jim: is there a way to wire the left door speakers together such that they run as a stereo channel off one input, or is this only for subwoofers?

Barry: Two doors, two speakers wired together means you have one input which cannot be stereo. It doesn’t matter what type of speaker it is, that is going to result in one channel of sound.

In this example the same input signal will be played back from the front left door and the rear left door. Is that what you want?

What do you want?

“the same input signal will be played back from the front left door and the rear left door.”

Jim: Isn’t this how it already is since all the speakers are mono?

It was mostly just hypothetical because I wanted to know if I should buy a 2 channel or 4 channel amp, but I understand now. Appreciate the help!

line drawing of Mono vs Stereo Signals
Mono vs Stereo Signals sent to two speakers
Barry: No. I think the confusion is because we’re using a prefix, “Mono”, to mean one, yet we’re talking about different parts of the signal chain.
The input starts with the source, or the program material. We assume you’re playing music that’s made to have Left and Right channel separation(Stereo sound).
The next step is a division of this signal that takes place at the radio. I don’t know what radio and vehicle sound system you have so I’m making an assumption that it’s the standard radio with 4 speaker outputs, Front Left, Front Right, Rear Left and Rear Right.
For the pleasure and comfort of the passengers we have all 4 speakers on 4 separate outputs. By adjusting the Balance and Fade controls in the radio you can find that you will be able to play a mix of as few as 1 speaker up to all 4, redirecting the emphasis or loudness throughout 4 quadrants of the interior.
Let’s go back to the music, which we assume has Left and Right separated, in Stereo sound. The radio sends the Left channel sound to both the Front Left and the Rear Left speakers, and so on for the right side. For your decision, we’re not done.

Choose 2 Channels or 4 Channels?

Why do we buy a separate high power amplifier for speakers?
  • Greater clarity
  • More power to better drive less efficient aftermarket speakers
  • and a bit more loudness and fullness to the sound.

Ask yourself two questions

  1. Do I want all 4 speakers, front and rear, to get these improvements?
  2. Is it possible I mainly want to improve the sound where I sit?
Choosing a 4 channel amplifier is usually a safe decision. Some car amplifier manufacturers don’t even offer 2 channel amplifiers, as the market has dictated they aren’t in high demand.
Normally we can still use a 4 channel amplifier as a 2 channel amplifier.
If you begin using the 4 channel amplifier as a 2 channel amplifier that offers an upgrade path.
Sometimes it makes sense to use the 4 channel amplifier as a 3 channel amplifier. 
Is it a horrible idea to have more options with one purchase? Talk with your sound system designer. 
Further reading:

Barry Schanz
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