Playing with the gains on the amp only serves to introduce or deduct noise. It's a false sense of security.
Gains should be set and left where they are, and that is why you tune it using the highest sound level you would like to use. In other words, if you crank your HU to 100% (noone does and its usually tuned at 3/4 volume), then you turn the gains all the way down...turn up the HU to 100%....then turn up the gains until the sound level is there W/O all the nasty noise/trash.....turn down HU....leave it alone and listen to it. That's it. It's not meant to be played with back and forth. It does need to be reset if your source changes, i.e. new HU, but not to be played with from song to song. That is what the HU settings are for. Turning up the gains doesn't turn up JUST the "bass". It turns up the entire frequency range of the amp, including distortion. Distortion/clipping is what tears speakers and amps apart. Gains are NOT a volume control. They are designed to match the output of the HU to the amp.
Don't take my word for it.....here you go:
Gain Controls… Level Matching Devices, Not Volume Controls
February 26, 2008
http://www.bestcaraudio.com/wp-content/uploads/2008/02/gain_control.jpg (http://www.bestcaraudio.com/wp-content/uploads/2008/02/gain_control.jpg)
I’m sure every contributor to BestCarAudio.com would agree that one of the most common misconceptions in the car audio industry is the purpose of the gain control on an amplifier. We all see it on a weekly, if not daily basis… The custom comes in with a blown sub and complains that “my amp is only 200 watts and the sub can handle 500 watts! What’s up with that?”
Truth is, in the 15 years that I have been doing this, I would say that 90% of the blown subs that I have encountered are due to improperly set gain controls, not big bad amplifiers! The purpose of this post is to explain what a gain control is.
To put it in it’s simplest form, a gain control is a level matching device. It matches the output of your headunit’s line outs (RCAs) to the input of the amplifier. When set correctly, it allows your head unit and amplifier to work together in an efficient and powerful manner. When set incorrectly, bad things happen! (yes, i know that many times, amps are hooked up to factory radios without rcas, and much of this post applies to that scenario also)
There are a lot of good and bad head units on the market today. One of the characteristics of a well built head unit is a higher output voltage on the RCAs. Some head units today exceed 8 volts of output. This is a far cry from the cheaper, 2nd and 3rd tier units that deliver 1-2 volts.
The purpose of the amplifier is to… well amplify. It takes a low level input (from the RCA leads) and increases it proportionally and sends it along the speaker wires to create your music. Now if some head units are outputting 1 volt and other are outputting 5 volts, there needs to be an adjustment. That is where the gain control comes in.
Lets say the intended output is 20 volts AC on the speaker leads (an arbitrary number for the sake of easy explanation). In the case of the 1 volt (AC) head unit, we need to increase the signal by a factor of 20. In the case of the 5 volt head unit, it only needs to be increased by a factor of 4.
The end result is that the amplifier does not have to work as “hard” to produce a similar output. Distortion is minimized since you are not amplifying tiny imperfections or induced noises on the input by a factor of 20, only by a factor of 4. The amp runs cooler, again improving performance and sound quality. Not to mention the longevity of the amplifier. When listening to music at lower levels, you will not hear that annoying “hiss” created by improperly set gain controls.
Now all of that can be a great argument for a high voltage preout (another future post), but what about the gain control? The gain control is there to allow you to properly setup an amp with any variety of headunits. When set correctly, all is good. What happens when it is set to high?
In simple terms, when the gain is artificially set to high, you are asking the amplifier to produce an output that it is not capable of. When this happens, you end up with DC current on the speaker outputs. This is also know as clipping. CLIPPING KILLS SPEAKERS!!!
Going back to an earlier part of this post, lets imagine that “Tony” has a 200 watt amp and a sub that will handle 500 watts RMS. A lot of customers would think that there is no way that the 200 watt amplifier will blow out the 500 watt sub. Guess what? It happens every day! Here is why:
Tony’s expert friend tells him to turn up the gain all the way. “The sub handles 500 watts, the amp is 200, CRANK IT UP! That gain is just another volume control!” So tony does this and the amp gets over driven, produces clipping (DC current on the speaker lead) and the next thing he knows, the car is filled with the smoke and odor of a burned voice coil. I am sure that ever one of the contributors to www.bestcaraudio.com will agree that this is very, very common.
It is far better to have an amp that puts out equal or more power than what the sub can handle. You set your gains properly, and the sub will live happily ever after.
So how do I set the gain control? There is not “one-size-fits-all” setting. It needs to be set up by a person who knows what they are doing. Your local Mobile Electronics Specialist is a good start. At our store, we do not charge to set gain controls when th equipment is purchased from us. We charge a small fee to cover our time when setting up stuff purchased elsewhere, but this is money well spent. When set properly by a professional, your equipment will last and give you years of enjoyment.
Posted by Mitchell Schaffer Owner of Mobile Edge in Lehighton, PA Mobile Edge is a leading provide of quality aftermarket accessories and installations in Eastern Pennsylvania www.MobileEdgeOnline.com (http://www.mobileedgeonline.com/)
[email protected]