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Foxie

Gain Setting and Impedance

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Foxie

Gain Setting

An amplifiers gain control determines at what voltage on the pre-outs the amplifier makes it's maximum power. It is simply a means to allow different headunits/processors to be connected to the amplifier - it is not a volume control, and should not be used as such.

There are two ways to set the gain on an amplifier - one is the easy way, which is shall detail here, the other is the more precise way, but it requires the use of an oscilloscope and a series of test tones.

Wire everything up so you're ready to go.

Start with the gains at zero.

Play a track that has some clear vocals in it (for front speakers) or some deep bass (for subwoofers), and leave it on repeat.

Increase the volume on the headunit to a little off full volume - this is to avoid sending a clipped signal through the RCAs. For example, on my Alpine headunit, at 35/35, the output signal becomes clipped - at 33/35 it doesn't.

Slowly raise the gain on the amplifier until you can hear audible distortion.

Back down a touch.

Listen to the track all the way through. Are there any distorted notes? If so, back down a little more with the gain until the whole track is crystal clear.

Job done.

Get yourself a beer (NB: Don't drink and drive!).

If you find that after doing this your system is a little quieter than you were expecting, then you need to be looking at getting a more powerful amp, altering the position of your speakers, or sound deadening.

Raising the gain any more won't do anything but harm.

Impedance

Impedance is measured in ohms ( Ω ), and is the AC equivalent of resistance in DC circuits.

It is important to anyone in ICE because it is the impedance of the circuit that determines the power output of any amplifiers.

Basically, it is how much the circuit resists the amplifier's attempt to push power round. A drop by half in impedance means it is twice as easy to get power round, so you get (roughly) double the power. A doubling in impedance means you get half the power, etc, etc.

For example, an amp that does 50Wx4 @ 4Ω will generally do near 100Wx4 @ 2Ω, but only 25Wx4 @ 8Ω.

All in-car amplifiers are stable to 4Ω, and generally down to 2Ω also. However, not many are stable down to 1Ω, so it is essential to be careful when wiring your speakers.*

The only exception to this is regulated amps - these are amps that maintain the same power output in spite of the impedance of the circuit. Certain JL amps..etc.. are regulated, amongst others, so watch out for these, these are usually known as "Class D"

* This is when the channels are unbridged. It is important to note that most amps are only stable down to 4Ω once bridged.

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Guest bass mekanik
Gain Setting

An amplifiers gain control determines at what voltage on the pre-outs the amplifier makes it's maximum power. It is simply a means to allow different headunits/processors to be connected to the amplifier - it is not a volume control, and should not be used as such.

There are two ways to set the gain on an amplifier - one is the easy way, which is shall detail here, the other is the more precise way, but it requires the use of an oscilloscope and a series of test tones.

Wire everything up so you're ready to go.

Start with the gains at zero.

Play a track that has some clear vocals in it (for front speakers) or some deep bass (for subwoofers), and leave it on repeat.

Increase the volume on the headunit to a little off full volume - this is to avoid sending a clipped signal through the RCAs. For example, on my Alpine headunit, at 35/35, the output signal becomes clipped - at 33/35 it doesn't.

Slowly raise the gain on the amplifier until you can hear audible distortion.

Back down a touch.

Listen to the track all the way through. Are there any distorted notes? If so, back down a little more with the gain until the whole track is crystal clear.

Job done.

Get yourself a beer (NB: Don't drink and drive!).

If you find that after doing this your system is a little quieter than you were expecting, then you need to be looking at getting a more powerful amp, altering the position of your speakers, or sound deadening.

Raising the gain any more won't do anything but harm.

Impedance

Impedance is measured in ohms ( Ω ), and is the AC equivalent of resistance in DC circuits.

It is important to anyone in ICE because it is the impedance of the circuit that determines the power output of any amplifiers.

Basically, it is how much the circuit resists the amplifier's attempt to push power round. A drop by half in impedance means it is twice as easy to get power round, so you get (roughly) double the power. A doubling in impedance means you get half the power, etc, etc.

For example, an amp that does 50Wx4 @ 4Ω will generally do near 100Wx4 @ 2Ω, but only 25Wx4 @ 8Ω.

All in-car amplifiers are stable to 4Ω, and generally down to 2Ω also. However, not many are stable down to 1Ω, so it is essential to be careful when wiring your speakers.*

The only exception to this is regulated amps - these are amps that maintain the same power output in spite of the impedance of the circuit. Certain JL amps..etc.. are regulated, amongst others, so watch out for these, these are usually known as "Class D"

* This is when the channels are unbridged. It is important to note that most amps are only stable down to 4Ω once bridged

Good write up :)

couple of small points though.

1) It isnt just impedance that determines an amplifiers output. the efficiency and input voltage will also have a big effect on output.

2) "Certain JL amps..etc.. are regulated, amongst others, so watch out for these, these are usually known as "Class D""

That is wrong. ALL JL Slash series amplifiers have regulated power supplies but ONLY the mono amplifiers are Class D Amps. The multichannel amps are ALL Class A/B circuitry except the 500/5 which is a hybrid class D AND class A/B.

Class D refers to digital circuitry- NOT to a regulated power supply. These are normally only ever used on mono amplifiers (there are exceptions to this rule butthey are rare) the advantage of a digital mono amp is more output and a better level of efficiency (typically 80% or so on a class D whereas Class A/B circuitry hovers between 50 - 60%)

Edited by bass mekanik

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