The importance of amplifier coils

[Patthehat033 10+ year member]

I am a bit confused on how an amplifier "amplifies the current".

Okay so if you have 12V plus say 30 AMP's going into your amplifier from your battery. You are putting in 360 watts of power.

When you add the coil to the process you increase the voltage say to 24V and now you are only working with 15 AMP's. These are probably not realistic numbers but that is besides the point. What is the point of increasing the voltage if the wattage is the same?

Or do I have my math wrong does the voltage go up and the amp's stay the same?

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[brandinooooo 10+ year member]

HowStuffWorks "How Amplifiers Work"

 

[ahole-ic]

I am a bit confused on how an amplifier "amplifies the current".
Okay so if you have 12V plus say 30 AMP's going into your amplifier from your battery. You are putting in 360 watts of power.

When you add the coil to the process you increase the voltage say to 24V and now you are only working with 15 AMP's. These are probably not realistic numbers but that is besides the point. What is the point of increasing the voltage if the wattage is the same?

Or do I have my math wrong does the voltage go up and the amp's stay the same?

Those torroidal transformers you're referring to step the voltage up on the input side. It is rectified and cleaned up. Since the signal passing through a speaker is AC current and not DC, the amplfier will basically takes that power you just boosted and cleaned up and mixes it with the input signal.

(what is the point of stepping up the voltage? Higher voltage is easier to store, and easier to work with. Low voltage/high current is very inefficient and there is TONS of heat.)

So, you were not understanding that your speaker's input needs to be AC so the cone can move back and forth instead of just locking in 1 direction.

2 you can't get more out than you put in. You touched on that but it was like you didn't believe it.

 

[martiandancer31 10+ year member]

if the amp didn't step up the voltage, it could only output 12V, and as a result of that it would only be able to deliver 12 amps to a 1 ohm load. That's not a lot of power. Thus, you either need to decrease the impedance, or step up the voltage if you want to deliver more power. Hence, the reason for stepping up the voltage.

 

[VWBobby 10+ year member]

There's 2 basic modes of operation..... High current, low voltage (loads less than 1 ohm) or low current, high voltage (loads over 1 ohm).

Voltage = Potential energy (like a large lake or water reservoir)

Current/Amperage = Rate of flow or flow of energy, fast moving stream or river

It takes more force (current) to drive a speaker at low ohm loads than it does at higher ohm loads. Other amplifiers might only be stable down to 2 ohms and not capable of higher drive currents. Instead, they convert some of the car's current into voltage and drive the speakers at a higher voltage when running at 4 or 8 ohms.

voltage: Electric voltage

current:Electric current

The amps with the huge toroidal coils are usually stepping the voltage from 12V up to 70V or higher to drive larger transistors or banks of transistors. They are running in a "high voltage" mode. Depending on the design, this can be pretty in-efficient. Think of the big surfboard amps with multiple huge toroidal coils and 30+ FET's.... Other very efficient amps like a MMATS, BASH, Tru can be upwards of 85-95% efficient and use very few components in comparison. Much smaller amps.

Its much easier for an amp to deal with higher voltage at low current. Easier to switch voltage on and off at higher speed than it is to switch large amounts of current at high speed (remember, music/audio is AC).

This is why Class D subwoofer amps can drive very low ohm loads and still have an efficiency of 80% because it is switching almost completely off and back on at a relatively slow rate of speed. A Class A/B amp is partially on all the time (Class A) and switches to full current when the bass/music hits (class B). This is why a Class A/B amp has a lot less efficiency (around 55-65%) when putting out the same power as Class D. Up until very recently, nobody could make a clean sounding Class D full range amp, so the only choice was A/B for years.

 

[maylar 10+ year member]

I am a bit confused on how an amplifier "amplifies the current". ?

It doesen't. An audio amp amplifies power. The load (speaker voice coil) draws current from the amp depending on the voltage applied to it. The combination of voltage and current is power (watts). The coils in an amplifier's power supply allow it to "step up" the voltage from the 12V battery to supply a load that needs more than that.

Okay so if you have 12V plus say 30 AMP's going into your amplifier from your battery. You are putting in 360 watts of power.

The current going into the amp is a function of the power being delivered to the load plus some overhead (losses, efficiency) required by the amp itself. The amplifier won't draw 30 amps from the battery unless it's delivering 360 watts to the load (actually less, depending on efficiency).

When you add the coil to the process you increase the voltage say to 24V and now you are only working with 15 AMP's. These are probably not realistic numbers but that is besides the point. What is the point of increasing the voltage if the wattage is the same?

OK... let's pick some hypothetical numbers. Say the amp is putting out 24V to a 2 ohm coil. The speaker will draw 24/2=12 amps from the amplifier. The power to the speaker is 12A * 24V = 288 watts. The amplifier must get that 288 watts from the battery. So with a 12V power source the amplifier will draw 288/12 = 24 amperes of current (this assumes 100% effieciency, which is not true but you get the point).

So the input POWER to the amplifier is dependant on the output power, and input current is a function of the battery voltage. The amp draws what it needs to feed the load.

Input power from the battery is PowerOut/Efficiency. Input current is InputPower/SupplyVoltage.