DC powered amplifier voltage rails?

[yepimonfire]

Generally, an amplifier that is hooked into a standard 120VAC outlet has a fixed maximum rms voltage from the internal power supply, however, I’m wondering how this would work with an external supply often used in a lot of the mini amps you can get on parts express.

Many of these will allow you to use a range of voltages, for example, the lepai amps specify 12-24v. Is the DC input voltage the max voltage supplied by the amplifier, or does it not work that way? I did notice with the lepai amp, swapping the 12v 2.6a supply with the 19v 7.7A supply used to power my gaming laptop significantly increased the amount of output I could obtain before clipping, what I’m not sure of if this is simply due to more current availability or both more current and voltage.

Anybody who is versed in amplifier design have an answer to my question?


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[slipperybidness]

Generally, an amplifier that is hooked into a standard 120VAC outlet has a fixed maximum rms voltage from the internal power supply, however, I’m wondering how this would work with an external supply often used in a lot of the mini amps you can get on parts express.

Many of these will allow you to use a range of voltages, for example, the lepai amps specify 12-24v. Is the DC input voltage the max voltage supplied by the amplifier, or does it not work that way? I did notice with the lepai amp, swapping the 12v 2.6a supply with the 19v 7.7A supply used to power my gaming laptop significantly increased the amount of output I could obtain before clipping, what I’m not sure of if this is simply due to more current availability or both more current and voltage.

Anybody who is versed in amplifier design have an answer to my question?


Sent from my iPhone using Tapatalk

More voltage on the supply rails allows you to get more power. When you design an amp power supply, the voltage at the supply rails is a critical parameter to determine how much power the amp is capable of producing.

Power = VI
I = P/V

So, for a given constant power, if you increase the voltage, the current draw is actually less.

Yes, in theory the input voltage is the max voltage that the amp can supply to the output. In practice you will never actually reach that voltage due to non-ideal losses and supply voltage sag when the P/S is loaded.

 

[Speedskater]

Better power formulas are:
Power = I sq. x R
Power = V sq. / R

The resistance/impedance of the loudspeaker is what it is (although it varies with frequency).
So the formulas is the previous post are not changeable.

 

[slipperybidness]

Better power formulas are:
Power = I sq. x R
Power = V sq. / R

The resistance/impedance of the loudspeaker is what it is (although it varies with frequency).
So the formulas is the previous post are not changeable.

Identical power formulas

 

[mtrycrafts]

Identical power formulas

Yep, there are a number of ways to express the power formula.

Any will get you there if you have the numbers to plug in.

 

[everettT]

Yep, there are a number of ways to express the power formula.

Any will get you there if you have the numbers to plug in.

But does that answer the OPs questions? Are were there questions? Wait now I'm confused.

 

[mtrycrafts]

But does that answer the OPs questions? Are were there questions? Wait now I'm confused.

Well, no, it doesn't directly answer the OP I just agreed with slippery.