How much amps required for 40w amps to run smoothly?

[Rangwan]

I'm starting to have my first DIY speaker system having bought some amp kits for it. After finished that, I then have to find the power supply summing total power is about 40w RMS (consuming about 3.5A).

So, I've bought 5A power supply for it thinking that it's enough. As a result, the mid/high is fine, but the bass is just crackling providing an intolerable ugly sound .

By the way, to prove that my amplifier sucks, I've run for my 2.2Ah 20c lipo for them and the sound is perfectly fine.

So, how much ampere needed to sastisfy this amp system?

[joshnz]

Re: How much amps required for 40w amps to run smoothly?

you forgot to supply working voltage

[Rangwan]

Re: How much amps required for 40w amps to run smoothly?

All of them are 12v amps.

[joshnz]

Re: How much amps required for 40w amps to run smoothly?

40w max is 3.33amps.
A 5amp supply should be fine.
If it still does it you can but some high capacity capacitors near the amp chips.

[999999999]

Re: How much amps required for 40w amps to run smoothly?

What type of amps are these, for car audio? If so, they actually run at 13.something volts in a vehicle environment, you may not actually get 40W from 12V. Then, are you using them with 4 ohm speakers?

A 40W @ 12V amp will not only consume 3.3 Amps, that would make it 100% efficient which none are. You need to measure voltage when the bass cuts out to see if the power rail is drooping. It could be something else like different wires or connector resistance or the power supply isn't actually capable of 5A.

Are you certain these are really 12V amps? If you simply supply an amp with too low a voltage you will have a similar problem, most 40W non-automotive amps need more than 12V.

[Th3_uN1Qu3]

Re: How much amps required for 40w amps to run smoothly?

It could be something else like different wires or connector resistance or the power supply isn't actually capable of 5A.

Or the compensation scheme in that power supply is less than stellar. Audio amplifiers draw pulsed loads from the power supply (obviously, since music has quiet parts and loud parts, it isn't even all the time), and this is pretty difficult for a SMPS to keep up with.

Sometimes, more output capacitance does the trick, since it basically slows down the rate of change of output voltage in response to a sudden load pulse, and the power supply control loop has more time to catch up.

[Kiriakos GR]

Re: How much amps required for 40w amps to run smoothly?

All of them are 12v amps.

And so I will guess that you got a 12V AC transformer ? !

The design of true well made PSU for amps is tricky !
DC stabilization and large electrolytic like 10.000mF is must have.

[Th3_uN1Qu3]

Re: How much amps required for 40w amps to run smoothly?

I think he's talking about a SMPS - there's less likely to go wrong when using a plain mains transformer, but the size of the transformer and the required filter capacitor after the diode bridge is significantly larger compared to a switching supply.

[999999999]

Re: How much amps required for 40w amps to run smoothly?

It would've been easier if we knew exactly what these amps are. Automotive amps should have fairly good HF noise rejection due to the dirty vehicle electrical system. Any ready made amp *product* should already have a fair amount of capacitance in it.

Seems unlikely it uses a 12VAC PSU, why put a step up power rail circuit in an amp when it could've just used a higher voltage transformer, with an automotive type expecting ~ 13.something VDC.

[Rangwan]

Re: How much amps required for 40w amps to run smoothly?

What type of amps are these, for car audio? If so, they actually run at 13.something volts in a vehicle environment, you may not actually get 40W from 12V. Then, are you using them with 4 ohm speakers?

A 40W @ 12V amp will not only consume 3.3 Amps, that would make it 100% efficient which none are. You need to measure voltage when the bass cuts out to see if the power rail is drooping. It could be something else like different wires or connector resistance or the power supply isn't actually capable of 5A.

Are you certain these are really 12V amps? If you simply supply an amp with too low a voltage you will have a similar problem, most 40W non-automotive amps need more than 12V.

I mean there's 3 small amps that has combined power of 40W and those amps feeds on 9-16v.

[999999999]

Re: How much amps required for 40w amps to run smoothly?

^ I don't understand what that means, can you be more specific about the individual amps? Unfortunately I am now drawn away on work so I may not be able to reply about it but the info is also a help to others so we can collaborate to find an answer.

Generally speaking, the typical non-automotive amp operating on 16V or less DCV, has very low wattage, it seems likely the true sum is lower than 40W if using these power sources.

[Rangwan]

Re: How much amps required for 40w amps to run smoothly?

By the way, how much capacitance needed to remove the annoying main hum?

[999999999]

Re: How much amps required for 40w amps to run smoothly?

That also depends on the design of the power supply and the amp.