Would this work well as the power supply for a class D amplifier, example, the Sure products?
I fully agree with BIGT for this question. I have never used this particular laptop power supply, but I have used about half a dozen other laptop power supplies, some very extensively, to use as amplifier power supplies, and generally it works quite well, especially with a simple mod.Those Sure amps actually require very little power. Although their specs say that they can draw up to a certain amount of current, they will NEVER draw that much current unless you send pure sinewaves through all of the amp’s channels at full volume (and I doubt you’ll be doing that regularly). For example, the Sure 100Wx4 amp states that it can draw *up to* 16A, but in reality you will almost never go above 10A, and that’s assuming you’re using a 30V power supply and you have 4 ohm speakers on all 4 channels. If you use higher-impedance speakers, or if you don’t use all 4 channels, then the current requirements will be less. And, if you use a power supply with a lower voltage, then the current requirements will also be less because the lower the supply voltage with these Sure amps, the less power they can output (see my review of the Sure 100Wx4 amp for details about that).If you used this laptop power supply at its highest voltage of 22V, then that 100Wx4 amp will never draw more than an average of about 4A when playing music, assuming 4 ohm speakers on all 4 channels (I know this from extensive experience with that amp). However, that is the AVERAGE current that it will draw. The short-term PEAK current that it will draw is more like 15A (again, see my review for details about this). So, if you used this laptop supply at 22V with that 4x100W amp, then it will probably have issues when those 15A peaks come along because this power supply can only deliver an absolute max of 5A.However, one way to deal with these current peaks is with capacitors. If you put large-value capacitors in parallel with the power supply, then that will reduce the size of the current peaks drawn from the power supply (because the capacitors will take care of the current peaks, to some extent). For example, by putting 20,000uF worth of capacitors in parallel with the 22V power supply for that 4x100W amp, the current peaks that the power supply will have to deliver will drop to about 9A (again, I have actually tried this in the past). More capacitors will reduce this even more, but there is a limit to it. So, with these added capacitors, this particular laptop power supply could almost be capable of powering that 4x100W amp. If you didn’t use all 4 channels, or used higher-impedance speakers, then it most definitely could.Note, however, that some laptop power supplies don’t like it when you put large amounts of capacitors in parallel with them. Doing so will trigger the over-current protection circuitry in some of these power supplies when you turn them on, which may prevent them from fully turning on until you remove the capacitors. However, other laptop supplies are just fine with it.Also note that so far I have only talked about the 400W Sure amp, which is the most powerful Sure amp that PE has. All of the other Sure amps require much less power than the 400W amp, and thus this power supply would do just fine for them. Even the 2x100W amp would be fine, although I’d suggest putting large capacitors in parallel with the power supply if you use that amp (4700uF or more would probably do for that amp). All the other lower-powered Sure amps almost definitely would not need extra capacitors when using this power supply.However, one thing to note about this laptop power adapter is that, like all laptop power adapters, it produces quite a bit of noise in its power output, which will be heard to some extent in the speakers. Some people don’t care about this, while others find it quite annoying.Finally, something to note about these Sure amps is that they only produce their maximum advertised power output when using a power supply of the maximum rated voltage. For example, the 4x100W and 2x100W amps can be powered by power supplies with voltages ranging from 12V to 30V, according to the specs. HOWEVER, as you can see in my review of the 4x100W amp, you will get VERY little power output when using a 12V supply (around 13W per channel). You will only get the full advertised power (or at least, somewhere near it) when using a 30V supply. This laptop adapter can output a maximum of only 22V, so you will not be able to get the full rated power output from most of the Sure amps when using it because most of the Sure amps are rated for up to 30V. It’ll still be pretty loud, and many people won’t care that they’re not getting the absolute maximum power, but it’s something to keep in mind.
Date published: 2013-08-07