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BrianG · 08.31.2007, 02:24 PM

I was assuming class AB (eff ~60%) in my battery current calculations, but that's still a LOT of current!

Any 12v amp over ~16w rms (and that is assuming BTL output) will require a switching power supply to boost that 12v to whatever the amp needs. BTW: BTL stands for Bridge tied Load. Anyway, let's say you have a 100W @ 4ohm mono amp. The output would need 20v rms. Convert that to peak voltage (28.3v), then add a few volts because transistors are not perfect switches (31v), multiply by two since signals go positive and negative. So, you'd need at least +31vDC and -31vDC rails, or 62vDC total. Hard to get 62vDC from 14.4vDC without a switcher.

Aside from the switching PS and maybe extra output transistors for the low impedance loads for auto use, there really is no difference between a car and a home amp.

Powerful amps like that are difficult to make because of the current at 14v required, kinda like why we prefer HV setups. Plus, it's expensive. Plus, why? I mean; unless you're competing or running a mobile movie theater, why would you need that kind of power?

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BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	08.31.2007, 02:24 PM I was assuming class AB (eff ~60%) in my battery current calculations, but that's still a LOT of current! Any 12v amp over ~16w rms (and that is assuming BTL output) will require a switching power supply to boost that 12v to whatever the amp needs. BTW: BTL stands for Bridge tied Load. Anyway, let's say you have a 100W @ 4ohm mono amp. The output would need 20v rms. Convert that to peak voltage (28.3v), then add a few volts because transistors are not perfect switches (31v), multiply by two since signals go positive and negative. So, you'd need at least +31vDC and -31vDC rails, or 62vDC total. Hard to get 62vDC from 14.4vDC without a switcher. Aside from the switching PS and maybe extra output transistors for the low impedance loads for auto use, there really is no difference between a car and a home amp. Powerful amps like that are difficult to make because of the current at 14v required, kinda like why we prefer HV setups. Plus, it's expensive. Plus, why? I mean; unless you're competing or running a mobile movie theater, why would you need that kind of power?