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Papa Wuehle 26th September 2012 06:33 PM

Car battery as power supply
Newby here. Audiophile, have built speakers, but not electronics.

At our cabin we use a solar powered off-the-grid audio system. Sounds great, I think because power is clean. Solar panel>a bank of car batteries> inverter >audio system.

Desire best sound. Thought of upgrading to a pure sine wave inverter. Or...

Can we eliminate the inverter and build/modify a power amp to run directly off 12v car batteries? Can a car amplifier provide good sound in this situation?
Right now we are using NAD separates.

Also, thinking this might be a good idea for a cleanly powered home system, but would desire top quality there.


Rundmaus 26th September 2012 08:39 PM

If the inverter is not an (expensive) pure sine wave generator, the power you're getting from this is far from clean. Lots of harmonics and the risk of saturating power transformers with a non-sinusoid waveform.

If it sounds better than on the normal grid supply, it is psychoacoustics. You thought the power was clean --> it must sound better.


Papa Wuehle 26th September 2012 09:47 PM

Not just psychoacoustics, liquor influenced psychoacoustics!

But humor me; I'm still interested in the question. What are the technical aspects of building/converting a power amp to run on DC?

It seems logical that a DC powered amp would/could be better than an amp run from an inverter. Forgive me if this question is too simplistic, but doesn't a typical home(vs. auto) power amp convert AC to DC through it's power supply? Why not just use DC directly from a battery bank? An auto power amp uses DC, so obviously it's done. That leads to the question, is an auto power amp inherently inferior or could it's circuitry be used a the basis for a quality home power amp?


wintermute 26th September 2012 10:03 PM

you are correct home amps rectify the AC to get a "DC" supply to feed the amp circuitry. Any car amp with more than a few watts output is probably using an inverter internally, as 12V is just not enough to give much power output.

The inverter is needed to step up the voltage to something higher. If you ran some car batteries in series then you could get a higher voltage. four in series would give you +- 24V if you make the earth point between battery two and three.


Xoc1 26th September 2012 10:12 PM

High power car audio amplifiers use DC to DC converters to generate the rail voltages needed - a single 12V supply can not provide a high power output.
Low power car amps running on 12 directly, operate in bridge mode into a 4 ohm speaker to produce approx. 18W max!
The use of bridge mode eliminates the need for a output capacitor on the single ended supply but means the speakers are floating at approx 6V (half the supply voltage)

boyofwax 26th September 2012 10:41 PM

If you want to have top quality and use battery's put them in series and feed a quality amp with it. Maybe interesting to switch between battery and psu.

Don't use step up units or BTL amps. You can get very clean moderate power with one battery and single ended (class A). I use MOSFET's SE.

Suricat 26th September 2012 11:09 PM

Your power supply, although not getting a clean sine, is perfectly capable of coping with it through normal filtering.

Before venturing in buying a so called high end inverter, or even worse, hooking up a pool of car batteries, borrow a scope and measure the ripple you get on your supply DC output (in your NAD). You might want to measure it at home also, and why not, with your computer "noise killer" power bar. You will be surprised.

It is boring but for better sound, your best bet is the speakers alley.

But this is me.

Have fun.

markgolf 26th September 2012 11:38 PM

hey finally my first post. I too live off the grid 1600 watts of sunshine feeding 880 amphours of 24 volt deepcycle batterries. The big difference is pure sine wave problems with most electronics from the inverter very clean power according to my scope ,cleaner then my on grid neighbours.I have had some issues from charge controllers. I have tried many and some cause noise in certain electronics;
worst noise in a cheap sub plate amp.I think it is the PWM charging algorithm in some charge controllers.
The only other issue is the need to conserve electricity.I do run an old tube amp on occasion and i like the sound but not the inefficient heat.My latest subwoofer project uses horribly inefficent (high xmax and mmd low sensitivity(83dbat 1 watt))drivers.200 watts is not enough more like 1200 watts .In stereo that would max my inverter and cause my lights to dim like when im welding. But the ribbon line speaker project will be a good fit if only i had bought the magnets when they were cheap.
Or maybe I'll get that 4000 watt mastervolt sine inverter ive been drooling over and get the windmill working again and finally put the turbine in the stream so I can build that SE SIT or OTL amp .


AndrewT 27th September 2012 09:37 AM

get yourself an alternator and couple it to the chainwheel of a training "bike". Use that to get your AC power. The faster you pedal the louder the music !

If you want DC for music from a DC source (solar panels) then use a DC to DC converter.

Tyimo 27th September 2012 10:26 AM


If you want DC for music from a DC source (solar panels) then use a DC to DC converter.
Could you suggest me a good one?

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