Is there an easy way to get 24 VDC from a 12 VDC car battery.

[gary350]

It seems to me I remember a voltage doubler circuit from years ago that charged 2 capacitors each to 12 VDC from a car battery. The caps are wired in series so the output is 24 VDC.

Take a look at this amp on ebay. It needs 24 VDC. My son bought a set of speakers for a car with no amp. I was wondering if I can get this to work 68 watts per channel. 4 ohms per channel one channel to each 4 ohm speaker.

One more thing. The LM3886s have no heat sink but that is not a problem. Wonder if I can use 1 large heat sink or if I need 2 seperate heat sinks? I wonder if an electrical connection between the 2 IC heat sink lugs will be short circuit.

**broken link removed**

 

[dougy83]

that ebay amp says it wants +/- 24VAC (so would work with +33 & -33 VDC rails). It might be easier to look for an old car amplifier built specifically for 12V than to make a converter

 

[gary350]

OH.......I see that now. I was looking at 24-0-24V or AC 26-0-26V I did not notice the AC at the beginning. Hum, now what. I guess that shot that idea.

I have a 300 watt DC to AC converter then I would need an 24 VAC transformer about 140 watts. That is nuts. He needs a real car amp.

I might buy one of these to pay with all I need is a 24 VAC transformer I probably already have one.

What do you think about the HEAT SINKS???

 

[Reloadron]

Hi Gary

I have a 300 watt DC to AC converter then I would need an 24 VAC transformer about 140 watts. That is nuts. He needs a real car amp.

Beyond the inefficiency losses the DC / AC inverter likely outputs a modified sine wave or maybe a square wave depending on quality. A standard transformer like 120 volts / 24 - 0 - 24 volts may not care for anything other than a sine wave input. Actually I don't see a simple economic solution to getting that amp mobile.

Ron

 

[dougy83]

Have you considered buying a prepackaged (including case/voltage converter/heatsinks/connectors/etc.) one that runs off 12V? e.g. https://www.ebay.com.au/itm/New-Pow...-Amplifier-Black-/260859383038#ht_4252wt_1139 it's only $55 and has twice the power of the one you're looking at.

 

[tcmtech]

At those basic voltages and power level it could be done with a simple push-pull or 555 timer IC driven power inverter circuit.

Granted the efficiency will be marginal and there will be no real input to output voltage regulation but I have seen a surprising number of similar designs used over the years in name brand car audio amplifiers built back in the late 80's and mid 90's.

The other option is to rework a common power inverters HF transformer and feedback circuit to produce the necessary +- 30 volts.
Many of them use surprisingly simple voltage feedback circuits that can be adapted to control a different output voltage range. The rest is basically rewinding the little HF transformer and removing the output inverter circuitry.

Either way if nothing else it could be a fun DIY learning project!

 

[gary350]

Have you considered buying a prepackaged (including case/voltage converter/heatsinks/connectors/etc.) one that runs off 12V? e.g. https://www.ebay.com.au/itm/New-Pow...-Amplifier-Black-/260859383038#ht_4252wt_1139 it's only $55 and has twice the power of the one you're looking at.

WOW 2800 watts, 700 watts per channel that would blow the diaphrams out of the two 100 watt speakers. That would pull 233 amps from the car battery. LOL. I think it would pull so much power from the battery the car head lights would go out at night. I don't know what I would do with 2800 watts, some teenager would love that. Wire size 0000 is rated 225 amps, wire diameter is .460" almost 1/2" thats so crazy its funny. The user would have to buy a 2 wheel utility trailer to haul all the speakers. I am looking for something fun to play with this would be work.

 

[dougy83]

Those are 700 pretend watts. It states the real RMS power is 70W per channel max.

Just like my "180W" pc speakers a used a 0.25W transformer as the power supply. PMPO =/= RMS power

 

[tcmtech]

If you read closer you will see that its rated at 70 watts per channel RMS into 4 ohms.

I have a pair of Audiobahn amplifiers that are supposedly built to put out around 2400 watts RMS into 1 ohm bridged. They are just over 2 feet long and weigh about 40 pounds a piece and the power connection points look like small welding cable lug connectors plus they use 4 50 amp fuses in parallel and the audio guys seem to feel that the speaker that they should be connected to should be rated to handle the proportional wattages for the given ohms ratings. 1200w at 2 ohms, 600 watts at 4 ohms and so fourth.

Here is what one does to an average honda body! https://www.youtube.com/watch?v=YuXmGIeekTE

The car audio nuts using them seem to rate them rather well also!
**broken link removed**

My point is I seriiously doubt those New-Powers are 2800 watt amplifiers!

 

[cowana]

It's also worth noting that that 2800W apmlifier has a 10A fuse!

10A at 13.8v = ~140W, which ties in with the 70W/channel figure they give.

I think the amp would be likely to realistically give about 50/60W per channel.