hello
I would like to ask the diyaudio community if any one has built an amplifier for the car roof mounted megaphone and if so can you share a schematic.
I would like to ask the diyaudio community if any one has built an amplifier for the car roof mounted megaphone and if so can you share a schematic.
On last elections I used an old 50W Grundig head unit and worked fine, since the horns were 8 Ohm.
i remember in the 60's a 12v class B, good for that application. Terrible at sound qualite, yet good enough. Very simple, underbiased, gross crossover distorsion, no risk of thermal runaway, good at high volume.
There used to be transformer-coupled amps for PA on 12V car/truck batteries.
Today, almost anywhere in the world there are cars, there are large car-sound amplifiers for "boom cars". 160 honest Watts is no longer a big car-amp (1000+ Watt monsters exist). Such an amp needs to be wired direct to the car battery with an appropriate fuse and heavy wire. Find horns with 16 or 8 ohms, parallel down to 4 Ohms, you get 20W-40W per horn which should get your message out.
You need a mike preamp in front. While this is not a hard project, a musician's mixer gives more control and can be run from a cigar-lighter 120v/240V inverter.
Today, almost anywhere in the world there are cars, there are large car-sound amplifiers for "boom cars". 160 honest Watts is no longer a big car-amp (1000+ Watt monsters exist). Such an amp needs to be wired direct to the car battery with an appropriate fuse and heavy wire. Find horns with 16 or 8 ohms, parallel down to 4 Ohms, you get 20W-40W per horn which should get your message out.
You need a mike preamp in front. While this is not a hard project, a musician's mixer gives more control and can be run from a cigar-lighter 120v/240V inverter.
gooday
thanks all for your replies. the project I want to do like that of the ahuja amplifiers from India where there is provision for 220vac input and 12vdc.
thanks all for your replies. the project I want to do like that of the ahuja amplifiers from India where there is provision for 220vac input and 12vdc.
I'm pretty sure the standard practice was to use a straight Class B circuit (not Class AB) to maximize efficiency at the expense of sound quality. Battery powered and 1970's technology made the choice for them, remember these are essentially hand held devices adapted to car mounting. They didn't re-invent the wheel just because they had a nice alternator to power them.
Today we have more options, a simple class AB circuit and away you go. I don't think I would spend much time trying to repair the original unless it was trivial to do so.
Today we have more options, a simple class AB circuit and away you go. I don't think I would spend much time trying to repair the original unless it was trivial to do so.
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