well, it seems car's manufacturers give us hard life :-)

Regards

Tal Bejerano
AMC - ISRAEL


-----Original Message-----
From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On
Behalf Of Peter L. Peres
Sent: Monday, July 01, 2002 8:56 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: Bridge Amplifier


On Mon, 1 Jul 2002, wouter van ooijen & floortje hanneman wrote:

>A way to get more power from the same supply voltage is to use a
transformer
>to lower you speaker's impedance. You can for instance use a the secondary
>of a 12-0-12 transformer as autotransformer. (speaker between 12 and 12,
amp
>between 0 and 12: effectively halves your speaker's impedance, quadruples
>the power).

Except that at 4 ohms speaker impedance the primary will be seen as a
2ohms load with umpteen losses (the windings will have a comparable
resistance to the 2 ohms).

All higher power car amps use dc/dc converters to up the voltage. Doubling
the supply voltage will go a long way in the direction you need, Tal. For
a simple solution, try a simple switcher from National. It will be noisy
only if you lay out the boards badly ;-).

Peter

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