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Dan2 18th May 2008 10:08 AM

"transformers" inside car amp??
i have a small car amp that i opened up, and found 2 parts that look just like transformers. i just want to know what they are for, 'cos last time i checked, transformers don't work with DC

luka 18th May 2008 11:15 AM


You are right, but there is high freq. choped DC driving trafos, so you have +12v ,0v ,+12v more then 20000x time a second, which is why this are so small compared to 50/60Hz ones. So this trafos do work with AC, which you can get from DC

Dan2 18th May 2008 11:39 AM

are you talking about a SMPS?? cos this is a small chip amp (17Wrms x 4) and doesn't have a smps.

DigitalJunkie 18th May 2008 11:49 AM

They're probably filter chokes. Are the in series with the +12V input?

luka 18th May 2008 11:49 AM


Oh ok, in that case I don't know what you mean, I should some pic if you have... Those IC are amps, that don't need nothing else but DC voltage, so no need for smps

Dan2 19th May 2008 08:25 AM

yes they are in series with the 12v input.

so do they filter out the alternator niose??

luka 19th May 2008 09:10 AM


They do a bit, but they are there so that they filter out noise that is comming from amp, so that it doesn't go into car electrical system, it filters both way I guess

EWorkshop1708 20th May 2008 05:33 AM


Originally posted by Dan2
are you talking about a SMPS?? cos this is a small chip amp (17Wrms x 4) and doesn't have a smps.
Does your amp have high-level input? (speaker-level)

On some amps i've opened, they all have 2 little transformers on the input side to take the speaker level down to the proper input level. It's a line-level convertor built in the amp for folks with Car stereo's without RCA plugs.

Dan2 20th May 2008 11:13 AM

this does have a high level input, but it has 100R resistors that go to 220k resistors and to the gain pots. these transformers are no where near the inputs.

So i think we have established that they are just noise filters.

thanks guys ;)

EWorkshop1708 20th May 2008 09:43 PM

Input filters..........I don't see that many car amps with them. You must have a good amp, most amps I see have no snubbers or filters.

Glad you figured it out. :)

What amplifier is it? What IC's does it use to drive the speakers?

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