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syko82 12th August 2002 03:15 AM

Home Amplifier Help
I was wondering if anyone has done anything with the LM3875 chip for making an amp. :confused: I thought it would be pretty simple to do this, but I need some rather newby help. Can someone explain what type of power supply I should use with this chip and should I use the typical application schematic?

I appreciate any help that anyone can offer, please share your knowledge :)

If anyone can almost spell this out for me that would be great.

dshortt9 12th August 2002 03:31 AM

You can search the forum for info on using this and similar IC's.

Try this link

BrianGT 12th August 2002 03:31 AM

Welcome to the forum!

There is a good thread here on the LM3875:

I found this by using the search engine. You should try it and you might find more useful information.

Good luck in your projects.


Jean 12th August 2002 03:45 AM


Try project19 Its got very few components and sounds good. For the power supply I am using Avel Lindberg 100va 25-0-25 toroid, bridge, and two 10,000uF panasonic caps. I am building two more channels and going to try bi-amping my speakers.

Also consider getting circuit boards from Rod, he is very helpful.

fender4 12th August 2002 04:05 AM

Hi syko82,

Be sure to visit the Amp Chip DIY board here. This board specializes in amps based on IC's like the LM3875 and LM1875. I have built a stereo pair based on a design similar to this one, and it is currently my favorite amp.

It's an easy, fun, and cheap project that gave me great results! :)

Good luck.


syko82 12th August 2002 04:17 AM

thanks for the help everyone. in your schematic right above, what was the amp rating on the transformer?

do you think that single power supply could work in parallel supplying up to 5 of these chips? You know, home-made home-theater :p

Jean 12th August 2002 04:30 AM

I use one 100va for 2ch circuit, two toroids total. According to the secondary current is 2 A. I am using AVEL p/n Y236404.

fender4 12th August 2002 05:20 AM

I used one 225VA 18-0-18v Plitron transformer to power two LM3875's, but that is probably overkill.

You might want to try under the Miscellaneous category for cheap toroids. They have a 120VA 18-0-18v that is really inexpensive, but I wouldn't use more than two chips per toroid, IMO.


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