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Old 24th December 2005, 06:02 PM   #1
diyAudio Member
Join Date: Sep 2004
Location: Chicago
Default LM3875 board 4 sale

I have a stereo two-way board using LM3875T chips that I would like to sell.

The VAS has single ended inputs, third-order Butterworth HPF, Linkwitz Transform, baffle step compensation EQ stage, and LM317/LM337 regulation.

The power stage has one single-ended LM3875 for high freq range output, and two in an H-Bridge configuration for low freq range output, each for left and right channels, making a total of six. There are DC servo correction stages on each and DRV134's are used to drive the bridges.

There is also space and layout for a signal-sensing relay power on section, but this has not been populated and has no effect on the other parts of the board, but can be experimented with. I can sell you the high power relay for this stage also.

The board is populated with six FM Series 1000/50V lytics, film bypass and follows many high speed circuit rules, including ground plane and bypassing. Right now the board is populated with OPA2134 and DRV134 for VAS, OPA227 for servos, and LM317/LM337 for regulation. All DIPs are in sockets.

The passive devices are high quality but not esoteric, polypropylene film caps in the direct signal path (NO electrolytics), and metal film resistors, There is no solder mask or silk screen on the FR-4 board. Power is flown to the board, as are signal lines.

I would like to avoid posting layout or shematic, but I will email both to interested parties and answer any questions. I will also support getting this board up and running. This board sounds really amazing and has a great amount of things happening in a small space. This is an opportunity to take a huge step forward in either getting an active speaker system going, or experiencing power operational amplifiers without having to deal with the hassle of ordering parts or doing the layout, etc.

There is something like 150USD in parts alone on this board, plus the board and the layout time and IP, so I would like at least that. I'll give it a couple days and the board will go to the highest bidder. Thanks. Please email with concerns at the following

waste232002 'at' yahoo dot com

Sound Mind, Sound Body, Sound Man
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