A rebuilt Kenwood SP-820 speaker box

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The first two photos show my first pass at modifying this item. I decided it was big cabinet going to waste so I built a modified version of the VK power mate into it. This has two 6 Amp battery charger power transformers and three pass transistors and will safely supply 10 Amp with peaks up to 15 Amp. with the aid of a fan. Looking at the photos you can see the very poor six dB per octave high and low pass filters are still there.

I had already built a box using the Silicon Chip Multi Function Active Filters so I decided if Jaycar still had some of these kits I would fit one in this cabinet. This meant I had to also build a circuit board for an LM386 power amplifier and a 12 volt regulator. I did not want to run the filter/amplifier from the Powermate supply because this would not be used very often. I managed to find a small 10K Log pot fitted with a switch so I removed one of the push button switches and modified the bracket that held the switches to mount the pot. This switch turns on and off a 15-0-15 volt 150 mA transformer and the rectifier and regulator are on the circuit board with the LM386 amplifier. NERC club member Eric turned me up an adaptor from the short splined shaft to a quarter inch shaft so I could use the knob in the photos.

I am looking for a photo of the inside of an unmodified SP-820, I have lost the early photos I took of the box. I think the SD card went through the washing machine and was hung on the cloths line. If you have an SP-820 I would appreciate a photo to add to this page. I make my photos 900 pixels wide but any size will do, I will adjust it to my fit.

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Written by and Copyright, Phil. Storr © Last updated 20th April 2014