3 Way Amplifer Project . . . . .

Well, in bits and pieces i had 3-way filter and LM4780 modules, but i always wanted to make a compact and high power amplifier system. Progress is ON! and just the integration of modules is remaining... Check out the pics -->

3-way filter will also come inside. Front will be glass panel. And inputs will come at right front glass panel and the heatsink.

Power Supply is in seperate enclosure. Regulated to 30 V using a pair of LT1083 (free samples :) ). I plan to put a higher VA Transformer later.

3 Way Active CrossOver.

I made 3-way active crossover circuit based on a project published in 'Electronics World', it was basically a 3-way subtractive cross-over. Its online version can be found at - 3-way subtractive X-over.

I made its PCB but when i run it, to my dissappointment, the output signal level was quite Low. Meantime i compared a subtractive crossover design as compared to a 24th order Linkwitz-Riley X-over, i decided to make a new filter based on Linkwitz-Riley design by Rob Elliot Project 09.

Its PCB is ready, just a little soldering is pending. Very eager to see it sing.

Make@home PCB drill.

A simple PCB drill can be made using taperecorder motor. The shaft of an old motor can be grinded using a file to form a drill bit as shown in figure. Shaft has to be grinded to form this shape.

Using a small ball-point pen refill as coupling, join the motor and this drill bit. And ur portable PCB drill is ready.

The tool point may need sharpning after drilling a number of holes. And it produces a decent quality hole. The dia of holes very much depends upon the dia of tool, which can be adjusted by repeat grinding.

Making Gainclone PCB at Home.

Since single unit of gainclone amplifier is quite small, its quite easy to build its PCB by Laser toner transfer method. I myself had made around 15-20 PCBs for Lm3886, 4780 and for filters.

A lot of material is available online for making PCBs, so i won't go in details but like to share on certain things I found from experiance:-

1. Laser Printer should be used at Best Quality mode at Bond paper setting.
2. Cut the Copper board (blank PCB) to correct size of desired PCB.
3. Get the laser print on transparency sheet or a Glossy paper and put the sheet on copper board, Ensure that transparency sheet should be bigger than the copper board around 2 cms from all sides. (This is a key point in getting un-distorted track transfer on copper board).

4. Keep 5 layers of newspaper on a flat board, put copper board, put the transpancy sheet, again keep 5 sheets of newspaper. Put hot clothes iron (full temp) on top with a little pressure for 2 minutes+ . (some smoke may come from newspaper,don't worry)

5. Let it cool for a minute and then peel off the transparency sheet slowly from board. The tracks may break at some points as the toner never always get stick fully to copper plate. Use a fine permanent marker to complete the broken tracks. The permanent marker usually stays if the etching time is not too long, so use a strong etching solution.