2 circuits on 1 PC board with common ground plus added tone control.

Circuit #1 works great I can hear people talking 2 blocks away with only the electret mic but too far to know what they are saying with no reflector. The will reflector made the amp more sensitive to far away sound. Factory made earphones are all 3 wire so I am forced to use ground as the common wire I hope that is not a circuit problem?

I also want to use 1 power supply = 8 D batteries = 12.6v I tested 1 amp on 6, 7, 8 batteries it is amazing how much better the circuit works on 8 D batteries.

Circuit #3 show the 386 amp with tone control I hope this works? I borrowed this tone control circuit from another amp circuit.

I am using a wooden dowel rod like a rifle barrel with reflector on each side of the barrel and gun sights down the barrel. I saved empty cereal box card board to cut out 20 pie shapes for the reflectors, I need to do geometry to calculate the shapes of each slice of pie. When this is finished it should work much better than the one I built long ago.

I could use some help getting this circuit correct.

gary350 said:

I need to do geometry to calculate the shapes of each slice of pie.

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Ideally the reflectors should be paraboloidal.

alec_t said:

Ideally the reflectors should be paraboloidal.

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i don't know if visibility is an issue, but a parabolic reflector is an obvious item. you might also look into a"shotgun" or "organ pipe" microphone. such a microphone is made from 1/4 inch aluminum tubing, is about 24 to 36 inches long, and about 4 inches diameter at the base and 1/4 inch diameter at the end then a funnel is attached to the large end with the electret in the funnel stem. there are (i made a 36 inch microphone) 37 pieces of tubing each cut to one inch shorter than the one before it (beginning with a 36"inch tube in the center). the assembly looks like an abstract spiral staircase when it's complete. the way it works is, all off axis sounds get phase cancelled, and only sound coming from directly on the axis of the microphone are in phase. the tubing assembly can be painted to blend into the background (don't block the tubing with excess paint). it's a bit more work gluing tubing together, but the finished product is less obvious and can look like a piece of tree branch

alec_t said:

Ideally the reflectors should be paraboloidal.

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And the hardest part is finding a parabola segmentl formula for a shape like this about 14" across with a 3" deep dish. Online calculator says 3" deep dish 14" diameter has a focal point of 16.34" but no math to calculate the parabola shape? This was high school geometry, I have been out of school too long to remember how to calculate a certain shape parabola.

You can draw a parabola with a string, a pencil and a square.
See the example here:

rjenkinsgb said:

You can draw a parabola with a string, a pencil and a square.
See the example here:

https://cs.smith.edu/~orourke/MathOverflow/nmd11-DrawingParabola.doc

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YES that solves that part of the problem.

The basic formula for a parabolic function is y= x^2.
Lord knows why I'm even commenting on this ridiculous thread...