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Basic inline preamp diagram required.

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drummerdimitri:
I watch movies on a projector but the 3.5 mm output signal is too low so even when I turn the volume to the max on my sound system, the loudness is not satisfactory.

Would like to assemble a basic preamp to double the output voltage of the signal. Does anyone have a circuit diagram I can use to assemble this device?

Tek Tech:
A simple one-transistor amp should work. One for each channel.
They can be cascaded if you need greater amplification.

[Edited from emitter follower. Thanks to Benta's observation one post below]

Benta:

--- Quote from: Tek Tech on April 26, 2019, 04:34:23 pm ---A simple emitter follower should work. One for each channel.
They can be cascaded if you need greater amplification.



--- End quote ---

Just a little problem: emitter followers have a voltage gain of less than 1. Not the right solution.

moffy:
Attached is a possible solution. Use an LM833 dual, you get 2 opamps therefore stereo. Has a gain of 2.2 but you need a +/-12v supply as well.
Caps should be non polar (not electrolytics) and avoid ceramics for the 1u.

MarkF:
Here is a pre-amp for a condenser mic.  Maybe you can tweak the gain for your case.

   

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