I have this “Vintage” device it is a Mic Amplifier, advertised as Palos Gadget. I think the price of this toy is around PHP 35 at the SM Store.

I am surprised that is still works, I just inserted an LR44 1.5V Button Cell and it turns on. It amplifies voices using an elecret mic. Upon opening the casing, there is a small PCB with through hole components and three transistor that looks like for amplifying audio, it maybe is a class A/B amplifier but the output is going to a
single piece earphone.

I have reverse engineered the schematics which you can download below:
PALOS_SPY_AMPLIFIER

I planned to connect the output part to a 5V PC Speaker but it did not worked and it just made a transistor hot.
This is still a good product.

I will create a simple Electret Mic Pre-Amp later.

A video demonstration will be available soon.

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