Making “Pre-Amplifier” between Microphone and the Main Amplifier

My another photo blog “LQ Laoshi’s Photo Gallery”(outside wordpress)


Recently I made an electric device so that my mom could talk to me from her room to my room. However that device could not amplify my mom’s voice well. The reason was that sound level by the microphone unit was too low. So I needed to put a “Pre-amplifier” between the microphone unit and the main amplifier. I looked for it by amazon.co.jp. and ordered it. The issue was that it was not a unit but a kit. That meant I had to assemble many parts.



This was delivered yesterday.



The package was from a Japanese company. I would say what Japanese do is elaborate, maybe too much. The package is being put in thick plastic bag. There are a lot of detailed explanations on the sheet of paper, including the circuit diagram. The parts are neatly divided in three small plastic bags. Those elaborate things are basically good, but often ends up high price. This kit costed approximately 12 USD. I think that high prices and excess qualities are typical to Japanese products. It must be a disadvantage in current harsh international competitiveness.



So I needed to solder each parts one by one on the small circuit board.



This is the bottom side of the board. All the parts were soldered, but wires were not yet. I should say my soldering is not good becasue there was a poor soldering at one point. When I turned on this unit first, actually this didn’t work. I checked my soldering and found a poor soldering. I melted it again. And then this pre-amplifier became functional. I haven’t done these soldering electric parts for so long. This time was the first since the last time 30 years ago.



This is the top side of the board.



I put the pre-amplifier into the box. It seems as if the left space in the box would have been designed for the pre-amp unit from the beginning (Actually not).



And I put the device again on the column in my mom’s room. This time I put indications to tell her what the switch is and where the microphone is. My mom shows the early sign of Alzheimer’s disease. So for her it is difficult to learn anything new. She always try to push the volume control to turn on it, although it is not to push but to rotate. Anyway I have to tell her how to use this, on and on.


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