Audio-Technica AT-MA2 (Modified) Microphone Amplifier

There were few options for devices that could supply the necessary power (2-5V) for a microphone suitable for measuring earphone acoustic characteristics, and this model was the only one within budget, so I purchased it.

It should be fine for general use, but for acoustic characteristic measurements, there was an unacceptable level of noise. Therefore, I modified the device by replacing the electrolytic capacitors with polymer solid electrolytic capacitors and film capacitors to eliminate power supply noise. My goal was to reduce the noise to a level inaudible to the human ear when the gain is maximized with no input, but due to the small size of the casing and the inability to modify the original circuit, I couldn't quite reach that level.

Additionally, I made the operational amplifier socketed for easy replacement. I tried replacing the operational amplifier a few times, but it didn't have much effect on noise reduction, so I reverted to the original one. I did notice a slight change in sound quality when swapping operational amplifiers. If noise reduction isn't the primary goal, replacing it with a high-performance operational amplifier might be a good option.

The cost of the modification parts exceeded the price of the unit itself, which is why the current price is as listed.

Please refrain from price negotiations.