|Melcor Discrete OpAmp|
Some pictures of my Melcor Discrete OpAmp. Discrete opamp means instead of buying an NE5532 IC chip, (which is very cheap, like $0.80 per chip), you build the opamp using discrete parts, like resistors, capacitors, transistors. Total cost per module is a few dollars.... maybe $2 or $3???
This is compatible with the API 2520 discrete opamp, and therefore, these DOA (discrete opamp) modules can be used in mic preamplifiers, just like the API 312. Just add a mic input transformer and the 2503 API output transformer (or equivalent), and you got yourself an API-like mic preamp.
I've tested them on an oscilloscope, and it looks great, but haven't done ear-testing yet.
On a breadboard, with wires, testing in an inverting amp configuration. The ceramic capacitor you see parallel to the resistor is to prevent oscillations.