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Hey - I am interested in learning about the internal workings of mic preamp amps. Obviously, one of the best ways to do this is to build one from scratch. after i get comfortable, i want my final project to be a stereo pre. what kind of things really make or break a mic preamp? some of the things i am thinking of adding would be a M/S decoder on one channel, DI on both inputs, switched gain (with continuous knobs for trim), obviously phantom power on both. what else would you add to a preamp to make it stand out ?

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Boswell Fri, 06/01/2007 - 04:57

z120129 wrote: im asking more about after i learn about the basics, what features would be cool to add(so i can start learning about them now)

"The basics" includes learning about what features are useful and what are not. I would start there.

Actually designing a good preamp with those features is several levels up in competency after you have mastered the basics. Things like switchable HP filters, selectable M-S decoding (which involves two-channels not just one) and variable clip level indicators are all things that feature-rich preamps would offer after the standard items of gain trim and phantom power out.

Link555 Fri, 06/08/2007 - 16:37

The Pre-amps I have designed in the past have been pretty simple. The main points I typically concentrate on are:

1)The power supply-very import to get a very clean rail or rails.

2)The differential Input to Single sided converter-Either XFMR or solid-state. OR you could make completely differential amplifier, much more difficult.

3)The Amp itself-Opamp, FET, Tube etc... Your choice

4)Differential out put conversion- xfmr or solid state.

5)The Phantom Power supply- Make sure you have enough current to drive your mics.

6)A Polarity Switch-This one is typically a simple wiring change.

7)A Pad -lower the gain of the amp.

8)A High Pass Filter- Usually tuned at 80Hz typically 2nd order.

After those are good, and then if you still wish to add gimmick features, go for it. Although for your first time I think you will have enough on your plate.

Get access to an oscilloscope, and waveform generator, multi-meter and a decent soldering iron.