EEVblog #629 – How To Design a Microphone Preamplifier

Part 7 of Microphone Technology with Doug Ford, former head designer at Rode Microphones.
This video Doug takes you through the design of the Rode NT3 and NT1000 microphone designs.
There is a ton of stuff in here:
Closed loop unity gain JFET and bipolar follow circuits.
Bootstrapping out miller capacitance.
JFET biasing.
How to eliminate expensive high value resistors.
How to add a bridged-T network to add marketing “pizazz” to a microphone.
How to stop oscillation in closed loop systems.
How to test and design closed loop systems for stability.
Dominate pole compensation.
Traps for young players in power amplifier stability.
How circuits with capacitive loads oscillate.
Emitter degeneration.
Parasitic inductances and their effects.
How to design a low noise and ultra high dynamic range valve based microphone preamplifier.
Microphone power supplies.
And how to design an amplified zener current source.

All other videos in this series are HERE

Forum HERE

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  1. I’m was happy that you guys made fun of the asswipe musicians, producers and studio “engineers” who complained about the mic being too “flat” sounding. There are a lot better EQ circuits that you can feed a flat mic into and do whatever you want with the signal. It’s not like they don’t EQ the shit outta the vocals tracks anyway!!?
    EVERYTHING should be flat. It would make weeding out the shit SOOOO much easier!! Anyway, I feel better now. Doug is cool and I really like seeing vids where you guys talk audio. Interesting stuff, keep it coming!
    How do they measure the freq response of a microphone anyway?

  2. Absolutely amazing series. Just curious, when you started filming, how long did you think it would go?

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