Wednesday, November 16, 2011

Modified microphone preamplifier with INA217

I really like the microphone preamplifier with INA217. No noise, very good sound and dynamic, no feedback, very high (max 10.000x) gain, very simple application. Lot of websites testing and comparing this design with another industrial devices. The article, when this is the best mic preamp and the cost is USD5 only, maybe not true. Not only the INA217 required, you need PCB, transformer, 2 potentiometers, input and output connectors, power supply.

I modified the original design recommended on the datasheet. The original application circuit on datasheet is really simple and very good microphone preamplifier. I added a better unbalanced/balanced converter after unbalanced jack input. I have this feature before, but now I have better circuit. The another modification is the output. Because this preamp is mono, the simple connection to stereo system is not the best. The result may increase the crosstalk between left and right channels. This is the reason why I included two line driver circuits to separate left and right channels. Finally because this new design contains 3 integrated circuit, I inserted 3 "power filter" for less noise.

The modified preamp design with input unbalanced/balanced converter and output line drivers:

The PCB with simple connectors:

The same design without connectors, because this PCB can be inserted to the mainboards of modular mixers. The connectors changed to P4 header:

Now here is the list of features:

  • Balanced input
  • 6.3 jack as Unbalanced input, but with unbalanced/balanced converter
  • Gain adjustment
  • Volume adjustment
  • Connector for 48V phantom power
  • Switch for 48V phantom power
  • Switch between unbalanced jack and balanced XLR input
  • Divided line driver inputs connect to stereo systems
  • Power filter circuits for all 3 integrated circuits for less noise
PCB sales of this project
Module name Size
PDF SCH PCB image Tested Price (US$)
Des. Sim.1 Full2 Sim.1 Full2 Man3
Mic preamp pro with connectors
79x104 82 Yes Yes Yes - - No 13
21 Ask
Mic preamp pro as mixer module
67x103 69 Yes Yes Yes - - No 11
19 Ask
How to order? Please read the rules carefully!

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