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The VP-Gainswitch Rev A.1 PCB is a board designed to add a stepped gain switch mod to any of our mic preamps. This mod will easily work with any of our older mic preamps. Simply desolder and remove the Bourns pot and install the two jumper wires shown from the VP-Gainswitch PCB to the main PCB. The VP-Gainswitch PCB, along with a Grayhill 71 series switch and appropriate resistor set, will create an equivalent to a 25k CCW log pot, which is perfect for an API style mic preamp circuit. With this set, you can expect the following 12 gain steps: +25.39dB +29.53dB +33.48dB +36.46dB +39.52dB +42.52dB +45.45dB +48.44dB +51.48dB +54.46dB +57.48dB +60.43dB From my tests, the actual gain may vary a little but should not differ more than +/- 0.1dB. The above measurements where taken from a VP26 preamp loaded with a gar2520. This preamp did have the t-pad attenuator installed. An Audio Precision Portable One Plus was the test instrument. ***Please note: Complete Gainswitch bundles including the PCB and Grayhill switch can be found here.

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