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Old 29th April 2016
Originally Posted by aracu View Post
In order to get the high frequency noise from the mics on the actual recording the
recorder and preamps must have a similar frequency range.
My mic preamps are all current feedback designs and do 30 mhz, far beyond any ADC. Track at 192k hz and you can encode a good amount of untaimed high frequency noise. No, you won't hear it directly (my cat can) but those random noise frequencies can enharmonically beat against audible frequencies causing intermodulation distortion. That is another reason why I avoid class D monitor amps here.

Examine any of your condenser mics on a scope and you will find the other dirty little secret: many popular brands have considerable polarization osciallator leakage onto the audio. It looks like a fat band riding over the audible waveforms. When timebased it shows the oscillator frequency.

That also causes intermodulation distortion and adds more noise to the upper regions. It has in severe cases overloaded my mic preamps at higher gains as that leakage is not attenuated with my wideband mic preamp designs.

Careful layout and screening can reduce that leakage to almost nothing. Many of my mics have been modified to do just that. Sometimes a small piece of copper foil will do the trick if placed over the oscillator transistor and underneath it.