adalogue
Member
Following up on a previous post of my buffer module, I've been working on baselining a 500 series test rig and have some noise issues.
When I apply a resistive input load (200-300 ohms) to my buffer module (or mic preamp), I get a noise spike at around 9 kHz and its harmonics These plots or for a Radial Cube, but I get similar results with another rack. I checked the Cube PSU lines using an o-scope (FFT) and do not see such a spike. If remove the input load, the spike goes away. I've tried turning off my LCD monitors and other potential interference sources and can't track it down.
I tested the noise floor of my interface with the same input load and don't see the same spike, also shown in plot as "DAQ Noise Floor".
I'd really like to test module noise floor with an input load and not open, but I won't be able to if I can't track this down. It might not look that bad in the plots (-124 dBU), but when I add 60 dB of gain from a mic preamp it looks horrible. Anyone have any ideas?
When I apply a resistive input load (200-300 ohms) to my buffer module (or mic preamp), I get a noise spike at around 9 kHz and its harmonics These plots or for a Radial Cube, but I get similar results with another rack. I checked the Cube PSU lines using an o-scope (FFT) and do not see such a spike. If remove the input load, the spike goes away. I've tried turning off my LCD monitors and other potential interference sources and can't track it down.
I tested the noise floor of my interface with the same input load and don't see the same spike, also shown in plot as "DAQ Noise Floor".
I'd really like to test module noise floor with an input load and not open, but I won't be able to if I can't track this down. It might not look that bad in the plots (-124 dBU), but when I add 60 dB of gain from a mic preamp it looks horrible. Anyone have any ideas?
