Lexicon Primetime Input Filter Null Test

[Pat Maki]

Just brought an M93 back to life and need to calibrate it. This'll be my first time and have a question.
Where it says "null should be at least -35 dbm", how do I measure this? I've converted volts and watts to dbm, but not sure if that's that right way here?

 

[radardoug]

Dont get too worried about dBm. You are looking for a null level, so -35dB below your reference level signal.

 

[Pat Maki]

Dont get too worried about dBm. You are looking for a null level, so -35dB below your reference level signal.

Thanks @radardoug. I've applied a -13.99db reference signal, turned on the device and read -57.05db on pin 1 of U13, which is 43.06db lower (-) from the reference signal. So how i read this is that null is achieved, thus no change to the variable resistor is needed. Any flaws in my logic here? Many thanks.

 

[radardoug]

No, spot on.

 

[Pat Maki]

Excellent. Thanks again for the sage guidance @radardoug!