locked Re: Received Audio Level scale floor different with different sound cards

Michael Black

I'm seeing a lot of noise on your waterfall.   I've seen problems with some computers having really bad internal noise.

Let's talk signal levels....

Speaker level is in the region of 1V to 100V
Pro Line level is in the region of 1.228V (something we don't see in our ham equipment)
Consumer Line level is in the region of 316 mV
Microphone level is in the region of 2.5mV to 23mV -- this is where the 20dB boost is needed for those microphones that are at the low end of this range.

I've seen people plug their headphone jack into a microphone -- talk about over driving the audio chain!!!! You have to turn down the rig's speaker volume to just about minimum to make this work without harmonics....all the splatter RTTY operators are used to seeing comes from a lot of the older rigs where there was no decent audio connection other than a headphone jack.

USB devices that have the gain control are likely expecting microphone levels.

We should be seeing line levels coming from the rigs.

0dB on most Windows audio driver levels means "no amplification or attenuation" and should be either mid-range or the far right of most audio drivers. 

Mike W9MDB

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