USB Sound cards detected as "microphone" instead of "line
in" decrease the decoding quality in digital modes
A lot of HAMs love to use
external USB Sound Cards that are embedded in digimode interfaces.
Just to name a few:
Kenwood and Yaesu TRX with built in USB Audio Interface
- The Yaesu
- Microham USB
III (and maybe others)
all other interfaces that utilize USB Soundcards that use the chipsets
What is the problem?
sound cards with chipset TI PCM2900 series PCM2904 and below
combination with Windows Vista and later show up as microphone instead
of line in.
As a consequence, windows adds 30 db to 50 db of gain and clips the
Many HAMs have workarounded this issue by turning the output of the
interface and the level in windows all the way down.
This reduces the dynamic range and puts the signals into the noise
How to check if my sound
card interface is affected?
Go to Windows Control Panel -> Hardware and Sound -> Sound
Go to the "Recoding" tab, select your device and click "Properties".
Go to "Levels", right click to the slider and select "decibels".
If 100% on the slider reads +30db, you are affected by the bug.
If the device was properly enumerated as a line in device, 100% on the
slider would be 0db.
The solution is to lower the slider to 0 db.
On my computer, -0.4 db has been the closed value I could get and it
Increase the output of your interface and see the difference.