Right-click Start ▶ Device Manager
Expand the node Sound, video and game controllers and double-click the Realtek device or right-click it and select Properties.
Switch to the Driver tab and click Update Driver.
Select Browse my computer for driver software.
Select Let me pick from a list of available drivers on my computer.
You should see these two entries. High Definition Audio Device is the driver from Microsoft and the other one, as the name already tells, is from Realtek. Choose High Definition Audio Device and click on Next.
Continue by confirming the update warning with Yes.
If you have any trouble with the Microsoft driver, then you can easily switch back to the Realtek driver by repeating the first 3 steps until you reach the following dialog and by selecting Roll Back Driver.
Run Soundpad and go into the device preferences at File ▶ Preferences ▶ Devices ▶ Recording devices. Check your microphone, apply and restart Win-Audio or your computer to finish the configuration.
It isn't possible to make Soundpad work with the Realtek audio drivers without drawbacks. We could change the installer again, but then Soundpad would be affected by the DSP offloading of Skype and Lync and won't work in these applications.
The only way to make Soundpad work is to install drivers from Microsoft instead of the pre-installed Realtek ones. If you don't have specific requirements, that are only fulfilled by the Realtek drivers, then this solution should work without disadvantages.See above how to install Microsoft drivers.
Older boards like Rampage II or Maximus III use older not faulty drivers. Newer motherboards like Rampage VI Extreme or Maximus VIII Ranger should not be affected, as they use newer ASUS audio drivers, which supposedly use the fixed driver components from Realtek.
Install the drivers directly from Realtek instead of the ASUS ones.
The ASUS drivers contain an old version of the component Nahimic, which cannot be loaded by the Windows Audio Service, and this leads to a well-defined fallback behavior where all effects of the microphone are turned off, including Soundpad.
The faulty component in the ASUS drivers is from May 2016, the Realtek one is from June 2016 and the error is fixed there.
You won't get the SupremeFX suite of the ASUS drivers, but at least the original ones have the bug fixed and their standard effects like Noise Suppression work.
If you want to have SupremeFX working as well, then you might download the Realtek drivers, extract them, find the file NAHIMICAPOlfx.dll and replace the buggy one in C:\Windows\System32. The file in System32 will be locked by the Windows Audio Service, so you can restart your computer and then try to replace it or shutdown the Windows Audio Service before replacing the file.
Here is a link to the latest Realtek Drivers.
Install hotfix KB5004244 through Windows Update.
Re-install Soundpad afterwards, or run Soundpad, go to File ▶ Preferences ▶ Devices, select your microphone and Restart Win-Audio.