I'm planning to make the hardware control. Using a small pot to control the crossfeed level 
You can do a lot of stuff with the SigmaStudio.
I have an ancient Philips CD-ROM with audio playback controls and SPDIF (TTL level) output. So I use it as a transport, no computer needed, just power supply.
That output gets in the TOSLINK transmitter, and then in Hifiberry DAC+ DSP. There I run my own profile, and output to FiiO R7 and into Yamaha HS7 (with the EQ by amirm running on the DSP) or FiiO BTA30 Pro for LDAC Bluetooth to Sony WH-1000XM2 headphones (with appropriate AutoEQ headphone equalization and above shown Meier crossfeed running on the DSP)
It's a crazy setup, but I enjoy tinkering...
You can do a lot of stuff with the SigmaStudio.
I have an ancient Philips CD-ROM with audio playback controls and SPDIF (TTL level) output. So I use it as a transport, no computer needed, just power supply.
That output gets in the TOSLINK transmitter, and then in Hifiberry DAC+ DSP. There I run my own profile, and output to FiiO R7 and into Yamaha HS7 (with the EQ by amirm running on the DSP) or FiiO BTA30 Pro for LDAC Bluetooth to Sony WH-1000XM2 headphones (with appropriate AutoEQ headphone equalization and above shown Meier crossfeed running on the DSP)
It's a crazy setup, but I enjoy tinkering...