The STA Effects are based on STA (Summing Tube Amplifier) technology that uses two signal paths. One of them is processed by modulation or spectral change and the other is clean. These two signals are mixed on a vacuum tube.
Audified have added a brand new plug-in, STA Delay, so STA Effects now contain Preamp, Chorus, Flanger, Phaser, Enhancer and Delay.