There are two Seperate effects units built in and Four aux for flexibility for effects and foldback. The Opera 24-4 combines 20 mic/line channel strips with two stereo, line-only strips and four stereo returns, making a total of 32 different ways of getting a signal into the mixer . Similarly, the Opera 32-4 features 28 mono inputs. All the input channel strips have Dual DSP effects units built in and Four aux sends, and unlike some desks that use buss switching, each of the Opera24-4 sends feeds its own dedicated buss. Sends 1 and 2 may be switched as a pair to function in either pre- or post-fade mode, While Sends 3 and 4 are used for the built in effects or can be used as Post-Fade Aux sends. Other features on all the channels are a built-in Compressor with a dedicated Volume control , 4-band, fixed-frequency EQ system with Low, Low-mid, High-mid and High , Low Cut , Mute , PFL and more. The routing system is quite conventional, with separate routing buttons for L-R, 1-2 and 3-4, where the Pan control steers the signal between left and right, or odd and even numbered busses in the traditional way. A large channel Mute button is located below the Pan control, and all channels have the benefit of a Solo switch as well as green and red LEDs indicating -20dB and overload signal levels. A clever touch is the Solo/Mute status LED which blinks if a channel is solo'd, but remains on if the channel is muted. The Opera is designed for the latest in modern engineering techniques, and every detail in this uniquely capable small footprint mixer has been carefully thought out to provide the very best mixing experience.