The Tonelux OTB16 is a 16 channel 1U mixer with 16 balanced inputs and a Tonelux discrete summing bus. Each channel has a level control and a panner. The access to the OTB16 is through 2 eight channel D-sub inputs at a level of +4dBu nominal.
The summing of the 16 channels is through the famous Tonelux TX-240 and TX-260 discrete op-amps, and then through the main output transformer, which can be adjusted by the MASTER fader pot, which comes out of a pair of XLR connectors. Additionally there is a monitor output for monitoring or for expansion, which is balanced but transformer-less. Two additional balanced inputs to the MIX bus. The pre-fader monitor output can be plugged into the BUS input to extend the number of channels with a second or third OTB16. 120 or 230 volts AC powered 50/60 Hz.
"Overall, the Tonelux OTB16 serves well as a 16-channel summing mixer in a small package, and its stereo bus coloration is one of the more euphonic and all-around useful flavors I have heard in a summing amp. You don’t get heavy tube coloration, and you don’t get an overly aggressive retro console sound — just a nice finishing touch provided by clean electronics and a well-chosen transformer. " -Tape Op