The TOA M-243 is a highly flexible rack mount mixer with two monaural and four stereo inputs, plus one stereo and two mono outputs. There are also mix bus .sub-inputs. and a stereo record output. It is designed especially for commercial systems that require mixing and matrixing a combination of mono and stereo audio sources to one or several outputs, and in which stereo sources may have to be summed to mono and monaural sources sent to L/R outputs.
The compact, single rack space M-243 can be easily configured to serve as anything from a single mono or stereo mixer to a mixer with six regular inputs and three outputs. Each output also has its own separate sub-input.
The M-243 is ideal for a variety of systems, including boardrooms, conference rooms, health clubs, restaurants and background music (BGM) applications. For example, in a restaurant, the M-243 can simultaneously and separately control stereo classical music in the dining room, stereo easy listening music in the bar and foyer, plus BGM and paging of customers when their tables are ready.
The M-243 has two monaural line inputs (#1 and 2) that are switchable between balanced XLR microphone level or unbalanced 1/4" phone line level, and four unbalanced L/R stereo inputs (#3~6) with RCA-type jacks. Input 6 has both RCA type and 1/4" phone jacks connected in parallel. Each of the inputs has its own volume control and a set of three assignment switches for assigning the input to any combination of the three outputs. The two monaural inputs each have an automatic compressor to prevent excessive input signals from clipping the mixer output. Each also has a high pass filter to filter out unwanted low frequencies, particularly for speech use, and a -20dB pad in the mic input circuitry to accommodate high output or close-talked microphones. Filter and pad on/off switches are internal to prevent any tampering.
The M-243 has other line level inputs: a L/R stereo sub-input and mono sub-inputs 1 and 2. These directly feed the mixing buses and their associated outputs. The stereo sub-input is configured so that by connecting a monaural signal to the left channel, it will be fed to both the left and right output channels. Among other applications, one of the monaural outputs could be fed into the stereo sub-input as a sub-group mix for the stereo output.
A unique feature of the M-243 is an automatic muting function (switchable on/off). This detects signal on either of the monaural inputs and mutes any of the stereo input signals assigned to the L/R stereo output. This is very useful for priority paging that auto-mutes BGM or for automatic program selection. For example, in a sports lounge, the TV audio could automatically mute the BGM whenever the TV is turned on. Meanwhile, because the stereo input assignments to the mono outputs are unaffected, the same BGM signal could still go uninterrupted to the associated restaurant system that is being fed from one of the mono outputs.
Three sets of output mixing buses are provided to feed the three sets of main outputs: L/R Stereo, Mono 1 and Mono 2.
Each output has a separate volume control on the front panel. The L/R Stereo output also has bass and treble shelving-type tone controls. Each of the mono outputs has an internal switch that allows it to function as a sum of the stereo output. There is also a L/R stereo recording output from the L/R stereo mix bus prior to the output EQ and volume.
Other features include provision of colored control knobs for the different control functions; a clipping indicator that lights when any signal in the output section reaches 3dB below clipping; an internal ground lift switch that separates the audio and chassis grounds to avoid ground loops; an included security cover for the assignment switches and a power switch with a power-on indicator. The M-243 occupies only one standard 19" EIA rack and includes removable rack mounting ears.