The Control Room Source Selector
The source selector is divided into an internal and an external switch set.

The external control room select
There are 5 external sources available. The 2 surround sources 6CH-A and 6CH-B are used for external 5.1 signals. The three inputs 2CH-A, 2CH-B and 2CH-C are used for external stereo sources. The stereo source selector can be expanded up to a total of 17 inputs if the optional playback module and talkback modules are installes. These modules contain additional stereo source selectors with 8 inputs each that can be connected to the 2CH-B and 2CH-C inputs of the internal selector.

The internal control room select
A switch block with 10 switches is used for the internal control room select unit. Besides the main master output MIX the output of the external selector and all the 16 audio goups can be selected. The groups are arranged to stereo pairs and can be selected independend of the setting of the input channels, where the group bus amps are located. The group switches of the control room selector are internally connected directly to the output of the group buss amps.

A summing function ADD makes it possible to mix the outputs of the external and the internal source selector. This function give the choice to simulate the result of a final mix by adding an external mix to the internal signal at the output of the main mix master or a group.

The Control Room Insert and the Meter Send
The output of the control room select section drives an 6-channel insert section. and the meter send in parallel. If internal meters are installed and how they are arranged, depends on the configuration of the particular console and can be determined by the customer. The outputs for the external meters are always available on the connector panel.

The control room insert can be used for the integration of additional control room devices like a bass redirection system, or are crossbar matrix to redirect the input channels, which is not part of the S3-CT modules. An external device is activated by the INS switch. Several additional devices for the intergration in the console's meter bridge will be available in the next future.

Downmix Matrix, Cut-Solo-Section and Operation Mode Selection
The Cut-Solo section offers three choices to modify the arrangement of the channels. The section is driven by the output of the control room insert. In normal operation mode, the 6 switches L, R, C, LS, RS and LFE simply cut the single channel. If SOLO is activated, these switches operate like a Solo in Place system. If one channel is selected, all the other channels are muted. It is possible to activated more than one switch at a time to listen to any desired set of channels. The TO-CTR switch redirects one seleted channel to the center speakers. If more than one channel is selected at a time, an internal priority table determines what channel is routed to the center speaker. The TO-CTR function works in Solo mode only and is automatically disabled if Stereo or Mono is selected or is one of the additional speaker sets ALT or MINI are active.

The Downmix Matrix
The output of the Cut-Solo section drives the input of the stereo / mono Downmix Matrix, that converts the 5.1 surround signal into a stereo signal. The left surround-channel SL is added to the front-channel L and the right surround-channel SR is added to the right front channel. The level of the SL and SR channels can be adjusted by the pot S > F in a range from 0 to - 6 dB. The 3 dB center detent is calibrated. The center channel is mixed into both the L and R front channels. The level is controlled by a second pot with the same range from 0 to - 6 dB and a calibrated center position of - 3 dB. The LFE channel is added to both front channels like the center channel, however, this channel passes an internal low-pass filter with a cut off frequency of 80 Hz. The level of the LFE is fixed at - 6 dB, but a general level control with +/- 10 dB control range allows correction of this channel.

If the Stereo Mode switch is pressed, the output of the downmix matrix is switched to the front left and front right channels. All the other channels are muted.

The Mono Matrix adds the Left and Right output channel of the Stereo Downmix Matrix. This signal is routed to both the stereo channels if the MONO switch is pressed. The Left - Right Reverse switch and the Phase Reversal Switch, which operates on the right channel only is driven by the output of the Mono switch.

The entire Matrix and Control Room Mode selection operates independently of the master's operation mode. Since the functional principle of the downmix matrix leaves the Left and Right input channels unchanged, a stereo signal passes the matrix without changes. If the master's operation mode is switched to Stereo, all the surround channels are muted. It is therefore not necessary to consider the master mode setting as far as the control room setting is concerned. The operation of the control room section is not different with a stereo input signal if the Downmix Matrix is activated or not. This principle is also valid for any other internal or external stereo input signal.

However, the alternate speaker systems ALT and Mini are limited to stereo format. If one of these systems is selected the Downmix Matrix is automatically inserted to feed these stereo signal with an appropriate signal. Of course, the Mono matrix is functional all the time.

Volume Control and Output Select
A 6-channel rotary pot is used for the volume control. The output of this pot feets the electronically balanced output drivers via the DIM circuit that attenuates the signal of all channels for 12 dB. The DIM function can be activated by the local switch and by a remote control input as well. If the optional talkback module TBO is installed any talkback and listen function can activate the DIM. This is determined by jumpers on the TBO module. The CUT function mutes all the speakers but not the separate headphone amplifier. The ALT and MINI switches select one of the two alternate stereo speaker systems and force the control mode to stereo as described above. Mini has the highest priority. If Mini and Alt are activated at a time, the Mini system is selected.

Headphone Amplifier
A Headphone Amplifier completes the monitor set of the surround console. The input is always driven by the output of the Stereo Downmix Matrix post Mono switch, Left - Right and Phase reversal and has its own volume control. PFL can be assigned to the headphone system by pressing the PFL switch. If PFL is active, the headphone output is automatically switched over to the stereo PFL signal. An additional Level pot determines the PFL level independently. The output of the headphone amp is available on a 1/4" TRS jack on the top plate of the module and can drive any kind of headphone.

The PFL and SOLO System
Both systems operate totally independent. The Solo System is a real 'Solo in Place', that cuts all channels that are not in solo mode. A Safe switch on each channel disables the Solo function for the particular channel. The Control Room Module contains a Solo Off function, that leaves the solo state of the channels unchanged but disables the cut function as long as Solo Off is active. With this switch it is possible to toggle between normal and solo mode. The console's Solo state is indicated by the lamp in the Solo Off switch.

The PFL System operates in stereo and is acutally an additional stereo summing bus that is fed by the channels, groups and aux master sections when their PFL or AFL function is active. The system operates always in adding mode. All stereo sources drive the PFL buss in stereo, the mono channels drive the left and right pfl bus in parallel. The calibrated, balanced output of the PFL buss amplifier is available on the connector panel. In addition to the audio signal a control signal is routed to the PFL control bus. This control signal can switch over the speakers section of the control room module, and the headphone amp as described above. If the PFL-OFF switch is not pressed a PFL signal switches over to the output of the PFL buss amp automatically. As mentioned above, it is also possible to rout the PFL signal to the headphone amplifier, it the respective PFL-ON switch is pressed.

With a normal console setting the PFL signal has always more level than the master buss. An additional pot makes it possible to attenuate the PFL signal. The calibrated PFL output can be used to drive an addional stereo set of meters that read the PFL signal.

The PFL-OFF switch display the state of the PFL control bus and makes it possible to disable the automatic switching functions. Like Solo Off it leaves the state of the particular PFL switches unchanged.

The Aux Master Section
The master amplifiers for Aux 3, Aux 4 are installed in this unit. Every master section has a rotary pot for the master level, a cut switch that mutes the output and an AFL switch to control the master output. An internal jumper determines if this switch operates in AFL (default) or PFL switch mode. The TB and OSC switches enable the talkback to aux line and the oscillator to aux line. These functions are avaiable if the optional talkback and oscillator module is installed. .

VCA Group Masters
The SCR51 surround console comes with 4 combined VCA and Cut-Groups that can control the main mono, stereo and 5.1 input module faders. 2 of the VCA masters are installed in the S3-MS5 master module. There is one 100 mm VCA fader and a cut switch per group. The groups operate as vca groups unless the cut switch is pressed. A group cut activates the cut of the associated channels and overrides the fader settings.