I61b Control Room Unit
A versatile stereo control room regulator unit with all required functions for 4U frames
The control room unit I61b provides efficient and simple management of the headphone and loudspeaker systems in the control room. The module can be installed in any slot of a 4U high extended frame or in slot 9 of any 4U high frame. In combination with a source selection module, I21 or I64 and a level meter I12, a complete monitoring system can be assembled.
The control room unit is equipped with volume and balance control, an adjustable DIM circuit, phase flip switch that changes the phase of the right channel, MONO switch, PFL, headphone output and volume control and an ALT and MINI switch that sends the output to a second and third set of loudspeakers.
The inputs of the I61b unit are electronically balanced and are medium impedance for a level of + 6dBu. The inputs are usually connected with the output of a control room select module I21 or I64. Naturally, connection to any arbitrary source is possible.
The selection of the PFL signal, which can be supplied on a separate input, takes place either via the PFL switch or via a control signal, which is separated by an opto coupler, in this case the PFL switch indicates the combination. The control signal comes directly from the INTEGRATOR mixer. A potentiometer controls the volume of the PFL signal. A Jumper makes it possible to feed the PFL signal to certain channels. The DIM circuit is adjustable by a potentiometer between 6 and 24dB. Also here the release can take place by either the DIM key or by a control signal. An opto coupler also electrically isolates this signal; both control signals operate within the range of between 9 volts to approx. 30 volts.
The PHASE switch flips the phase of the right channel and the L-R switch reverses both the left and right channels. The MNO switch converts the signal to mono by use of an internal matrix that can be set to 3 dB or 6 dB mode by an internal jumper. The BAL control makes it possible to correct the center of the speaker system. The characteristic of the pot is optimized for a pure direction control without affecting the total loudness. In the L and R positions of this control the opposite channels are muted. The rotary volume control is selected for minimum ganging error. A 24 position stepper switch is available as an option.
The AL-SP switch selects the second (alternate) speaker set; a third speaker set can be selected by the MINI switch. Only one system is active at a time. CUT mutes all systems except the headphone output.
The outputs of the control room unit are electronically balanced. The maximum level is more than + 30 dBu. At the 94 dB position of the volume control, the overall gain is 0 dB with the BAL control at center position. The headphone output has its own level control. The output is well suited for all commonly available headphones.