M905B — Studio Monitor Module

M905B STUDIO MONITOR MODULE

1) Designation Strip

Source selector designation strip. A plastic covered designation strip for the identification of selector sources.

2) Studio 2 Announcer Headset Level

A stereo control which allows adjustment of the headset level of the announcer in Studio 2.

3) Studio 2 Mute LED

A green LED which tallies the operation of the mute function for Studio 2.

4) Studio 1 Announcer Headset Level

A stereo control which allows adjustment of the headset level of the announcer in Studio 1.

5) Studio 1 Mute LED

A green LED which tallies the operation of the mute function for Studio 1.

6) Talkback to Announcer 1 Pushbutton

This button enables the talkback path to the monitor speakers in Studio 1, and optionally, the Studio 1 Announcer Headset.

7) Input Source Selector Switches

Ten electrically interlocked momentary switches which control the stereo solid state audio switches within the M905B. These switches select the source that the M905B will provide to both Studio 1 and 2. The active source selection is tallied via illumination within the active button.

8) Studio 2 Guest Headset Level

A stereo control which allows adjustment of the headset level for the guest in Studio 2.

9) Studio 2 Monitor Level

A stereo control which allows adjustment of the speaker monitor level in Studio 2.

10) Studio 1 Guest Headset Level

A stereo control which allows adjustment of the headset level for the guest in Studio 1.

11) Studio 1 Monitor Level

A stereo control which allows adjustment of the speaker monitor level in Studio 1.

12) Talkback to Announcer 2 Pushbutton

This button enables the talkback path to the monitor speakers in Studio 2, and optionally, the Studio 2 Announcer Headset. Inputs

The ten stereo inputs to the M905B Studio Monitor Module are brought into the module through edge card connector P1.

The inputs are coupled to the SA14-273 10x1 Stereo Selector Assembly through 273J3 and 273J3, where the switching function takes place. Please refer to the subassembly section of this manual for a detailed description of this assembly. The M905B has two signal paths that are identical, for both Studio 1 and Studio 2. The description of circuit operation is the same for both studios.

Studio 1 Monitor Section

Please refer to schematic sheet B 905-02-003/1.

Studio 1 Monitor Outputs

The left output of the SA14-273 is coupled into the M905B through C1. This signal is current switched through R3 by U1 in normal operational mode. The left signal is then ac coupled into the summing node of U4A. The right output of the SA14-273 is likewise coupled through C2, R8 and U2 into the summing node of U4B. The outputs of U4 are connected to the front panel mounted Studio 1 monitor level control. This signal can be muted by grounding the external mute pin of the module, or by assigning the appropriate muting buss to U5, the solid state audio switch, with LK1, LK2, and/or LK3.

The mute LED is lit whenever that state has been enabled, no matter the source.

Integrated circuit U6 provides a balanced signal for the Monitor Outputs capable of driving a 600 ohm load.

Talkback to Announcer

Depressing the front panel switch "Talkback to Announcer", causes the mode of the monitor speaker to change. This switch places the sum of the SA14-273 outputs in the left channel of the monitor speakers, with diminished level based on the adjustment of R4 and R6. The right channel receives the input audio that is present at the talkback input at edge connector P1-41.

The LED integral to SW11, Talkback to Announcer, can be illuminated by connecting P2-21 to ground. This can be used to tally incoming talkback to the console cue system.

Studio 1 Announcer Output

The Announcer Output can be selected to be the same signal feed as the monitor speakers by placing LK4 and LK5 in position 1-2. Alternately, with LK4 and LK5 in position 2-3, a clean stereo feed from the SA14-273 output is coupled to the headset level control R43.

The dual balancing amplifier consisting of U7 provides output drive to the announcer's headset position.

Studio 1 Guest Output

The guest headset position gets a clean feed from the SA14-273 selector outputs at all times. This dual balancing amplifier consisting of U8 and all related components is schematically identical to the Announcer Output. The level is front panel adjustable with dual potentiometer R60.

Power Supply Decoupling

The power supply for the M905B is decoupled from the console power buss by the active decoupler consisting of Q1 through Q6. Q1 and Q2 are a darlington connected pass transistor for the positive power supply, while Q3 and Q4 perform the complementary function.

Capacitors C112 through C115 help to further smooth the power supply response.

A separate +6 volt power supply to drive the logic circuitry on the module is coupled down from the +18 volt supply by Q5 and Q6.

Fusing resistors R151 and R155 protect the module in the event of a catastrophic power supply fault. C1 Capacitor 33 uF/10 V ITT 33M10 C2 " 33 uF/10 V " " C3 " 33 uF/10 V " " C4 " 0.1 uF/100 V Sprague K104K20X7RFVBWN C5 " 0.1 uF/100 V " "

C6 " 10 uF/25 V ITT 10M25 C7 " 10 uF/25 V " " C8 " 10 uF/25 V " " C9 " 10 uF/25 V " " C10 " 10 uF/25 V " "

C11 " 100 pF Philips 638-03102 C12 " 22 pF " 638-10229 C13 " 0.1 uF/100 V Sprague K104K20X7RFVBWN C14 " 100 pF Philips 638-03102 C15 " 22 pF " 638-10229

C16 " 0.1 uF/100 V Sprague K104K20X7RFVBWN C17 " 33 uF/10 V ITT 33M10 C18 " 33 uF/10 V " " C19 " 0.1 uF/100 V Sprague K104K20X7RFVBWN C20 " 10 uF/25 V ITT 10M25

C21 " 100 pF Philips 638-03102 C22 " 22 pF " 638-10229 C23 " 0.1 uF/100 V Sprague K104K20X7RFVBWN C24 " 100 pF Philips 638-03102 C25 " 22 pF " 638-10229

C26 " 10 uF/25 V ITT 10M25 C27 " 100 pF Philips 638-03102 C28 " 22 pF " 638-10229 C29 " 0.1 uF/100 V Sprague K104K20X7RFVBWN C30 " 100 pF Philips 638-03102

C31 " 22 pF " 638-10229 C3

M905B STUDIO MONITOR MODULE

Gain: 10 dB ±1 dB.

Frequency Response: ±0.2 dB from 20 Hz to 20 kHz.

Noise: Less than 70 dB below nominal output with 10 dB "in hand" over 20 Hz to 20 kHz bandwidth.

Harmonic Distortion: Less than 0.1% from 20 Hz to 20 kHz at +24 dBm output or less.

Source Impedance: 600 ohms or less, balanced / unbalanced.

Input Impedance: Greater than 20k ohms balanced. Greater than 4.5k ohms unbalanced.

Input Level: +4 dBu balanced, -6 dBu unbalanced.

Output Level: 0 dBu, nominal.

Output Impedance: 60 ohms or less, balanced.

Channel Separation: 60 dB.

Crosspoint Attenuation: 75dB.

Power Requirements: ±24 volts DC, 150 mA.

Ambient Temperature: 0 to 50 degrees Celsius.

Weight: 750 grams (26.5 oz.). GENERAL

M905B STUDIO MONITOR MODULE

The M905B Studio Monitor Module provides the monitoring and talkback facility for two remote studios within the Renaissance Radio Console system. Typically these would be used for a news booth and an announce booth with two headphone monitoring positions (in addition to a monitor speaker output).

The M905B is capable of selecting one of 10 stereo line level sources for monitoring in the remote studios. All audio switching is realized within the module for muting and talkback using solid-state active switching (no relays are employed). The source selection is tallied with an LED indicator which is integral to the pushbutton.

Each of the two studios controllable from the M905B has three level controls associated with it. There is a control for the monitor speaker feed (Monitor Level), the announcer headset level (Announcer), and the guest headset level (Guest).

The Monitor Level can be muted by using the console muting buss structure. Each studio is individually assignable to one of the three muting busses within the console. Muting does not effect the Announce or Guest Headset feeds. A front panel LED indicates when the associated studio has enabled the mute buss in the console.

An input is provided on the M905B for sending talkback audio to a selected studio (via a momentary pushbutton). The tally lamp within the talkback button is uncommited and may be used for externally signalling the console operator from the remote location. Enabling the talkback will shift a mono sum of the selected source to the left speaker of the studio (This level may be diminished with internal controls). Talkback is then placed on the right channel of the monitor feed.

The Announcer may also have the talkback audio assigned to his headset in the same fashion as the monitor speakers. Printed circuit board links provide this feature.

In all cases, the Guest Headset feed is unaffected by either muting or talkback operations.

The M905B may be used in place of an M905A monitor module. However, the cue speaker will not function. The Studio 1 Monitor and Announcer controls will effect the Control Room Monitor speakers and the console Headset Level respectively. Please note that in this configuration, it will not be possible to drive low impedance headsets.

All outputs are actively balanced and are configured for a nominal output level of 0 dBu.

The M905B is packaged in the standard Renaissance modular package, 1.50" wide x 16.2" high x 6.6" deep.

The module derives it's power from the console system ±24 volts. OPERATIONAL

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