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Purple Audio LLC A Professional Audio Equipment Manufacturing Company. Home of the MC77 Limiter and Biz mic preamp. Gear resources for repair, PDF schematic library - Altec, Ampex, Gates, Pultec, Telefunken, UREI.

4RU Master Section System

This system is extremely flexible and could be used in a variety of applications.

It was designed for:
  • Replacing master section in existing consoles
  • Stand alone monitoring & mastering
  • For use with our own Super 8 mixer system
It also could be used for remote switching of shared sources in industrial or residential applications



There are currently 10 master section cards plus an extender for use in the system. Some cards are available in multiple configurations to perform different functions, or with optional features.
  • 4RU #0 Extender
  • 4RU #1 Sixteen balanced Mono sources, switchable in mono or stereo. For use in monitoring of auxes or busses.
  • 4RU #3 Five mic preamps for talkback and listenback / Stereo solo summing / Oscillator.
  • 4RU #5 Source switching for studio & three cues.
  • 4RU #6 Outputs for studio & three cues.
  • 4RU #7 Balanced inputs for Stereo Buss Summing / Sum and trim offset for column source select / Stereo Solo summing.
  • 4RU #8 Eight Balanced Stereo sources, switchable. Transformer or differential input. For use as column source select.
  • 4RU #10 Stereo buss card. Also use for aux & buss amps in the Super 8 system.
  • 4RU #12 Large system control room & studio source select.
  • 4RU #13 Control room outputs or headphone amp.
  • 4RU #15 Small system control room source select.

Below are pictures and description of all of the cards. These cards were all designed to solve various monitoring needs for our own retrofit and custom console projects. These cards are available for purchase in any combination with or without control surfaces. For more information please email us.



Common features of all cards:
  • System cards fit vertically in 4RU card frame or can be mounted horizontally in 2 RU chassis.

  • The input/output card edge connector is a Sullins 36/72 pin dual row connector.

  • Audio power supply rails are +/-18 VDC.

  • Relay voltage is 12VDC – all relays are fed DC and require a ground closure.

  • Logic voltage is 5VDC.

  • Relay and logic voltage share ground.

  • For information about our discrete opamps and our universal opamp footprint, see the opamp page.
4RU #0 - Extender

Single piece or system price - $150 		 
4RU #1 - Control room source router

Sixteen Balanced Mono sources, switchable in mono or stereo. For use in control room monitoring of auxes or busses.

This card uses two three line BCD decoders to switch between each of the eight inputs in the row.

Odds & evens in any combination can be selected for stereo monitoring.

Output is balanced and doubled on two sets of pins.

For use in control rool monitoring of auxes or busses.

Single piece or system price - $450. 		 
4RU #3 - Five mic preamps for talkback & listen back / Stereo solo summing / Oscillator
Single piece or system price - $350.  
4RU #5 - Source switching for studio & three cues

For use in large master section systems.

This card requires unbalanced sources to be fed from a 4RU #8 card.

This card requires an output card, either one 4RU #6 or multiple 4RU #13 cards.

Each of the three cues switch between three unbalanced sources and unique differential inputs. Differential inputs are stereo and use a Burr Brown OPA2134.

This card uses three line BCD decoders for source selects.

The card is also designed to source select for studio loud speakers (SLS). SLS source can be selected between the three unbalanced sources above and the control room select.

If you require these cues to be soloed into the control room the card can not be fit with the SLS portion.

Single piece or system price - $275 		 
 


A typical control surface for 4RU #5 and #6 cards
 
4RU #6 - Outputs for three stereo cues & SLS

Stereo Output amplifiers for four stereo inputs.

Mute, dim, & talkback relays available for each pair.

Output balanced with DRV134 IC.

For use with 4RU #5.

Single piece or system price - $350. 		 
4RU #7 - Stereo in / Sum, offset / Stereo solo summing amps
Balanced input for monitoring stereo buss on large systems.

Input is either differential or transformer input. Output is unbalanced, doubled on two set of pins and is designed to feed both 4RU #12 Control Room Source Select and 4RU #5 Stereo Buss card.

Sum is used with multiple 4RU #8 cards in a large monitoring system to sum columns together. Offset trim is used to adjust the level on a chosen column for matching level off two track returns.

Stereo solo summing amplifiers sum console solo buss and feed out through a pot into the solo inputs on cards 4RU #12 or 4RU #15.

Single piece or system price - $350.

 		 
4RU #8 - Source switching for column select

Eight stereo balanced sources with differential or transformer input.

Differential transformerless input available discrete or IC.

Transformer input version has discrete dual emitter follower or IC buffer.

Outputs are unbalanced.

Single piece or system price - $375 (Differential & Discrete) 		 
4RU #10 - Stereo Buss

Voltage or current summing input opamp.

Insert send balanced on board with DRV134 IC or external output transformer.

Switchable insert return: Insert out, A return, B return.

Differential insert return.

Fader loop.

Output amp driving four outputs.

Two outputs balanced with Burr Brown DRV134 ICs, two outputs balanced with split winding off output transformer.

Card can also be used for buss or aux summing.

Available with mute, solo & with jumpers for talk back.

Single piece or system price - $825 		 
4RU #12 - Control room and studio source for large systems

Unbalaced input A column, B Column, Stereo source, aux input, stereo solo.

Dual buffered meter outputs.

Swap & mono function.

Meter outputs switchable between stereo buss or follow control room select.

Available with solo over function.

Dim function for relative dim.

Studio source select: A Column, B Column, Stereo Buss, Follow Control room.

Outputs for control room pot & dim pot.

Return for Dim pot used with relative dim.

Single piece or system price - $350 		 
4RU #13 - Control room output

Inputs from control room pot and dim pot for isolated dim.

Outputs four pairs of speakers with trims selectable with BCD Decoder.

Isolated dim for control room.

Dim function for talk back / listen back.

Dim function available for Left and right separately for use in 5.1 system.

Left, Right, and Both speaker cut.

Balanced output via output transformer or DRV134 IC.

Single piece or system price - $700 		 


4RU #13 - Headphone Amp

Same card as above but stuffed as Stereo headphone amplifier.

Left, Right, and Both earpiece cut.

Single piece or system price - $225 		 
4RU #15 - Small System Control Room source

Six balanced stereo inputs, available with trimmers.

Unbalanced Stereo solo input.

This card uses a three line BCD decoder for source selects.

This card stuffed with differential inputs using discrete class A opamps, also available with IC.

Mono summing amp is discrete class A also available IC.

Meter bufer with pick off at top of control room level.

This allows user to see whatever is selected to the control room.

Solo, mono, swap, two tracks.

Outputs for control room pot & dim pot.

Return for Dim pot used with relative dim.

Single piece or system price - $650 		 


4RU #15 - Small System Control Room source

As above, but with transformer inputs instead of differential opamps.

Transformers buffered by dual discrete class A follower.

Single piece or system price - $750 		 

Large Mastersection Panels