homemade monitor switch

[Purusha]

Hi Brian, I just checked your monitor controller picture and it looks like something I want to build for my studio but without any meters. Do you have some nice schematics which you could share?

 

[zarat]

I couldn't find anything "off-the-shelf" that did everything I wanted. So after talking about it for a long time I did something about it.

Passive remote relay switching except for a buffer stage around the various sum/difference selections.

 

[Kev]

all wires come to the control unit ?

are all your sources +4 balanced ... or did you gain and balance them first ?

how about a block diagram to see how you went about it

 

[zarat]

Th only connections to thr control unit are a D25 for all switching, 5pin XLR for signal i/o to the volume pot and 2pin 5volts power.

At the rack:

One unit is a 2 x 8 i/p switcher (bal +4, cal'd at source).

Second unit is buffer stages containing phase inversion and summing (the combination of relays set by the middle row of switches via diode logic). This also drives the volume control, meter panel and headphone amp.

Third unit contains output routing/pad/mute relays.

The D25 loops through all rack units.

The top row of switches are latching. The other two rows are momentary with latches and relay drivers. The bank switch selects which which bank of 8 inputs on the bottom row.

One big improvement would be to remote the volume control, but over the 3 meters to the rack, I have not had any problems.


Sorry, I don't want go into real detail - this may yet be a commercial proposition...but I hope this may be an inspitation to others.

 

[Kev]

[quote author="zarat"] ... One big improvement would be to remote the volume control,
... this may yet be a commercial proposition...but I hope this may be an inspitation to others.[/quote]
cool
... the relay volume boards from Mikkel can help or the Texas PGA chips
and
... good luck with the commercial unit

 

[weiss]

I built this unit for my friend/client Dave Gardner, who operates Magneto Mastering in Minneapolis:

http://www.brianroth.com/projects/gardner/monitor-control.jpg

The primary signal path is totally passive.  The "input" switch is a 12 pole Electroswitch.  Each of the three stereo inputs requires two poles per channel. , hence the need for 12 poles.  Any unused input is terminated into 1200 Ohms since the entire system was designed as a 1200 Ohm load fior the sources.  The Shallco stepped attenuator is also a custom 1200 Ohm unit.

The "output" switch is also an Electroswitch 12 pole part.    Each output tip/ring pair requires two switch poles per channel since any unused "destination" is shorted to avoid crosstalk.

Active circuity is required for the "mono" listening mode as well as for the meter buffers.

If I did this sort of gizmo again, I would be tempted to use relays.

Bri

wow this thing eats rack space!