FOH / MONS / STAGE dedicated comms system/mixer project
« on: July 28, 2019, 09:35:42 AM »
Hi to all of you !

I'm Piotr, I'm located in France and I'm sound engineering mostly in live music.

I'm very often puzzled by some of the difficulties of an easy communication in our working environnement between the different locations. There are different solutions used, depending on the company, the festival and so on... mostly via small dedicated mixers, and two input powered speakers (https://www.behringer.com/Categories/Behringer/Loudspeaker-Systems/Portable/B205D/p/P0957#googtrans(en|en) for example).

Maybe this is sufficient, maybe not, maybe there's a simpler way especially concerning the routing, inputing and outputting of utility signals as TALK mics etc... and sharing/providing them to incoming productions.

So I've started a project, based on the usual setups on concert and festival stages, and discussions with my fellow colleagues in France and Switzerland, that intends to simplify the routing and mixing of the various sources needed: FOH talk, MONS talk, FOH shout, MONS shout, STAGE wireless talk, STAGE IEMs...

Basically the idea is to have two 19" racks, one at FOH, one at MONS, that are dedicated mixes (5 sound sources to 3 mix busses), with 4 analog lines running (either/or XLR and CAT5 analog as in the RATCAT family http://soundtools.com/products/catfamily.php).

I have a basic knowledge of electronics, I have successfully built a lot of projects (9K preamps, 1176, 51x 500 racks...), I'm learning KiCAD...

At this point I need help !!! I'm not an electronics designer so there's a lot of things I need to clarify.

The project calls for "basic blocks": MIC/LINE preamps (no 48v), MIC Splitting (easiest probably done with transformers ?), LINE Receivers to LINE OUTPUT, SUMMING stage (with mutes and level control probably) and LINE OUTPUT stage.

I've investigated a simple INA217 based preamp as for example in:


I've investigated basic mixer topologies as for example in:


I'm trying to figure out which way to go and design then build this project, so before going further I'm hoping for some general wisdom and remarks from GROUPDIY where I've always found a lot of answers !!!

I clearly need a method to put it all together, so I would happily read your comments as to the steps you think I need to follow: general idea > basic synoptic > schematic > PCB design...

I need to narrow down the building blocks to simple and easy to implement solutions: which MIC/LINE preamp, which SUMMING solution etc...

And of course what are the bad ideas I need to throw away !!!

That's it for the opening post !!!

Looking forward to your insight and ideas,


« Last Edit: July 31, 2019, 08:36:00 AM by Piotr »
"Various disguises are regrettable but necessary, if you want to make it through the day !"
Nomeansno - "Everyday I Start To Ooze" in "0+2=1" - Alternative Tentacles, Virus 98, 1993


Re: FOH / MONS / STAGE dedicated comms system/mixer project
« Reply #1 on: July 28, 2019, 11:27:17 AM »
As to clarify the general intention, here is a basic synoptic, which omits the local details of the racks (input connectivity and switching).

The FOH rack is basically a passive input/output "patching" box, no mixing necessary, just connectivity.

The MONS rack is where the mixing/summing/routing takes place so I guess active is the only solution.

There are basically four different situations that need to be dealt with:

Situation A : FOH with House desk / MONS with House desk
Situation B : FOH with Production desk / MONS with House desk
Situation C : FOH with House desk / MONS with Production desk
Situation D : FOH with Production desk / MONS with Production desk (where the house communication system is generally not used but remains in use for the other shows.)

Tell me what you think. Tell me what to clarify.

Thanks in advance !!!

« Last Edit: July 28, 2019, 11:47:28 AM by Piotr »
"Various disguises are regrettable but necessary, if you want to make it through the day !"
Nomeansno - "Everyday I Start To Ooze" in "0+2=1" - Alternative Tentacles, Virus 98, 1993

Re: FOH / MONS / STAGE dedicated comms system/mixer project
« Reply #2 on: August 07, 2019, 01:57:43 PM »
I’ve been thinking about this issue quite a bit lately. There are a bunch of ways to route it, and it ends up being pretty show specific.

At the shop where I work, we recently added a 4 channel XLR to our PA drive line:
Shout in, shout out: these lines connect a microphone at monitors to a powered speaker at FOH, and vice versa. We use little 2 channel powered speakers for shout, so you can add another custom mix at your discretion. The third line is for clear com, so we can look cool talking on our phones and the fourth line is a line from FOH that we usually use for the foh engineer to talk to stage.
We talked about building boxes, but keeping most stuff at mic level seems to have cut out some of the technology.
 I was focused on a solution for monitors that saves resources.
Im sure you’re familiar with the SC48 aes loop trick, most of the workarounds inside the console tend to burn up resources.
Both the S6L and the Digico offerings have in the box solutions but they are harder to set up than a dedicated hard line.
From the monitors perspective, I sometimes want an  iem mix that includes some band and or tech talkback, as well as a solo bus, and be able to cue up a guitar at the same time Im listening to the player talk to me from the stage TB. This is usually built into a file, but something that doesn’t burn up resources could be cool.
 I was thinking of:

Party line talkback/ pgm in>>
Cue mix from console in>>(paralled to cue mix wedge out)
Clear com audio in>>
FOH/ tech shout>>

{Passive or acvive switching rack}

>>Balanced stereo line out for wireless iem
>>headphone amp out
>>cue mix wedge out
>>clear com audio out

Personally, multiple mics for multiple destinations works for me, so I don’t accidentally say something to the artist that was meant for the FOH guy.


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