Yamaha LS9 Stereo/Mono Question

Discussion in 'Sound, Music, and Intercom' started by Bob Cervera, Oct 17, 2018.

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  1. Bob Cervera

    Bob Cervera Member

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    I've answered countless questions on various forums. This is the first time I've ever asked one...

    I have a Yamaha LS9-32 that I use in a broadcast environment. Mostly through MIDI controls and mix-minus configurations I've modified the board to act more like a broadcast board and less of a recording board and it works great!

    There's only one thing I can't figure out how to do -- assuming what I want to do is even possible. Among the many audio sources on the board, four of them are stereo analog. As such, they occupy eight of the board's inputs -- 4 x (L/R) = 8. Each input is pan-potted full left or full right on the stereo output, then linked to a single fader to control both channels of each source with the one fader. The problem is sometimes I need any combination of those specific sources to be mono -- or both channels pan-potted center.

    The ideal way to accomplish the task -- from a user standpoint -- is to simply press one of four User Defined Keys that latch each of the sources to mono (both channels on any of the sources panned to center), then press the same key to put the source back into stereo (one channel panned left, the other channel panned right). I'd like all that to happen without affecting any of the board's other settings or configurations.

    I'm currently using the Stereo bus as the main output (not LCR) and various Mix channels patched to the omni outs for other outputs. I'm not currently using the mono bus, the matrix bus or any of the racks that are built into the LS9.

    I've been using the User Defined Keys to call up preset scenes to accomplish the task, but that's really not versatile enough. There are times I need to throw only one of the sources to mono while the rest remain stereo, or any two sources in mono while the other two remain stereo, or any three sources... well, you get it, right?

    Am I asking too much from the LS9? Any thoughts and/or questions are quite welcome!
     
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  2. Aaron Becker

    Aaron Becker Well-Known Member

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    As I understand it - you want to have a User Defined Key to switch the stereo link of two channels from "linked" to "not linked." AFAIK, there isn't a way to do this on the LS9 (or any board in its class, for that matter). The LS9's User Defined Keys seem to serve a specific purpose, Yamaha's preset definitions of what they can do.

    I'm trying to think of a work around where you could use the custom layer of the faders to always have them on their own faders and then link them only when needed, but that doesn't solve your "problem" of having to manually link or unlink the channels.

    You could do a whole lot of "safe recall" and only have the scenes change the stereo/mono pairing, but that seems like a headache waiting to happen (just my opinion).

    I think your best bet is just manually changing the stereo/mono link properties on an as-needed basis.

    Perhaps someone else will come along and know better than I!
     
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  3. FMEng

    FMEng Well-Known Member Fight Leukemia

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    This is why TV production consoles sell for 10 times more $. They are designed for the task at hand.

    You could build an external summing network and do it before it even gets to the console. Add a toggle switch to it to go between stereo and mono. Or you could use an RDL ST-MX3 mixer and have a separate fader for a mono sum of that source.
     
  4. Bob Cervera

    Bob Cervera Member

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    I very much appreciate the two responses so far! What I'm trying to do doesn't "make-or-break" my workflow. It's something I hoped could be done and I needed confirmation that it's time to break off the chase.

    FMEng -- I agree that the way the LS9 is being purposed is not its intended use. At first I hated that this stage board was dropped on me and that I had no choice but to make it work. However, I must say, with the modifications I've made, the LS9 is actually working out elegantly in my broadcast environment and I'm quite happy with it now! I like your idea to use an external summing network with physical toggles. I hadn't thought of that and I think it's the best solution. I'll get working on that!

    Again -- thanks much to both of you!
     
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  5. RonHebbard

    RonHebbard Well-Known Member Premium Member

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  6. Bob Cervera

    Bob Cervera Member

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    That's an awesome story, Ron! I have some age on me, too. I remember the AM tube days as welll. My AM transmitter used a huge tube in the final stage amplifier. Now my full-power TV transmitter is all solid state and air-cooled. I don't have to chase voltage swings nearly as much anymore nor do I have to "burp" any tubes! Luckily my eye sight is still pretty good. I never thought stereo imaging could be that important to someone who's sight-challenged. Thanks for sharing.
     
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  7. TimMc

    TimMc Well-Known Member

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  8. Bob Cervera

    Bob Cervera Member

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    Hey Tim...

    I've looked and looked and looked and I can't find anything related to "Make Me Mono" in this forum. Any chance you can provide a link? I'd like to make something myself. I'm pretty handy like that, but I admit I don't feel like doing the math to figure out how to sum the balanced left & right channel inputs to dual mono outputs while not changing any levels or impedances. I thought an interwebs search would work, too, but finding a schematic to do what I want has proven quite a bit more elusive than I imagined!
     
  9. TimMc

    TimMc Well-Known Member

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  10. FMEng

    FMEng Well-Known Member Fight Leukemia

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    The problem with most cookbook or manufactured options is that they don't allow for switching between stereo and mono. Here is a schematic of what you need. It is a balanced, stereo to mono network with a switch.
    Bal Stereo to mono.jpg
    This is designed to work properly with a typical, low impedance source (50-600 ohms) and high impedance (5K-20K ohms), bridging input.

    The 470 ohm resistor value is not critical, anything from 300 to 560 should work fine. The resistors must be well matched to maintain good common mode noise rejection of the balanced circuit. Use 1%, metal film resistors. The switch is DPST. The wires of the balanced pairs, inside the box, should be tightly twisted together if they are longer than an inch or so. That is also the case with pairs to each side of the switch.

    If the audio on the left and right channels is nearly the same, there will be a small increase in level when switched to mono. The increase could be up to 6 dB. This is the compromise of keeping it simple.

    Let us know how it works if you build one. Photos are nice, too.
     
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  11. Bob Cervera

    Bob Cervera Member

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    That's awesome, FM! Thanks much for the diagram! This is not a current priority project. It's a project I'll work on when the dust settles on others. I know this project is on the horizon, so I inquired about how to do it while I waited for things to happen with higher priority projects. When I do wire this one up, though, I will most certainly report back with pics when it's done. Thanks again!
     
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  12. Jay Ashworth

    Jay Ashworth Well-Known Member

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    Sure, but what's more dangerous? 35,000V? Or 1,000A? :)
     
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  13. GreyWyvern

    GreyWyvern Apollo Staff

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  14. RonHebbard

    RonHebbard Well-Known Member Premium Member

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