phantom power patching q

brendandwyer

brendandwyer

New member
posted at G*slutz but they're a little slow today and i'm trying to order my cabling and connectors.....

I'm about to begin installing our Pm2000 console. I was planning on wiring the last 8 channels to a mic patch panel for use as preamp channels, but i'm concerned about one thing.

Each console channel has a 48v selector switch. The console also has a master 48v switch.

I will be wiring the multitrack recorder normalled to the xlr channel inputs on channels 1-24.

Is there a risk of say, channel 5's 48v switch being thrown and damaging the recorder? If so i would forgoe the 8 channels for mics, unless there is a better way to do this.

Thanks
 
brendandwyer said:
posted at G*slutz but they're a little slow today and i'm trying to order my cabling and connectors.....

I'm about to begin installing our Pm2000 console. I was planning on wiring the last 8 channels to a mic patch panel for use as preamp channels, but i'm concerned about one thing.

Each console channel has a 48v selector switch. The console also has a master 48v switch.

I will be wiring the multitrack recorder normalled to the xlr channel inputs on channels 1-24.

Is there a risk of say, channel 5's 48v switch being thrown and damaging the recorder? If so i would forgoe the 8 channels for mics, unless there is a better way to do this.

Thanks
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The PM2000 is an older console and yesterdays electronics had much less protection from over voltage/shorting than today's. Personally, I would keep the board away from patchbays for mic inputs. Effects busses will be safe.

If you really want a definate answer, go over to Pro Sound Web and ask Fletcher. He has one in his studio currently.
 
MCI2424 said:
The PM2000 is an older console and yesterdays electronics had much less protection from over voltage/shorting than today's. Personally, I would keep the board away from patchbays for mic inputs. Effects busses will be safe.

If you really want a definate answer, go over to Pro Sound Web and ask Fletcher. He has one in his studio currently.
Click to expand...

thanks!

I agree that routing Mics through the PB is bad. But what i'm really worried about isn't routing the mics through the bay, but rather that because there is a global phantom power switch, does accidentally hitting one channels Phantom power (connected to a multitrack) run the risk of damaging the multitrack.

i'll go over and ask him though.
 
Assuming the inputs to any piece of equipment are balanced, a DC signal would never get past the transformer/resistors so it would not do any harm to the desk/preamp/whatever.

Why is routing mics through a patchbay a bad idea? We have patchbays at uni half-normalled to the mic boxes out in the live room. Provided the patchbay is balanced (and your patch cord) there's no issue in doing this; in fact I'd recommend it as it's so handy.
 
pezking said:
Assuming the inputs to any piece of equipment are balanced, a DC signal would never get past the transformer/resistors so it would not do any harm to the desk/preamp/whatever.
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Resistors won't necessarily solve that problem, and you can't depend on a bit of kit to always have input transformers. When you make a phantom connection through a patchbay, you can briefly have one side unconnected such that +48V potential appears on one leg and is thus unbalanced.

That said, the solution to the problem is capacitors coupling the input (or a transformer that can take the DC) and a few diodes to prevent AC overvoltage. Any modern gear that lacks those can be rightly considered a piece of crap, since you always should assume that horrible things are coming your way from the outside world. But it's always best to know for some particular gear whether or not it is adequately protected.
 
If I remember correctly from my classroom days, you should be fine, and for one very basic principle in electronics:


parallel voltage. In parallel, 48v plus another 48v does not equal 96v. It equals 48v.

So in other words, the myth of adding phantom power to phantom power should not result in a pretty fireworks show. If it does, then something else was the cause.

Now would I try to disable the phantom power at any stage but the preamp stage? Probably, but that's because I'm paranoid anyway. :)
 
LeeRosario said:
If I remember correctly from my classroom days, you should be fine, and for one very basic principle in electronics:


parallel voltage. In parallel, 48v plus another 48v does not equal 96v. It equals 48v.

So in other words, the myth of adding phantom power to phantom power should not result in a pretty fireworks show. If it does, then something else was the cause.

Now would I try to disable the phantom power at any stage but the preamp stage? Probably, but that's because I'm paranoid anyway. :)
Click to expand...

what i'm getting at is that at no point would i be intentionally flipping on 48v on a monitor channel, but if i were to by accident, is there potential damage.

If so, should i disable the 48v on channels 1 -24. i think you've answered yes :)
 
LeeRosario said:
No potential damage :).

However, your monitor input shouldn't be involving the preamp stage, which houses your 48V, pad, phase, hipass/lopass, trims etc. The idea of a monitor channel is to be able to hear what your getting past having boosted, and applying any EQ and/or dynamic FX. No further coloration from the board.

That's why there's a difference between channel line input (comes just after your mic lines) and a monitor input.

When I say channel line input, I'm implying all the things that happen before your signal hits the multitrack recorder (MTR). The monitor input comes after the MTR. So there shouldn't be phantom power anywhere near that stage.

What you describe sounds like you're trying to route your MTR back into your mic line inputs and frankly while it won't hurt your console, I personally wouldn't have routed it that way. This also depends on the console and on how elaborate the design. If it's an inline console, then you're in bussiness, but if you have no way to route your monitor inputs (half normalled, not fully normalled) then you might have to go another route.

In terms of phantom power, the only time I would probably be very weary of using it is when you're using a ribbon mic that wasn't made for 48V. That is easily a more possible senario.
Click to expand...

this is the yamaha pm2000 console. The only choice for channel inputs are the interstage patch points on each channel, or the channel inputs. I've been talking to fletcher @ merc who has one and i think he's doing it the same way. I don't think returning the MTR to the patch points is the way i want to go.

Thanks!
 
brendandwyer said:
what i'm getting at is that at no point would i be intentionally flipping on 48v on a monitor channel, but if i were to by accident, is there potential damage.

If so, should i disable the 48v on channels 1 -24. i think you've answered yes :)
Click to expand...


No potential damage :).

However, your monitor input shouldn't be involving the preamp stage, which houses your 48V, pad, phase, hipass/lopass, trims etc. The idea of a monitor channel is to be able to hear what your getting past having boosted, and applying any EQ and/or dynamic FX. No further coloration from the board.

Then the other issue is this fully normalled thing you got going on here. You don't want your monitor input fully normalled for one very simple reason: Mixing.

There's flexibility there that you should have, which is why you'll usually see studios with half normalled monitor inputs. You want to be able to split off copies of your signal if you need to.


One thing: there's a big difference between channel line input (comes just after your mic lines) and a monitor input.

When I say channel line input, I'm implying all the things that happen before your signal hits the multitrack recorder (MTR). The monitor input comes after the MTR. So there shouldn't be phantom power anywhere near that stage.


So to put it more simply, it's like if you wait 3 hours to get on the rockin roller coaster ride at disney, but then the second time you bypass the entire line with a speed pass. You'd be damed if you have to wait 3 hours again for a 2 minute ride. The 3 hour line being line your channel strip before you get to the MTR, and the actual ride itself being like an MTR.

What you describe sounds like you're trying to route your MTR back into your mic line inputs and frankly while it won't hurt your console, I personally wouldn't have routed it that way. This also depends on the console and on how elaborate the design. If it's an inline console, then you're in bussiness, but if you have no way to route your monitor inputs (half normalled, not fully normalled) then you might have to go another route.

In terms of phantom power, the only time I would probably be very weary of using it is when you're using a ribbon mic that wasn't made for 48V. That is easily a more possible senario.

But in the end, if you HAVE to reroute your MTR back into your preamps, then just be aware that you'll be passing your signal through the entire channel strip twice.


I hope this helps you out a little better.
 
brendandwyer said:
these are multitrack outputs to console inputs
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Why would you be running the line level outputs of the multi-track to the mic level inputs of the board. Doesn't this board have line inputs? That is what you are supposed to use for the multi-track returns.
 
Farview said:
Why would you be running the line level outputs of the multi-track to the mic level inputs of the board. Doesn't this board have line inputs? That is what you are supposed to use for the multi-track returns.
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this console is a yamaha PM2000 a FOH console. 32 inputs on XLR, no line inputs.

MTR line level outputs to PM2k channel inputs. External preamp outputs to MTR inputs. All via patchbay.

i'mnot using the board preamps on channels 1-24, only channels 25-32.
 
brendandwyer said:
this is the yamaha pm2000 console. The only choice for channel inputs are the interstage patch points on each channel, or the channel inputs. I've been talking to fletcher @ merc who has one and i think he's doing it the same way. I don't think returning the MTR to the patch points is the way i want to go.

Thanks!
Click to expand...

very good. Fletcher has a good reputation as far as I've heard, so a good man to talk to.
 
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