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Need assistance with Neutrik combo connector and Phantom power
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NuSkoolTone
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#1
13th September 2005
Old 13th September 2005
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Need assistance with Neutrik combo connector and Phantom power

Hey guys, searched the net and got some background but not a definitive answer and thought maybe you guys could help.

I currently have an A&H mixwizard that I use for live shows and have it racked in a mixer rack with it on top and my outboard below. In the back of the rack I installed rack rails and am installing patch bays so I have flexibility. I also want to make a psuedo patch bay for all the inputs outputs to the mixer because getting back there once it's mounted is a REAL PITA.

Here's the issue on the mixwiz mic inputs, if you plug in the 1/4" input it automatically disconnects the XLR input to that channel. So I cannot connect the two at one time and just patch it to one or the other, I would have to permanently choose. Being that every situation can be different, it's not the best solution.

So I came across the Neutrik combo jacks and thought it would work great! I could plug in a 1/4" or XLR and it would just get fed to the XLR input on the mixer.

Then it Dawned on me: PHANTOM POWER that each channel has! I know my dynamics can usually handle it, and currently I don't use ribbons live, BUT when the 1/4" comes into play, WHAT IF a keyboard or guitar gets plugged in while the phantom is on? BOOM right? From what I'm reading it appears it would be a very BAD thing. With 48V on the pos and then ground on the other, I figure that voltage has got to go somewhere, and I don't want to blow the output circuitry of an expensive keyboard. Of course, I could wire this all up and be VERY careful about the phantom being activated, but mistakes DO happen and want to minimize that risk while getting full utility of the mixer.


Any suggestions? Is there any way to wire a Neutrik Combo jack so that the phantom only applies to the XLR and not the 1/4"? I see lots of prosumer gear that seems to handle this but I would bet they have discreet curcuitry in there that handles this routing. Is it a matter of a couple of resistors on the TS pins? It would be too expensive, but am I looking at transformers?


Help!
#2
14th September 2005
Old 14th September 2005
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If I recall the Neutrik Combo connector brings ALL the connections out seperate on the back. That is the 1/4" inputs are not connected to the XLR inputs. It's up to you how you want to wire them.

-Tony
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NuSkoolTone
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14th September 2005
Old 14th September 2005
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Quote:
Originally Posted by tmarra
If I recall the Neutrik Combo connector brings ALL the connections out seperate on the back. That is the 1/4" inputs are not connected to the XLR inputs. It's up to you how you want to wire them.

-Tony
Tony,

Thanks for your reply. You are correct. To use them as I want I would have to bridge the TS/TRS and XLR contacts.

The issue is dealing with phantom power and if there is any safeguards I can wire in to avoid accidentally sending phantom down a line signal.
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14th September 2005
Old 14th September 2005
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Just bridge your inputs on the other side of the mic input blocking caps that are already on pins 2 and 3 of the XLR mic input.

Ooops. OK so I re-read you post and I'm guessing you want to do this external to the MixWizard. So that means you need to install some caps between the Mic XLR and Line TRS on your external panel. I think 100/63V should work fine.

-Tony
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14th September 2005
Old 14th September 2005
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Quote:
Originally Posted by tmarra
Just bridge your inputs on the other side of the mic input blocking caps that are already on pins 2 and 3 of the XLR mic input.

Ooops. OK so I re-read you post and I'm guessing you want to do this external to the MixWizard. So that means you need to install some caps between the Mic XLR and Line TRS on your external panel. I think 100/63V should work fine.

-Tony
Tony,

Thanks ! That's exactly what I'm looking for. However could you be more specific? are we talking 100pf/nf? Are we talking about polarized caps? Which way? And this will keep phantom going to XLR, but will stave it off from the TRS?

Could I just bridge the XLR and TRS connections with caps instead of solder/wire?
Caps would only go across form pins 2 and 3 right? Remember this is all one connector, just with discreet pins I beleive.

Thanks again.
#6
16th September 2005
Old 16th September 2005
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That would be uF as in micro-farrads. Since phantom power is +48 on both signal connectors, you should put the + side to the board and the - side to the line. You may want to bypass the big electrolitics with a polyester or polypro cap of about 1uF (this will not be polarized.



-tINY

#7
17th September 2005
Old 17th September 2005
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That's it just like tiny said. You could put them right on the Combo connectors. Just make sure that the Electrolytic caps are larger than 48V (that's why I mentioned 100 MicroFarads @63Volts) or they will explode on you. stike

-Tony
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