Phantom Power +48v into AXE-FX2 MarkII XLR inputs - is it safe?

blackcom

blackcom

Inspired
I read a while back somewhere that Acle from Tesserect had to send his AXE-FX to service several times because the live soundengineer had
sent +48v into the XLR inputs.

What is the status of today on this subject. If a soundengineer does this by accident, will it damage the inputs on the AXE-FX?

...I just ordered my second AE2 for live usage so I need to know this, hehe...
 
phantom power is needed for the mic, not the XLR input, that sound engeneer did not know his craft! a phantom power supply unit has two XLR connectors, one for the mic and the other that goes to the console or in this case the Axe, but that one does not contain any power what so ever.
 
nicolasrivera said:
phantom power is needed for the mic, not the XLR input, that sound engeneer did not know his craft! a phantom power supply unit has two XLR connectors, one for the mic and the other that goes to the console or in this case the Axe, but that one does not contain any power what so ever.
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Huh?

A lot of desks have phantom power built in on their inputs. Can be accidentally left on, I think the question is what if it is left on and you connect the axe..

Blackcom, you could always give the engineer jacks instead of XLR, with the bonus that he won't be putting your axe through some terrible mic preamp.
 
nicolasrivera said:
phantom power is needed for the mic, not the XLR input, that sound engeneer did not know his craft! a phantom power supply unit has two XLR connectors, one for the mic and the other that goes to the console or in this case the Axe, but that one does not contain any power what so ever.
Click to expand...

Yes I kow this.
Also, most desks has built-in +48 switches on all XLR mic inputs.
Ill try and simplify my question even more.

Question: If the live sound engineer turns on +48v BY ACCIDENT on the XLR cable that goes into my AXE-FX2 MarkII will this damage my unit?
 
blackcom said:
Yes I kow this.
Also, most desks has built-in +48 switches on all XLR mic inputs.
Ill try and simplify my question even more.

Question: If the live sound engineer turns on +48v BY ACCIDENT on the XLR cable that goes into my AXE-FX2 MarkII will this damage my unit?
Click to expand...

I uesd a pair of countryman Type 85 DI Boxes back the days (2008 - 2010), just to be safe! Most devices had capacitors at their symmetrical output line driver amplifier, I read somewhere that Cliff didn't use capacitors to block DC from a signal line to improve sound quality - there are also specific components, that made such capacitors needless such as the famous THAT 1646 Line Driver. The THAT 1646 is able to block 48V internaly by design. Maybe Cliff can chime in here, if he used THAT 1646 line driver ICs on his output circuits....

http://www.thatcorp.com/datashts/THAT_1606-1646_Datasheet.pdf
 
FractalAudio said:
No. Why on earth would you apply phantom power to an unbalanced output?
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There are quite a number of mixers out there where phantom power is either on or off. So if they have mics that need it then it'll get applied to everything. The answer is to use 1/4" or other line inputs instead of the XLRs
 
hippietim said:
There are quite a number of mixers out there where phantom power is either on or off. So if they have mics that need it then it'll get applied to everything. The answer is to use 1/4" or other line inputs instead of the XLRs
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Wouldn't that be only over XLR though and not 1/4th" outs ?
 
Phantom power is only sent through the microphone input of a mixer, not through a balanced/unbalanced 1/4" jack. The only way you'll get phantom power to the AxeFx 1/4" outputs is to have 1/4" on one end and XLR on the other.
 
My assumption was that the poster was considering connecting to the 1/4" ins via an XLR to 1/4" cable and my suggestion was to just use 1/4" line ins.
 
muttonhead said:
Phantom power is only sent through the microphone input of a mixer, not through a balanced/unbalanced 1/4" jack.
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This is not necessarily enough. Think about the use of snakes with XLR 1/4" combo jacks for input but are XLRs at the input to the mixer.
 
When I wrote that response, I was thinking of mixers with separate mic and line inputs. In that scenario, it's probable that there will be no phantom power on the line in jacks. I own a QSC Touchmix mixer and went and connected a TRS cable to channel 16, which is a combo connector. Turned on the phantom power for the mixer and checked with my meter, no phantom power on the TRS cable. I plugged in an XLR cable and there was 48 volts on pins 1& 2....oops, 2&3!
I've not seen any snakes using combo connectors, so I wouldn't know what type of connector they're using, but I have replaced some combo connectors on mixers and some powered speakers, the combo connectors are quite "busy" looking as far as pins going to the circuit board. I'm guessing that they would be a switching jack with as many pins as they have going to the circuit board.
Doing a Google search brought up a few snakes that have combo connectors and with some of the prices, I'd guess that they would pass 48VDC on the TRS part. Cheers!
 
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Neutrik combo jacks have separate pin outs for the XLR and 1/4" inputs so it's easy to make sure that only the XLR gets phantom power. A snake with combo jacks doesn't have that luxury so they have the XLR and 1/4" wired together to the single XLR output.
 
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