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Can the Axe-Fx III tolerate phantom power?

Mark Scrivener

Inspired
I just realized that I connected output 3 (right side) to an input channel that had phantom power on and left it that way the entire gig. Anyone know if the outputs are designed to handle this? Dumb move on my part I know.
 

Zedhed

Inspired
Are you feeding the phantom powered signal back into the Axe from the device producing it? If not, I can't see how that would have any affect on the Axe.
Even if you were, it's probably ok since the device producing phantom power is still only sending out line level signal. I'm pretty sure the phantom power is only being sent to the Mic & not to the device outputs.

Edit: Looking on the net reveals some interesting info, here for example.
https://www.sounddevices.com/the-danger-of-applying-phantom-power-to-unbalanced-outputs/

The best thing to do is test Output 3 to see if it's still working. If it is, then...all good.
 
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Mark Scrivener

Inspired
The outputs of the Fx III (ch 1, 2, and 3, both L& R, so 6 total) were connected directly to a mixer, and phantom power was turned on for the input that Ch 3 R was connected to.....so yes, Ch 3 R saw phantom power. The Fx 3 was essentially the "mic" connected to the mixer....
 

l4mpi

Member
One additional thing to keep in mind is that even though the Axe FX might tolerate a lot, other connected devices could be less forgiving. On the II XL a band mate once fried my tube power amp with phantom power, as the power amp was connected to the 1/4" output1 left jack and he plugged an XLR cable with phantom power into the balanced output1 left jack. The Axe FX was perfectly fine but there were two cooked resistors in the power amp... luckily this happened at rehearsal and wasn't too pricey to repair. I guess the phantom power got transferred to the unbalanced cable as to my understanding both output types are internally wired to the same source.

No idea if the same thing could still happen with the Axe FX III but the manual seems to imply that the output1 jacks are wired similarily to the II XL. Anyways, I'm not volunteering to find out :) So at least when you use both the balanced and unbalanced output1 jacks simultaneously, you should always check that phantom power is disabled before plugging in the XLR cables.
 

Mark Scrivener

Inspired
Channels 3 and 4 are not phantom power tolerant as they are 1/4" jacks. However if you plugged them into your mixer using 1/4" cables then you're fine. A mixer only applies phantom power to XLR inputs.
Makes sense. In my case, Out 3 right was connected to my mixer via an XLR to TRS cable. Out 3 & 4 are unbalanced, and I assume the +48V would have appeared at the "ring" in the TRS plug, which probably does not come in contact with anything on the FX 3 (only tip and ground are used), so the phantom power was not actually connected to the FX 3. Had it been an XLR to TS connector, the Axe would have seen the 48V.

I just checked out output 3 on my FX III and both L & R outputs are functioning fine, with no obvious degradation. And the mixer input that had supplied phantom power to the FX III still works fine, including providing 48V when requested. Life is good!
 

Rex

Legend!
...I assume the +48V would have appeared at the "ring" in the TRS plug, which probably does not come in contact with anything on the FX 3 (only tip and ground are used), so the phantom power was not actually connected to the FX 3.
The Axe’s unbalanced outputs use Humbuster, which uses the ring connection.
 

Mark Scrivener

Inspired
The Axe’s unbalanced outputs use Humbuster, which uses the ring connection.
Interesting. So if you plug a TRS cable into a Humbuster jack, which of the 3 contacts on the TRS actually connect to the jack?

A TRS to XLR cable should be wired:
Tip - pin 2 ("Hot")
Ring - pin 3 (Neg)
Ground - pin 1 (Ground)

The phantom power (48V) is applied across pins 2 & 3 through resistors (goes to tip and ring on our TRS). So ideally there should be no voltage between tip (or ring) and Ground (they are floating). If tip & ring are shorted then that should be OK as well due to the resistor network. If ring is shorted to ground then tip would be at 48V relative to ground.
 

Rex

Legend!
A diod in a tr cable or humbuster cable to avoid any kind of voltage from the Mixboard with +48v to a Trs Output
Both a TR cable and a Humbuster cable have only two connections in the end that goes into external equipment. Putting a diode in the signal path is never a good idea, unless you want half of your signal to be chopped off. :)
 

Zedhed

Inspired
I'm not trying to be a smart ass.....but isn't it easier to make sure proper connections are made in the first place? If the sound guy is the guilty party in not checking such things...maybe time to get a new sound guy/gal.

Just best practice IMHO.
 
I'm not trying to be a smart ass.....but isn't it easier to make sure proper connections are made in the first place? If the sound guy is the guilty party in not checking such things...maybe time to get a new sound guy/gal.

Just best practice IMHO.
Hahaha, yeah, the best answer. But sometimes you don't know what the sound guy is doing (small shows when going direct).
Both a TR cable and a Humbuster cable have only two connections in the end that goes into external equipment. Putting a diode in the signal path is never a good idea, unless you want half of your signal to be chopped off. :)
Oh, I didn't know that, so the signal is send and then the signal returns from that same lead (Sorry if that doesn't make sense, kinda hard to explain myself in a different Lenguage) ? I thought it would be good to have that diod to have extra security.
 
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