phantom question

S

Steve Tarak

Sophomore
Jan 12, 2011
199
0
0
Indy
One of the groups I mix utilizes an Allen Heath for in ear monitoring. A problem has developed with the phantom power on one channel. The stage mics are hard split to me and a Presonus 24 and I noted at a Wednesday show a crackling / sizzling on this channel. We isolated this to the phantom power button on the AH. When depressed, the channel would exhibit 40 to 50 hz hum, sizzling and cracking sound. I bypassed the split snake, went direct to my board and finished the show. This buttom is constantly on, it does not get turned on and off and we've had no issue for more than a year.

What anomolies can happen w/ phantom power? Can they cause any crap out of another mixer channel, be that Presonus, or other? I've had phantom fail all together, but not this symptom. Appreciate any input.

thanks,

Steve
 
Re: phantom question

I'm not clear on all that is connected, but sometimes audio connected to a phantom power capable input that isn't using phantom power can have a problem with a protective DC blocking capacitor that has broken down and is not blocking the 48V from some low level circuitry. A common problem with early wireless mic receivers.

JR
 
Re: phantom question

Phantom was not on at both mixers. Cabling was checked first - no issues. 15 channels connected to both mixers. Four channels utilize phantom. One being a condenser vocal mic, two drum overheads and a bass D box (the offending channel) . No issues noted on the other channels. I'm w/ Tim, should not be an issue from mixer to mixer. I'm inclined to say a possible button issue, however, with this button not being activated / deactivated on any regular basis, I'm yet unsure why this has occurred. We're 10 shows in w/ the Presonus, w/ no issues other than this.

In analyzing this, is it possible, without iso splits on the snake, that the two mixers won't play well together? Again, I've had not issues - nada - for a long time.

Could a faulty 1/4" bass cable or battery snap connection (within the bass - Modulus) cause the phantom to crap out?
 
Last edited:
Re: phantom question

John Roberts said:
D box? Direct box? If that's what's different about the offending channel, maybe it's the bad actor.

JR
Click to expand...

Hello,

In regards to both console's phantom being activated...it shouldn't cause a problem in properly working equipment.

As others have written, it's more than likely a problem with the bass Di and cabling. Check the ground lift on the DI.

Hammer
 
Re: phantom question

Steve Tarak said:
Cabling was checked first - no issues.
Click to expand...

How did you check the cabling? Did you simply run a cable tester or did you swap things out? In my (limited) experience, I have most often found that issues with phantom can be traced to cables......which check out fine on a cable tester but when checked by listening in the cans will have audible degradation of sound quality, often accompanied by various noise issues. That's why I only use a cable tester as a backup. I check all my cables and snake channels every spring by ear.
 
Re: phantom question

No multipin on the split, just xlr fanouts. Cords are swapped out first with known working ones - allows me to check those removed while the show goes on. Visually checked first, tester second. The fanout is being checked tonight.
 
Re: phantom question

Steve Tarak said:
No multipin on the split, just xlr fanouts. Cords are swapped out first with known working ones - allows me to check those removed while the show goes on. Visually checked first, tester second. The fanout is being checked tonight.
Click to expand...


I've got transformer isolated splitters you can borrow if you want to eliminate his EWI Poor Man's splitter for trouble shooting. (have a one channel into 3 for just removing the one channel, and also have 16 channels in a small rack)
 
Re: phantom question

Sometimes the problem can be that the phantom maybe should be active on both consoles. I've seen consoles that shunt common-mode DC back to ground when phantom is disengaged, causing it to drag down the other console on a passive split. Some power-hungry mics and DI's don't like the lower voltage.

There is no danger in having phantom from two sources - the spec calls for 6.8k resistors in series to limit the current.
 
Re: phantom question

One other work around, use a Passive DI on the bass instead of his J48 (a JDI for instance)

That will check and let you know if the problem is related to phantom power or his DI.
 
Re: phantom question

and it was his splitter. Damned shield to pin two short. Intermittent, and well hidden within the cord wrap. Interesting results for sure. Pure garbage. I'll know better next time. And thanks everyone. Steve, appreciate the offer to help.
 
Re: phantom question

That kind of fault is often as a result of the cable getting crushed of overstressed in some other way, testers etc have a hard time finding it often the only way is to connect it up and listen on the solo for that channel at a low level and shake/ tug at everyhing till you locate the faulty cable/connection. Another one I've seen lately as some of the snakes we've got are getting old is the actual contact in the female connector gets loose and the poor contact causes a really nasty crackle or bang when phantom power is present and something touches it. G
 
Top Bottom