Phantom power

[Floyd Eye]

We had a lot of trouble with the sound last night. Subs weren't right, my bass rig ( which is in no way even hooked up to the PA) was farting. Loss of power in sub channels on the PA, etc.. Turns out the phantom power switch on the mixer was inadvertently turned on. Which got me to thinking, if we use our condensers ( which require phantom power) for overhead drum mic'ing, does the mixer automatically send it to the right mic and will it be affecting all the other stuff like it was last night?

[oldhousescott]

More expensive mixers allow turning phantom power on or off for each individual channel. Most mixers for general PA use have a global phantom power switch, like your mixer. It really shouldn't be a problem for most microphones, even dynamic mics or ribbons as they have transformers in them that block the DC from getting to the mic element. That is, provided you are using low impedance mics with XLR connectors. If you're using high impedance mics with TS phone jacks, all bets are off. It depends on how the mixer manufacturer handled the input circuit.

For other devices you might be plugging into the board, you'll just have check the specs. Most DIs are fine with phantom power (active models can actually use it to power the unit), but some are not, like the older HK Red Box. Most devices will clearly state on the unit that they can be damaged with phantom power it that's the case. If you're running pedals straight into the board, then, yeah phantom power could be a problem.

It's hard to imagine how having the phantom power on could cause the problems you describe. Even if you shorted the channel inputs, you'd only draw 14 mA per channel. For a 16 channel board, that's less than a quarter amp current draw (and would require only a 10w power supply). Not saying your experience is invalid, I'm just having trouble wrapping my brain around it (not an uncommon occurrence).

[Floyd Eye]

All I know is we figured something had to be hooked up wrong. I double checked all the connections and everything was hooked up right. I looked up and seen the light on for phantom power, turned it off and everything was back to normal. All of our mic's are low impedance with XLRs. The only thing running off the board are vocal mics and a few drum mics ( not condensers). I have a GX5 hooked into the mono out of the Yamaha powered mixer so we can run a sub and the mains off of it and the monitors off the powered mixer. We use the sub mostly for the kicks. We get some kick coming through mains and monitors though, I guess because the powered mixer is controlling mic levels even though the mains are being powered by the GX5.

[GCDEF]

Phantom power should have any negative effect on anything. The mixer will send phantom power to whatever channels the manual says it does, but everything that doesn't require it should ignore it. Something is seriously wrong with your mixer if turning on phantom power caused all those problems.

[Floyd Eye]

Phantom power should have any negative effect on anything. The mixer will send phantom power to whatever channels the manual says it does, but everything that doesn't require it should ignore it. Something is seriously wrong with your mixer if turning on phantom power caused all those problems.

That's great. More PA problems.

[GCDEF]

That's great. More PA problems.

Was that the powered mixer or the passive one?

[Floyd Eye]

Powered. And looking at the manual. it says real big to not hook phantom power up to anything other than condensers. It says it will send phantom power to all XLRs as well as some of the other jacks.

With it switched off everything operates perfectly. We were having serious problems getting the sub to thump like it normally does and I suppose since we were jacking around with the levels on the kick mic's the frequencies were seriously screwing with my bass rig. The instant I turned off phantom power, the sub started thumping like a bastard, just like it always has, my bass rig started acting right and all was well.

By the way, we will very soon be buying a big ass, 2 ohm stable power amp. In case you were curious about my other adventures in stupidity. :rotflmao

[Floyd Eye]

Is it possible that the kick drum mics are not ignoring the phantom power? They are cheap ass "Superlux" mics.

[GCDEF]

Is it possible that the kick drum mics are not ignoring the phantom power? They are cheap ass "Superlux" mics.

It's possible I guess, but just about any dynamic mic is unaffected by phantom power, or at least should be.

[Floyd Eye]

From the manual:

"When using phantom power do not connect any devices other than condenser microphones to the XLR jacks."

[ronzie]

From the manual:

"When using phantom power do not connect any devices other than condenser microphones to the XLR jacks."

Floyd, it would appear that the psu that creates the +/- 48 (phantom) is on the the fritz (it could be a ground issue,also). A properly working phantom supply wouldn't hurt a flea, including properly implemented ribbon mics.

If you have a dmm, set it for 200 volts dc. With no mics plugged, measure across pins 2 & 3 and you should see no voltage. Then check across pin 1 & 2 and pin 1 & 3. That's where the 48vdc should show up. Then plug in a few mics and look for the same thing under load. Just be careful anytime one trouble shoots, even though phantom barely pulls any current...

Judging by what you're describing, the phantom supply is not it's own and is derived from the main unit supply. It's taxing the main unit when on and under load.

[GCDEF]

From the manual:

"When using phantom power do not connect any devices other than condenser microphones to the XLR jacks."

Yeah, but they don't mean it. That's just a disclaimer to cover themselves on the off chance some obscure something is damaged by it. If that were really the case, if you used phantom power you couldn't use anything but condensor mics in every channel. Dynamic mics are're usually affected by phantom power.

[Floyd Eye]

Hmm. Thanks for the info brother. We never use the condensers with this powered mixer because there aren't enough mic channels, so with any luck the problem does not occur when we switch over to the passive board, which also has phantom power. One of the reasons we want to use a full board is so at larger venues we can use the overhead condensers.

Thanks GCDEF, I appreciate all the help you have given over the last few days.