Sparking DI.... bad?

behndy · #1 08-15-2009, 10:23 AM

hey all. just played a gig last night. it's the first time i've used my pedalboard/poweramp setup live. it's efx stuff and then the end of the chain in a Tech 21 Sansamp PBDI.

when the soundguy was plugging the mic cable into my DI there was a loud pop and some sparks. he flinched back, did a good Keanu "whoaaaa", i asked him should i turn off the DI while he's plugging in (the pedal board was powered up), and when he plugged in after i turned off the power to the pedal board... no sparks, no speaker killing pops.

SO.... is this normal? should i always make sure the DI is turned off when plugging a mic cable in? was the soundguy's setup just goofy? did i do some damage to my DI?

thanks!

-0behn desu0-

Couvy · #2 08-15-2009, 10:27 AM

Sounds like a phantom power issue?

behndy · #3 08-15-2009, 03:51 PM

hmmm.... the pedal board is like 7 pedals, all into a One Spot power supply. are you saying maybe the sound guy was trying to provide phantom power thru the cable? i've never run anything with phantom power so i'm not real educated on how it works.

bongomania · #4 08-15-2009, 06:05 PM

It's not that he was trying to provide phantom power, it's that on most mixers phantom power is globally "on" or "off" for all channels, and in this case it was switched "on". I'm betting that caused a problem with something on your pedalboard, some common ground that caused a discharge.

behndy · #5 08-15-2009, 06:52 PM

so.... if the sound person has to have phantom power enabled for the other DI's that they're using onstage, will my stuff be okay if i just have my gear powered down when he plugs in?

or should i check to see if they're running phantom power and if they are have mine run off of phantom power? i don't know if the Sansamp PBDI DOES run off phantom power.... i'll have to check.

thanks!

Joe Gress · #6 08-15-2009, 06:55 PM

I'm pretty sure sparking anything=bad.

bongomania · #7 08-15-2009, 10:31 PM

Quote:

Originally Posted by behndy

so.... if the sound person has to have phantom power enabled for the other DI's that they're using onstage, will my stuff be okay if i just have my gear powered down when he plugs in?

or should i check to see if they're running phantom power and if they are have mine run off of phantom power? i don't know if the Sansamp PBDI DOES run off phantom power.... i'll have to check.

Unfortunately there's no one right answer. Some gear is vulnerable to phantom power, some gear is not. Some gear may be less vulnerable to 48V when powered down, but some gear may be just as vulnerable whether on or off.

If the PBDI is designed to be able to run off phantom power, then it shouldn't matter if you happen to have a 1-Spot powering it when it gets plugged in to the PA channel. It should be able to take it. So then another question that comes up is, even if the spark occurred at the connection to the PBDI, was the discharge from the XLR + pins, or from the ground pin, or from the chassis? Because for example if the common ground (via the chassis or via the neg./common wires of the patch cables) was the cause of the sparking, then it might not have been the PBDI at fault.

All of this is really just to reinforce that there's no obvious correct response to the situation. I have no solution for you, other than to check that all of your cables are in good condition, and find out for sure if the PBDI runs on phantom.

WalterBush · #8 08-15-2009, 10:54 PM

All of the Tech21 DIs work off of phantom power.

+48v shouldn't cause any visible sparking at all, by itself, though. A popping sound through the PA is all you would have heard.

It sounds like there's a grounding problem at the club you were playing. It's a common problem; all it takes is someone "fixing" something by using their neutral as a ground, or vice versa.

This kind of problem is usually discovered by the bass player when plugging in a DI, since it requires the mxing board and your equipment to share a common ground; neutrals carry voltage under load, and when a hot neutral and a ground from another circuit meet, well, sparks fly. I got severely shocked when gripping two XLRs, one in each hand. Found out later it was because someone had mis-wired the replacement plug on my used bass amp.

Guitarists don't usually find out unless they get shocked through the mic while playing, and drummers don't have to deal with it, either.

My advice is, get a home receptacle tester at Home Depot, and learn to use it; should cost about $8+the time it takes to listen to the guy tell you how to use it, or your time reading online, and could save your life, no joke.

Bubba Ghanoosh · #9 08-15-2009, 10:55 PM

Also, make sure the SansAmp's PHANTOM & GROUND CONNECT switch is in the right position. The following is verbatim from the PBDDI manual:

"With a mixer only: If you are plugging your bass into the Bass Driver and taking the XLR Output to a mixer --and do not have any other grounded equipment connected in the setup--you will have to engage (depress) the switch to connect the ground and activate the phantom power.

With a mixer and bass amp: If you are going to the mixer via the XLR and using the 1/4” Output to feed a bass amp (with its own AC ground), you should set the switch in the up position for “Ground Lift” mode. If you experience hum and/or buzz with the switch in either position, there is probably a problem with the AC outlets you are plugging into.

NOTE: If using vintage equipment without proper grounds, take extra care connecting it to modern grounded equipment.The inadequacies of the ground in vintage gear could result in damaging anything it is
connected to.

NOTE: While operating under phantom power, we recommend keeping a 9V alkaline battery installed at all times to avoid the previously mentioned “pops” when lifting the ground (see above)."