How safe are our basses plugged into phantom powered DI boxes on gigs?

[jazzyvee]

I guess this applies to basses generally not just alembics. But i have read in the past that Marcus Millers Stars Guitars active electronics were trashed when it was met with a faulty phantom powered di. I don’t know how true that is, but is plugging directly into a phantom powered DI a risky thing to do especially with such expensive alembic basses. Generally i use the Di on my F1-x or my own passive Radial Pro Di, both of which are transformer isolated. But some multi band gigs i have done i have been asked to plug into a di box straight off the bass.
Is there a risk to having the bass electronics fried with 48v?

[edwardofhuncote]

I left my Wire Dunce hat at work. (the Chief Electrician makes me wear it...) So I'm anxiously waiting for advice here too. As soon as this lockdown order is up, I have a charity fundraiser thing to play in which the sound guy quite adamantly insists on DI boxes and monitors. As a general rule anymore, I don't argue with anyone who is taking work offa' me... and they do have extremely nice equipment at this venue, so I'm less concerned about it being faulty.


I am curious if my Alembics are at risk from stray 48v phantom power. I mean... that even sounds pretty awful. Well... I wuz on dis gig one time, an' sum' stray fantum powah towup my bass, right at soundcheck.

[JimmyJ]

My understanding (which is pretty basic) is that any "name brand" phantom powered DI box would never fail in a way that passed voltage up the input line. At least I've never heard of it happening. If the box they want you to use looks totally homemade you might just ask what's in it.  Common answer would be a transformer which clears up the question as that would remove any phantom power.

Where people can get into trouble is if they try to plug directly into a board's balanced input using an XLR-1/4" adaptor.  If one leg of that balanced input is grounded and phantom is turned on then it would be possible to have voltage appear on the 1/4" side of the adaptor.  Although I have the feeling that modern equipment might even have safety circuitry to prevent that.

I don't know if our basses have any kind of safeguard against stray voltage coming back up the line.  That's a good question for Mica.

Jimmy J

[jacko]

Jimmy. I had an Eden Navigator that fell foul of just that phantom power issue from the desk. Fried a couple of output transistors (or so I was told - I'm not an electrical engineer so couldn't disagree). It didn't kill the pre-amp totally but reduced the gain so much I had to have the QSC PLX2402 power amp very near full volume to be heard on stage.  I very quickly bought an ART isolation transformer after that and never let anyone else plug my gear in. Nowadays, like Vee I have a passive radial DI on my pedalboard which always puts a smile on engineers faces (at least it did in march 2020).

Graeme

[StephenR]

Hey Graeme, I have never used the DI on my Eden Navigator, good to know there are potential issues.

I started carrying my own DI about 10 years ago, been using an Avalon U5. It was only fairly recently that I was made aware that if the output of the Avalon goes into a mixing console where the phantom power is always on, or always on, it has the potential to fry the Avalon. But, I don't think that would affect the electronics in my bass. I have never had a problem with the Avalon but now I always mention to FOH to make sure the bass feed is not sent to a phantom powered channel. I generally play gigs where we hire our own FOH guy, when that is not the case I am extra careful.

[mario_farufyno]

Oh guys, you'd have opened a hole new world of fear in me, now... never got concern about DI letting phantom power pass through. Will start carrying my old retired passive transformer DI with me. And probably also reactivate the old pal: GAS.

[jazzyvee]

Here is a link to the incident around Marcus Miller's bass being destroyed by a DI Box surge.
https://www.guitarworld.com/features/the-story-behind-marcus-millers-1977-fender-jazz-bass

[mario_farufyno]

Hey, electronic experts, a little lecture could be usefull now...

[mario_farufyno]

As far as I know, phantom power is plus and minor tension going through 2 and 3 prongs of a XLR conector (the 1 being conected to ground) and they cancel each other when both reach each transformer coil's extremities. I supose if cable or soldering is deffective it could create a DC at the other end but thought they all had some kind of capacitor/resistor circuit or diod to block any DC flow. Makes sense?

[gearhed289]

I don't think we all need to start ditching our active DIs because of a very small amount of accidents. They're such a commonly used piece of gear on basses, keyboards, etc. from corporate events, to major tours, to the club down the block. If it were really a major concern, I think there would be more reports of mishaps.

[edwin]

I had my Eden Navigator go down a couple times because of phantom power. The first time I replaced the dozen or so transistors, but I haven't gotten around to doing it the second time. If I ever do, I'll just run some transformers on the output. Other than that, I've never had a problem. Of course, I always bring my own DIs.

[keith_h]

I have never had phantom power damage to my Navigator but having read about others who did I went with an isolation transformer for mine from the time I picked it up. Since I have no idea how well other people's gear I am attaching to is maintained I look at it as cheap insurance.

[jazzyvee]

Bump, these days if I'm travelling without my F-1x, then I take my Radial PRO DI II and use that in preference to their DI , not had any complaints.