Amp fried when soundchecking... what happened?

[LexiconBand]

My darkglass microtubes 900 got fried and stopped working when soundchecking a gig this weekend. I have it powered by a furman power conditioner in my amp rack. The amp was working and sounding fine. The sound guy then plugged an xlr into my balanced output to run my bass to the board(a super old POS "studiomaster"). He plugged into a channel on the snake and walked back to the board. All of sudden my amp makes this crazy clicking sound and I see that the power light is flashing on and off super fast. Immediately turn it off, unplug the balanced out. I didn't see any smoke but could definitely smell that something had burned.

Thankfully my amp is covered under warranty but I'm wondering if anyone has any idea how this happened? Was it a power surge from the phantom power on the mixer channel that sent 48v to my balanced out? According to the sound guy the channel he plugged me into doesn't have phantom(I don't feel like he is very competent so not sure if that is to be trusted). It's also got me scared from here on out to plug my balanced out into anything I don't trust to be 100% functional. I've never heard of something like this happening and would like to prevent it from ever happening again.

Is there a safer way to run to the mixer? Should I introduce a small mixer into my signal chain and use a DI box? Has this happened to anyone else?

I truly don't think it was a fault in the amp itself. I've never blown an amp in the 15+ years I've been playing and the timing of him plugging in the xlr into my balanced out has me thinking it had to have been something with the mixer that caused it.

Any help appreciated!

 

[bholder]

I think you're right to suspect that xlr connection. I hope the manufacturer covers it under warranty, they might contest it if phantom power was on when it should not have been. Anyway, good luck with it.

 

[LexiconBand]

Even if phantom power was on, that still shouldn't have fried the amp though, right?

 

[abarson]

A good DI design would block any DC voltage coming in, and this has been implemented for decades. It would be very disappointing if Darkglass omitted DC blocking from their design.
Of course, there could have been a problem with the mains power that the Furman doesn't address, and it didn't have anything to do with the XLR. Only getting it serviced will provide the necessary clues.

 

[Chris 'Wighat' Jordan]

A direct box could provide isolation from the board.

 

[Bob-I]

There's no figuring this out, don't bother trying. Sometimes things just break.

In SS components there is a condition called infantile failure. It means the components fail when they're new. If they don't fail when new, they tend to run for many years trouble free. It's been suspected that this may be caused by voids in the silicon that are formed when the silicon substrate is grown and is undetectable, but no one really knows.

Most likely they'll replace it under warranty and you'll run the new amp for 20+ years.

 

[anderbass]

If your amps DI is designed to handle phantom power, maybe that mic cord or that line in the snake was defective/shorting your DI's output to ground...

 

[Jim Carr]

@LexiconBand — Sorry to hear of your woes! When going into a PA (maybe half the time), I never use an onboard DI, balanced out, or whatever—have had assorted problems and complaints, though never a meltdown. An active Countryman type-85 has been my go to DI for years and has never failed. The sound guys always compliment the sound of my instrument, no matter what it is.

It will protect your preamp, too. Obviously, I rely on the sound people to make a good sound with my signal when using a DI, but I try to cover the stage with my rig.

 

[Ben B]

When I read that the problem happened right after connecting the amp's DI to the xlr cable, I immediately suspected phantom power was the culprit. I have heard of older amps from maybe the 70s or 80s that had xlr DIs that were not safe with phantom power. But your amp is a fairly new design, so, I have a hard time believing it would have an issue with phantom power. So, it may be just a coincidence.

What I would do is get your amp fixed or replaced is under warranty. After you get it back, I would call the manufacturer and ask them if it is phantom power safe. I'm sure they will say it is.

 

[chadds]

The most obvious solution is don't do sound checks.

Problems pop up then.
You play with wild abandon that you never recreate that night.
The whole band composes a new song spontaneously that of course doesn't get recorded.
Your band's chops are completely pinnacle and no one heard you.
If the back line explodes during the actual performance you get audience sympathy.
There it is.
Avoid soundchecks.

 

[Jay Corwin]

I seriously doubt phantom power would cause this.

 

[LexiconBand]

Thanks for all the responses. Gauging from what everyone has said, I'm leaning towards this being an anomaly. My main concern is to insulate myself from future problems. I wanted to make sure I wasn't doing something stupid or needed to always isolate my balanced output from direct connection to a potentially sketchy board by using a DI. I already have a new amp as this was covered under warranty, however I will follow up if I hear anything additional from either the manufacturer or dealer I bought it from.

 

[agedhorse]

@LexiconBand — Sorry to hear of your woes! When going into a PA (maybe half the time), I never use an onboard DI, balanced out, or whatever—have had assorted problems and complaints, though never a meltdown. An active Countryman type-85 has been my go to DI for years and has never failed. The sound guys always compliment the sound of my instrument, no matter what it is.

It will protect your preamp, too. Obviously, I rely on the sound people to make a good sound with my signal when using a DI, but I try to cover the stage with my rig.

As somebody who has designed products with DI's all my professional life, as well as worked in the pro audio industry the same amount of time, there is no reason a properly designed DI should be a problem. There are tens of thousands of my DI circuits functioning night after night without any issues whatsoever.

The only fault that can destroy a DI or an amp that I see from time to time (maybe once or twice a year) is where power is incorrectly wired so that the chassis is hot relative to the building/system ground, causing high fault current to flow between grounds... but in this case the damage to the amp is secondary to the potential damage to the player. In fact, this is no different than any other gross fault like dropping your amp.

 

[Jim Carr]

As somebody who has designed products with DI's all my professional life, as well as worked in the pro audio industry the same amount of time, there is no reason a properly designed DI should be a problem. There are tens of thousands of my DI circuits functioning night after night without any issues whatsoever.

The only fault that can destroy a DI or an amp that I see from time to time (maybe once or twice a year) is where power is incorrectly wired so that the chassis is hot relative to the building/system ground, causing high fault current to flow between grounds... but in this case the damage to the amp is secondary to the potential damage to the player. In fact, this is no different than any other gross fault like dropping your amp.

I have to add that the DIs on my Mesa M9 and my GB Shuttle 6.0 never gave me any problems.

 

[LexiconBand]

As somebody who has designed products with DI's all my professional life, as well as worked in the pro audio industry the same amount of time, there is no reason a properly designed DI should be a problem. There are tens of thousands of my DI circuits functioning night after night without any issues whatsoever.

The only fault that can destroy a DI or an amp that I see from time to time (maybe once or twice a year) is where power is incorrectly wired so that the chassis is hot relative to the building/system ground, causing high fault current to flow between grounds... but in this case the damage to the amp is secondary to the potential damage to the player. In fact, this is no different than any other gross fault like dropping your amp.

So I shouldn't fear plugging my balanced out without utilizing an external DI directly to the board in the future?

 

[agedhorse]

So I shouldn't fear plugging my balanced out without utilizing an external DI directly to the board in the future?

Assuming it's properly designed, I don't see any problem. Otherwise, we wouldn't put that feature on the amp, right?

 

[Engle]

As somebody who has designed products with DI's all my professional life, as well as worked in the pro audio industry the same amount of time, there is no reason a properly designed DI should be a problem. There are tens of thousands of my DI circuits functioning night after night without any issues whatsoever.

The only fault that can destroy a DI or an amp that I see from time to time (maybe once or twice a year) is where power is incorrectly wired so that the chassis is hot relative to the building/system ground, causing high fault current to flow between grounds... but in this case the damage to the amp is secondary to the potential damage to the player. In fact, this is no different than any other gross fault like dropping your amp.

And that's why we should carry an outlet tester and check the power before plugging in our gear. And don't drop your amp...

 

[popgadget]

I have seen "warnings" on DI outputs about phantom power on many pieces of equipment, my Demeter HPB-1 being one of them. When I asked Jim Demeter about it, he said that with the (optional) Jensen transformer, I had nothing to worry about. I asked if there was a blocking capacitor or other protection on those without the transformer option, and he said there was, assuming the phantom was 48v, but as it's a non standard standard, the warning is there to be safe.

 

[ole Jason]

@Darkglass I know you can't comment on what could have happened to his amp but can the amp be damaged if phantom power is applied to the XLR output?

 

[agedhorse]

I have seen "warnings" on DI outputs about phantom power on many pieces of equipment, my Demeter HPB-1 being one of them. When I asked Jim Demeter about it, he said that with the (optional) Jensen transformer, I had nothing to worry about. I asked if there was a blocking capacitor or other protection on those without the transformer option, and he said there was, assuming the phantom was 48v, but as it's a non standard standard, the warning is there to be safe.

I do not know of any phantom power above 48 volts (which has DIN limits of 52 volts), and yes there are standards that are well documented such as DIN P48, P24 and P12 and how they are implemented.