Eletrical damage to mixer and equipment. Suggestions?

[AngloSaxophone]

I had a disaster last week while recording and I'm curious if anyone has a suggestion on what went wrong.

I was using the PreSonus Firestudio recording system. For inputs I had 1 bass amp, 2 guitar amps, three drum mics, and a small PA system. I was outputting from the Firestudio mixer to a PC with firewire. We had all this equiment distributed to a few different circuits in our house.

So we had everything connected and then we plugged in the mixer. This is when disaster struck. There were highly visible blue sparks zapping the back of the mixer and the computer. We quickly unplugged everything. The Firewire express card on the PC was fried, and we replaced it. The mixer was also ruined, luckily we had insurance on this and got it replaced.

Then disaster struck again. This time we played it extra cautious and distributed the equipent to different circuits in the house and also used surge protectors on everything. I had a moment where my foot was touching the 1/4" output line from the PA and when I touched the metal casing of the PreSonus mixer I could feel a little shock. I should've stopped there, but I thought my mind was playing games on me. We plugged everything in again, and when we turned on the mixer, there was visible from not only the mixer but also the bass head and PA system. WTF?!?! The bass and PA were unusable and two of the inputs in the PreSonus were fried.

Does anyone have ANY idea what could be causing this? I tested the voltages on all the outlets in the house successfully. I mentioned this to someone at a repair shop and they suggested it might be a ground loop (not sure what this means). I've just never experienced anything like this before when recording. Am I doing something wrong?

[dvdhawk]

Sorry to hear that, that sucks!

When you say, you "tested the voltages on all the outlets in the house", how exactly did you do that?

If you're welding, I'd bet the farm either one of the other outlets in the house is wired incorrectly, or an extension cord if you used one or more. Something is wired wrong - either Hot to Neutral, or worse yet, Hot to Ground.

If you tested the voltages by sticking the probes from a voltmeter into the hots and neutrals of the receptacle only observing the voltage reading that's only a partial test. You need to observe the voltage from hot to neutral, hot to ground, and neutral to ground to be thorough on each receptacle. [you may very well know this, but for anyone else who might stumble across this thread in the future] On a standard 15-amp grounded (3-prong) Edison receptacle, the smallest slot is the hot, the slightly larger slot is the neutral, and the ground is pretty obvious. If you don't have a receptacle tester, you should get one.


And I'm sorry to say - for future reference, you could easily run almost any home recording gear and a small PA on a single 15 or 20 -amp circuit as you would find in most homes. - Two circuits at the most. Pulling everything from all over the house introduces the potential for things like this and more ground loops etc.

Do some more testing and let us know what you find.

[AngloSaxophone]

Thanks for the quick reply!

I tested the outlets both with a recepticle tester and by verifying 120V on each outlet and power strip. We weren't using any extension cords. Everything checked out. I did this before the second "burnout".

[dvdhawk]

Is there a "polarity" switch on the bass amp or guitar amps, like you would find on an older amp that originally wouldn't have had a grounded plug?

[matthewfreedaudio]

You asked "Am I doing something wrong?"

Well, obviously you are. You have electrical wiring problems in your place. Call an electrician.

Your recording gear may also be faulty. Have a qualified electrician check them out and have the questionable pieces inspected at a musical instrument repair shop.

Production Sound Mixing for TV, Film, and Commercials.
www.matthewfreed.com

[DrGonz]

Okay lets pretend that you have all your Hot Neutral Ground lines in your outlets of your house wired correctly... So you have a bass amp, 2 guitar amps, a PA system, a mixer, Presonus Firestudio and a computer all plugged into some/one outlets. Or maybe your all scattered around the house... I don't know... You say on your posting that your all on different circuits the first time it happened then to be safe the next time your all on different circuits again. So, I would guess the first time you all were plugged in the same room, but the next time you all took more precautions. 15 amp lines will either blow a fuse or trip a breaker depending on the year of the house and wiring yadi yadi yadi. So, maybe you have an un-fused line running through your house? That can cause fires and all sorts of stuff to happen. CALL AN ELECTRICIAN AND STOP KILLING YOUR GEAR AND PUTTING YOUR OWN LIVES AT RISK!!!

Okay lets say that's not what happening then... Neutral is a type of ground as it is the point that draws the current or voltage back from the hot line. When you disconnect something you remove your negative terminal first as to avoid a spark or discharge. So, lets think here... AC: amperage = wattage/voltage... So, a bass amp that has 400watts is equal to>>> I = W/V... So, look at the fuses in your appliances and think hmmmmmm.....??? I have guitar amps that I work on all the time Fenders, Roland, Marshall, Traynor, Carvin, Peavey... you get the idea. Most have fuses from 1 amp up to 5 amps. So, a 400 watt amp draws 3.3amps = 400w/120v. Then you add two 100 watt guitar amps and maybe a 25 watt mixer... Totaling another 1.86 amps. So now we have about 5.2 amps on this one circuit. Lets say the the PA system is about 300 watts (which is just a guess) then we now have a total of 7.7 amps running on this one circuit breaker that can reach as high as 15 amps. So, lets say the computer has a 500 watt power supply, so lets add another 4.2 amps to that... about 12 amps currently on a 15 amp circuit and we are still in the clear. So moving around the house to different outlets is not the problem in my opinion.

So, looking at the specifications of a Presonus Firestudio device I read>>> "This mic to line boost is generally a preamplification of over 400 times the voltage of the original mic level signal." That is significant is it not? I mean really what the Hell does that even mean? I am not really an authority on this at all but reading that one statement it makes me wonder about ohms law. I also read this statement as some form of sales man ship of this device to the people that will buy it... That meaning who knows exactly what they are saying and if any of it is really true. Now, take all of your ideas and shake them at this one statement... "This mic to line boost is generally a preamplification of over 400 times the voltage of the original mic level signal."

How are you sending each amplifier into this device? Give us WAY more information as to help you in this situation you find yourself in... And stop ignoring electrocution through your input/output cables connecting these devices together. My thought is that something more needs to be said about how you are connecting all devices together as to make more sense out of your situation.

ADDED Edit: "I had a moment where my foot was touching the 1/4" output line from the PA and when I touched the metal casing of the PreSonus mixer I could feel a little shock. "

Look at this obvious problem in your signal foremost. Get rid of the PA and see if that is the problem and examine what you are really doing on this stage of the output of this device. Line level voltage multiplied by 400 times seems to be a problem in my opinion or maybe I am just stoopid!!!

[djmukilteo]

I was using the PreSonus Firestudio recording system. For inputs I had 1 bass amp, 2 guitar amps, three drum mics, and a small PA system. I was outputting from the Firestudio mixer to a PC with firewire. We had all this equipment distributed to a few different circuits in our house.

WOW!...So just to clarify...inputs 1, 2 & 3 with 3 microphones in front of your 1 bass amp and 2 guitar amps?
Then you had inputs 4, 5 & 6 which were 3 mics for the drum set....
And were you running something like a line out from the PA system into the mixer??...or were you just using the PA for stage monitors?
What kind/brand of PA system was it?

So we had everything connected and then we plugged in the mixer. This is when disaster struck. There were highly visible blue sparks zapping the back of the mixer and the computer. We quickly unplugged everything. The Firewire express card on the PC was fried, and we replaced it. The mixer was also ruined, luckily we had insurance on this and got it replaced.

So everything happened at the back of the Presonus mixer right?
That sure sounds like you fed something pretty high voltage or high current into the mixer inputs.
Or you got an open hot 120VAC wire somehow touching the mixer!

Then disaster struck again. This time we played it extra cautious and distributed the equipment to different circuits in the house and also used surge protectors on everything. I had a moment where my foot was touching the 1/4" output line from the PA and when I touched the metal casing of the PreSonus mixer I could feel a little shock. I should've stopped there...

when we turned on the mixer, there was visible from not only the mixer but also the bass head and PA system. WTF?!?! The bass and PA were unusable and two of the inputs in the PreSonus were fried.

Again what microphones did you have plugged into the two inputs that fried?
And if you were micing the bass cabinet how was the bass head amp or the PA system tied into the mixer?....you didn't somehow connect those amp outputs directly to the mixer or something...??

The only other thing would be a huge short inside the Presonus, because that seems to be the source of the flames and sparks....

[Kapt.Krunch]

For inputs I had 1 bass amp, 2 guitar amps, three drum mics, and a small PA system. I was outputting from the Firestudio mixer to a PC with firewire. We had all this equiment distributed to a few different circuits in our house.

Inputs? Direct or mic'ed? Mic'ed inputs would have no physical connection to another device, so anything mic'ed won't cause that. That leaves anything directly connected as possible culprits.

A "few different circuits"? As already mentioned, circuits...or even individual receptacles...can be wired incorrectly. You could have a problem if something is directly connected with the hot and neutral wires crossed on one. Also, it is "possible" that different circuits are running slightly different voltages, creating a voltage difference between two connected devices. As mentioned, you need to properly analyze the circuits. You may even find some weirdness with voltage between ground and neutral.

This time we played it extra cautious and distributed the equipent to different circuits in the house and also used surge protectors on everything. I had a moment where my foot was touching the 1/4" output line from the PA and when I touched the metal casing of the PreSonus mixer I could feel a little shock. I should've stopped there, but I thought my mind was playing games on me.

Something about all that doesn't make sense. If it were distributed to different circuits when it blew the first time, why would it seem a good idea to do that again? And...what possible scenario could cause your "foot to touch the 1/4" output line from the PA"...while you were touching the mixer? Just wondering. That sounds weird.

We plugged everything in again, and when we turned on the mixer, there was visible from not only the mixer but also the bass head and PA system. WTF?!?! The bass and PA were unusable and two of the inputs in the PreSonus were fried.

Was the bass direct from a bass amp "preamp out"? Apparently, the "PA system" was? (Hopefully, they were "Pre-out" or "Line out"...and not "Speaker out"?)They had to be, or they wouldn't have been electrically connected so one could take out the other. ANYthing that was connected directly could have caused it. Maybe something in something went bad the first time, and every single piece of equipment that was to be directly-connected wasn't tested fully to be sure none was bad when you plugged them all back in?

You should have only connected the new interface to the computer, and tested to be sure that was OK. Then, you should have plugged in another device to power it on...but NOT connect it until you checked the voltage potential across both devices with a voltmeter....AFTER you tested each individual unit for proper operation.

After a catastrophic failure like you had, you should NEVER just plug everything back in together, and apply power.

I suspect you had something wrong, it blew things up, you reconnected everything without checking EVERY possible cause...and a part that was still bad made it worse? Or, you are running bad voltage differentials/shorts/etc. from different circuits.

We weren't using any extension cords.

Hmmm... just extra long 1/4" connection cords, or mic cables...and the amps, etc. in different rooms to be close to all those different circuits throughout the house? Not that it really matters...it just sounds odd that all this is connected to a bunch of different circuits without extension cords.

Kapt.Krunch

[djmukilteo]

I'm pretty sure the OP took amp outputs and plugged them directly into the mixer (both times).
That would do it right there....only explanation I can think of....and a very common thing I've seen with people who don't know. That's why I asked about what was plugged into what!
I don't think it's the AC power because everything was fine until the OP plugged the mixer in....then BAM!

Everything went right through the mixer and overloaded the mixers PSU the wrong way, took out the FW card right back to the PC card. And then the second time it came back through the bass amp and PA.
So you have to ask the question....how could that happen if they weren't connected directly to the mixer?!?!
And what was on the two inputs on the mixer that "fried"....

[AngloSaxophone]

WOW!...So just to clarify...inputs 1, 2 & 3 with 3 microphones in front of your 1 bass amp and 2 guitar amps?
Then you had inputs 4, 5 & 6 which were 3 mics for the drum set....
And were you running something like a line out from the PA system into the mixer??...or were you just using the PA for stage monitors?
What kind/brand of PA system was it?

No the bass amp head, guitar amp, and PA were plugged directly into the mixer. There was a Beta 52 micing the Bass drum, a codenser mic overhead of the drums, a condenser for the snare, and a condenser for the other guitar amp. I cannot remember the model of these mics as they were borrowed from a friend.

Again what microphones did you have plugged into the two inputs that fried?
And if you were micing the bass cabinet how was the bass head amp or the PA system tied into the mixer?....you didn't somehow connect those amp outputs directly to the mixer or something...??

The inputs that were fried were the bass head and the PA system. They were plugged into the mixer via their line outs. After this whole ordeal, the PA, bass head, and the guitar amp that were plugged directly into the mixer were all fried as well.