#1
Hey,

(i hope this is the right place to post this)

The other night in our practice room, we were using a behringer ub802 to amplify our small combo guitar amps (and bass and mic).



the setup we were using was:
Bass straight into the left side of the 3rd channel (line in 3/4).
mic into the 1st channel.


For a while we only used one amp, which was connected to the left side of the 4th channel(line in 5/6) through its headphone out. No problems so far, but when our second guitarist arrived, we connected his amp to the right side of the 4th channel (also through its headphone out.)

immediately after turning them on, however, both amps started smoking and, well, they're dead.

after that we played for a little longer by connecting our guitars straight to the 2nd channel and the left side of the 4th channel.


Is the reason the amps blew that we connected them to the left and right side of the same channel? Is it safe to use other amps through the 2nd and 4th channel (we seemed to have no problems with this setup)

(both amps were small, cheap behringer modelling combo's)

thanks in advance.
#2
Quote by fretjuuh
Is the reason the amps blew that we connected them to the left and right side of the same channel?
Probably not.

What output from the second amp did you use?

Also don't the amps work at all now?
They emit no sound whatsoever?
Do they turn on at least?
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.
#3
We used the headphone out on the second amp too.

The second amp was a little bit wet, but i didn't notice that until it was too late so that one might have short circuited i guess. I don't see how this could've harmed the other amp though.

Amp one turns on, but doesn't make a sound.
Amp two turns on but starts smoking from somewhere near where the headphone jack is attached to the circuit board.

We have backup amps, so that's not really the problem, i was just wondering if it would be safe to connect them the same way we connected the guitars after blowing the amps. (Again through the headphone outs, but to separate channels)

Any ideas how to fix the amps are, of course, welcome though
#4
I no reason that the headphone out would not be fine. However, it occurs to me based on your results that you may be using a mono jack that could be shorting out one of the channels on the amp.
#5
Could that destroy the entire amp though?

if so, i think that might be the problem. kinda stupid of me, should have thought of that.
#6
Yeah, there's no obvious reason why that would happen, and even the 'mono' concern mentioned shouldn't have caused any damage, given the signal levels present at the headphone out (although since it's the only theory advanced and I don't have a better one, I'll not throw stones...).

I've done things similar to what you did in various forms several times without incident, not sure why it jammed you up.
“Ignorance more frequently begets confidence than does knowledge.”
Charles Darwin
#7
I guess it's just bad luck then. i'll see if i can find some more information on this, if not, i'll just try connecting the amps to seperate channels.

thanks for the help!
#8
Plugging a headphone out into a mixer should never cause a problem with an amp. Even one on the left and another on the right. So IMO the only obvious issue is the possibility of shorting the headphone amplifier with a mono jack. I wouldn't expect that to kill the amp. But it could fry the headphone output. And if there is some circuitry that mutes the main speaker when the headphones are plugged in then that might kill the amp's output.

I wouldn't discount this due to bad luck and do a repeat performance. I would make sure you use a stereo headphone jack and then either use one of the channels to the mixer, or run into both the right and left. Just make sure that you don't short one of the channels to ground. Since the amp is I assume mono and headphones are stereo, the amp is probably sending the single mono output on each of the stereo channels. If you short one then the other is probably shorted as well since they may be both coming from the same headphone driver circuit.
Last edited by fly135 at Jul 24, 2014,
#9
I'm guessing something else is at work here and that we don't have quite the full story yet.

You still had the amp speakers connected internally, right?
Phantom power was switched OFF, right?
#10
Quote by dspellman
Phantom power was switched OFF, right?
I reckon that wouldn't have been a problem - the amps were connected to line inputs.
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.
#11
yes, the internal speakers were connected, but the headphone out mutes them. (they wires are also soldered to the speakers, so i reckon they're not meant to be disconnected)

the phantom power was not turned on (and, indeed, the amps were connected to the line inputs)

Edit;

This was our entire setup at the start of our practice session:

Bass -> line in 5/6 (left) } -> everything throught
mic -> channel one } -> 2-track left/right out to
guitar -> amp -> headphone out -> line in 3/4 (left) } -> a hifi installation.

this setup had no problems whatsoever. everything worked fine
_________________________________________________________
next is the setup after connecting the second amp:

Bass -> line in 5/6 (left) } -> everything throught
mic -> channel one } -> 2-track left/right out to
guitar -> amp -> headphone out -> line in 3/4 (left) } -> a hifi installation.
guitar -> amp -> headphone out -> line in 3/4 (right) }

with this setup the amps started smoking and died (the amp in the right channel was a little wet, as i said before)
_________________________________________________________
next is after blowing the amps:


Bass -> line in 5/6 (left) } -> everything throught
mic -> channel one } -> 2-track left/right out to
guitar -> dano fab distortion -> line in 3/4 (left) } -> a hifi installation.
guitar -> channel two }

this setup seemed to be fine as well, everything worked as it should.


the Bass used is an Ibanez SR300
the mic is a Shure sm58

the amps were two behringer modelling amps that come with beginner's sets, so it's very hard to find them on the internet. both were 15watt, i believe, their volume turned to 10, the rest i don't know.

that's the entire situation.
Last edited by fretjuuh at Jul 24, 2014,
#12
You sure you didn't feed speaker out or external speaker out into the mixer?
With Behringer's equipment being so shoddy you never know, I had a Behringer mixer smoke out on me in similar fashion after several years of use when I connected it to a cab emulator device that needed phantom power. Incidentally, that setup worked for over 2 years.
I'd advise you to just ditch the amps as there is no way repair on them would be cheaper than getting new...unless Behringer is willing to cover the repair, after all this is all an advertisement on how well their products smoke
#13
nope, only headphone outs (at least that's what the amp says they are)

i guess i´ll just try using other cheap amps then and hope the same thing won´t happen again.

thanks for your answers, everybody
#15
If the blown amp that turns on has a fx send, try that into the board just for kicks, you might be able to use it if only the power section got fried.

I think at this point your mixer is also very suspect so I'd thread very carefully there. Maybe try plugging in dry guitar into the line in on the channels that you had while it caused the meltdown and see how it fares.

How about the electrical mains in the building? Having two amps fail at the same time...I am thinking it might've been something with the central power or maybe both were connected on the same power strip and it blew?
#16
Good idea. Just keep plugging those mono instrument cables into headphone jacks.


Well, this is helpful.

But i guess I'll use a stereo cable next time.

How about the electrical mains in the building? Having two amps fail at the same time...I am thinking it might've been something with the central power or maybe both were connected on the same power strip and it blew?


The hifi installation and the mixer were on the same strip and those work fine.
#17
Quote by fly135
Good idea. Just keep plugging those mono instrument cables into headphone jacks.
I don't really see how that could have been the problem.

I mean it's good to be careful, but that's being paranoid.
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.
#19
Quote by diabolical
Might want to write to Behringer and see what they'll offer considering that two of their products blew at the same time...that makes for some really bad press, they might offer repair.



I might give this a try

Quote:
Originally Posted by fly135
Good idea. Just keep plugging those mono instrument cables into headphone jacks.
I don't really see how that could have been the problem.

I mean it's good to be careful, but that's being paranoid.


I don't really think this was the problem either, as the first amp was also connected with a mono cable and it worked fine for hours.
#20
Quote by Spambot_2
I don't really see how that could have been the problem.

I mean it's good to be careful, but that's being paranoid.
As a general rule I would not ever assume it's ok to short an audio output. That's not paranoid, it's smart.
#21
Quote by fretjuuh
I don't really think this was the problem either, as the first amp was also connected with a mono cable and it worked fine for hours.
The side you were shorting wasn't the side you were listening to. You did this with two amps and you are willing to do it again. Bad idea. That includes listening to spambot.
#22
Quote by fly135
As a general rule I would not ever assume it's ok to short an audio output. That's not paranoid, it's smart.
No, seriously, I genuinely don't see why using a cable with TS jack ends have been a problem, nor what he would have shorted with what, nor what would have changed if he used a cable with TRS jack ends.
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.
#23
Quote by fly135
As a general rule I would not ever assume it's ok to short an audio output. That's not paranoid, it's smart.


So a stereo cable would be a solution for that part of the problem, right?
#24
Quote by fretjuuh
So a stereo cable would be a solution for that part of the problem, right?
When you use an instrument cable you are shorting the right headphone output to ground. There is no way of knowing if that can cause damage without knowing the circuit design. It may be fine, it may burn out instantly, or it may just build up heat and cause a failure after a period of time.

Since you performed that experiment on two amps and had two failures I wouldn't try it again. I would either get a TRS to two TS cable.... or use a stereo headphone 1/4" to 1/8" adapter, connected to a 1/8" to stereo RCA cable, into a RCA 1/4" adapter plug. The later is easily found at Radio Shack. A music store or ebay will carry the 1/4 TRS splitter cable. I have both kinds of cables and adapter jacks on hand at my house.
#25
Quote by Spambot_2
No, seriously, I genuinely don't see why using a cable with TS jack ends have been a problem, nor what he would have shorted with what, nor what would have changed if he used a cable with TRS jack ends.
Headphones jack have a right and left channel. This picture should answer your question.

#26
Quote by fly135
Since you performed that experiment on two amps and had two failures I wouldn't try it again.
While that may as well be the problem, the following quote would make me think otherwise:
Quote by fretjuuh
I don't really think this was the problem either, as the first amp was also connected with a mono cable and it worked fine for hours.

Also even if that was a problem, that would have fried the headphones amp at most, while here the amps don't even turn on anymore.
I wouldn't see how that would have led to the two amps stopping working at the same time, too.

I'm still calling for electrical problems with the mains, together with behringer quality.

As for the TS vs TRS jack, I still wouldn't think that was a problem as I have never really had any problem with shorting a channel to ground, though even if he wanted to avoid that a TRS to TRS jack cable wouldn't work - the inputs on the mixer are balanced.
I mean he would avoid shorting the right channel to the ground but he wouldn't hear anything
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.
Last edited by Spambot_2 at Jul 27, 2014,
#27
So in your last post you couldn't even understand that an audio output was shorted and then in this post you are an expert on equipment. I'm not saying it was in fact the cause. I'm saying I wouldn't do it again.

You don't even know how a jack is constructed electrically. So how in the hell are you so brilliant in knowing about circuitry? You are doing the same talking out your ass as you did to me in the other thread. I have no problems with people offering other suggestions as to the cause. But you contradicted me and said it's paranoid to think that shorting a headphone jack is a bad idea. You should shut the F*** up and not address my posts. Because you are always wrong.
#28
My impression; two unrelated faults. One is beer related and the other is from using the wrong cable. Basically, you done goofed twice on the same day.
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