Need help fast! Voltage drop causing clipping??!?!

[bryan_kilco]

Hey guys, I had posted about a month or so back about a problem we were having with a Behringer Europower PMP2000 pa setup.

We had speakers that had NO ratings anywhere on the cab or speakers, we were told that we were over-powering the speakers, which was causing the amp to basically cut out at a "clipping" level.

So, we bought Behringer speakers that were designed as a package deal with the amp we have, everything was fine for about 3 practices, then the problem came back again. I discovered that when the Bass level is up on a vocal channel, the amp clips/cuts out faster than if its turned down. The clip light does NOT come on. The amp has "circuit protection", which I'm guessing is what is kicking in.... but why would this work fine for a few days then suddenly start acting up?!?!!

First we tried running a fan on the rear panel for some extra ventilation - no luck there.

I figure.....we may have a voltage drop. We jam in a shed that I'm pretty sure is wired for 240V. We have one outlet box with 4 outlets which we run 2 x 50' extension cords arcoss the room.

Could the line coming in to the shed, plus the added 2 x 50 footers be causing enough of a voltage drop to cause this problem?!?!

I've been searching online forever and really cannot find an answer to this problem.

AND...if the voltage drop is a concern, we are basically frying all our amps, correct?

EDIT: just read a review of this thing and apparently a lot of people have this same problem. Guess we need to invest in something of better quality like Peavey or Mackie?

 

[colonel kurtz]

Hey guys, I had posted about a month or so back about a problem we were having with a Behringer Europower PMP2000 pa setup.

We had speakers that had NO ratings anywhere on the cab or speakers, we were told that we were over-powering the speakers, which was causing the amp to basically cut out at a "clipping" level.

So, we bought Behringer speakers that were designed as a package deal with the amp we have, everything was fine for about 3 practices, then the problem came back again. I discovered that when the Bass level is up on a vocal channel, the amp clips/cuts out faster than if its turned down. The clip light does NOT come on. The amp has "circuit protection", which I'm guessing is what is kicking in.... but why would this work fine for a few days then suddenly start acting up?!?!!

First we tried running a fan on the rear panel for some extra ventilation - no luck there.

I figure.....we may have a voltage drop. We jam in a shed that I'm pretty sure is wired for 240V. We have one outlet box with 4 outlets which we run 2 x 50' extension cords arcoss the room.

Could the line coming in to the shed, plus the added 2 x 50 footers be causing enough of a voltage drop to cause this problem?!?!

I've been searching online forever and really cannot find an answer to this problem.

AND...if the voltage drop is a concern, we are basically frying all our amps, correct?

EDIT: just read a review of this thing and apparently a lot of people have this same problem. Guess we need to invest in something of better quality like Peavey or Mackie?

what up bryan...

what's the gauge of the wiring running to the shed, and how long is the run from the electrical panel??

 

[bryan_kilco]

what up bryan...

what's the gauge of the wiring running to the shed, and how long is the run from the electrical panel??

I honestly am not sure. There is a panel in the shed, but there is also a wire running out underground to a pool/pump etc.....I'd say 50-70 feet.

I'm pretty sure its the crappy gear, after reading a bunch of bad reviews.....just a shame....but, then again, I could be totally wrong. I dont understand why the problem would occur, then go away for a few days and come back after changing speakers.....

 

[ahjteam]

Get a power conditioner, like this (if you can afford, get a furman or monster with voltage reading):

http://www.thomann.de/gb/phonic_ppc_9000_e.htm

 

[bryan_kilco]

I've got a Furman already....not one of the really great ones but still....

But, I havent been running the PA thru it....just my rack gear and amp.

 

[Omega_Void]

...if the voltage drop is a concern, we are basically frying all our amps, correct?

Low voltage shouldn't do any damage, it just reduces the headroom.

It's excessively high voltage that cooks circuitry, 'cos the current draw increases proportionately and the wattage of heat produced is voltage times current.

That and the fact that a lot of components have maximum voltage ratings, and will be damaged by over-voltage even if they don't get hot at all.

I discovered that when the Bass level is up on a vocal channel, the amp clips/cuts out faster than if its turned down.

Bass eats headroom and demands lots of current. Since you say others are reporting similar problems with the same model, I don't reckon you're losing headroom due to low mains voltage. This suggests your amp is having a problem when called upon to supply lots of current for a sustained period of time -- i.e. cycles longer than 100Hz.

The clip light does NOT come on. The amp has "circuit protection", which I'm guessing is what is kicking in.... but why would this work fine for a few days then suddenly start acting up?!?!!

If the circuit protection is reacting to overheating then it would kick in when the ambient temperature is higher, but maybe not on a cooler day.

Don't know what the circuits are like on that amp, but the protection schemes I have heard operating don't sound at all like normal clipping. thay have very distinctive and unpleasant sounds.

On your experiment with the fan -- was it a powerful fan? Did you direct it into vent holes or just blow air over the outside of the case? Come to think of it, are there fans inside trying to blow air out of the vent holes? Putting a fan outside blowing in would be counterproductive if that were the case...

Another possible cause of problems is inductive kickback from the loudspeakers, but having the "right" speakers for the amp ought to rule that out...it ought to.

I dont understand why the problem would occur, then go away for a few days and come back after changing speakers.....

It quite possibly would have gone away and come back whether you'd kept the same speakers or not. Electronics can a bugger for misbehaving like that. Also possible that the new speakers have slightly greater impedance at lower frequencies than the old ones, resulting in slightly reduced current draw. That suggests the problem is due to a cumulative sort of damage which takes time to build up to the tipping point, and is self-healing so goes away when not stressed.

My money here would be on bad (or undersized) electrolytic capacitors in the power supply. The dielectric in these is an oxide layer on the aluminium anode, which is very thin. Excessive current draw can degrade the dielectric and the capacitor starts leaking current. The problem is self-healing because when current demand drops off, the ally grabs oxygen from the electrolyte fluid and rebuilds the damaged dielectric. That would explain why the problem goes away and comes back.

Another possibility would be a bad connection. A dry solder joint may have enough contact still to pass small amounts of current, but not enough to pass large signals without distorting.

Also conceivable that Behringer skimped on the heatsink, making thermal performance marginal. Or possibly they got a duff batch of insulating micas, and heat isn't being conducted from the power transistors into their heatsink efficiently enough.

If I had to guess, though I'd look first at the big capacitors in the power supply. There's been a plague of crappy electrolytics in recent years, supposedly due to Taiwanese manufacturers using a stolen electrolyte formula which they didn't realise was incomplete. And even the good electrolyics are are one of the most common components to fail eventually.

If you do find the caps are bad, replace them with something decent e.g. Nichicon, United Chemi-Con, Panasonic.

Or you could just get a Peavey or a Mackie or something. Chances are the Behringer could be repaired quickly and simply, but it could turn into a troubleshooting saga if you're not lucky. And then all the knobs will fall off in a year or two anyway.

 

[colonel kurtz]

I honestly am not sure. There is a panel in the shed, but there is also a wire running out underground to a pool/pump etc.....I'd say 50-70 feet.

I'm pretty sure its the crappy gear, after reading a bunch of bad reviews.....just a shame....but, then again, I could be totally wrong. I dont understand why the problem would occur, then go away for a few days and come back after changing speakers.....

yea 50-70 ft. isn't enough to make for any kind of significant voltage drop, and if you were pulling too many amps, you'd just trip a breaker

moral of story: don't buy behringer!

 

[bryan_kilco]

yea 50-70 ft. isn't enough to make for any kind of significant voltage drop, and if you were pulling too many amps, you'd just trip a breaker

moral of story: don't buy behringer!

Thanks for the replies guys!

We were blowing the fan on the rear panel of the thing. It has like 2 tiny vents and I am not totally sure if there is a fan in it or not. If it was up to me, I would have saved and got something better from the get-go, but I didnt make the choice here and money was an issue.

 

[colonel kurtz]

yea...bandmates/singers can suck like that...