QSC 1450/rig problems

nickrs540 · #1 11-08-2011, 01:05 PM

Hello Tb'ers

Im having some problems with my rig and I hope you guys with your infinate knowlege can help me out

So my rig consists of an Ibanez SRX-505 into a Line 6 rack mount bass POD, BBE 882, and a QSC 1450 into a GK Neo 4x12.

I play in a hard rock band where I switch between distorted and clean through out the set. My problem is that randomly while playing a song (usually with distortion) my QSC just cuts out completly. The power light stays on, but it shows that its not receiving any signal. I was thinking it could be some protection built into the amp where it would stop if it was being damaged by input, but when ever I play im never clipping the amp. I checked all the cables and everything is plugged in fine. The problem also happened when i had my P bass running through it also, so I have no clue whats up

Does anyone have any experience with this problem?

will33 · #2 11-08-2011, 01:20 PM

Protect modes can kick in because of heat but also because of intermittent shorts as well.

It's time to do the old scientific process of elimination to find the problem component. I'd start by checking every cable in the whole chain. Sometimes one little strand of the wire can fray off and cause a bit of shorting. When every cable is known to be good, start with just the pre and the amp, adding/switching out one component at a time until the problem is isolated.

will33 · #3 11-08-2011, 01:23 PM

It helps to have 2 pre's, 2 amps, 2 cabs, 2 basses, etc. to definitively isolate the problem. May have to borrow some gear from a friend if you don't have doubles of all these things.

nickrs540 · #4 11-08-2011, 01:34 PM

Thanks will33,

I guess now I will just have to spend a little bit of time seperating all the parts. I do have back ups of each (different brands and models though) so I will start mixing till I figure it out.

Im just curious because it only happens on a couple situations. It first happened with my 5 string; my B was clipping the amp and eventually it just stopped working and came back up every 15 secs or so. Second time it was with distortion and my BBE on for a bass boost to make up for the cut with the distortion channel. Third time my P bass was clipping a tiny bit when I played very aggresive on the E. Each time it was the same thing, but I was never over doing it with the clip it was just everyonce in awhile when I plucked real hard (cept with the distortion where it didn't clip at all).

will33 · #5 11-08-2011, 01:42 PM

That does sound like clipping is related to the problem, although a slight clip now and then shouldn't cause a shutdown. I did have one poweramp once where one of the thermistors went bad. It's like a temperature sensor that tells the amp when it's getting too hot. The amp "thought" it was overheating when it wasn't. Took quite a while to figure that one out (I'm not a real tech) but once we figured it out, it was only a few dollar fix.

I have no idea if your problem is related to that but something to keep in mind should the problem end up being isolated in the poweramp.

nickrs540 · #6 11-08-2011, 01:59 PM

Ok, I'll make sure to remember that for when im testing things out.

Thanks again

BassmanPaul · #7 11-08-2011, 03:10 PM

From the manual:

BRIDGED-MONO PRECAUTIONS:
This mode puts a high demand on the amplifier and speaker, Excessive clipping may cause protective muting or speaker damage. Be sure the speaker
has a sufficient power rating.

If you are bridging the amp you could be suppling more power than a single cabinet can take.

Try running on one channel and see if you can replicate the problem.

nickrs540 · #8 11-08-2011, 04:40 PM

I am using it bridged, but im only running the amp at about half on the (gain?) knob. When I turn it up more then that (counting on the settings I have in my pre) I usually clip excessively. The cab im using is a GK Neo 4x12, supposed to be able to take 1000w 4ohm. I think the protective muting sounds like it could be a valid culprit. I might just not be noticing the clipping as much as I thought I was. I do tend to get a bit rowdy on stage and not notice what im doing haha.

BassmanPaul · #9 11-08-2011, 05:25 PM

If you are using overdrive as an effect you could well be masking the clipping that's going on.

will33 · #10 11-08-2011, 06:07 PM

Quote:

Originally Posted by BassmanPaul

If you are using overdrive as an effect you could well be masking the clipping that's going on.

+1

Overdrive masks a lot of problems, not only in clipping amps but also in blowing speakers. It's hard to hear the difference between overdrive effects, clipping amp and a speaker crying "please stop", especially at higher volumes.

nickrs540 · #11 11-08-2011, 06:58 PM

That makes alot of sense. Do you think with overdrive the clip light wouldn't come on?

Im also vary careful about the care of my speakers regarding how much they can take. Im always watching how much they move under different EQs and effects. I have messed up too many speakers relying on wattage ratings and such to not be careful anymore and watch what i'm doing haha. Its more the amps im worried about messing up, I can't really see what's going wrong until I either smell fire or it just stops working.

walterw · #12 11-08-2011, 07:16 PM

does it ever go out without the amp's clip light coming on first?

ChrisPbass · #13 11-08-2011, 08:18 PM

Quote:

Originally Posted by will33

+1

Overdrive masks a lot of problems, not only in clipping amps but also in blowing speakers. It's hard to hear the difference between overdrive effects, clipping amp and a speaker crying "please stop", especially at higher volumes.

this

is

true

dmusic148 · #14 11-08-2011, 09:25 PM

Quote:

Originally Posted by nickrs540

.... power light stays on, but it shows that its not receiving any signal.

No signal. There you go. It's probably not the amp, but something ahead of it. Try bypassing (HARD bypass, with cabling) the BBE. Gig. No result? Do the same with the POD. It's almost certainly NOT the amp. Something else is failing to deliver signal TO it. Betcha.

nickrs540 · #15 11-09-2011, 12:01 AM

Quote:

Originally Posted by walterw

does it ever go out without the amp's clip light coming on first?

The only time I remember it going out without the clip light on was when I used distortion.

Quote:

Originally Posted by dmusic148

No signal. There you go. It's probably not the amp, but something ahead of it. Try bypassing (HARD bypass, with cabling) the BBE. Gig. No result? Do the same with the POD. It's almost certainly NOT the amp. Something else is failing to deliver signal TO it. Betcha.

It would make sense, but it seems that the amp having a clip protection enabled would make more sense from what i've noticed. When ever it goes out I let it sit for about 15 secs and it comes back just like it was without messing with any thing. Also if it goes out and I turn it off and on again it will start working like before. The only thing im really curious about now is when I used distortion the amp wasn't clipping, but it still went out. I do bypass the BBE unless im using distortion for a bass boost, so maybe the BBE is getting the amp to clip without the light going on because of the distortion?

T-Bird · #16 11-09-2011, 12:20 AM

Hi.

Quote:

Originally Posted by nickrs540

I am using it bridged, but im only running the amp at about half on the (gain?) knob.

The position of the knob has little or no relation to the output power by itself.

Even though Paul was kind enough to quote the manual and the mention of clipping alone resulting protection, sounds more like a high temperature or low voltage problem to me.

Any way to monitor the wall voltage?

When was the last time the amp was cleaned?

:cough: Do clean Your amps every once and a while. NOT for the faint at heart. :cough:

Regards
Sam

nickrs540 · #17 11-09-2011, 12:00 PM

I don't have any way to check the wall volt right now. If you think that could be a problem I might be able to borrow one from someone.

This problem just started happening just recently. When the amp the stops working its still showing that there is power in all the components. The amp just acts like it cuts off the signal into it. The power light is still on, just the signal light doesnt come on at all and there is no sound coming out of the amp either.

I have never cleaned the amp before, but after seeing that thread I think im going to open it up this weekend and check how its looking. It's only 1 year old, but I wouldn't be suprised if its pretty grody from all the nasty bars we tend to visit haha.

BassmanPaul · #18 11-09-2011, 12:43 PM

With less than a year of service I doubt that gunk would have had enough time to accumulate.

I'm beginning to wonder if you have a crossover problem. Did you try to replicate the problem using a single channel?

nickrs540 · #19 11-09-2011, 01:02 PM

Not yet. I'll try one channel at practice tomorrow.

T-Bird · #20 11-09-2011, 07:51 PM

Hi.

Quote:

Originally Posted by BassmanPaul

With less than a year of service I doubt that gunk would have had enough time to accumulate.

^What Paul said.

Unless You're playing in very, very dusty locations, like in the middle of the desert or next to a ferromagnetic ore mine, not much dust build-up in a year in occasional MI use. Those amps in my thread were on at least 10 hours a day, every day, for god knows how many years.

If Your amp is 1 year old, it's still under warranty, right?

Use the warranty for what it's there for, and DO NOT void it by opening the amp.

Regards
Sam