CRUSH 100BXT - Noisy 'Line Out'

[muzbuster]

On 3 occasions at 3 different venues we have tried to connect from my Line Out to the DI input of the house PA or mixing desk but they complain about the amount of noise that comes out that channel.
* Should I be using the XLR Direct Out instead ?
* Are there impedance or signal level constraints published for Line Out / Direct Out connections ?
* What is the correct wiring configuration for the XLR connection ?
* Is it possible the amp is faulty ?
Thanks for any help or suggestions

[Phlowen]

It's possible the amp is faulty, but it also sounds like you're running into lazy/stubborn sound guys...which I totally understand because as a sound guy, the last thing I want to do is take a direct signal off of an amp...I'd way rather mic that bad boy.

But that aside, it could be a grounding issue...a good sound guy would be trying to isolate your power...making sure the buzz wasn't because you have different parts of your rig plugged into different electrical circuits. Do your best to make sure your amp and any pedals are all plugged into the same outlet/electrical circuit.

Along the same line of reasoning: Going straight from the amp's DI to the house Input could certainly result in a ground buzz since your amp and the FOH desk are probably on different electrical circuits.

One of the first things a decent sound guy would try is lifting the ground on the direct box (assuming you were using a direct box). If you weren't, I'd definitely recommend at least putting a direct box between the amp's LI and the board (for the reason stated above of different power circuits between the board and your amp). Or, use your XLR out and see if that works better.

If none of these solutions fix the issue, there are only 3 possibilities (that I can think of):
1. The LO of the Crush 100BXT is noisy (I don't know, might just be how this amp is?)
2. Your sound guys don't like what you're trying to do and are going to complain regardless
3. Your amp is faulty.

[muzbuster]

Thanks Phlowen. My most recent experience was in a recording studio and the main sound guy spent some time (~20 mins) and several configurations and mains outlets to isolate the problem without success. He seemed very keen to find a solution so I could still use my amp. Mine was the only amp that had a problem. In the end we didn't use my 100BXT but went directly into a DI box from my guitar/pedal rig.

Having said that, I'm not absolutely sure we tried all the possible mains circuits in the studio to try to avoid possible earth loops as you suggest however - the DI box we ended up using successfully was plugged into the same mains outlet that we had tried with my amp.

So, having got to that point, by excluding the 100BXT altogether to eliminate the noise, I was left wondering if the 100BXT has a known history/problem with Line Out that produces noise.

[Phlowen]

Well it's good to hear you had a guy who was actually trying to figure out the problem for you!

I also for some reason thought we were talking about a guitar amp. It's a bass amp...and that's making all of this make more sense.

I had the 50BXT. I really only used it as a monitor/practice amp but I always found it to be quite noisy.

Is your bass active or passive? Personally, when I play bass, I prefer running straight into a DI, and using the line out of the DI to plug into my amp so I can hear/feel myself on stage and the house gets my direct signal. BUT...I've also never had a bass amp I really LOVED and I play an active bass.

With your amp, the Line Out is unbalanced, which can be noisy. You'd be much better off using the XLR out (which is balanced and also has a ground lift). Did you try that in the studio by chance? Your XLR out also has the Pre/Post switch...that could help you isolate if it's the amp...potentially anyway.

If your XLR Out (or Direct Out as they call it) also really noisy (despite lifting the ground...despite pre/post mode), then it's either the amp in general, or your amp being faulty.

Keep in mind, this is supposed to be a practice amp, not necessarily a high quality recording amp.

[muzbuster]

Hi again. I'm playing a passive bass guitar - Ibanez Artcore 200 - and yes we did try both the unbalanced Line Out and the balanced XLR output and the pre/post; ground lift etc. on the amp. So we think we've tried most options - which leads me to think there is a problem with the amp.

So it comes back to .... is there a generic issue with the 100BXT's or has mine just developed a fault. Either way it would be good to know. I would much rather take it to a repair guy with some history or background if others are familiar with this problem in the 100BXT.

[Phlowen]

Googling around, I found a couple of other people who said they use the line out live regularly and didn't report any buzzing or noisiness.
So, unfortunately, sounds like it might be your amp.

[muzbuster]

Yep. I think you're right. Thanks for your help.