What is wrong with my amp?

Swampman Cory · #1 09-11-2011, 05:39 PM

My amp's making a noise, and I would like to know why. I'm not worried about it, but before I go out and buy a tube or something, I figure I'd ask you guys what the problem is. I figured the easiest way to do this would be to link to a video:

Amp Problem - YouTube

Text:
My amp essentially makes a scratchy white noise sound. Like a dirty pot on a bass except it just keeps going and going. Muting the input doesn't change it, and the gain doesn't affect it, but the pre-amp volume and the master volume both stop the noise when turned to zero. Genz Benz Shuttle 9.0 into a GB 112.

lowfreq33 · #2 09-11-2011, 05:46 PM

Could be the tube. Your best bet is to email Genz Benz, you'll probably hear back first thing tomorrow.

JimmyM · #3 09-11-2011, 05:56 PM

That's not a problem, that's their vinyl record emulation circuit

I'd say you have a fried pre tube, too. Not entirely sure but it's always the first place to look on a hybrid.

Windreaper · #4 09-11-2011, 06:18 PM

Took a look at the block diagram and agree with the gentlemen above, probably a preamp tube (the tube is, not surprisingly, between the gain and volume pots).

EDIT: I've also had a bad resistor cause similar behaviour but in your case I would try re-seating (and replacing if that doesn't work) the tube before shipping the amp anywhere.

agedhorse · #5 09-11-2011, 07:25 PM

2 possible causes that come to mind. The first is a bad tube OR a tube that is not fully seated. Check to see that the tube and the tube carrier PCB are fully seated.

The other thing to check is that the gray shielded jumper is fully seated in it's header connectors. This would be marked CN-9 and is located towards the right side of the PCB (one end is behind the master volume control). Pull the wire gently towards you them push the header firmly to seat it. Occasionally one of the pins will not fully seat and will become slightly intermittent.

Check all of this with the unit unplugged from the wall.

If this doesn't solve your problem, PM me and I'll get it sorted out for you on Monday.

agedhorse · #6 09-11-2011, 07:27 PM

Quote:

Originally Posted by JimmyM

That's not a problem, that's their vinyl record emulation circuit

If I could develop a GOOD one of these I could probably retire

seamonkey · #7 09-11-2011, 07:40 PM

Quote:

Originally Posted by agedhorse

If I could develop a GOOD one of these I could probably retire

It's already free

iZotope Vinyl | Authentic Lo-Fi Vinyl Simulation for Pro Tools, VST, MAS, Audio Unit, and DirectX audio applications

PS - Bypass switch would sure help people to diagnose these problems, and save a gig.

Swampman Cory · #8 09-11-2011, 07:55 PM

Thank you to all of you gentlemen. I'll try swapping out the tube sometime this week and I'll go from there.

JimmyM · #9 09-11-2011, 07:57 PM

Quote:

Originally Posted by seamonkey

It's already free

iZotope Vinyl | Authentic Lo-Fi Vinyl Simulation for Pro Tools, VST, MAS, Audio Unit, and DirectX audio applications

He said a GOOD one.

Quote:

PS - Bypass switch would sure help people to diagnose these problems, and save a gig.

Why have a tube only to bypass it? Makes no sense.

agedhorse · #10 09-11-2011, 08:04 PM

Quote:

Originally Posted by Swampman Cory

Thank you to all of you gentlemen. I'll try swapping out the tube sometime this week and I'll go from there.

Let me know what you find out.

Swampman Cory · #11 09-11-2011, 09:05 PM

Update: I don't know which specific thing did it, but after opening the thing up and checking the seating of the gray shielded jumper (and a couple of other things I just tried pushing for the heck of it) the noise is gone. Thank you agedhorse for advice, and for wicked customer service.

I get to sleep happy tonight.

beezerjoe · #12 09-11-2011, 09:25 PM

I know it's working now. Usually when I get noise out of my any of my tube gear the first thing I do is tap on the case of amp fairly hard with my finger. If you have a tube going bad some times the tube will go microphonic and you will here the tap come right through your cabinets. Just a quick troubleshoot that I do when my amp has an issue.

Pilgrim · #13 09-11-2011, 09:25 PM

You CANNOT beat this - problem solved - online - on Sunday - in 4 hours.

I defy any other amp manufacturer to match that!!!!

One more reason I am a happy Genz-Benz owner.

Swampman Cory · #14 09-11-2011, 09:31 PM

Quote:

Originally Posted by beezerjoe

I know it's working now. Usually when I get noise out of my any of my tube gear the first thing I do is tap on the case of amp fairly hard with my finger. If you have a tube going bad some times the tube will go microphonic and you will here the tap come right through your cabinets. Just a quick troubleshoot that I do when my amp has an issue.

Duly noted. That may come in handy in the future.

Mktavish · #15 09-11-2011, 10:14 PM

When in doubt ,,, check the signal route

JimmyM · #16 09-11-2011, 10:28 PM

Good job, Andy...you rock the CS, bro!

agedhorse · #17 09-11-2011, 11:15 PM

Fortunately, most of the problems are really simple, something as simple as a tube not fully seated or an effects loop return switch hanging up.

I handled touring product support for the pro audio industry for a long time and if you know the stuff inside and out, troubleshooting over the phone (even if English is not the native language) can be pretty productive. I also handle the pro touring player's support for GB, fortunately not a heck of a lot to do but I get to talk with some mighty cool folks (like yourselves).

And, if the problem returns, we will be on it like we always are. No worries man, you are covered!

Jim Carr · #18 09-12-2011, 12:31 AM

I love these guys—and my GB Shuttle 6.0!

Mktavish · #19 09-12-2011, 12:57 AM

Hmmm me thinks someone needs to check into shock exorbing the head from the cab.

Mktavish · #20 09-12-2011, 12:58 AM

A 1-2 inch peice of foam placed between can do wonders ... depending on your cab and output.