Genz Benz ShuttleMAX 12.0 Noise/Hiss Problem. Bad tube?

[cyprus]

So yesterday at practice I was getting my gear plugged in and going, and I noticed that I had some hissy noise coming out. I thought it was my instrument cable, because I hadn't used it in a while (normally use a wireless, but forgot to the charge battery) but when I unplugged it, the noise was still there. Tried hitting the mute button, which usually cures all problems, but it was still there. It only happened when I was on the tube channel. The FET was super clean like my Genz usually is. Every time the band stopped, I could still hear it in the background.

I don't know if was possibly an electrical problem, maybe a cable wasn't grounded right or something. Or maybe I have a bad preamp tube?

I'm gonna be trying it out tomorrow at a different location with a different cab, see if still does it. In the meantime, any ideas?

Much thanks in advance.

[hasbeen]

a ground would create a hum or buzz....not a hiss.

Did you get any microphonic squeal from the tube? Also, how did you have the tube channel levels, gains and eq set?....including the signal shaping circuit?

Try putting everything back at 12:00 and see how it sounds.

[Doug Parent]

I think I have a bad tube also, I have pretty loud pink noise coming from my 9.0 Shuttle regardless of the mute switch or anything else.

[agedhorse]

Where are the controls set (for both of you guys)?

It's possible it's a bad tube, but let's check to see that a knob or switch didn't get accidently bumped first.

[Doug Parent]

The position of any knob or mute switch makes no difference.
It's stable constant pink noise at 85 db (guessing) I tapped on the top enough to vibrate something inside and the noise eventually went away and I had the sound of my bass coming through like normal, however it does this consistently now everytime I turn it on, so I can't gig with it. I'm picking up a new tube tomorrow and will report the results.

[mh72nc]

I had this issue with my GB 9.0. It has a tube preamp but no fet. I smacked the top of it, cause it was irritating me, and the hissing stopped. Hasn't come back in a month. Don't know what was causing it, but it's something to try

[Doug Parent]

hmmmm interesting. Wonder if this has been an issue for others?

[agedhorse]

Change out the tube first, it's the most likely culpret. If that doesn't take care of it, we'll get it sorted out in no time.

Sometimes the noise can be caused by an intermittent connection inside the tube which is why it may improve when tapped. It can also be imputities in the vacuum which generate noise as the electrons collide with the impurity atoms (be it oxygen, nitrogen, etc.)

[Doug Parent]

Originally Posted by agedhorse

It can also be imputities in the vacuum which generate noise as the electrons collide with the impurity atoms (be it oxygen, nitrogen, etc.)

I hate it when that happens.

[agedhorse]

Originally Posted by Doug Parent

I hate it when that happens.

I almost added pot smoke to the list of impurities

[Doug Parent]

Replaced with a Groove Tubes 12AX7 (it's what GC had in stock, which sounds muddier than the Ruby it replaced.)
Situation handled.

[agedhorse]

Excellent. Give Jeff a call and let him know what happend and how you resolved it. We like to keep up to speed on what's happening in the field.

[Doug Parent]

Hate to bother him with another phone call.

[agedhorse]

Originally Posted by Doug Parent

Hate to bother him with another phone call.

This is how we stay on top of things.