Shuttle 9.0 issue

[popgadget]

Last night my Shuttle started making a lot of "white noise". It still worked, but with a lot of hiss. Between sets, I opened it up, removed and reseated the tube and daughter board, and then it was fine. Both the board and the tube seemed to be fully seated prior to me removing them. Has anyone else experienced anything like this? I am concerned about a reoccurrence. Any suggestions?

[RocketMusic]

I'd keep a close eye on it, listen for repeats of the same symptom. If it crops up again, I'd replace the tube as a first step. I'd go ahead and get a spare tube now so you have it if you need it on a gig. If the issues persists after changing the tube, just give Genz-Benz a call. They'll help you trouble shoot it over the phone, or they'll take it to the next level (whatever that may be).

I'd also make sure the treble boost (HF Attack) button wasn't engaged accidentally (I'm sure it wasn't, but had to mention it)...

Also be aware of where you were and where you plugged in when this happened. I play at this one club in town that has some "good" outlets to plug into and some "bad" outlets. The "bad" outlets must be on the same circuit as some big kitchen appliances. They're noisy, and the voltage fluctuates like crazy. It also really helps us to have the lights plugged into the "bad" outlets, and everything else (stage amps and PA system) plugged into the "good" outlets. If we mix and match outlets with the sound gear, there's often random noise and sometimes even scarier stuff like shocks through mics.

Good luck! I hope it was a one-time thing!

[agedhorse]

Originally Posted by popgadget

Last night my Shuttle started making a lot of "white noise". It still worked, but with a lot of hiss. Between sets, I opened it up, removed and reseated the tube and daughter board, and then it was fine. Both the board and the tube seemed to be fully seated prior to me removing them. Has anyone else experienced anything like this? I am concerned about a reoccurrence. Any suggestions?

If this happens again, give Jeff a call at the factory. One failure mode of a tube as a tiny gas leak of the glass envelope causing impurities (air) into the vacuum that is where the internal components of the tube reside. Normally the electrons flow from the cathode to anode (current is defined the opposite direction) through the vacuum but when molecules of oxygen are present the electrons hit these molecules and generate noise.

The usual place for the leak to occur is the pin seals which are very complex though they look simple. When a tube is manufactured, a vacuum is drawn while the tube is hot and the top nipple is melted and pinched off. A bit of active metal resides on the getter and is flashed (burned) to scavenge any remaining oxygen. The result is the silver metallic deposit on the inside of the tube at the top. You can usually see the getter structure.

My dad designed servo amplifiers (essentially high bandwidth, high accuracy feedback type audio amps) for the aerospace industry using tubes. By far the biggest challenge reliability-wise was that of the tubes themselves. Military screened versions of tubes like the 12AX7 cost many, many times the cost of a consumer version. He remembers paying 10x as much for critical path tubes. That would make a $7.00 tube cost $70.00.

[popgadget]

It sounds like Aged Horse suspects the tube. The thing is that I didn't change the tube, I only re-seated it and the daughter board that it plugs into. If the tube had a leak, how would have my actions "cured" it?
Is this an isolated problem, or have others encountered it?
I do keep a 12AX7 in my gig bag, so if it returns, I will try a tube swap.
Other than this it has been a great amp, although now I'm curious about the Streamliner.

[agedhorse]

It's most likely either a tube (which I addressed by explaining the most common types of failure that causes this symptom) or that the tube was not fully seated into the pin receptacle contacts. If the problem does not return then it was the latter. If the problem returns it's likely the former and the noise may also be sensitive to temperature.

I go into some detail on explainations because I get enough PM's asking for more detail about how this stuff works. It seems that a good number of TB'ers have an appetite for information...

[steve f]

Originally Posted by agedhorse

If this happens again, give Jeff a call at the factory. One failure mode of a tube as a tiny gas leak of the glass envelope causing impurities (air) into the vacuum that is where the internal components of the tube reside. Normally the electrons flow from the cathode to anode (current is defined the opposite direction) through the vacuum but when molecules of oxygen are present the electrons hit these molecules and generate noise.

The usual place for the leak to occur is the pin seals which are very complex though they look simple. When a tube is manufactured, a vacuum is drawn while the tube is hot and the top nipple is melted and pinched off. A bit of active metal resides on the getter and is flashed (burned) to scavenge any remaining oxygen. The result is the silver metallic deposit on the inside of the tube at the top. You can usually see the getter structure.

My dad designed servo amplifiers (essentially high bandwidth, high accuracy feedback type audio amps) for the aerospace industry using tubes. By far the biggest challenge reliability-wise was that of the tubes themselves. Military screened versions of tubes like the 12AX7 cost many, many times the cost of a consumer version. He remembers paying 10x as much for critical path tubes. That would make a $7.00 tube cost $70.00.

Thank you for that excellent post.