Orange Amps Forum

Ok, so I looked in the tube layout section so that I could describe this correctly but there is no layout for the JR Terror in that thread. So, I'm just gonna give it a shot here. What I believe to be stage 1-2 or V1 of the 12ax7 positions ( looking at the front of the amp, furthest tube to the right) no matter what tube I roll into that position, it is seriously micro phonic . Tap on the tube, you can hear it in the speaker.

I've tried new tubes in that spot, sovtek, JJ and tung-sol, no matter what, you can hear the tapping. The reason this is irritating me is whether I have it in the half power of full power, I'm getting a nasty hum out of the speakers. No matter what volume and no matter how far or close I am from the speaker cab. This happens with all of my speaker cabinets. All are 16ohm.

I've tried new Power tubes as well. New set of Mullards, new set of RFt's and JJ's. The hum sounds similar to the sound of blowing into a bottle. Any ideas? My honeymoon is quickly coming to end with this amp .

Sorry you're having trouble.

Have you tried swapping any of the other preamp tubes? Does the humming stay the same volume no matter where the amp's volume control is set? Does the gain control affect the intensity of the humming? You say it sounds like blowing into a bottle. Is it a constant, sustained tone? Or, does it seem to rise and fall with your playing? If the amp itself is farther away from the cabinet, does that seem to lessen the humming? Does it really sound like 'ooooooooo,' or does it have any hint of a buzzing to it?

Just trying to get some more details...

Did you buy it new? Is it still under warranty?

not under warranty any more unfortunately.

Yeah, I've tried replacing tubes in all positions. I mainly focused on that one at first cause it was the only position making noise when tapped on.

All tubes are microphonic to a greater or lesser degree.
Higher gain amps are more sensitive to microphonic tubes - the higher the gain, the greater the amplification of everything - signal, noise, whatever.
Your problem does not sound like it stems from having a demonstrable degree of microphony from V1.
Microphonic tubes tend to add ringing noises during playing. When you have really microphonic tubes the amp can start to oscillate.

You describe the sound like 'blowing over a bottle' - this bring to my mind a noise profile with both high and low frequency components - a low frequency 'hum' which is probably 'mains hum' and a higher frequency 'shhh' time sound which may be more 'white noise' like, due to the high gain design with no noise gating.

Some folks have found that changing the fx loop tubes helps with nose on these amps, did you change these also?

If you're getting a buzzing type sound, then it is likely power supply ripple, like jontheid says. The indicates either 1) you have a very badly balanced phase inverter tube, 2) very un-matched power tubes 3) a faulty preamp tube that is amplifying the heater AC, or 4) a serious power supply problem in the amp (bad capacitors, for instance). You say you've checked the tubes, and I can only assume that your power tubes are properly matched. If that's all good, you need to bring the amp to a tech.

If you are getting a smooth 'ooooooooo' type of sound, that means the amp is oscillating. This can on rare occasions be a tube issue (like a very badly balanced phase inverter tube, which affects the feedback around the power amp), but more likely means that something in the wiring of the amp is feeding back on itself and it needs the attention of an amp tech.

That's my take. Any other ideas, folks?

You did try different guitars and different cables, right?

I did try changing the cables. After changing the PI tube with one out of another amp ( just to see if maybe I had a hand full of less than quality tung-sol's) the hum went away. So, moral of this story, even if you have a brand new replacement tube for every position , they may all just suck! I hate current production tubes!!!

Just wanted to say thanks to all of you guys who chimed in with advice. I was at wits end going with normal tube roll/replacement and still having issues. Appreciate it all!

Oh, yeah. I know what you mean. These days there's a difference between good tubes and new tubes. This past week I tested some brand-new tubes for a guy because one was red-plating immediately. He thought it was the amp's bias, but the tube failed the test - DOA. He had just bought it. Sometimes when you troubleshoot you need to have some known-to-be-good tubes laying around. Or, get the Orange tube tester