What Is a Microphonic Power Tube?

In the highly anticipated sequel to What Is a Microphonic Tube, TubeDepotTV's Rob Hull shows you what a microphonic power tube sounds like. It is a question he gets asked often, and he thinks it's good to know your enemy.

Category:

Howto & Style

Tags:

• vacuum
• tubes
• microphonic
• power
• tube
• electronics
• loud
• noises
• amps
• amplifiers
• orange
• woodstick
• castors

[shreddmaster666]

I just had the transformer replaced in my amp and the tubes are pretty old. I get wierd sounds out of my amp, but only on the gain channel. It sounds like someone installed a rotary phone in in it. Could it be bad preamp/poweramp tubes, or should i take it back to the shop?

[TubeDepotTV]

@shreddmaster666 - good troubleshooting is not only finding what is bad but determining what is good. Therefore, in an effort to eliminate the possibility of the tubes being an issue, I recommend switching the positions of all the preamp tubes. If the quality of the noise changes (more or less noise or sounds different), then the trouble may be a preamp amp tube. If the noise is exactly the same as before, then the preamp tubes probably aren't the issue.

[skull2510]

Does the microphonic sound come from the speakers? Or just the tube itself? I get these weird undertones when playing certain intervals up high on the G, B, and E strings. Kinda sounds like holding a rubber band up to your ear and strumming it. But the sounds seems to come out of the speakers not the tube.

[TubeDepotTV]

@skull2510 - the actual microphonics are a result of the tube. The microphonic tube is creating its own electrical "noise" that is being amplified and reproduced by the amp and becomes sound from the speaker. It sounds like you may have a microphonic power tube or you may have a bad solder connection.

[TubeDepotTV]

@Axeman2006 - Tapping on tubes with bare fingers, even while the tube is operating, is not problematic. Tubes are not like high vacuum light bulbs. Finger prints on the glass will not hurt a vacuum tube. Licking is another matter ... don't lick vacuum tubes while they are on. You will get burnt and it will be very uncomfortable explaining how it happened.

[TubeDepotTV]

@1kaptenqk - the comment I was responding to when I made the "licking" response was commenting on the use of my bare hands tapping on tubes. I mentioned that touching a tube while operating isn't a problem ... licking, well, that would be a different matter. Imagine explaining why one's tongue is burnt ... not a very positive response.

[1kaptenqk]

@TubeDepotTV wait, why would i like the power tube of a running amp? what did i miss

[TubeDepotTV]

@TheeAldeen - I imagine there is more than one electronics hobbyist in your town. Electronics is quite fun ... sort of like Legos but with components.

[TheeAldeen]

Dude seems like the Coolest Dude Ever. wish we had people like him in my town

[TubeDepotTV]

@Satchmoeddie - those darn slave driving managers. My shop at home doesn't have adequate AC and I've sweated into a few amps. I'm sure I'll sweat into several more this summer. Keep testing and fixin'