Tube lingo question

I'm not a tube component owner yet but am going to be in the very near future hopefully with a new preamp. My question is regarding the terms microphonics and tube rush as they relate to the sound. What are they and what do they ultimately do to the sound. Thanks.
'Tube rush' is a relatively continuous noise composed of random noise mostly in the middle and high frequencies. If the noise is predominantly high frequencies, we call it hiss.

'Microphonics' is electromechanical noise that is created within the tube when it's disturbed mechanically (by a hand wiggling the tube, by airborne vibrations [called 'music'], etc.). It may resemble the ringing of a bell. The noise is passed along the amplification path and varies greatly in level, from nonexistant to grossly unacceptable. Some amplifier positions/functions are more sensitive than others to microfonics*. For instance, my SET poweramps' 1st gain stages REQUIRE low-microfonics tubes, whereas tubes with unacceptable levels of microfonics in the 1st stage are rather quiet in the 2nd stage.

Generally, gain stages ocurring early in the signal path are more sensitive to tube rush and microfonics than subsequent gain stages.

Often (but not always) the use of some kind of tube dampers such as the excellent Tube Damping Instruments by Herbie's Audio Lab... ...will reduce microfonics; I use these things even on tubes that have no apparent microfonics.¤t=Fivetubes_700w.jpg

* One of my campaigns is to be rid of 'ph' when it masquerades as an 'f'.
Good explanation.

You really have to admire someone who single-handedly is setting out to reshape the English language. My hat is ophph to you.
Herman, I'm with you. Everyone knows ph sounds quite different than f -- you even shape your lips differently ;-))
Thanks for the explaination. If you have a highly microphonic pre-amp, will that have a negative impact when playing music or is it just a phenomenon that is notice when tapping the tube when not playing music?
Herman--TY. :-)

Gjames: "If you have a highly microphonic pre-amp (sic)...". Well, equipment very seldom is microfonic; TUBES are. So...if the tubes in a preamp* are highly microfonic, it probably is virtually unlistenable, with LOTS of ringing and banging in the signal. Of course it depends on how high 'highly' is.

The audibility of both tube rush/hiss and microfonics is proportional to how much a tube's input is amplified by itself and subsequent gain stages and by the sensitivity of the speaker. That's why, for instance, owners of high-sensitivity speakers have more trouble with these tube faults than others and why manufacturers such as Quicksilver and Music Reference make low-gain amps.

* It's preamp and preamplifier and not pre-amp or pre-amplifier.
owners of high-sensitivity speakers

Note to the language police:

It's high sensitivity not high-sensitivity, but since sensitivity is a noun it can't be used to describe another noun. It should be highly sensitive speakers or speakers with high sensitivity.

Also, if you are after the ph in microphonic why not the gh in high :>)
To language policeman Herman--yes indeed it's highly sensitive speaker, but it's also high-sensitivity speaker. A noun can't be used to describe another noun? It certainly can in compound modifiers such as four-door sedan and high-gain amp, where door and gain are indeed nouns. Each of us can't be correct ALL the time, but you're wrong this time, Herman.

And I not only can't FIX them all of those idiocies at the same time, I don't try, Herman. I guess the fony 'f' bugs me more than other English idiocies.



My pinkie must have slipped, thus inserting the hyfen inappropriately. Notice that I correctly spelled preamp in the original post. Thank you for the valuable inphormation, though. By the way, it appears you have way too much time on your hands and you should be spending it listening to your fonografs.
OK Jeff, you got me. I was looking for a grammar error in your post because it irritates me when people take it upon themselves to right the wrongs of other people’s writing. The ph thing is kind of cute but why bother to criticize preamp vs. pre-amp. It’s not incorrect anyway. It is a matter of style. For British writers it is common to find a hyphen used in this case.