Microphonic tubes. Nothing to really be concerned about.
Not a problem if your pre still sounds good. Microphonic tubes can actually sound very good, but it is system dependent.
Probably time to tube roll anyway since you just got your new pre. Experiment and have fun. You will be amazed at the difference tubes can make.
You did not mention the the tube manufacture and type you are using.
With the volume turned all the way down put your ear close to each speaker, do you hear a buzzing sound from either speaker or both...
I bought a new pair of New early 60s white label NOS Amperex PQ 7308 tubes a while back. After about 5 hours on the the tubes I noticed a buzzing sound in the right channel speaker, from my listening seat. I also noticed at a normal listening volume level, just a light tap on the top of the face plate of my Sonic Frontiers Line One preamp I could hear the tapping through the right speaker. Luckily I had bought the pair of tubes from a Tube Dealer and he sent me a new pair.
What tube damper are you using? I highly recommend the Herbie's HAL-O dampers. Below is a link.http://herbiesaudiolab.home.att.net/
You've got a microphonic tube. Since you only have one tube, get a new one thats been tested by a dealer for microphonics. Microphonics can effect the sound put out by your pre-amp even if you are not tapping the case. Vibrations come from many sources, including airborne.
Use currect production low noise tubes until you know the sound you prefer. Visit Audio Asylum tube forum and do a search on the 12AT7 you are using for suggestions on good currect production tubes. I don't use any in a line stage so I have no recommendations.
Re above comment 'microphonics can actually sound very good' - I would add 'if you like distortion'. In fact the presence of microphonics can give you some of that upper mid/high end distortion (glare, grit, grain, etc) that most folks hate.
I thought tube gear was always noisy, is it more than usual? : )
No I think you are confused. Tubes have a pleasant sounding noise. SS has a nasty sounding noise. There is a big difference....Wink.
Hell, I wouldn't even wink! SS sucks the music right out of the grooves and craps all over it! Hey, Nrchy, did you ever figure out how to bias that tube amp you bought? :-)
Wow, a lot of valve love in the room.
You've got a great hybrid preamp. I like the suggestions above. Go with something new and reliable to start, then roll into some NOS later. With only one valve, you can afford top notch NOS.
This was noticed after I rolled the stock Sylvania, with a NOS phillips tube, I dont know if it was doing it before, its not like I walk around tapping equipment (I like to tap my feet though), anyway maybe I need to re-install first tube, as of now I have no tube damper....thanks guys
YOu may not even have a microphonic tube. If you tap a tube directly, you will most likely hear a slight noise from your speakers. When tapping your chassis, depending on the tubes' isolation, you are most likely just transferring the tap to the tube. I'd be alot more worried if I were hearing noises WITHOUT things being tapped!
When I tap the chassis of my preamp it goes, "poommmmmmmmmmm".
This also shows the importance of a chassis designed to absorb resonances and not pass them to the tubes. Most units use folded sheet metal which is inadequate. Very few preamp manufacturers, except for the Very Expensive ones, use correct chassis.
Same with amplifiers. The cost of a truly high quality all aluminim chassis is quite high unless produced in truckload quantities. Even then it is much more expensive than the standard wood with aluminum top plate or folded stainless steel over cheap metal frames.
Chadnliz - this is fairly normal for a preamp. especially those with high gain. to some degree tubes are microphonic by the nature of their design. just like ice is cold by its nature. it shouldn't be a problem unless the music from your speakers creates a feedback loop through the preamp. otherwise just don't tap on the chassis while you are listening to tunes.
hal-O tube dampers may produce positive results in your system and they are inexpensive too. peronally i prefer a hint of microphonics since it adds to the airiness of the music.
>"This also shows the importance of a chassis designed to absorb resonances and not pass them to the tubes. Most units use folded sheet metal which is inadequate. Very few preamp manufacturers, except for the Very Expensive ones, use correct chassis"
I still have a Sonic Frontiers Preamp same as Chadnliz has now. The board the tube socket is mounted to is isolated very well. The build quality is very good.
As far as the preamp I am using now, Sonic Frontiers Line one, I can turn the gain control up quite high and tap on the preamp case with no microphonics what so ever from the tapping heard through the speakers.
Chadnliz. Your preamp sounds great with the Mullard tube I mentioned in one of your other threads. Nice warm tubey sound....
As pointed out, your tube is not microphonic just because you hear something when you tap on the case. If it just rings on its own or it continues to ring after you tap then it is microphonic.
Those who think tube gear is always noisy are sadly misinformed. I have an all tube system with 103dB efficient speakers. You can put your ear up to the speakers and hear very little. All components produce a certain amount of noise, even passive components such as resistors. If the equipment is properly designed then it will not be audible once you back away from the speaker a bit.
Newbee, tubes with some microphonics (if not ridiculous) can add a sense of realism to the soundstage. They can add a slight hall or venue presence that has nothing to do with "glare, grit, grain, etc." Unless the tube is overly microphonic some of the best sounding tubes I have ever had in my system have been slightly microphonic. And speaking of "distortion", that's inherent with tubes and is the very reason many of us prefer the sound of tubes to SS to begin with :)
Fiddler, I think there is a difference between 2nd order distortion and a 'ringing' caused by tube microphonics overlaying the music.
That in minor amounts folks can enjoy an artificial reverb like distortion caused by this ringing I wouldn't deny. Studios regularily add re-verb to the mix to enhance a recording, especially dry studio recordings.
But, folks should know there is a difference and by having microphonic tubes you are allowing a distortion to exist which you have no control over. While some recordings might well sound better, and some systems might well sound better, the obverse is also true. And, if you are playing music or components that have considerable energy in the highs already, you might well find that the minor amount of microphonics added to the mix was enuf to make the sound unpleasant, but if you didn't know why you would blame the recording or your system.
Personally, I avoid microphonic tubes as I want the signal to hit the amp as clean as possible. I've always steered clear of any 'signal enhancers' because over the long haul I've always ended up taking them out of the system even though initially their effect was attractive. Thats strictly my choice. Others can tune their system as they wish.
Thanks alot for all info, it only does it when forced by tapping, so I am not going to be to pressed about it, as always you guys once again teach me new things and I thank you all!
Newbee, the only thing I disagreed with in your first post was the implication that microphonic tubes somehow always sound bad.
Enjoying the effect of a slightly microphonic tube is no different than rolling a Mullard for warmth or a Telefunken for detail. Every tube adds its own particular "signal enhancement". None of them comes with an accuracy meter.
I won't deny that microphonics aren't accurate. But like warm Mullards or super transparent CCAs, every tube adds it's sonic signature one way or another.
I think you hit the nail on the head when you said, "Thats strictly my choice. Others can tune their system as they wish."
That's the real joy of tubes versus solid state, IMHO. Tubes offer so many options for one to tailor the sound of their system until they find the "accuracy" that sounds right to them.
Does it strike anyone else as odd that we (Audiophiles) expend great effort in selecting isolation equipment (brass cones vs aluminum cones, tennis balls vs. ball bearings, etc) to isolate a component such as a solid state amp or preamp, or CD player (or even a cable) which you can tap on as hard as you want without ever getting the slightest piff of sound through the speakers, but are willing to sit a pair of monoblocks with exposed tubes, which are commonly microphonic, right next to the speakers?
Honest1, LOL. Just too much. I'm going to avoid temptation just this once. No comment!!
Honest1, you nailed it, babe. I kept my 150lb/each Pass X-600s 6ft behind and towards the center of the two speakers. If I could have put them in an adjoining room without an excessive speaker cable run I probably would have been happier.
Ive always looked at setups with the mono tube amps next to the speakers and shuddered. To the uninitiated in tube amps (me) it appears that one of the many bass drum whacks in the Rite of Spring could turn KT88s into interesting fireworks displays. Ive been meditating a tube excursion in the near future and would love to read comments by present tube amp owners on this subject.
If you must put tube equipment in the same end of the room as the speakers usually you can put it in the center of the space between the speakers. Just put on some bass heavy music and move about finding the location where the bass response is minimal, usually well away from the back or side walls behind the speakers where the bass is reinforced by the boundries. If you are into TT's the same rational used for locating a turntable can be used for tube equipment.
FWIW, I've never thought that power tubes suffered very much, if at all, from the vibrations created by the speakers, but the small tubes are another issue. I have put large mono tube amps very near speakers (between the speakers) without any issues, but as indicated above I shy away from small tubes that aren't free of microphonics.