noise thru tube pre??

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.

C123666
>"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....

.
Jim