Tír Na HiFi

]I am using a B.A.T. vk-300 with a tube pre-section.When i use a set of Mullard ECC88's
with the amp there is a small ringing sound coming from the speakers,sort of like a mini triangle
going of in the room with certain frequences in the music.I first noticed the sound with my dog barking
and took me a little while to pinpoint where the sound was coming from.If i tap my amp with
a finger the harder i tap the more it rings.This is a new problem and the ringing sound isn't there with any other tubes.
Has anyone came across this before??.

Very common in guitar amps, so I know all about it. Nothing much you can do other than change the valve. NOS Mullards are usually not the worst so I am a bit surprised about this one. Loads of new chinese valves do this straight from the factory. Very annoying......

I found these kind of damping rings worked to defeat microphony http://www.ebay.ie/itm/10-Vacuum-Tube-D ... 516wt_1185

Worth a try
KM

Thanks Claus and Ken,
Good to know it's only a problem with the tubes and not the start of a problem with the amp..

Ken Moreland wrote:I found these kind of damping rings worked to defeat microphony http://www.ebay.ie/itm/10-Vacuum-Tube-D ... 516wt_1185

Worth a try
KM

I must give that a look. Not that I need them or anything but a man has to buy something geeky every now and again. Yis would kick me out if I didn't!

With some small valves if I tapped lightly with a pencil I could hear it through the speakers. Conrad -Johnston fit these as standard.
KM

Such tubes are said to be microphonic....... no cure I'm afraid, just hope that the next set you buy aren't as bad. Some tubes are known to be problematic in this area, others not so much. If you bought them from a reputable dealer, I'd be returning them and asking for a new set/refund.

Fran wrote:Such tubes are said to be microphonic....... no cure I'm afraid, just hope that the next set you buy aren't as bad. Some tubes are known to be problematic in this area, others not so much. If you bought them from a reputable dealer, I'd be returning them and asking for a new set/refund.

Eaxactly, when you hear this "triangle effect" with one tube, there is nothing to do except replacing the tube. I had in the past a similar problem with two 12AX7 Sylvania yellow label, and it'll get worst in time until I replaced it. :(

However, if the tube dampers won't solve this issue, it's still a good gadget to buy, I have dampers on all my tubes and found a real improvement in sound quality !

sdiesel77 wrote: However, if the tube dampers won't solve this issue, it's still a good gadget to buy, I have dampers on all my tubes and found a real improvement in sound quality !

No doubt DaveF calls them "Damp Fairies" ;)

ah now, nothin mysterious about microphony. Shark oil cables on the other hand.......... :)