Does it sometimes happen that you tubeamp rattles or whistles?? Well, tubeamps usually sounds great, but sometimes they also have "a great sense of humour"... Lots of people are now and then disturbed by a "glassy rattling" in their amps, or an ongoing uncontrollable feedback. Sometimes you may hear a "boiling" sound in your tube amp. Then, usually, it's time for a change of tubes. Rattling and feedback is usually caused by microphonic pre-amp tubes, the smallest noes, usually located in the inner row of tubes, inspecting you amp from the back side. The most common tubes will be 12AX7 (also named ECC83, 7025 or SPAX, depending on brand or "quality") or 12AT7 (ECC81 is equal). Poweramp tubes are usually 6L6 (sometimes with add-ons as GC or GCA). You'll generally find these in American amplifiers as Fender, Mesa/Boogie etc. The more powerfull "Hi-Fi"-version of those are called f.ex. 6550 or KT-88. In addition -in the smaller Americans, you may find in amps like Fender Deluxe Reverb, 6V6-tubes. British amps, like Marshall, are often using EL-34 tubes (or shall I say valves??). They also have a "more rigid" cousin named KT-66. Vox-amplifiers often carry EL-84's, looking a bit like preamp tubes "on stereoids".

Poweramp tubes may also be microphonic, You can check that with a "Bic-pen" or a screwdriver's shaft or similar, carefully tapping them one by one ( using a hammer would be a bad idea). It will be wise to always have some spare power-tubes available (remember! does your amp carry 2 or more powertubes, you should change them in pair - pairs are divided inside out... if there are 4 powertubes, nr. 1 and 4 is one pair, 2 and 3 is pair no. two) If your amp carries different types of preamp-tubes, you should have at least one of each in your spares collection. Generally, yor "first" preamp-tubes will be the most sensitive ones, the ones closest to your jack-input (where you are plugging your instrument into you amp). Sometimes, changing the internal order of your preamp tubes wil be a proper "first-aid." If you have a "safe spare-tube", you may replace one tube at a time with that, to find your "cheater".

Place your amp on a table, or similar, rear of amp towards you. On most "sensable" amps you will, after eventually having removed some "protective covers or grids", you will have yor tubes right in your face... the poweramp-tubes will usually be closest to you, with the preamptubes in the inner row. Pull your "suspected" tubes straight out, notice the largest gap between the pins (preamp tubes or EL-84's) or take notice of the direction of the "center-guide" (6L6, EL-34 ect.) Tubes may be hot, so use a napkin, sweater or tissue to protect your fingers.... Myself, I generally use TAD-tubes. They are good at finding proper tubes and to match them well.

Above, you'll see the rear of a Budda 18w.. inside the three metalshields to the left, the preamp tubes are located - in the middle, 2 EL-84 powertubes and far right, a rectifier-tube. Often, modern amps have silicone-diodes as rectifiers, but some "feinschmeckers" will prefer tubes to rectify the current. The center picture show metal-shield removing (push in and turn"a litlle bit" counterclockwise).Top right, I've tried to show the largest gap between the pins (preamp tubes or EL-84's) below that you may have a glimpse of "center-guide" pointing downwards to the right - meant to guide you safely into the powertube-socket GOOD LUCK!

Of course we can do the job for you, but you'll need no excuse to just show up for a cup of coffee, either. You are always welcome to check our collection of instruments, amps or records - or a nice chat.....