Then I check the power tubes on my Maxi-matcher and since I test, match and grade all my tubes this gives me the info I need to select tubes that will bias up properly for fixed bias amps. For EL84 fixed bias amps and depending on the players style we will try two or three sets of power tubes in different heat ranges to hear what sounds best. I can usually get the bias real close by selecting different grades of tubes with the exception of the Mesa rectifier series and the Peavey 5150 s and ultras. I do not believe in the method that most people who compare tubes use, which is to set the tone controls to one place and leave them for the entire test. I disagree with this procedure because it does not allow you to get acquainted with the capabilities of the tubes.
Some tubes get sweet when treble is dialed in and some get very piercing.
It s very important for tubes to be able to handle added lows, mids and highs without getting flabby, harsh or piercing otherwise you will turn your amp into a one trick pony. I do keep a good well matched set of all the currently made tubes such as Svetlana s, Sovteks, EI s and a host of NOS power and pre-amp tubes such as RCA, Philips, GE, Sylvania, Telefunken, Mullard, Brimar, GEC and Amprex to name few for the purpose of comparing them to the JJ line of tubes. The following are my opinions and the opinions of the vast majority of my customers. I will keep this to the most common power and pre-amp tubes. This tube has a very harsh mid and upper mid-range.