12AX7

July 6, 2008 | Leave a Comment

The 12AX7 is a high-mu twin triode which operates in typical service as a class A amplifier, in the preamp stages of high fidelity, musical instrument, and public address amps, as well as professional line and microphone preamps, and many other audio and communications devices. The demand for the vintage USA and European versions of this tube are beginning to outstrip the supply, and, as a buyer, you need to carefully consider what is available, the device you will use it in, and what your budget allows. The highly regarded vintage brands of Telefunken, Mullard, Amperex, and RCA come at an appropriate premium price over other brands. While this higher price is justified (these tubes sound wonderful and are very long lived) other vintage brands are often just as good. Brands like GE, Sylvania, Tung-Sol, Motorola, Raytheon, and Zenith are often overlooked, but usually perform just as well as the more famous vintage brands, which makes them a terrific value, especially as the stocks of New Old Stock (NOS) tubes vanishes. Indeed, some of these were made by RCA for these other labels, and others like the Tung-Sol and Sylvania have their own followers who prefer these brands over the higher priced premium labels. There is intense hype out there about the 12AX7, and even some absolute fantasies. Some of the European labels have strong snob appeal, which can cloud accurate judgment of these very good tubes, and many self-proclaimed tube experts have either praised or shot down some vintage brands which deserve neither. If you are new to tubes in general, or are replacing a set of Russian or Chinese current production 12AX7 tubes with vintage NOS, you would do well to try several different brands and hear for yourself the sonic nuances. Then you would be well advised to lay in a stock of the brand of your choice "for a rainy day".