the ultimate guide to tube-rolling: 12AX7
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The 12ax7 / ecc83
These are miniature dual triodes with a high voltage gain, commonly used in preamplifiers. They are still in production, made by New Sensor in Russia, Shuguang and Quanzhen in China, and JJ Electronic in Slovakia.
Low noise and microphonics, but if you have a really high-gain phonostage, or want a more relaxed top end, the Mullard would be a better choice. Gorgeous mids, great dynamics, and a nice 3D soundstage.
Customers rate this tube very highly, with reviews praising a “clean” sound with good bass, and a “great top end”. Reviews also point out “3D imaging”, great detail, and overall huge value for money.
The filaments are almost completely encased, so these won’t glow as brightly as other 12AX7s.
Very low noise and microphony, so this tube is well suited to touchy preamps and high-gain phonostages. Smooth midrange similar to NOS Mullards, but not quite the same. They are more relaxed on top, so a good choice for bright systems you want to tame. If you want more a more energetic presentation, consider the Tung-Sol 12AX7.
All indications are that these are a worthy alternative to the expensive NOS version of this tube. Reviews talk about smooth mids but with detail and good bass. Customers who found their systems harsh or edgy, loved what these did to the sound. Sweetness, naturalness, quietness, tight bass, good soundstage are words that come up again and again. One caveat is, if your system is laidback, these might make it too dark.