Balanced Electro-Harmonix 12AX7 Preamp Tube
The Balanced Electro-Harmonix 12AX7 preamp tube has a nice balanced sound, a very low noise floor and excellent performance in terms of microphonics. The lack of microphonics may be due in part to the return of a shorter plate structure or better materials. Try them in various amp stages to test their characteristics in the different positions.
What are balanced triodes?
The 12AX7 is a dual triode, meaning it is two tubes in one, with both sides amplifying the signal (in amps where both triodes are used). These balanced tested tubes have equal gain ratings on both triodes, which can help reduce noise and microphonics in the preamp section of amps
For more technical specs on 12AX7, read here.