For our discrete electronic modules (TC and TCT families) we use transistors that our experience, component testing and noise selection, have shown to be well ahead of the rest. We have tested several hundreds of different types and we continue to select the most superior audio-grade components with improved operation and lowest noise.
For our integrated electronic modules we use several operational amplifiers (IC op-amps) depending on their function. In the case of our tone control modules (NTBT and NTMB families) this unit is a time tested, rugged and extremely accurate amplifier with a distortion level well below 0.005%. We like its tonal clarity* and low noise.
All tone controls introduce what is called "phase-distortion". This is inherent in bass, mid or treble boosts. As long as one part of the spectrum is enhanced over another, phase distortion occurs. But different tone control circuits have different phase distortion characteristics. In terms of our perception of their sound they have different "flavors".
The taste for a particular variety of spectrum shaping (bass or mid or treble boost) and phase distortion is a very individual thing. In recognition of this we have kept the early TCT family modules, improved them and will continue to improve them.