What are S4A tubes?

S4A stands for selected for audio. This means that these tubes are specifically intended for audio applications. The special characteristics of these tubes are extremely clean and low-distortion reproduction, with very low background noise in terms of microphonics, noise or hum. These tubes are mainly used for music reproduction in audiophile tube devices, for example tube preamps and power amplifiers, DAC outputs, CD players, phono preamps and tube filters, but also in the studio and microphone sector for recording and playback, for example tube microphones, mixing consoles, tube compressors, amplifier modules, EQs and preamps. The tubes are hand-selected at the factory by BTB Elektronik for low distortion and low noise. The matched / balanced option makes sense in all multi-channel systems, such as stereo or surround, differential amplifiers and phase inverter stages.