What is important when upgrading tubes in Unison Research amplifiers, and what should you pay attention to?

With Unison Research amplifiers such as S6, Sinfonia, Triode 25, Simply Italy and Simply Two, a tube upgrade depends especially on robustness, clean matching and the right tonal tuning. Depending on the model, types such as EL34, KT88, ECC82 and ECC83 are used. Since many of these units put considerable stress on their tubes during operation, not only the correct type should be chosen, but also a quality that proves itself over the long term. This is exactly what we pay attention to when selecting our upgrade tubes.