Well I have to say that I am pretty happy with the combo of ECC83 combo of balanced, high gains and goldpin from JJ in my pre-amp I've just read that RTF's are "hard rock" tube so I thought how would they compare say, to JJ ECC83 hi-gaing ? I am really into warm, pronounced mids, rolled of highs, and tight bottom end, harmonicly complex euro typa pre-amp, JJs answear that requirement pretty well so I read that RTF is a german "hard rock" ECC83 tube so it got me wondering.