I am using two Kondo M7 Phonos in combination with KSL Sfz or other transformers like Silvercore. The used tubes are decisive! In one of my M7 I am using General Electric ECC83 and some French CIFTE ECC82 NOS tubes.
In my second M7 I exchanged the tubes right now. NOS Siemens Halske ECC83 and Philips 12AU7 (= ECC82) complete the setting. What a difference to new Slovakian tubes (which are not bad) – really unbelievable!