The REF 2 MK II has 6) 6H30's, 1) 6L6, and 1) 5AR4. The only reason for a "tubey" sounding REF 2 MK I is "tubey"(microphonic) tubes. If the tubes are rolled for accurate/transparent, NOS 6922's, the sound will be also. Siemens and Telefunken CCa's will both provide a clean, accurate, non-tubey presentation. As with any pre-amp, mic or phono stage: Tubes MUST be screened for noise before purchased. The CCa's were a specially selected, low-noise 6922 variant, but that doesn't guarantee all will be quiet enough for your pre-amp. A less expensive, but still excellent option, is the Siemens E188CC. I had them in a couple ARC pieces I owned(very extended, lucid and transparent). I'm using 6) Siemens CCa's in my VK-D5 now, and love 'em.
