I have finished, for now, tube rolling in my Torii MKIV and focused on the CSP 2+ preamp. Due to inexperience with preamps, I did not expect much change to sound quality by rolling these tubes. I assumed that the amp primarily did that, and the preamp did…..something else.

I have been surprised, however, what a difference preamp tubes make in my listening experience while not changing anything in the amp. It is hard to make quick comparisons, but I have my favorites.  

The most pleasing arrangement was replacing all three preamp tubes with RCA 6SN7 Gray Glass and the rectifier with an RCA Cunningham. I have also tried three Sylvania 6SN7 or RCA 6CG7 as inputs and RCA 80 Globe as a rectifier. All were good, but the Gray Glass/Cunningham option was most pleasing.

Before concluding this experiment, I thought of asking for any other suggestions. I have read positive reviews for Sylvania 6SN7GT 2-hole or 3-hole "bad boys."  On eBay, they can be a bit pricey. I have had good luck ordering tubes from Surplus Sales Nebraska, but I don't think their current supply includes the Sylvanias mentioned here.  


So far, I have replaced the input tubes altogether as a trio. If I were to replace only the lead tube, leaving the left and right channel tubes alone, would that also affect SQ? Or should I keep the lead tube the same and change the other two inputs? It is undoubtedly more economical to replace just that one tube.

Are there any other 6SN7 tubes or something different than the 6sn7 (like the 6CG7) to recommend as inputs for my preamp?  

Thanks, Tony