Fully compatible with the Zen amps. Probably also the Toriis. Can be cheap and plentiful, I've bought about a dozen over the last year and a half, but the ones that are clearly the best sounding were expensive, a 'seventies pair the seller said was "rare" and I found that after they broke in they are excellent tubes--very clear and open mid-range, sweet treble and tight bass. With most tube complements they can be just a tad lean though, but the dynamics and clarity are worth it. Not unlike the 6N1P and 6N5P types, but airier and more "agile" sounding.

I've used them in all positions and currently am using them as the driver tubes in my CSP3 with the 25th Anniversary mods which I think is where I like them most. In the input position I have one of Steve's 6N5P and as a rectifier I'm using a Cunningham Type 80 Globe. Nice setup!