5AS4A vs. 5U4

I have Mullard 5AS4s in my SLI-80 and they sound wonderful; much better than the RCA 5U4GBs that I had been using. At first the RCAs impressed me with their dymanics. A much "juicier" sound. However, the highs were somewhat harsh and hurt my ears. Tried to tame that with Mullard 6DJ8s in the front. After I switched to the 5AS4s, I went back to Amrerex PW 6922s. Lovely sound. More natural, not fatiguing. The Mullard 5AS4s look like fat EL34s. Tall and straight. I've since found some Australian tubes that appear to be the same construction. Have not listened to them yet; so I don't know if they sound the same. Good luck with your amp. My friend at Cary will be pleased with your choice.

current tubes: USA Amperex 'pinched waist' 6922s; Sylvania 6SN7GTBs, FAA issue ca 1969; GEC KT-88s; Mullard 5AS4s.

John,
Thanks for the fantastically comprehensive response! I'm looking forward to experimenting in the days and weeks ahead. Tell your friend at Cary that I'm in love with the amp.
Peter

I used Mullard GZ37's with very favourable results.