My amp is an Aronov LS-960i. It can run KT-88, 6550, KT-90, EL-34. I am going to be purchasing a set of 4 NOS Tung-Sol 6550 for the amp. Pre section uses 4 12AX7. Pre has a set of 4 NOS Amperex Bugle Boy 12AX7's purchased from Andy at Vintage Tube Services. The 6550's will also come from Vintage Tube.