ST120 with KT88 vs KT120 vs 6550

I'm about to take ownership of a fully upgraded ST120 and coming from a ST70.

I currently run a quad of JJ EL34's and a quad of OS Mullard EL34 XF2's.

So trying to decide on which quad I should use in the ST120. Can someone describe the sound of KT88 vs KT120 vs 6550 in the ST120?

It will come with Sovtek 6550we's, but considering buying the Gold Lion KT88's or Tung Sol KT120's

My VTA ST120 kit came with Sovtek KT88 tubes. I rather quickly changed those to reissue Gold Lion KT88's and I subsequently got a quad of Tung Sol KT120's. I now rotate the Gold Lion's and the Tung Sol's every 6 months or so. The Sovteks were not very good but the Gold Lion's and Tung Sol's are both great and I can't really tell any difference between them. Either should work well for you.

eickmewg wrote:My VTA ST120 kit came with Sovtek KT88 tubes.  I rather quickly changed those to reissue Gold Lion KT88's and I subsequently got a quad of Tung Sol KT120's. I now rotate the Gold Lion's and the Tung Sol's every 6 months or so.  The Sovteks were not very good but the Gold Lion's and Tung Sol's are both great and I can't really tell any difference between them.  Either should work well for you.

Thanks for the feedback. Trying to decide on which ones I'll pick up first.

I built my ST120 March of 2018. I did some reading on tubes and saw a couple mentions that 6550's were all around pretty musical and KT88's were a little less so but had a bit more bass. I ended up getting TungSol 6550's and like them a lot.

I haven't had listening experiences with any others but got a deal on some KT88 EH's. I haven't tried them yet. Before I got the EH's, I was considering some Gold Lion KT88s for way down the road.

I'm sure you know this but the center 12AU7 has a big affect on the sound of the amp.

Hope this helps and doesn't start a war...

Thanks New2tubez for your feedback

Been reading what you said about the center 12au7 making biggest impact. Mine will have a OS RCA clear too but will be researching those as well.

Thanks for the great info Bob and the explanation of the 6550we. I have ST70 now with a couple upgrades but it’s not one of yours. The ST120 I’m getting is one of your fully modded/upgraded version from 1.5yrs ago. Can’t wait

Kray wrote:Thanks for the great info Bob and the explanation of the 6550we. I have ST70 now with a couple upgrades  but it’s not one of yours. The ST120 I’m getting is one of your fully modded/upgraded version from 1.5yrs ago. Can’t wait

I was suspicious? of how the Sovtek 6550WE's would sound, having heard their KT88 years ago. I can say Bob has got it right, I am pleasantly surprised with how nice these sound in my M-125's. I had intended tube rolling them quite quickly, that is not a priority at all now, and my new amps are not yet really 'run in'.