KT88 recom. for quicksilver mini mono's

Jax2, Got to wonder what you mean by "tubey 6550 approach"? In compared to KT90's yes, but in comparison to KT88's? I would think the KT88's, at least the ones I have heard, have all sounded warmer, more sparkly, and less linear than 6550's. Did you have something specific in mind?

Tvad, FWIW, in three different amps, each of the 6550's and KT88's (both SED's) had the same sonic signature, albeit the overall sonic preference was different because of the design of the amps (Cary, Sonic Frontiers, & Primaluna). The KT88's had a warm(er)upper bass, and bright(er) in the upper mids. The KT88's seemed a bit more extended and had an overall tone much more (to me) reminescent of 'tubey sound'. The 6550 has a slightly rolled top end, neutral mids, and deep powerful bass without upper bass emphasis. The sonic's of the 6550 reminds me of the KT90 except for the roll off, and maybe a bit more power from the KT90 in the bass.

My observations about the overall nature of tube types seem consistent (to me anyway) with comments I have heard from others. Obviously different brands of each type will sound different and the application (to amp) is critical. FWIW I bought the Cary mono's with KT88's - the bass was big dense thumps, I replaced these with 6550's and the bass became clean, impactful, and linear. To compensate for the soft uppers, I put some compensating tubes in the driver position in the amp as well as in the source(s) used with the 2 amps in which I use the 6550's. Now, with one amp (SF) the KT88's provide a perfect couple with a Wadia CDP driven direct. I've never liked 6550's in that amp - just too cool for me.

JMHO, I'm sure everyone has their own valid opinion.

Marco, Mesa Baron Tri Tube mod was 6L6, EL 34, and ?. I was under the impression that it limited to KT types, not 6550's.

I thought the tri tube mod in the Mesa Baron was 6l6's, EL34's and KT88's. I was not aware that it would also take 6550's. I never made the conversion on my Baron (I just stuffed it into a box into my attic where its gathering dust) to the tri-tube - a little birdy at Mesa talked me out of it - so I can't be absolutely sure. I googled this out of curiosity and found no authoritive comments contrary to my belief's.

Could you perhaps have been given a demo of the difference between the KT88 and EL34's? That would be my WAG based on your description of the sound.