KT88 recom. for quicksilver mini mono's

I once tried some GE 6550 in my VAC amp. Compared the the KT88, the 6550 were rolled off and had looser bass. I would characterize the VAC stock KT88 tubes as sounding more linear in that particular application.

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.

Your observations and mine illustrate that there is no universally applicable observation, which brings me back to my original point that tube amps are generally voiced with a particular type and brand of tube, and it's likely that any other tube used in that amp will not sound as well as the tube that was used to voice the amp.

Did you have something specific in mind?

Yes, my experience rolling one type against the other was in a Mesa Baron (tri-tube) amp. There I found the KT88's to be a bit too hard and clean for my tastes, giving the Baron an almost SS sond to it. I longed for something a bit more warm in comparison. At the suggestion of a few folks (Jon at the Tube Store, and the tech guy at Mesa among them), I tried 6550's instead...I think they were Svets, but it's been a while...maybe in a previous post of mine...anyway, sure enough, in that amp and system, and to my ears, the 6550's sounded warmer and had a wonderful midrange, with a bit of sacrafice to the bass. On that amp the bass compromise was no problem as it is a prodigious performer there. The tubes were Svet's in both cases as I recall. This is over five years ago I think, so details are open to correction, but the overall impression is quite accurate, I'm sure.

Marco

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.