OK I'm calling a meeting to everybody here, especially @richdytch and anyone else who's recently been intrigued by (or should I say mislead by) mixed quad power setups on the Elise. @mordy you may be interested, and @UntilThen feel free to add anything too. Motivated by the rekindled interest that has sprung up here recently on multi-tube power setups, I thought I'd spend the evening doing some direct A/B comparisons of multi quad power tubes compared with higher caliber single power tubes. Although this is coming from somebody who owns essentially all the flagship power tubes (GEC's, slotted graphite plate Bendix 6080, Mullard 6080, RCA 6080, TS 5998, 421A, etc.), I had done this assessment objectively, without any preconceived notions on which setup type or appearance should sound better - sound is the most important thing in the quest is for audio nirvana. So I dusted off my old 6SN7 to dual 6BL7 adapters from the closet where they have been since earlier this year while I have since moved many, many steps up above them on the audio fidelity latter. I had to swap tubes around a few times to discover my favorite pairing, which was 6BL7 + GE 6SN7 GTA with 'Bad Boy' 6SN7's as drivers (shown below). After three distinct warning signs from the Elise (more below), initial impression was that this sounds quite great, and scales well with my improved upstream gear (DAC components) into the Elise. Tonality and dynamics were OK, but nothing moved me too much. Next up RCA 6080 as powers: Tonality was the same but the RCA 6080's are more vivid, organic, intimate and smooth. Putting back in the former quad powers makes it sound somewhat dry / sterile / non-engaging by comparison. note: the black disks under the tubes are 'socket savers' which aid to prolong the lifespan of the sockets and save the Elise from frying. The "one tube per socket" setups do not need an adapter, but the socket savers are nice. Next up: GEC 6AS7G as powers: A whole new level of realism and enjoyment has opened up. It seems a little difficult to explain the sonic differences between these and the quad setup so I'll explain by analogy. The comparison seems akin to coming out of a dusty, cold humid room where you're sometimes chaffed by sandpaper versus this where you're inside a lofty, luxurious reality and far away from that nasty artificial reality experience of a former life. Next up Tung Sol 5998 as powers: (after having just listened to the multi quad setup again) Gobstoppingly more lifelike and deeper into the scene with realism and truuee-life energy packed to the brim compared to the quad setup. Drums are now real and no more artificial feeling I was getting from the quad setup. Layering / imaging is improved by what seems like a hefty 400% Next, the mixed quad setup of dual 6BL7 + dual EL3N: Sounds very "back row", while retaining all of the negative qualities of the above multi-quad setup which to me were dull, flat, slightly fake, and non-engaging. I also compared the quad setup to my Bendix slotted graphite plate tubes and the sound from the Bendix was much "deeper into the scene", much more vivid, sweet and 3D. To an untrained listener, or even a pro user on a fresh day, those mixed quad power tube setups could sound good - even great. But after comparison to the power tubes which are universally undisputed champions, these really don't hold any water to a proper setup of good power tubes, as the way our expert engineers at Feliks Audio designed it to be used: "one tube per socket". Folks to put it into literal perspective, I received three warning signs from the moment I switched on the Elise with mixed quad power tubes: both a hum on one channel then a channel imbalance which morphed into a rippling distortion sound in one channel until it fully warmed up, and a sound that developed on right channel like rustling of leaves and remained on the Elise even with a complete tube change out to native-class tubes. Dual 6SN7 + dual 6BL7 on Elise: You're doing it wrong, and you're endangering your Elise. Something isn't completely sound electrically with this setup and Elise is trying to tell us so. Invest just $20 or so on RCA 6080's and you'll get a vastly better power tube setup. Myself and at least two others have bought a pair from Langrex in the UK and received them in mint condition, in no time with expert packaging! Here's the link (just email them with your inquiry), you'll thank me later I assure you!!!! While at it, I also gave it a go with miniature power tubes; replacing each of 6SN7 and 6BL7 with one pair of either 12AV7, E80CC and ECC88 via their 6SN7 adapters, to which I got appalling results. Appallingly horrible! Very loud hum in both channels, super low volume, and a very ugly sound after turning off the amp, akin to rustling of dishes in a sink... believe me I would not make up something like that! And now my Elise is off with everything unplugged in hopes that rustling sound in the right channel I hear even with native tubes, will dissipate - one that began only when I inserted in that evil mixed quad contraption. Suffice it to say that as far as I'm concerned, any non-matched types of power tubes should never be used as powers in the Elise - and by that I mean that a possible exception may be had for quad 6BL7-only or quad EL3N-only, rather than mix & match types. For me personally, quad power tubes will never again touch my Elise, with the only exception of quad EL3N.