Quicksilver MidMono Owners & Past Owners

The sweet spot and beautiful music from the Mid Monos is the Tesla EL34s, as Mike already recommends. MIke and I talked about it a while back, and those amps were originally designed by him for those EL34s, circuit, plate voltage and all.  

My buddy runs the Mid Monos with nice EL34 magic, for warm, emotional, holographic mids, more of the vintage tube sound. Just gotta love it.  I run QS Mono 120s, specifically designed for KT120 / KT150s with higher plate voltage - and we compare. Each of us run similar efficiency speakers yet different sized rooms which matters too - along with the type of sound and control you are looking for from your particular speakers. Is more woofer control desired or high volume?

The later model mid-monos do support up to KT120 and KT150s too.  Check your original owners manual if you have it on hand. If you are not sure and it's a much older Mid Mono version, Mike can tell you if the transformers will hang and not get too hot. Give him the serial #, for those amps, i.e. are they older screw-speaker terminals -or- the later generation brass-bannana speaker binding posts - ?

KT88s will give you more neutral presentation, still musical, yet bigger and cleaner sound, with more refinement yet you'll lose some of that more forward EL34 midrange magic, tone, voicing. You'll notice how I keep mentioning this part.  

KT120s will have a little more deep bass grip and slam with authority on the woofer drivers, however you are leaning into the more analytical and neutral sound. Again further away from the EL34 magic in those particular amps. I believe the later model MMs are 475 plate voltage optmized for those EL34s, and not the upper 650v plate voltage like Mono 120s have, optmized for the bigger KT 120/150 tubes. What I've concluded about the QS amps and my formers is runing the tubes in their optimimum operating window. Mike really knows how his amps run each power tube.

If it were me and I wanted a slight change, and extra set of power tubes for the Mid-Monos, I'd opt for the new re-issue Gold Lyon KT77s as I'm more of a huge fan of that EL34 sound. KT77s are kinda like a bigger EL34 and retain a lot of that EL34 magic. Like others here, you might just end up swapping back to EL34s too, fwiw. 

The last point is your speakers - what brand/model, ohms/impedance, db sensitivity at 1w/1m?  And, what are you looking to try or change about the sound, if you can share more? This added info might help to steer you in a different direction, if that's what you truly want to change or to try something different from Telsla EL34s.  

Thanks everyone for your responses.

@hilde45 I didn’t know QAS existed so will I be scouring thru the posts for some useable info.

@oddiofyl I have a feeling I’ll also end up back with the EL34s.  Coincidentally I have a Tool Shed amp and preamp in my other system.  Matt does great work and you can’t beat the WE 300Bs.

@mark200mph stay tuned and check out the FB site.

@decooney really good info here.  Mike was pretty adamant about the NOS Teslas when we talked several years ago – I have 2 sets.  Has your buddy ever tried 6550s?  I had a Cary SLA 70 Sig many years ago and I ran it mostly with Mullard EL34s but when I wanted a bit more bass grip I’d swap in 6550s.  The Cary was driving Klipsch Belles.  I still have the Mullards but the 6550s went with the amp when I sold it.  I don’t see anyone mentioning 6550s.

Regarding speakers, I have 2 systems that I can switch between.  The MidMonos are currently in my smaller room driving Omega Super Alnico Monitors, which are 8ohms and 95dba efficient.  This is where I listen to vinyl and is a very sweet-sounding setup (my profile has details).  In my larger room I run Volti Rivals which are 6ohms and 100dba.  The MidMonos are heavenly with the Rival’s wooden midrange horn.  I’d prefer to keep the monos in the bigger room but I need more output on phono than the Tool Shed amp (8wpc) provides.  The extra 6+db really makes a difference in the sound quality and presence of my analog rig.

To @whiteknee - while I cannot speak to the Toolshed amp, I've owned several Cary and DH Inspire amps, EL34s, KT88s, and KT150s mostly. They are different amps from the QS mid-monos, which should have more grip than the PP SLA70, imo.  I'm not a huge 6550 tube fan person but they do sound different in different amps, most of what I've heard with them is a more "glassy" sound, and I'd probably take really good EL34s or KT77s over them in the Mid Monos. However, that's just my opinion and I've not heard your amps on the Omegas, yet a friend owned the Omega Super Alnico Monitors, and tried so many different tubes with 4 different Dennis Had Inspire amps with his Alnico Omegas. He liked 6L6s a lot with his horn speakers, and he's the guy that originally got me and a few others to try KT77s.

Hard to say really without hearing your setup, room, amp/speakers. What tube characteristic do you want more or less of, etc.   I can understand why you might want to try different tubes with those amps and your speakers.  Seriously, I'd contact Mike. He uses big Klipsch to develop those amps. Ask him what the 2nd-next tube to try in your Mid-Monos might be and tell him about your speakers, send a pic, he can help give secondary ideas.  I'll be curious if he just says to stick with your Tesla EL34s, LOL :) 

 I have a twenty year old pair of QS Mini Mite monoblocks with EL34 output tubes that I've owned from new. I think cost wise  that the EL34 is the best sounding tube for this as well as the mid mono amplifier. 

Mike also told me he voiced the Mid Mono amps for EL34.   That's what I have in now and will probably keep.  

My amps are the second version with binding posts and the power and output transformers are the same size.  He said do not use KT90.  Apparently not all kt90 are the same and that amp can't handl3 them.  

I liked the EH green label EL34 that I bought the amp used with.   The JJ EL34 have meat on the bones , warmer better bass.  The EH had more mid and upper energy.