845 Tube vs KT90

Warren I received a PM from a member who also said he loved the 845 magic, just wrote a second Pm and said this of the 845 on orch: "positions each section of the orch , can hear individual instrument solos"..."floating harmonics in space" IOW not restricted/confined. He also mentioned he does not like a bloated thick/heavy midrange again we are giving our opinions so whats great sounding to one, may not be too another. My friend here in BR, a Agon member , has the Vandersteens 3's. He loves what they do, to me they are too thick, I feel fatigue. I guess he feels my Thors are too 'thin/sharp/cold", which to me is my ideal speaker.
transfer this to amps, the 845 may suit some perfectly, and I've yet to find out. Of course we have 845 amps all the way from the Ebay chinese offerinfs at $800 intergrated to the big $12K Cayin mono blocks, also the famous and rare Jadis 845 monos.
In the PM J also mentioned that "orch is the acid test of any amp/system". I agree.
In my current system, the JOR (Jadis's smallest offering) is not bringing out all the potential the Thors hold. And if I get the Tyler W2's in the future I need something that will A) meet the demands of the Seas drivers/bring out the potential B) deliver orch with the separation of each section, fine lines/sharp/details. Which is the character of the KT90. I'm willing to give up some of these qualities to the 845 in exchange for "floating harmincs" "the 845 magic".
I'm not far from Houston, maybe there are audio dealers there with the 845 amp.

I can't comment on the KT90 tubes, but I do have some experience with 845 tubes in different set-ups, and I think it could be of help.
A while ago I borrowed a well-designed and well-built pair of 845 SET monoblocks from a befriended dealer. It had 300B's with anode choke as driver, and a 6SN7 first stage. On his own speakers they performed well. On my ESL57's they gave a very flat soundstage, same as you describe. Even the general direction of the instruments was very vague. The instrumental timbres were not natural; everything sounded alike.
Earlier I had borrowed a 300B SET (again with 6SN7 as first stage), and that gave the same results.
But: I have also listened to 845 push-pull monoblocks (Mingda MC300845-AB) on my speakers for a few hours. Apart from being a push-pull amp, the tube line-up was very much the same as the 845 SET's: Anode choked 300B as drivers, first stage with 6SN7, and no global feedback. The result was fantastic, with good depth and placement, and a very good rendering of the instrumental timbre. The most lively and involving sound quality I have experienced so far, while the other amps with exactly the same tubes were the biggest disappointments I ever had.
The only reason I didn' buy them is that I can't stand the sight, especially with their protection cages. Every now and then I still think of buying them and have something different made.

Same as other people have commented: It's not just the type of tube that means success or failure. I do have some idea what it is that makes the difference with my speakers. ESL57's are a reactive load, so the amps needs to be able to deliver a good peak current. That makes SET's not very good candidates, because they are low-powered amplifiers with a relatively high output impedance. The push-pull 845 amp had 70 Watts, so could still deliver enough peak current despite its high output impedance. My own Fisher SA16 (EL84 push-pull) has low power but with a very low output impedance, which also makes it work well. Until it runs out of steam in really big orchestra pieces, that is...
I can't really explain how this translates into things like soundstage, so it's not a proven fact but an idea that seems to make sense. And, I am not familiar with your speakers so perhaps your experiences will be different if you would try an 845 PP amp. Don't jump to conclusions just because I had a good experience with these.

The best thing is to listen to as many different types of amps as you can on your own speakers. I hope you have a few friendly dealers near you. Learn what works well or not: SET's, push pull, OTL, high or low power, whatever. And trying to get an idea what makes the difference can help you find your way through the wilderness.
I take my speakers to the dealer if he won't give anything on trial, which is not very practical with ESL's but well worth it in the end.

Bartokfan,

I think you are trying to use the wrong tool for the wrong job in your amp search. The vast majority of 88dB speakers are not intended to be used with SET amps. It's no wonder 300B amps sounded flat.

To build on Audiofeil's analogy, that's like bring a Yugo to a tractor pull.

Before asking for suggestions you really should find out(or tell us) the impedence curve of your MTM Thors. 88dB by itself is not that difficult to drive, but are they 4 or 8 ohms? Do they dip to 2 ohms at some frequencies? It's going to be the dips that cause all the problems.

Also, what is your price range?

Personally, I don't think SET amps can truly handle dynamic peaks of large orchestral at medium-high volumes unless you are using 100dB+ speakers. I've got 95-97dB speakers and that is a stretch.

If you really have your heart set on 845 SETs, then I'd look at the manufacturers that are famous for high-current/high-output SETs - Dehavilland 845G-SE, Art Audio Concerto($12k), KR Audio (non-845, but high powered).

Be prepared, good high-powered SETs will cost a lot. The output transformers and power supply necessary to handle that kind of current cost a lot of money.

Remember that dynamic peaks with well recorded vinyl can be 14-20dB higher than the average listening level. So, if you normally listen at 85dB, you will need 32wpc without clipping to handle 106dB peaks effortlessly. Which will likely be a 50-60wpc, at the least, to stay in it's lowest distortion range. Good classical cd recordings can bee even more demanding.

My personal opinion is that in the high-powered category, really well implemented push-pull is just as good SET, maybe even better. It's definitely cheaper to with PP to get an equal level of performance. And you'll have a lot more choices.

Why not check out ASL Hurricanes (200Wpc, KT-88), Art Audio Concerto or Opus Ten(KT-90 or 88), Cary SLA-80(KT-88).

Aren, Dark, thanks for helpful imput.
Both of you raise my awareness of what the 845 SET (most are low powered, thus higher sensitivity speakers are best option) are alla about. Aren you mention the Ming Da, is that the ones that weigh in at 375 lbs!!! I saw a pair for sale here last month, a sweet deal at $3500. But alas too heavy for my back to move around. Besides they are rather large and not all that attractive. They were 80 watt push/pull. I also heard a big Audio research + ARC pre on Magnapans at a dealer in New Orleans months ago, they sucked the amp dry with no dynamics on orch. I hearda Conrad Johnson on Martin logans once and sucked dry with orch. The cayin 300/Silverline Sonata combo could not bring any life to orch. For light jazz/vocal the 300/Silverline was UNREAL, liquid and sur-realistic.

I do not know all the specs on the Thor/Seas, just know they are not the ideal speaker for tubes. Jadis' famous high power trans deliver the power for orch presentation from the Thors.
I'll share alittle story(yet again) on the ability of the JOR's power for its size. I first got it in and a friend asked to bring it over and hear it on his Mirage 1's, beast ofa spaeker for tubes, close to the level of demand as the Vandy 3's. We unhooked his massive Audio Research VT200 and ARC pre and to his surprised delivered some slam , but even better details than his ARC setup. But obviously the JOR would blow with continued use.
Anyway based on the above comments, I may just stick to what I know I like best, which the KT90 does overall. Budget? yea that is up in a ?. If the yr goes as i hope, a used JA80/KT90's may be my best option for the music i listen to. as in all things audio, compromise. Dark may a good point " really well implimented push/pull is just as good as SET's maybe even better"
Appreciate all the imput, sets my course straight.

I've owned both JA-30's and JA-80's (numerous NOS KT-88's, EL-34's and KT-90's) when I had Crosby Modified Quads and they were great sounding amps. Yes the music and picking speaking to fit that music are the two most important things to do. I switched in the nineties to Wilson's and two Audio Note Ankoru's (PSE, two 845's for output and a 300B for voltage driver for each mono amp). Miss the quads at certain moments, but the Wilson's with 845's fit my taste much better all around than anything I could do with the JA-80 with any KT-88 or KT-90 tube type. The 845's are my choice for amps now. Perhaps looking at Wytech's products might produce music magic at a sensible price. Speakers must be >91dB sensitivity or better. Take a look at Coincident Speaker Tech for a speaker you might like with your tube choices.

http://www.coincidentspeaker.com/