Single ended = large images?

I guess I don't understand how images can be considered too large. Are you saying images were larger than normal size humans, anything up to human size would not be unnatural to my mind.

Perhaps images seem excessively large due to sound wave interactions with room boundaries muddying up images. I've found judicious room treatment with differing combinations of absorption and diffusion does wonders for imaging.

My room is 13' x 30' , length extends into open kitchen which makes actual L even greater. I run speakers on short wall which means they fire down L. I've used and continue to use 845 and 300B SET amps, along with DHT preamp, this with extremely modified Klipschorns. Also have two Rel subs (crossed over at 32hz) which integrate with Khorns magnificently. I have near human size images that remain distinct within a large sound stage. Images sound extremely  natural to me in that they don't have sharply defined outlines, rather they decay and interact with other images very much like unamplified performers on a live stage. I did purchase a Pass XP-22 pre last year, image outlines more sharply defined which I didn't appreciate, one of the reasons I sold it.

In any case with 89db efficiency speakers you'll likely need 845 amp to adequately run them, and then you have to think about impedance slope, steep slopes require a lot from amp.I used to run 90db Merlin VSM with 845 amps, no issues as they had easy impedance load.

Many years ago I ran Cary SLM-100 push pull monoblocks, Dennis liked those leaky Jensen coupling capacitors, very warm relaxed caps. I remember experimenting with various Mundorf and VH Audio caps. In any case I don't recall any imaging or sound stage issues with these.

I don't doubt you can alter imaging to some extent with the feedback dial,  but this may open up a whole other can of worms. Tonality or tonal balance can be tricky when changing feedback.

To reiterate I don't see any alternative to 845 SET in your situation. You could try a variety of DHT tubes run in parallel or push pull mode for more power, another thread running at the moment discussing these. It seems you've had a good taste of SET, like it, so I'd suggest sticking with DHT tubes. I ran push pull amps with 6550, EL34, KT family tubes for years, I evolved such that for me DHT is the end of journey. Per usual amp/speaker integration key, those Cary's may have been just right for you with the proper match of speaker. As for specific 845 amp recommendations I've owned Art Audio Carissa Signatures, present is Coincident, very similar sound qualities. The exact 845 tube chosen has a relatively large bearing on sound as well, the Cary's may have had one of the warmer tube offerings.

@montaldo fwiw, I came from four different Cary amps [triode/ultralinear) and did the whole DH Inspire Hot Rod Triode thing for a while too. I mention this because I see you run QS V4s with KT150s. My current amps [now upgraded] are the QS M120s originally designed for KT150s, now running KT120s. Thankfully. I evaluated and changed the triode input/driver tubes first, and then upgraded the QS amps to the exact same Mundorf Coupling Silver-Gold EVO caps I ran in the former Cary amps. Bing! Personally, I don’t care for the coupling caps or the main power capacitors in the signal path that Mike runs in the larger QS amps. Spending up here for really good ones here helps, notably. Others will confirm this who’ve done it. Several others here have made similar changes [particuarly those with speakers less than 93db]. FYI, he uses big efficient horn speakers for his design work btw, and possibly those silver cables too, hmmm. This might be the cap gap debate with different use-cases and speakers like yours and mine with lower sensitivity and efficiency. With these upgrade/changes, I now like my QS amps better than any of my prior Cary or DH Inspire triode amps prior. The sound stage, depth, height and focus is just right. Not overly large or ehco extended, nor anything like that. Not at all. Sits in front and spaced apart accordingly and stage depth now where it needs to be imo. I know what you are talking about btw. This is something I was looking for too fwiw.

Wanna try something else instead? - Find a good local tech, get those V4s upgraded and you might be surprised. Some members here emailed me back doing the same - reporting amazing results too fwiw. My KT150s are stored btw, the KT120s are really nice after the caps get swapped out and some good interconnects used. Take it all with a grain of salt I guess. Best of luck.

Thanks guys!

sns: My two large I'm really talking more about instruments. 4 ft violin, 12 ft wide piano etc. it just doesn't ring true to my brain... Like my head is one foot from the violin or something. Let's be clear I don't have this kind of problem right now. The imaging is pretty perfect in my room with my quicksilvers. 

Decooney: thanks for the great thoughts about quicksilvers. Yeah my v4s had the caps replaced with mundorf before I got them. I'm struggling to remember which mundorf they are. It has occurred to me to upgrade to Jupiter copper and wax, or deulend, etc. But I have not tried KT 120's nor have I ever even heard them! Any specific thoughts on sonic differences between the KT150 and the KT120 in your quickies? I do like the dynamics I have and I hate to lose any of that.

The truth is I'm very happy with the sound of my system right now, but just wondering what's out there that I might be missing such as the set magic. YOU KNOW HOW THIS SICKNESS IS. Maybe what I should do is think about more amp upgrades and cable upgrades, and not go down the set road. If the big upfront images are just endemic to SET, I probably should save myself the brain damage. 

Decooney are there other upgrades to the Quicksilver amps besides the main caps? Would love to hear about anything. Interesting that you came from SET to Quicksilver.

I've never experienced instruments out of proportion to humans on any SET amp I've owned or heard at shows, or in other home systems. Now I do hear a certain sound stage difference between SET and push pull tubes or class a/b ss. SET's have this sense of bringing performers to the listening room, the others I hear myself more transported to the recording venue, no doubt this is a more up front presentation, may not be for everyone. Personally, I like both, wish I could afford and had the space for at least two reference system with these differing presentations.

Yes sns I think the "oversized" feeling and the distance perspective are one and the same. I don't like a forward presentation, and this perceived distance to the performers gives the illusion of size, to me. If all SET amps are forward-sounding, I should probably not go that direction. Does anyone know if a forward sound is just part of the territory, or if some SET amps don't have this?

Decooney: I am pretty sure the caps I have in my v4 amps are Mundorf Supremes.