Solid state amplifiers and sound stage, especially front to back "depth"

@yogiboy
Many moons ago a had a Sansui TU-919 tuner. It was one of the best tuners that I’ve owned!

Cool. I was a big Sansui amp and tuner fan too, had the AU/TU717 decades ago, held on to my TU-9900 FM tuner ’til a year ago. Replaced it with a modded MD-102 Magnum Dynalab FM Tuner years back. Listening with a 6SN7 triode tube preamp and dual mono KT150 tube amps with dual triode input section right now. With OCC interconnects the sound stage is at or just behind the front wall and to the sides of me in 3D. And crazy thing is, it’s just FM and some times I prefer it over streaming - believe it or not! Makes it difficult to want to listen to alternate DACS or Amps any more. Smacking hand, saying "just leave it the hell alone and don’t mess with it any more", sounds fantastic :)

The term "voicing" tends to carry over more from Guitar amp designers and modders looking for particular tones, overtones, and/or feedback designed into the circuit looking to achieve a particular sound result.

With professional and home audio, it seems many audio engineers focus primarily on specs and limiting distortion alone. Some others, changing component values, adding components, removing components, adding gain stages, or even adding complete circuits like negative feedback working to achieve a particular sound.  Agree or not, likely adding distortion in what they deem as "in the right places", also loosely referred to by some as voicing, fwiw. Results and opinions vary of course.    

A set-tube audio buddy likes to say, "at the end of the day, it's just your stereo", I'll add, call it whatever you want, you are the one listening to it. 

  

My 1993 B&K EX442 Sonata (350 wpc/4 ohms) puts me right in the studio whenever I listen to "Kind of Blue". It's pairing with my MMGs (out 3' from the wall) gives me an excellent soundstage in both width and depth.

@hartf36
Mine broke beyond parts-repair, 50yr tech tried four times to repair it, oh well, sold for parts. For 20+ years I was lucky to own and listen to my former dual mono B&K EX442-0 version of your amp. Your earlier version may have been a little more sweet sounding.   I've shared with @hilde45 how musical and 3D that amp could be [at times].  It was $2,200 retail in 1990 I think it was. The magic would only kick in after the dual mono transformers got really HOT, and that's what killed it inside over time. Frank at AVA says B&K copied his designs, whatever the case, some of the lineup back then sounded really-really nice for the $. Digital, preamp-processors, and Home Theater software is what caused them to fold in the end beyond recovery. Sad.  Had they stuck to simple 2ch audio, they'd still be around I gather. The meaty little SS affordability amps that could, and sounded a bit like tube once they got nice and toasty warm.  :)  

This can be true, and the weakest links in the chain can impact the end-to-end result. Without having different components to easily rotate in/out it can be more challenging to easily identify and where to upgrade next. Unless of course for the lucky ones who can afford to buy their top-4 components of choice and return-ship the other 3 after the are done with evaluating in batches, its another way to save time and cut to the chase faster. 

The OP swapped out his mono tube amps with depth for a solid state (SS) amp without depth. One swap back to validate the cause is not the recording, not the speaker placement, not room treatments.  

@sbank
.."Maybe certain ss amps that struggle with low end frequency performance in other aspects result in the perceived lack of depth?"..

Yes. And, agree some of the solid state amps you suggested don’t struggle with it. Swap in the right Pass or Coda or First Watt and it becomes interesting again. Not all ss amps are created equal as we see here once again. The great amp designers with "good ears folks" around them truly get it. Spec measurement engineers only looking to reduce distortion, not so much. Or, back to the modest mono tube amps and whoop, there it is!

@mahgister
Then it is the amplifier...

case closed...

When paying attention to the details, kinda seems that way doesn't it ;)