Rich; organic true balanced amp w good detail $6k

Suggestions welcomed & appreciated- here are the Criteria:

- fully balanced architecture
- rich, organic sound, extended bass, silky highs, but not at the expense of obscuring detail
- No OTL (too many tubes/heat)
- SS (Class A bias) or tubes OK
- 20-200 wpc ok, the lower the better though all things being equal- well built power supply crucial
- stereo amp easier to put on my Sistrum rack, but mono-bock architecture also considered if better performance
- $6k or less used would be ideal, but would consider up to $8k used if there are no world-beating contenders at the $5k-$6k used price point

Preamp is a modded Sonic Frontiers Line 3- extremely neutral, hence the desire for a richer-sounding amp to balance. High efficiency speakers from Coincident- large open concept room (main floor of house). Re: tubes, have used ARC VT-100 MKIII- good- airy w big soundstage, but meatier mids would be better. Also had Wyetech Topaz 20-watt SET, superb, if slightly lean in the mids (and not fully balanced, but shows you how powerful 20 watts can sound with a well-built power supply) For SS, am considering Pass XA.5 series (they now can run balanced from what I understand?); Clayton Audio M-200 (but unfortunately over the price-range).

Thanks in advance for any suggestions- I have an open mind, so bring it on!
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Sutts, you should also consider Ayre amps, fully balanced and lots of power for the low end, yet gorgeous "tubelike" sound. I have owned only the V3 but was extremely impressed with its performance on a no. of different speakers. Now I use the ARC VT100 Mk III but could gladly return to the Ayre if I wanted to eliminate the hassle of retubing and biasing.
Tvad- I am a previous fan of PP triode amps, and would gladly return to that option as well. What are some of the better PP triode amps you have heard? I had a older pair of modded altec 1570B's that were very good...

Sc- there is a local dealer for Ayre- which of their amps would sound the richest in the mids?
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Haven't we established that the Belles and Lamm amps are balanced, or are you discussing fully differentially balanced versus non-differentially balanced? Also, it has not been established whether Belles or Lamm monoblocks are differentially balanced or not.

I'm under the assumption that we are talking fully differential amplifiers, as the OP's first requirement was "fully balanced architecture", which I took as fully differential, not just balanced inputs. AFAIK, Belles and Lamm are not fully differential. The Belles MB-01 does run in Class A bias, which is what Sutts was looking for in SS, but in the Belles literature it only says that the MB-01 accepts fully balanced inputs, this does not mean that the amp itself is fully balanced.

Again, I know that fully balanced does not necessarily mean it will sound better, however, I do understand that if you are running a fully balanced system, it doesn't matter if you break the chain. A fully balanced source and amp won't run fully balanced with a single-ended preamp. Similarly, a fully balanced source and preamp will not deliver a fully balanced signal through a single ended amp.

There are many designs out there that have balanced inputs and outputs that are not fully differential designs. I guess it just comes down to is it a requirement for Sutts, or just a plus. For me, balanced is a requirement, for now. Just as if I go single ended in the future, buying a fully differential design would not be cost effective. Since it does cost more to do a fully differential design well, it would add no benefit if the other components are single ended. Just my $0.02.