VTL Tetrode/Triode

I think where we are seeing things different is in the presence part of our descriptions because we both agree that triode provides the most realistic rendering of the music.

For my system and ears the triode mode conveys much more detail and recorded room ambience, more direct palpable presence of the instruments than in tetrode (small group, preferably acoustic based music is forming the basis of this comment). Listening to Keb mo i feel that i could walk around him while listening to triode, not so defined in tetrode. For me tetrode tends to provide the wash of sound that you attribute to triode, though it tends to have more body/fullness, just not as pinned down and accurate..the slightly off clone that you describe.

Seeing that we agree on a number of our observations my guess is that the way our speakers (and rooms) deal with the different modes (and resulting drop in available power in triode) may play a significant part in our differences

What are your speakers/cables? To reiterate, I'm listening through Thiel 2.2's and either Satori or Au24 cable (though these impressions were formed only with the Satori, as I'm still evaluating the newer-to-me Audience cables).

Anyway, I'm not sure I can put a tag on which presentation is 'most realistic' so easily. I think it depends a lot on the recording and type of music. As I said above, in general I find tetrode more realistic in terms of qualities I would call 'physical'. But I think triode is more 'accurate' in its tonal and harmonic presentation. I've had some recent success in transforming the tetrode tonal balance more to my liking by both changing input tubes (the previous ones had become microphonic, and were brighter) and by placing tube dampers on them. However, I'm not quite done sorting this all out yet, because I've also gone from Svet 6550C's to EH KT-88's, and on top of that I haven't yet carefully evaluated again the tetrode/triode question with all the new tubes in place. Not to mention that I'm auditioning these speaker cables, which sound perhaps more transiently accurate but less warm than my reference, and I also just had a tweeter and crossover resistor replaced and that speaker is still breaking back in...it never ends :-)

Anyway, yes, my physical impressions are pretty much the opposite of what you describe in your second paragraph above, so apparently our 'clones' are 'slightly off' in different ways. Where you say triode gives you more detail, room ambience, palpability, walk-around transparency, and is more pinned-down in space, I feel tetrode does all those things better, with triode being the mode giving more body/fullness (if less extension and tautness). It's enough to make me wonder if our mode switches are wired-up the same way or if one's reversed! But I guess I envy anybody who's come to the comfortable conclusion that one mode is usually best for them...at some point here I'll revisit this question with the new tubes and post my findings.

I'm using Dunlavy Athenas, a VTL 5.5 pre, ARC CD-2 with harmonic tech pro silways between the CD and the pre and truth links from the pre to the amps (i needed 22 ft so budget had to fit in there somewhere).

I re-read your original post and noted where your switch had to be reinstalled...Putting it in 180 out could be the reason our interpretations are opposite.

As to the conclusion which is best it depends on the music, my mood and whether i have the ambition to get off the couch and monkey with the switch. If i had to live with only one it would be tetrode though...got to have that power when the application calls for it.

I was kidding about the switches being reversed - that's pretty unlikely with two monoblocks, and besides you can't mistake which mode has less power. Last night I did my first listening tests between the two modes with the KT-88's installed. I'm not ready yet to report with certainty, but preliminary results suggest that my impressions will be different with these tubes...

Zaikesman:

I'd be curious to get your report on the KT-88 tubes vs. the 6550s. I called VTL a couple months ago and they advised against any tube-rolling (at least for my amp). So long.