I posted the below over on the Susvara thread at the request of a user there and then got crickets in response - so reposting here fwiw. Hope it helps somebody.
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Ok so I have done as I promised and conducted A/B comparison for Burson 3xGT with V6 vs V7 Vivid op amps. I replaced all 6 op amps - volume and gain stage. Note that given the nature of the comparison and that I only have 1 3XGT, I made notes while listening rather than rapid back to back A/B. If you want that you’ll need to recruit someone with 2 units and a switch box. I used no EQ.
Chain is Roon (dedicated MacBook server- I recognize this is suboptimal but as it’s what I’ve been using with the V6s I kept it the same for V7s) ->Sonore Optical Rendu-> Yggdrasil OG-> 3XGt 2023 with SpO2 power modules. Tracks are Fruhlingsgefuhle by Melokind, Magnetar by Mark Lettieri, Beldiya by Triplego, Drover by Bill Callahan, Twice by Ludovici Einaudi (Reimagined by Mercan Dede). Susvaras are with OG Stock pads and cables (XLR)
On V6 I hear both good quality (texture) and quantity in the bass, with good attack and just right decay. Bass does not bleed into mids. Mids are quite forward though lower mids a bit less than upper. Treble is good, snappy, not sibliant and well extended. Soundstage was outside the head and instrument separation still good but not pinpoint. Head stage is perceptible about 2-3’ outside the head wider than deep- sometimes there is an echo that extends further into the distance. Detail retrieval is good - on the Melokind track I can hear some details high up in the treble register. Dynamic swings are good but not impressive- little sense of ‘blackground’
With V7 installed, FR is quite similar, but timbre is better- more realistic. Stage size and image precision and separation are all bigger/ better. Stage depth improves with images more widely separated in it. Images are more pinpoint and clearly defined with respect to each other. bass is impactful well textured, but the decay structure is even more believable. There is more ‘blackground’. Dynamic swings are bigger, especially noticeable above 70 dB.
I have to say, HD6XX and Arya were MORE elevated than Sus in all these regards. On HD6XX with V7, dynamic drivers LIT UP the bass - I think the V7s maybe are particularly good for DD headphones, I could feel the drivers moving. On Arya I was also hearing a lot more subtle details high in the treble register and imaging improved a LOT- really across the FR but most noticeably up there.
I did not notice these differences as much with Sus- they are still there but Sus is already so good- it more narrowed the difference between them and the lower tier HPs
Conclusion: The V7s are a worthy upgrade for the 3XGT. They elevate mid-fi HPs VERY MUCH in terms of dynamics and especially staging. For Susvara the improvements are there but more subtle. You can only polish a diamond so much- at least with this tool. A more powerful one may be needed. V6s are already doing a very good job with it.
At the end of the trials I am left still feeling ‘there is more’ for the Susvaras- especially in terms of stage improvements- yet I wonder if I will not have to invest MUCH more to squeeze that out.
Question (tube-amp lovers pls hold back here, I know what you’d do with it
) : where would you go next with the 3XGT and Susvaras?
A) use 3XGT as a pre-amp out into a solid state speaker amp (with the risks and benefits that entails) and attach Sus to the speaker posts via spades or an adapter box vs
B) use the 3XGT “headphone + sub out” feature to add a sub- other Sus users have reported positive experiences ie
@Pashmeister with the KC62
C) Or???