First of all a big thanks to John from Burson Audio for contacting me and sending V5i for free in exchange for my honest opinion.
I am not a reviewer and this my first review, so please bear me with this review.
The installation is very easy and simple.
My headphones are HD6XX, E5000, Kanas Pro and FiiO EM5 paired with XDUOO-XD05 Plus + FiiO M11 Pro
I was not able to find much differences vs the stock OPA1612 initially but as I spent more time with it the differences became more apparent.
The first and easy difference I was able to find is V5i has a touch more volume at all gains which is definitely a big advantage IMO.
I love warm, thick and lush sound so please take my impressions with a grain of salt.
I loved V5i pairing with all my headphones except EM5 which already has in your face kind of presentation and V5i made it worse for me. I did not like the pairing at all, I liked EM5 more with the stock OPA1612.
Lows:
With V5i the bass is fatter but surprisingly more controlled when compared to the stock opamp. With the stock one the bass is a touch tighter but it has less control with bassy songs.
Mids:
Mids is where V5i has it's charm they are more intimate, lush, thicker and liquid. Notes have the weight to them which I like.
Highs:
The highs have a little more sparkle and airy, with the stock opamp the highs can be harsh on some recordings. With v5i you can push the volume to higher levels without getting that harshness or sibilance.
Soundstage:
This is where things get little interesting. The stage definitely less wider compared to the stock one but the depth increased a little. With HD6XX the stage is less wider but at the same time it's more airy and holographic. It's more of a preference thing than which is better IMO.
The overall presentation is much thicker compared to the stock. It's a clear improvement when compared to the stock opamp on certain things.
If you prefer warm, thicker, airy and holographic presentation, it's a must try.