The VT25 amp and the 2A3 amps have very similar schematics. Both have been widely circulated on the web, so I think it's OK to share them here. One interesting difference is that the VT25 uses a bit of local feedback between the output tube and the driver. The 6SN7 driver doesn't have a lot of current going through it, so perhaps that local feedback is why I liked the sound of the VT25 amp a bit better. The 6SN7 driver on it's own can have a hard time controlling the grid of the output tube. The SV300BTE, which I also liked, uses a 6V6 driving a 300B through an interstage transformer, so there's plenty of "oomph" there. That was a very nice sounding amp, but it was also significantly more expensive.Years ago a friend loaned a Sun Audio VT25 amp from the mid 2000s. It sounded nice and the output transformers looked good on the scope too! I hope they are still using Tamura OEM OPTs.