W9TR - Sorry, I don't have a scope to measure that. However, I always solder a 47uf electrolytic + a 0.1uf MKP directly across the power pins of the op amp (with the exception of the Burson). This gives an additional mid punch as well as high frequency stabilization. I believe this also helps reduce oscillation from the +/- voltage rails.
Soundmig - if you have a very high resolution system you can view this on, Tyco Dog has posted many videos with tube rolling on the Shiit Freya. I can hear subtle differences between the tubes on my ultra high-resolution computer audio system, but odds are that you may not. The stock tubes that come with Freya aren't that great, in my opinion. Here's the two most important, in my opinion:
https://www.youtube.com/watch?v=z-kQaCdjylc
https://www.youtube.com/watch?v=NtL4jIEgfSc&t=200s
On the first video, the Electro-Harmonix tubes clearly are the fastest and highest resolution. They are actually faster with quicker attack and detail than the stock "JFET solid state mode" of the Freya! The Electro-Harmonix could actually come across as thin sounding on some systems (if you have an amp that is very fast and resolving, such as Bryston).
The Amperex 6SN7 tubes do not have the resolution of the Electro (and I have told many people this), but I just get chills whenever the Amperex comes on. It's very engaging and has a real "analog" sound to it. Many people have posted that Amperex is a magic tube. However, they are very hard to find (if you find a "real" NOS Amperex tube) and are VERY expensive.
On the second video, it's difficult for me to tell, but I think the PSVANE CV181-1 may be close to the fast resolution of the Electro-Harmonix, but I think PSVANE has more body (without the thinness) and will "sing" better. They are definitely expensive. The Shuguang "Treasure" seems nice, but it is darker sounding with rolled off highs. I think PSVANE is probably the best current manufacturer of preamp type tubes today.
They appear to have several "6SN7" type variants:
http://psvanetube.com/wordpress/purc...sn7-aka-cv181/
Don't take my statements as gospel. They are just my impressions by listening. But these are definitely tube-rolling ideas for the Freya (which is basically the same as op amp rolling).