Ok so I need to confess I swapped out the Mundorf SIO, I had listened to them long enough to know their signature in the Mainline is not for me they are super sounding caps and I am sure there signature would appeal to many. The 2.7uf worked well enough with the HD800 for me to consider the experiment worthwhile. But here's the thing after listening to them for a couple of days enough was enough and they just had to come out there was no way I could last a week!
So it was in with the Jupiter 3.3uf HT Bees wax, I left them running for a hour or so and then put the cans on for a listen and just grinned
there is absolutely no doubt to my mind they are just insanely good and in a different league to the Mundorf SIO which just don't sound anywhere near as natural to me. There are differences between the 3.3uf Jupiters and the 10uf Teflons but they are for the most part subtle each has its strong points the Teflon sounding super clean and are incredibly resolving. The Jupiters are more intimate with a softer and richer midrange that's just so inviting with the HD800's! Both caps apart from these subtle differences sound quiet similar and both have a beautifully natural sound thats beguiling in the Mainline. Probably I would stick to the 10uf if running a variety of cans to be on the safe side but if using higher impedance cans like the HD800 or Beyer T1 then running with a lower uf value boutique cap is definitely a option worth considering.