JAM by Duelund

Jupiter is far from thin sounding as an FYI. It is lush, sweet, and has full bodied tone. Still my favorite! Better bass than Duelund in electronics also. That has been my experience. 

How much time does take burn-in of Jupiter?
Do they sound bad during burn-in like Duelund RS do?

Yes these well damped, large and dense caps all take a good 300-500 hours to fully burn in. They will sound good after 100 or so and just continue to open up a get better. The larger the cap value the longer....closer to 500 hours. Many don’t wait long enough and change things far too early. They will sound good right away and up to 50 hours. At 50 hours or so things go worse unexpectedly. Yes, frustrating but true. However at 100 hours or so they start sounding good again and just keep getting better with time. This has been my experience and trust me when I say I have been through this cycle many, many times and know from experience.

I wish this were were not true as some think. However, it is the case and real on these caps.

I did burn in speed up for 4uF Duelund RS using Frybaby2 cable burner.
It helps. But in any case, it needs some number of hours of natural burn-in after a harsh Frybaby2 burn-in.

I received Jupiter capacitors and start running them in Frybaby2.
I think 3 days of a fast burn-in will be enough.