@exophile I have the Petit and have rolled 3 different tube pairs into it. But first, about the stock tubes: They are Slovakian unbranded JJ 12AX7s (at least mine are). The tube coolers come off quite easily. They are secured to the Petit with a red dampening glue/putty (not sure exactly). I simply heated mine up with a hairdryer, and they slid right off. Make sure you slide them off towards the pins. You might just consider leaving them on though because once they are off, they don’t fit snugly back on because the glue/putty gets smeared.

I have rolled Gold Lions, Tung Sols, and NOS RCA short grey plates. All sounded good, but the Gold Lions stood out. In particular, female vocals really stood out and sound incredible, like a curtain was lifted. All three sounded better than the stock tubes. The stock tubes are nice and quiet, and I’m certain EAT screens them for noise because the Petit is VERY sensitive to tube noise. If you decide to roll, make certain you are getting phono-rated noise tested tubes. If you buy from Upscale, that would be Platinum grade or “Kevin’s Stash”. Also, be very careful rolling as the sockets are PCB mounted and plastic.