Tube for MHDT Labs Paradisea+ DAC


I recently purchased this DAC from a fellow AG’er. Seller was not sure of the hours on the tube, a single GE5670 tube in the buffer stage.  I wish to purchase a replacement tube however not sure what to purchase. Any suggestions?

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Still have my Paradisea+ as backup for my Lampy. I have tried most of the contenders in mine including the WE396 and the absolutely best tube is the Bendix 6385. Be warned the Bendix is rare, quite expensive and might not be worth the effort.
I want to thank everyone for the comments. After listening to the Paradisea for a couple days I agree that, while lacking the last word on detail, it truly is enjoyable to listen to. Since I am dealing with a single tube, I think it would be fun to try several. Based on what I have been provided here I will look for a WE 396 and the Bendix 2C51 for contrast to the 5670 I currently have. 

On another note, what do users of MHDT think of the USB implementation? Have any tried a USB/SPDIF converter with one? I use Mac with Pure Music and CDs ripped to AIFF.