Hello Gents.
I'd spent over a year with the Tranquility Signature USB Dac. No doubt It was a very special Dac that, in my experience, bested a lot of more expensive Dacs. I've since moved on.
I'm now using the Ultra Fi Dac-41 which is designed by Larry Moore who also engineered and designed the Tranquility series for db Audio labs. To my ears the Dac-41 is a significant advancement for NOS Dacs and pretty much trounces the T Sig. If you've got $1295.00 put aside for a Dac upgrade, you ought to see if you can get your hands on one of these. For the sake of RSAD, I could use about any Dac I want up to around $5-6k but until I hear something better that's also a good value, I'm done.
For the T Sig. owners who'd like to stay with waht they have but would like to upgrade w/o spending too much $$$, Larry Moore at Ultra Fi can upgrade the T and T Sig by modifying the PSU and adding his Twin Reg circuit board. I've not heard it but I've come to trust Moore's work and I also know a few who have and like it a lot.
Hope my 2 cents is helpful.
Robert
RSAD
(Discalimer: While I'm not affiliated with db Audio Labs or Ultra Fi, I have become pretty good friends with Larry Moore as a result of mutual admiration for each other's work.)