I remember that once the TubeDac+ did come with Blackgate N's.
My guess in that the Blackgates are many, many times the cost of the Rubycons making continued use of them prohibitive. Also, for a little while the news was that Blackgate was going to cease production. So changing to another cap that's readily available makes sense, production-wise.
Soundwise, there was a thread over at diyAudio from Peter Daniel, who compared the Blackgate N's vs. the Rubycon ZL and ZA's. Here is the quote from Peter Daniel:
Post #32
After reading this thread I also experimented a bit with Rubycons. On first tries they also seemed to me like a better choice over BGs, but after playing with them closer, it's not always a case. Rubycons sound very open, clean, detailed, but also a bit klinical and in some setups may be too bright.
For instance, Rubycon 100/25 ZL sounds very good as coupling cap at the output of my DAC, and by some people was preferred over BG N I had there. The same cap sounded also very good as direct bypass on the DAC (instead of 47/50 BG N I was using). But both those choices of Rubycons cannot be used at the same time, as the sound is overly bright (so it's either on DAC or as coupling).
But 1000/50 Rubycon ZL sounds completely unleastenable in a GC and Panasonics FC are much better.
In coupling, comparing same values, I preferred ZL over ZA; ZA sounded softer and somewhat less real, more processed, although ZA indeed presents acoustic space better than ZL.
And here a link to the discussion:
http://www.diyaudio.com/forums/showthread.php?postid=574379#post574379So the Rubycons don't necessarily sound badly. To me they really didn't sound musical in that location, however.
BTW, seems that Blackgate is going to continue production, but at increased cost and fewer models:
http://partsconnexion.com/blackgate/future_productionOCT.htmBest,
KT
