Cary Audio SLP-5 Preamp Tube Replacement.

@immatthewj I have the LinLai E-6SN7 tubes in all 6 sockets since I used the SLP-05 balanced.  I don't use headphones so I have cheap throw away tubes in the other two sockets.  It has never been clear to me if you could leave those sockets empty or not.

I have only used the E-6SN7 tubes.  I have no experience with any of LinLai's cheaper tubes but I have tried different 300B tubes from them and generally I think you get what you pay for when you move up their product line.  I only buy from Aliexpress and don't think the premium from Viva or the other US vendors is worth anything despite their claims otherwise.  

The Linlai E-6SN7's were my tube of choice in the SLP-05.  As @immatthewj noted you only need 4 of them if you aren't running balanced.  My SLP-05 sounded a bit better with balanced ins and outs but not as good with mixed inputs but your experience might be different.  I just bought my E-6SN7's off Aliexpress.  No need to pay extra for the nonsense Premium Vacuum Tubes spouts to justify more than doubling the price.

@couger4u The Linlai E-6SN7 tubes fit fine in the SLP-05.  I tried a variety of NOS and new production tubes and I liked the LinLai tubes the best.  They are very transparent and neutral with excellent top and bottom end extension.  I think they excel at soundstage.  If you are looking for a tube that provides some sort of boost, either to the top or bottom end I don't think they do that, they are very uncolored but just sound very good.  I have dozens of pairs of 6SN7 tubes and the LinLai's have become my tube of choice.