I will be buying more of these
"This is the Heyboer 6135 18W output transformer. It is the best sounding 18W OT for an 8k primary and 4/8/16 secondary in my opinion. If you want to listen to soundclip comparisons of output transformers there are several online (obviously this is not the same as trying them yourself in your own build, but it's something to start with and free), including one by Granger Amps on the Classictone site and another on the Mercury Magnetics site. Not all of these comparisons feature this particular 18W OT but it's a good starting point to hear Heyboers vs. other brands. Mine sounds fantastic in an 18W build with EL84s, with 6094s and with 6973s in the output tube sockets. I use the 8 Ohm tap into an 8 Ohm Jensen P12R for my Denim Deluxe 1x12 combo. The 16 Ohm tap would be slightly louder with a 16 Ohm speaker. Many people like the Celestion G12M or G12H ceramic speakers in these builds but I prefer the Alnico voice a little more; just a personal preference and this Heyboer transformer is perfect for either speaker type. I will be buying more of these. Mojo has the best pricing I could find for these, too."