I geek out on transformers!
Here's a photo of a Rocker 30 with stock MM transformers. Also the first ones came stock with 6Ca7's instead of EL34's, which is a great sound if you ever want to experiment.
Not sure what was in between the MM's and Demeters, I've only ever seen the two. I'm think I heard Ade Emsley say they switched brands simply because it was cheaper and more convenient to get them made in the UK vs the MM's which are made in the US which does make sense. Patrick at MM says it's because Orange decided to go cheap
I'm not sure what testing the Demeters go through, they're pretty robust considering the abuse I've put them through and I haven't heard of any going bad.
I've personally exchanged emails with Patrick Selfridge at Mercury inquiring about R30/RV50 transformers and he says their transformers are spec'd and tested to handle 50% more wattage than the what the model suggests. Having bought some MM transformers from Patrick for the Rocker 30 I can say they do look to be better quality, have heavier gauge wire on the OT as well, around 16-18g on MM, and something like 22g on Demeters. But as far as performance I can say that the Demeters are really good. I noticed a smoother sound with the MM's, but I ended up using the Rockerverb 50 OT so it was bigger than the Rockers 30 watt OT.
Some of his replies:
"Hi Jon,
Those were designed for the original Rockerverb 50's, and we were the
original supplier before they decided to go cheap.
Thanks!
Patrick "
"Hi Jon,
Thank you for choosing Mercury!
Yes, the OR-CH is the one.
As for the OT, do we need to match the existing mounting footprint?
If so, let me know the center hole to center hole measurement of the mounting screw holes. I want to see if they are using the same smaller 30 OT or the 50 watt size.
Thanks!
Patrick"
"All of our outputs are rated for 50% over spec wattage, so our 30 watt OT would easily do 55 watts if that is what your power supply gave it. All dependent on power supply.
Let me know.
Thanks!
Patrick"