I think a little shot of history might be in order. Let’s look at resistors for a glimpse into Jim Thiel’s working ethos. Of huge importance to Jim was that of balanced design. He worked toward a performance plateau where all elements worked equally hard and efficiently to perform at maximum cost efficiency as a whole system. Let’s look at resistors as an example.
In 1977 we were struggling with the 03 - EVERYTHING was audible with phase coherence, and we wanted to upgrade all components; but we also wanted to keep our focus on cost effectiveness. Jim "built" some reverse-wound resistors from OFHP aerospace copper coil wire. Obvious improvement. Judged unaffordable. Audio grade resistors either didn’t exist or we didn’t know about them. Jim went to work with (what later became) ERSE and developed the present Thiel resistors. They are not "dime store resistors" although they look like them. They are actually made from good wire with reverse winding for a low inductance load, set into a ceramic tub for greater dissipation than a cylindrical case. It costs a fraction of the Mills and performs quite respectably. Balanced design.
That was Jim’s approach. How do we get most of what we want and pay a fraction of the cost. He was proud of those resistors; the early versions said "Thiel" on the case. You can buy that design from ERSE. They outperform normal sand-cast dime store resistors by a long shot.
That said, the Mills MRA-12s are better. BTW: the ones that Jeff Glowacki at Sonic Craft sells are the best. (Not just salesmanship.) I would replace the Thiel / ERSE resistors as low-hanging upgrade fruit. BUT there is a BUT. The MRA case is quite a bit smaller for a lower dissipation factor. So put the MRAs on little balls of Mortite or BluTac for 360° radiation and airflow. A happy coincidence is that the residual inductance of Thiel/ERSE vs MRA is nearly identical, so you don’t have to compensate as you would if going from a normal sand-cast to the MRA.
This crossover circuitry is extremely subtle and carefully tuned to include all elements. So swapping one form for another is not simple. I am venturing into the mire, and learn every day how little I know of the finer subtleties of the art. Be careful.
