I have a couple of cables already wired up for that, no transformers.
"Like that" being a cable with a 600 Ω resistor wired across pins 2-3?
In his article in Recording, Paul called it the "Gizmo" but I believe that name has already been used a few hundred times. The value for the resistor in the Gizmo is the value of the resistor that it takes when connected in parallel with the mic preamp's input impedance
, to equal 600 Ω (assuming you're loading an SM57). So if your preamp's input impedance is, for example, 2.5 kΩ, you'd need a 790 Ω resistor in the Gizmo to give you a 600 Ω load on the mic. For a 1.5 kΩ input impedance, you'd need a 1 kΩ resistor. For an input impedance of 30 kΩ - typical of a "ribbon" mic input - you'd need a 612 Ω resistor. Of course "close enough" is usually close enough.
Here's a Handy-Dandy Calculator
for two resistors in parallel.
I do have a KSM 8 and some other dynamics including a Heil PR40 so I'll give it a spin.
Well, there's probably nothing magic about a 600 Ω load on those mics. For the benefit of all your fellowmen, maybe what you should do is build a box with a male and female XLR on either side and, for a "normal" mic preamp input impedance, hang a 5 kΩ pot across the signal pins and twiddle it to find the sound you prefer. It might be different for different applications. There are a number of mic preamps that have selectable input impedance, generally in steps that will skip over your optimum value. The Cloudlifter-Z has a variable input impedance that covers a pretty wide range, and I'm starting to see instrument inputs with variable impedance as well.
I've heard of removing the transformer inside an SM58 too but I don't remember if they like it or not.
That's a different kettle of fish, and it depends on whether you like the transformer's distortion or not. As human nature predicts, the first experiments with bypassing the transformer produced a round of WOWEEEEE!!!!s, but then others chimed in with dissent, often saying that they'd rather take the distortion than lose the level boost that the transformer provides.
As in most things audio, it depends on both electrical and human factors.