Linnmaster,
I used 1:10 BentAudio Mu's for several years with my UNIverses (and other carts) before changing to an MC phono stage. You mentioned that some have loaded their UNIverse down to around 6.54 ohms. Since that is precisely the value we found optimum (in our system) I imagine you must be quoting one of my old posts. So first, let me say "hi"!
You're correct that the Mu's resistor posts are on the secondary.
All your math is correct too.
Your finding that 9.04 ohms sounds "really really good", but that 6.4 ohms was too low is unsurprising. Systems differ. The value that worked best in our system was not best when we tried our Mu's and UNIverse in other systems.
In our setup 6.4 would also have been too low. We found the acceptable range was very narrow. We could hear differences between 6.54, 6.55, 6.57, 6.58 and 6.59 ohms. These ridiculously tiny changes were made by putting TWO resistors on each set of binding posts. This fine tuning was the only way we could get the performance we wanted.
FWIW, Riken ohms sounded best to our ears/in our system.
How is it that the UNIverse is sounding so good wayy down at 9.04 ohms and also (potentially) between 100 and 125 ohms?
That hasn't been demonstrated yet. If it turns out to be true, my only guess is that, as Dave Slagle explained in a post last Fall, loading an SUT on the secondary only is an incomplete method that doesn't control winding resonance on both sides. Secondary-only loading controls resonance on the secondary side but may not be optimum for controlling primary side winding resonances. The optimal solution is to load each side (differently of course), with the primary side load controlling those windings and the cartridge. The solution offered by the Mu's is a compromise, and you may find one load controls one side better while another load controls the other side better. Oy!
That gets too complex for me! Our active stage is superior to our Mu's, so we haven't used them in quite a while. I'd urge you to experiment with two resistors on the posts however. That really helped us fine tune, and since your SUT is 1:20 while mine is 1:10, your setup will react more to small changes.
And also, is 100 ohms total on SUT's + phono the same as 100 ohms on an active gain phono?
No. They are quite different.
An active stage has no windings, primary or secondary, that need resonance control. The optimum sounding value with an active stage is almost always much higher than with SUT's, and the precise value needed is less critical. No one could hear a 2 or 3 ohm change through an active stage but, as you've just demonstrated, the same change through an SUT makes a huge difference. We play our UNIverse through the MC stage of our Doshi Alaap at around 200 ohms. I can switch to 75 ohms and the sound is slightly closed in, but the difference is far subtler than with an SUT.
The UNIverse, as Dan_Ed said, can surpass what the XV-1S is capable of, but it will require much work and fine tuning to make that happen. Unless everything in a system and setup are optimized to the nth degree, the UNIverse will only be a really good cartridge. It's ability to be an extraordinary, mind-altering cartridge requires a certain amount of fanaticism. Judging by your posts on this thread, I think you have potential. ;-)
