Dgad,
The very low impedance values Thom is discussing assume the use of stepup transformers. When I used stepups I also used sub-100 ohm values, and found that great precision was necessary to optimize the performance of any LOMC.
FWIW, our new high gain phono stage + the .24mv UNIverse are happiest somewhere around 150-225 ohms. If I go any lower it sounds exactly as you described, closed in or muffled. Cello's Supratek Grange + UNIverse sounded best around 100-125 ohms, IIRC.
Assuming your phono stage doesn't include stepups, you might be fine at either 100 or 200. If those aren't optimal I'd bet on something in between.
The very low impedance values Thom is discussing assume the use of stepup transformers. When I used stepups I also used sub-100 ohm values, and found that great precision was necessary to optimize the performance of any LOMC.
FWIW, our new high gain phono stage + the .24mv UNIverse are happiest somewhere around 150-225 ohms. If I go any lower it sounds exactly as you described, closed in or muffled. Cello's Supratek Grange + UNIverse sounded best around 100-125 ohms, IIRC.
Assuming your phono stage doesn't include stepups, you might be fine at either 100 or 200. If those aren't optimal I'd bet on something in between.