EAR MC-4. Very flexible and built like a tank. The MC-4 has 3 ohm, 6 ohm, 12 ohm and 40 ohm taps. The 3 ohm tap is 30x voltage gain and the 6 ohm tap is 24x. The 40 ohm tap is 10x.
How much gain does your phono stage provide? I run my phono stage in MM mode which provides 37 dB gain. Since net dB increase = 20 x log10(Voltage Gain), the MC-4 at 10x voltage gain is basically adding 20dB - total 57 dB for me. I use a Clearaudio Stradivari which is 0.7mV and 30 ohms.
Using the 3 ohm tap for your Lyra, you would have 29 dB gain and at 0.4mV, the phono stage woud see an voltage of 12.0mV. The 6 ohm tap would be about 27.5 dB and see a voltage of 9.60mV. When I bought my EAR, I did speak with Tim de Paravacini and he felt that you had to approach 14.0 mV to overload a MM portion of a well-made phono stage.
You might find it difficult to ID an SUT that will offer less gain at the low impendance you need to match. Can you make any adjustments to your phono stage?
I am no SUT expert, but that's my two cents.
Good luck.
