The Audio Research SP-10 made the Tympanis sing. It has a way with the bass that really took control of the Tympanis. Of course the midrange and highs were excellent too. The SP-10 worked great with the ribbon tweeter, giving it extension and clarity while never sounding harsh. Perhaps Bill Johnson used Tympanis to design the SP-10 with. Magnepan and ARC were worked closely together around this time. All I know is the SP-10 just blew away the Sp-6b, Sp-6e, Sp-8 and various Conrad Johnson preamps that we had in the store's system at that time.
The SP-10 maybe Bill Johnson's best preamp ever in many regards.