Using the HK3390 as a preamp only. Using the 9090DB as an amplifier only. Pushing a pair of 1992 Cerwin-Vega DX9s directly from the preamp at 4 Ohms. A pair of 1977 McIntosh ML-10Cs with a 1970 Sansui 5000A, and a single 1957 JBL C40 Harkness Lowboy with a 1969 Sansui 5000A in mono