You needed a preamp you just didn't know it. Try an Audio Research SP-11, SP-14 or SP-15. These preamps are designed for phone and they have separate gain and attenuator controls.
The Rothwell attenuators did not work for me either. I was attempting to reduce the gain of a 7 volt output CD player (2 volts is typical) and the Rothwell attenuators significantly reduced system resolution.
The Rothwell attenuators did not work for me either. I was attempting to reduce the gain of a 7 volt output CD player (2 volts is typical) and the Rothwell attenuators significantly reduced system resolution.