If so the input impedence of my amp is 150k , how would you construct a cable to match that ?""
Very carefully.:-)
Here's a plot for a speaker run. The load is 8 ohms, and look at the energy storage within the speaker cable.
Note that there is a minima of energy storage in the cable when the cable impedance matches that of the load.
What is important also is what is contributing to the energy storage. Below the load impedance, most of the energy storage is capacitive. This is the regime for IC's in general. It says that capacitance is the primary culprit.
When the cable z is above the load, which is typical of speaker wire runs, then the inductance is the primary culprit.
For you, 150K requires too much inductance to be very practical, so you would have to get the capacitance as low as possible.
Cheers, John
