There are two main considerations:
1)The cable should be well shielded, to minimize noise pickup. It's hard to be more specific than that, because success or failure would depend on how large and how close the nearby sources of electrical noise are.
2)The capacitance of the cable should be low, so that it does not roll off the highs in combination with the output impedance of the preamp. Determine the capacitance per foot of the cable (you may have to ask the manufacturer), then multiply by 16 to get the total capacitance, then calculate the capacitive reactance (impedance) at 20 kHz based on the formula 1/(2PiFC), where Pi is 3.14, F is 20,000 Hz, and C is the total capacitance in farads. C will probably be on the order of 500 to 1000 picofarads (a picofarad is a trillionth of a farad). If the result of that formula is significantly larger than the preamp's specified output impedance, you'll be ok.
Regards,
-- Al
1)The cable should be well shielded, to minimize noise pickup. It's hard to be more specific than that, because success or failure would depend on how large and how close the nearby sources of electrical noise are.
2)The capacitance of the cable should be low, so that it does not roll off the highs in combination with the output impedance of the preamp. Determine the capacitance per foot of the cable (you may have to ask the manufacturer), then multiply by 16 to get the total capacitance, then calculate the capacitive reactance (impedance) at 20 kHz based on the formula 1/(2PiFC), where Pi is 3.14, F is 20,000 Hz, and C is the total capacitance in farads. C will probably be on the order of 500 to 1000 picofarads (a picofarad is a trillionth of a farad). If the result of that formula is significantly larger than the preamp's specified output impedance, you'll be ok.
Regards,
-- Al