Gary L Koh
CEO, Genesis Advanced Technologies
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I confirm the following from the 911 data sheet inside the box:
Sensitivity Input: 770mV Unbalanced/Balanced
Impedance Input: 22.9kOhms Unbalanced, 1.88kOhms Balanced
The pre-power coupling 'rule of thumb' is that the ratio preamp output impedance to power amp input impedance must be greater than 10.
So in theory any source/preamp with an output impedance equal to or less than 2290 Ohms can be run single ended and 188 Ohms can be run balanced into a 911 without issues.
Preamps with robust output stages are typically around 50 Ohms. My tubed wavelength cosecant dac is 500 ohm, so I run it single ended. My Weiss media has an output impedance of 0.2 ohms so will drive it balanced with ease.
Weiss Medea+ / DartZeel NHB 18NS - 108 / TAD CR1