When it comes to line-level analog interconnections between source components and preamps issues relating to impedance compatibility are no different than when it comes to analog interconnections between preamps and power amps.
To assure impedance compatibility, in both cases the input impedance of the component receiving the signal should be at least 10 times as much as the output impedance of the component providing the signal, at the frequency within the audible range for which that output impedance is highest. In the case of many and probably most tube-based source components as well as many tube-based preamps output impedances are highest in the deep bass region, specifically at 20 Hz. And the output impedance at deep bass frequencies such as that can be much higher than the specified output impedance, which is usually based on a mid-range frequency such as 1 kHz.
Not meeting that criterion doesn’t necessarily mean that there will be a problem; it depends on how the impedances vary as a function of frequency. But meeting that criterion assures that there won’t be an impedance compatibility problem.
Many tube-based source components and tube-based preamps have specified output impedances that are reasonably low, but that can rise to thousands of ohms at 20 Hz. That kind of output impedance would result in significant rolloff and undesirable phase shifts in the deep bass region when driving 10K, regardless of whether the 10K is the input impedance of a preamp (driven by a tube-based source component) or the input impedance of a power amp (driven by a tube-based preamp).
Finally, as far as I can tell from the specs the input impedance of the Freya S is 10K regardless of whether it is used in active or passive mode.
Regards,
-- Al
Edit: I see you’ve added an indication of the source components you are using to your post just above. I would not expect those particular components to have a problem driving 10K.
To assure impedance compatibility, in both cases the input impedance of the component receiving the signal should be at least 10 times as much as the output impedance of the component providing the signal, at the frequency within the audible range for which that output impedance is highest. In the case of many and probably most tube-based source components as well as many tube-based preamps output impedances are highest in the deep bass region, specifically at 20 Hz. And the output impedance at deep bass frequencies such as that can be much higher than the specified output impedance, which is usually based on a mid-range frequency such as 1 kHz.
Not meeting that criterion doesn’t necessarily mean that there will be a problem; it depends on how the impedances vary as a function of frequency. But meeting that criterion assures that there won’t be an impedance compatibility problem.
Many tube-based source components and tube-based preamps have specified output impedances that are reasonably low, but that can rise to thousands of ohms at 20 Hz. That kind of output impedance would result in significant rolloff and undesirable phase shifts in the deep bass region when driving 10K, regardless of whether the 10K is the input impedance of a preamp (driven by a tube-based source component) or the input impedance of a power amp (driven by a tube-based preamp).
Finally, as far as I can tell from the specs the input impedance of the Freya S is 10K regardless of whether it is used in active or passive mode.
Regards,
-- Al
Edit: I see you’ve added an indication of the source components you are using to your post just above. I would not expect those particular components to have a problem driving 10K.