To add to my previous post: What can often be more significant than the ratio of the two impedances, as defined at the worst case frequency (which is usually 20 Hz for preamps having capacitively coupled outputs, which means most tube preamps as well as at least a few solid state preamps), is how much **variation** there is in the preamp’s output impedance over the frequency range. And in that respect what is by far the worst case situation among the two preamps that are being considered occurs at the balanced output of the Calypso, where "the balanced output impedance was 112 ohms at 1kHz and above, this increasing to 3900 ohms at 20Hz due to the finite physical size of the output coupling capacitors."
Differences in how preamp output impedance **varies** over the frequency range are IMO probably the main reason that some people report good results when the 10x guideline is compromised, and others do not. The less variation the better, if the 10x guideline is not met at 20 Hz or any other audible frequency.
Regards,
-- Al
Differences in how preamp output impedance **varies** over the frequency range are IMO probably the main reason that some people report good results when the 10x guideline is compromised, and others do not. The less variation the better, if the 10x guideline is not met at 20 Hz or any other audible frequency.
Regards,
-- Al