Congratulations on the pre. I myself use a passive pre in my setup and can attest to the transparency and accuracy.
The thing about resistor based passive is that they are incredibly transparent compared to most of the active preamps, because its extremely difficult to design an active circuit playing with such small signal levels which a preamp works with. Well designed ones are super expensive. OTOH, the resistor based passive because of the use of just passive components with minimum level of signal distortion, can be made very accurate.
However,
- They have no active circuit or a transformer (like a TVC) and hence no impedance matching. Low output impedance from the source and high input impedance of the power amp is required. Also a short low capacitance interconnect between the pre and power is essential to bring the best out of a passive.
- They only attenuate the signal coming from the source, hence a high source output coupled with high input sensitivity of the power amp helps.
I see that you use a Krell 250a, which has a very high input impedance of 100k, allowing the circuit to push enough current. No doubt you are not seeing the loose or uncontrolled bass and reduced dynamics many people face when they dont take care of the impedance matching while using a resistor based passive.
But I will be interested to know what volume levels you need to use on the pre, seeing that the input sensitivity of the power amp is pretty low at 2v. Probably you don't need much of the power which the power amp can provide and hence can get away with a low drive, or your source has a tremendously high output.
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