- Thread Starter
- #221
I have contacted Bruno directly and asked him what he things about the issue with 4ohm//2.2uF. This is the reply I have received:
Frankly, I appreciate him to reply, but am not sure that it covers the issue. So I have added an inductor of 330uH (quite high inductance) to the 2.2uF capacitor and got this impedance:
(The inductor used has 0.8 ohm ohmic resistance)
Though the NC 252MP now passes the usual test of THD+N vs. level at 1kHz, it is still unacceptable at higher frequencies, namely I tested 5kHz, THD+N vs. output voltage with BW22kHz.
So, the distortion of this amplifier (and probably any other Ncore) is not "load invariant", if we have complex load instead of pure resistors.
It’s actually not a problem with electrostatic speakers because the transformer has sufficient leakage inductance and series resistance to decouple the capacitive part. You only run into trouble with big capacitance directly across the output with no series impedance.
Frankly, I appreciate him to reply, but am not sure that it covers the issue. So I have added an inductor of 330uH (quite high inductance) to the 2.2uF capacitor and got this impedance:
(The inductor used has 0.8 ohm ohmic resistance)
Though the NC 252MP now passes the usual test of THD+N vs. level at 1kHz, it is still unacceptable at higher frequencies, namely I tested 5kHz, THD+N vs. output voltage with BW22kHz.
So, the distortion of this amplifier (and probably any other Ncore) is not "load invariant", if we have complex load instead of pure resistors.
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