assuming bass enhancement is off...
...there is one shunt capacitor and e two ferrite inductors to deal with.
I think I am going to try using back-to-back polar caps and DC bias before considering buying film caps.
The inductors have a cylindrical ferrite core that looks like a spool of thread, i.e. it has an H-like cross-section, so the windings are not completely surrounded by ferrite.
CFC10 copper air coil has slightly higher resistance but is prohibitively expensive (70€ per inductor).
At
www.intertechnik.de, I came accross I-bar (bar core) coils that have just the right resistance and are reasonably priced (<9E). This seems to be an air coil stuck onto a single straight rectangular sheet iron transformer core element. They claim very low distortion even at high power, 0.01-0.05% typ. third harmonic distortion. Actually, this is the only coil for which I have seen distortion values provided.
I can see that the flux in this material would be relatively low, the core not surrounding the windings a lot.
The question is, how does it compare to a good ferrite core? At Intertechnik, they concede that all ferrites have inferior large signal distortion due to lower saturation magnetization compared to iron materials. But they also claim that some optimized ferrites have superior small signal behavior. They are not clear about the reason, but it seems to be connected both to inductive losses and hysteresis.
They even have a selection table where their ferrite coils always rate for lower distortion than their silicon-iron CI and toroid transformer coils. Unfortunately, the bar cores are not included.
As I use mainly low listening levels, I am wondering whether I should replace my ferrites of unknown material quality with optimized ferrites or i-bar iron inductors.
Puzzled,
Eric