Capacitorless line-level XO?

[Nixie]

Looking at US patent 6115475, they show a capacitorless crossover. I'm wondering if this is doable for a line level XO instead, and more specifically one that would be transient perfect and have at least 2nd order roloff (http://www.geocities.com/kreskovs/CrossoverdocN.html). So basically can one do Kreskov's design, but without using capacitors?

[annex666]

I've looked briefly at the proposed design and it seems to be more of a focus on the "perfect" transient response of the filter, rather than a design free of capacitors.

It is perfectly feasable to produce a capacitorless line-level crossover - there are two ways this can be done:

1) The use of inductors as the frequency-dependant component.

2) The use of the opamp open loop dominant pole to create a closed-loop transfer function that is desired (this is a bit of a cheat as it isn't capacitorless - just that it relies on the internal capacitance that produces the dominant pole). This is more of a trial and error approach as the dominant pole is variable from device to device (and even from sample to sample of the same device) and is therefore not ideal for audio work.

I'm wondering why you would want to create a capacitorless crossover? The usual trend is to remove all dependance on inductors and create a design based entirely on capacitance - this removes the many problems inherant with inductors, namely their large size/weight, high cost, poor tolerances, saturation problems (with cored inductors) and RF pickup.

With correct circuit application almost all instances where an inductor is used can be replaced by either a passive or active capacitor-based circuit.