I've got a Linn LK-140 and 2 Linn Ninka. This equipment supports Bi-amplification with Aktiv cards to bypass the speaker internal filters. Is it worth investing in another amp and 2 expensive cards to get bi-amp ? Can anybody share his point of view on the subject with me ? Thanks.
You are talking about active operation of your speakers. Strictly speaking this is fifferent to the 'bi-amp' you refer to. Bi-amp simply refers to using separate amplifiers for each speaker drive unit for a two-way speaker: it retains the passive filtering within the speaker. Active operation also uses separate amplifiers for each drive unit, but dispenses with the passive crossover in the speaker and uses 'active' electronic filtering instead (this is the Linn Activ cards you refer to). The benefits are very good. I've not heard the exact setup you describe but others I have heard were much more dramatic, immediate, tangible and exciting the the equivalent passive bi-amped setup.
I meant to add that the 'cons' are that the amps cannot be used with other speakers as they will be actively filtered using modules specifically designed to match the Ninkas. Also, if the Ninkas have to have their internal passive crossovers removed they must not be used with other 'normal' amps otherwise damage could occur. I guess the active mods are all reversible so it's not the end of the world if you decide to change back in the future.