Aktimate mini's amp damaged?

[GuitarheadII]

Hi all,

I've got a pair of Aktimate minis (specifications: http://www.aktimate.com/Specification.htm, manual: http://www.redboxav.com/products/akt...-07-Final2.pdf), and I connected these to my computers soundcard via the 'line out' (lime green 3.5mm jack, onboard sound is ALC889, datasheet here: ftp://202.65.194.211/pc/audio/ALC889_DataSheet_1.0.pdf) to the Aktimates RCA input using a 3.5mm to RCA cable. The RCA input is designed to accept a 'line level' signal, however I have since realised that the soundcard output may be stronger than line level. I was wondering if someone who has more electronics knowledge than myself could answer, is it possible that I have damaged the amp and/or speakers by doing this? What would theoretically happen if I overloaded the amps line level input?

Maybe I'm just paranoid, but I've recently noticed a slight hum/buzz when I put my ear close to the speakers (even with no input is attached) - I'm not sure if this was there before or if it appeared recently.

I'm now planning to buy a 3.5mm to 3.5mm cable and connect this to the 3.5mm input on the Aktimates, which will be completely safe (the 3.5mm input is desgined for any mp3 player output).

Thanks