Problem recording Stereo audio (possible cause identified)

[shibatamiyawata]

Hello, as with quite a few other posters here, I'm having difficulty recording stereo audio using my 3DS.

Allow me to establish a few things first:
- my computer supports stereo line-in
- my male-to-male headphone cable is also stereo
- my headphone splitter outputs two stereo audio streams
I know this as my DS works perfectly fine. My 3DS however, doesn't.

The only additional component is the Noise filter, which I've concluded is the root of the problem (it works without it, so it isn't the 3DS either). Normally I'd set the 3DS audio output to Mono and just carry on, however, certain games (Professor Layton and the Miracle Mask) change the audio settings to Stereo upon loading the game. Likewise recording without the filter isn't a possibility either as the buzzing is very noticeable over the voice-acting and cutscenes. I'm not going to ask for another filter as this would be my third now, but if I remember correctly, a higher-quality filter was available for purchase - are they still available? If so, how much are they? (ideally in GBP, including P&P into the country) Or would it be worth waiting on the ability to record 3DS system audio over USB - I wouldn't be recording Miracle Mask for a few months, and I can record the other games which I intend to do before it in Mono audio quality if need be.

[loopy]

This is the other filter I used to sell, I don't carry them anymore.