The stock piezo pickup on my Ibanez electro-acoustic stopped working a while ago and instead of replacing it with another crappy one — as most under-saddle piezo sound awful — I decided to take this oportunity and make an upgrade. Since the stock preamp on my Ibanez acoustic still worked fine, I connected this passive pickup to the built-in preamp, using a very short TRS 3.5mm to TRS 2.5mm cable. The wire clips came in very handy for pinning down the cable and the old piezo wire — which I did not want to remove because it would have required more experienced hands than mine. The tuner, volume and eq on the Ibanez built-in preamp work like a charm with this new pickup. Tone-wise, I have never heard an acoustic pickup sound as natural as this one! The only way you could get a more authentic sound is by using an actual microphone — which you might want to avoid for loud environments.
So, if anyone was curios if this is working on a 12-string, the answer is it 100% does. However, in that case, you might want to adjust the individual poles.