Sick of letting those pecky violins, or worse yet a sax, outpower your poor little Irish flute? Let's power up!
Caveat: This is definitely a first draft version of the setup, but it does seem to work ok. I play a keyless flute. I'm not sure what might need to be tweaked for a flute with keys. I've tried this on D and C flutes, as well as a D fife.
Connect the microphone to the preamp and the preamp to the extension cable. These components are all 1/8" (3.5mm) stereo, which is standard for computer components. You will need the adaptor plug to convert this to the 1/4" mono plug that the amplifier expects. Be careful that you get the right adaptor: an adaptor with a 1/4" stereo plug will look like it fits but cause a weak and unstable signal.
The preamp (battery powered) is critical for powering the microphone and boosting its signal to something the amplifier can handle. It's a bit pricey but I've used it on a number of occasions to get good sound out of dodgy computer microphone systems. It also allows you to adjust the volume at your end, avoiding the potential for feedback created if you move close to the amp.
Now, attach the microphone somewhere convenient. One good approach is to put it on your clothing, e.g. on your left shoulder, which is a nice distance from the flute. Large safety pins are handy for this purpose. Another good location is at the foot end of the flute, pointing up along the line of finger holes. Attaching the mic onto the flute near the embouchure is not good, because it picks up a lot of breath sounds.
To attach the microphone to the flute, wrap a protective strip of leather around the foot to protect the wood, then wind a rubber band around the leatherh (not very tight). Tuck the microphone under a couple loops of the rubber band. Adjust so it's not in the way of wherever you like to park your little finger. A big advantage of this microphone is that it's small, so it doesn't get in the way of your fingers or weigh down the end of the flute. Caveat: for a fife, you may need to adjust where you perch your right little finger.
Put the preamp on your lap or hook it to your pants. The 3' microphone cable is a nice length for reaching up to the flute and it isn't heavy enough to mess up how the instrument handles. (This mic is also available with longer cables.) The preamp separates the flute and microphone from the longer extension cable, preventing the extension cable from pulling on the flute.
You might or might not need the windscreen, depending on where you mount the microphone and where you're playing. They are cheap, so it's best to get some and experiment. Get more than one: they like to run away into corners and lose themselves.
To avoid feedback, position the amplifier so it is well separated from the flute and/or pointed away from the flute and/or behind you so your body is between the two. Use the preamp to adjust the volume without getting near the amp.
Finally, remove the rubber bands and leather stuff when you put the flute away. It might or might not damage the wood if you leave it on for extended periods and you don't want to find out the hard way.