A jarana has many of the same characteristics as a ukulele. Since ukuleles are so popular, I would recommend searching for information about amplifying ukuleles.
One option is simply to point a directional condenser microphone at the sound hole. This works well if sound levels aren't too high on stage, and the player is not moving around.
You can also get microphones which clip onto the sound hole. This way the player can move around, but feedback and sound leaking from other sources are an issue.
Alternatively, you're looking at ways of turning your acoustic jarana into an electric-acoustic jarana.
An electric guitar pickup detects the vibrations of the strings directly, which it can do because they are metal and cause disturbances in a magnetic field. For the nylon strings of a jarana, ukulele or classical guitar you need a different solution.
- An internal microphone - a microphone secured to the inside of the instrument
- A soundboard transducer - a little disk that attaches to the soundboard and translates the vibration into an electrical signal. Sometimes more than one is used, to sample different parts of the soundboard surface.
- An under-saddle transducer - a rod shaped unit that fits under the saddle and picks up vibrations there.
The microphone and the soundboard transducer are able to pick up more of the character of the instrument, but are more prone to feedback (the kind of howling feedback you tend to associate with a microphone). Under-saddle transducers are less prone to feedback, but tend to sound a bit more sterile, since you are picking up the saddle's vibrations before the instrument's body has been able to give its character to the sound.
Usually all of these are fitted permanently, often with the lead socket placed at the base of the instrument where a guitar's strap button would be.
It's possible to fit a combination of these.
Fitting is tricky for a few reasons. It may involve drilling into the instrument. The placement of components could affect the tone of the instrument when played unplugged. Placement of soundboard transducers affects the tone. Loose wires rattle. Working inside the instrument through the sound hole is fiddly.
For these reasons, you may prefer to ask a professional to do the fitting.
You have choices here. If you want to amplify the sound of the instrument without adding any extra character to the sound, then plug into a hi-fi amp or a PA. In either case, you'll need a pre-amp to bring the signal from instrument level to PA level.
Pre-amps designed for acoustic guitars will do a good job. Ones recommended for ukuleles especially so, I suspect.
Alternatively, use an acoustic guitar amp. These are designed to add colour to the signal from an acoustic guitar, and often provide effects like reverb and chorus, without doing the kind of overdrive and distortion that electric guitar players want.