The Ehrlund Acoustic Pickup (EAP) is a linear microphone for acoustic instruments. We emphasize the term "linear microphone" because this is what Göran Ehrlund (inventor and manufacturer of the pickup) calls it. It uses a special patented "contact mic" sort of design to sense both vibration and sound from your musical instrument's top.
So, we're not sure exactly what's going on within that mysterious triangle, but we can tell you that whatever it is, it sounds really good!
Note that we also have a separate description page of this very same item which is specifically focused on using the EAP on an upright bass (see related items) - however, the actual item being sold is the same product regardless of which page you order it from.
Ehrlund recommends their mic pickup for use on a large variety of instruments, including violin, acoustic guitar, banjo and many others. In our own tests on upright basses, we found that the Ehrlund mic pickup has a very open, quite "microphone-like" sound - realistic, and not very "direct" sounding (as pickups can often be.) However, it doesn't have many of the drawbacks of a microphone - among them, increased feedback, easily picking up other nearby instruments onstage. So the initial impression is that you get the realism of a mic with the convenience of a pickup. It's almost too good to be true!
However - you know what they say about things that seem too good to be true... As with most any pickup, mic, or other amplification gear, know this: how your instrument sounds acoustically directly affects how it sounds when amplified. If you haven't changed your strings in 15 years, or your instrument buzzes or has weird vibrations when you play certain notes... all of these things will probably be apparent through the EAP. It is, after all, a contact mic which combines both vibration and "through the air" sounds to create its tone.
Assuming a quality instrument, though, people using the EAP with a variety of acoustic instruments report that it reproduces open, realistic highs, and has transparent sound - sounding very much like a "real" microphone on guitar, cello and upright bass. This means that this is a pickup that should sound like "your instrument, only louder" - which is what most of us are looking for!
It's super easy to install; the element is simply surface-mounted with a non-permanent, non-marking adhesive putty (tack-it). So you can easily try many locations on the instrument surface, which is good; the pickup's tone can change rather noticeably from (even quite small!) adjustments in location and placement. So it's wise to spend a little time before your gig fine-tuning the EAP to find the best possible location - finding "just the right spot" where it will sound the best (for you) can take a bit of patience and experimentation.
Photos on this page are simply examples of locations to try - you may find that a completely different spot is the "magic" spot on your particular instrument!
As long as you have a little time to spend, the trial and error really isn't a big deal, thanks to the "tack it" install method - So you can easily apply, test, remove, try a different spot, test, etc. As recommended, the material is rolled into small balls and applied to the 3 corners -- though I've even heard that some customers have tried other adhesive placement options as well. Even how much "air" is between the instrument top and pickup can make a very noticeable difference in the tone you get.
The long and short of it: Finding the best spot to put the pickup, as well as how firmly to affix it, fine-tuning the settings on your amp, etc.; all of these efforts will truly pay off with superior sound.
Also included with the EAP is the Ehrlund Preamp. It was designed to be used with the pickup, and Ehrlund pretty strongly recommends that you use his preamp for the best possible results. However, most high-quality acoustic instrument preamps can also be used, so if you already have one that you're attached to, give it a try! The included preamp features simple adjustments: a Volume Control, a "High/Low" Level Switch (Ehrlund recommends different settings depending on the instrument; check the manual), and a Phase Switch for helping to reduce feedback. It also properly buffers the signal for whatever you're plugging into. We sell the EAP packaged with the Ehrlund preamp because most customers will easily get the best results that way. But if you choose not to use the preamp in favor of another (or none at all), you won't break anything!