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A Magnetic Pickup for Acoustic Guitars

$384.54 list, $249.95 street


by Jon Chappell



Miking up an acoustic guitar with a couple of sensitive condenser mics may be the ideal way to capture an acoustic guitar, but it’s just not practical in most stage and live performance situations. That’s when guitarists turn to the non-microphone approaches for amplifying their acoustic guitars—namely, pickups.


There are two approaches you can take: 1) vibration-sensing transducers that use piezo-electric technology; and 2) magnetic pickups, which react to the metal strings’ movement within a magnetic field and convert those fluctuations into electric current (operating the same way electric guitar pickups do). Each approach has its strengths, but Fishman has had a long history in developing both, and their latest entry into the magnetic world is the BlackStack, a user-installable magnetic soundhole pickup for steel-string acoustic guitars.


The pickup and associated components come in an attractive metal mini-briefcase, with an engraved, playing-card motif on the exterior (see Figure 1). Once you install the pickup, you may not need the case (unlike, say, a microphone), because the pickup will probably stay with the guitar. But you can always find some use for this handsome enclosure.


Figure 1: The BlackStack comes in a handsome metal case decorated in a playing-card motif.


Opening up the case reveals the pickup, the connecting cord, mounting hardware, a cork sheet (for protecting the plastic mounts from your guitar's finish), a hex driver (Allan wrench) to adjust the pickup's individual polepiece heights, a stack of poker chips, and a deck of playing cards (see Figure 2). A pretty nice little collection of swag, along with the essential components for installing the BlackStack pickup.


Figure 2: The contents includes the pickup, mounting hardware, a cork sheet for finish protection from the brackets, the cord, and the swag: poker chips and a deck of playing cards.



The BlackStack is a battery-free, passive-electronics humbucker design. It has six individual pole pieces that align directly under the strings (see Figure 3). Using the supplied hex driver (Allan wrench), you can vary the output of each individual string by raising and lowering the corresponding pole piece. Having variable pole pieces means you can also compensate for differing string heights on guitars with different saddle radiuses. The pole pieces are the only adjustable aspects on the BlackStack. There is no master volume or tone control on board.



Figure 3: The BlackStack has six individually adjustable pole pieces to balance the strings' output levels.



The connection of the pickup to the cable is a special TA4 mini-XLR to 1/4" endpin jack. The cable is five feet long and well constructed and thoroughly shielded (see Figure 4).


Figure 4: The pickup assembly and accompanying five-foot cord.




Out of the box, the BlackStack is meant to be installed only temporarily—that is, with the clamps screwed down by hand (and therefore easily removable), and with the cable and output jack assembly coming out of the soundhole. For a more permanent installation, with the jack mounted to the endpin hole (which must be drilled out), the manual recommends taking the guitar to a professional repairperson and refers you to the website for further instructions. For temporary installation, you’ll have to secure the cable and jack, so that it doesn’t flop around when you play. I just use low-tack masking tape and affix the cable to the underside of the guitar.


The pickup comes with the mounting hardware separate, but it takes just a couple of minutes to position the two brackets, insert the metal bolts, and tighten the mechanism to the guitar’s top. The brackets are pliant plastic, which may cause some guitar owners concern for their guitar’s finish, so Fishman, acknowledging this concern, supplies a thin cork sheet, from which users can make inserts and shield the plastic from touching the top directly. I didn’t bother with these, as I planned to remove and re-apply the pickup at various intervals. I wouldn’t leave the pickup mounted for, say, four months at a time, or through a seasonal change.


The provided instructions are rather scant. There are no photos, only written text about how to install the pickup. But fortunately, it’s so straightforward, I managed to find the optimal position without a photo (and viewing the demo video on Fishman’s website provided further visual reinforcement). Again, for permanent installation, the manual refers you to the installation guide available on their website.



The Blackstack is described by the manufacturer as voiced with a vintage “roadhouse” sound, which I found was good for classic rock, garage rock, and filling out a rhythm section part with a convincing acoustic guitar sound. It’s got the high-end shimmer that will cut through and a nice bass punch that singer/songwriters and bluegrassers will appreciate. The BlackStack does not overwhelm you with low mids (the “mud”), as some other magnetic systems do, and I found that this quality allows a BlackStack-configured acoustic to fit very well in a mix.


Listen to the audio clip (BlackStack\_1.mp3) to hear the even sound that results across all the strings, when fingerpicked or strummed, and how the highs (particularly the lead lick at the end) reads quite well. Many guitarists use magnetic pickups on acoustics not just for convenience, but to mix with and augment the miked sound with the punchy and sustained quality in the low end that magnetics deliver so well. For this use, I found the BlackStack handy for goosing up the bass character in an otherwise anemic miked sound. Because it’s so convenient to temporarily strap on a BlackStack in a recording situation, it provides yet another sonic tool available to the player or engineer.




For guitarists who want a quick and convenient amplified solution for acoustic guitars that don’t already have a pickup installed, the BlackStack, with its passive circuitry, user-friendly and temporary installation design, and variable pole piece adjustment scheme is about as easy and versatile as you can get. But I really liked the even sound and realistic acoustic guitar signal, finding it versatile for many ensemble situations and even in an exposed, solo setting. Fishman’s BlackStack may be black and have a humbucker-like vibe to it, but its sound is subtle, woody, and acoustic through and through.





  • Humbucking magnetic coil with cutting vintage sound
  • Passive design for battery-free operation
  • Adjustable pole pieces allow for perfect string balance adjustment and help to compensate for varying string heights between instruments
  • Included 5 foot cable featuring premium TA4 mini-XLR connector to ¼” combination endpin jack / in-line connector for easy install and removal
  • Use out-of-the-box with included cable or create your own custom endpin jack solution


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