There are two ways to approach amplifying an acoustic guitar: trying to duplicate the natural sound, only louder, and NOT trying to sound naturalistic at all. This post is about the second approach.
I love playing acoustic through an electric guitar amp (as opposed to a dedicated acoustic amp). True, the tubes and speakers amputate all high frequencies. But if you think of the instrument not as an acoustic guitar, but an idiosyncratic electric variant, it opens up amazing possibilities.
More often than not, I prefer to play acoustic gigs that way. I did a fun benefit show last year playing rock and R&B covers with a band consisting of Flea, Tracy Chapman, and drummer Dawn Richardson. Tracy had a beautiful, ultra-hi-fi acoustic tone, and the ratty, rumbling sound of my acoustic through a small combo was — well, let’s just say it was a very strong contrast.
Admittedly, relatively few players exploit this technique. One notable exception is Daniel Lanois. He’s best known as a producer (U2, Peter Gabriel, Bob Dylan, etc.), but he’s also a phenomenal player who does amazing things with an acoustic guitar, an inexpensive magnetic soundhole mic, and small vintage Fender amps. I’ve watched him play up-close a few times, and he’s incredibly adept at conjuring a variety of tones and controlled feedback from this setup.
It’s definitely a white-knuckle playing experience. You have to listen carefully and nix unwanted feedback with quick damping technique. But it can be so expressive!
I’ll talk more about the technique in a bit. But first, check out this short video demo featuring distortion and other stompbox effects, controlled (and not-so-controlled) feedback, and a lot of awkward twisting and turning as I grapple with the tone:
Mind you, I’ve got nothing against “normal” amplified acoustic sounds. While I can’t stand the brittle quack of under-the-saddle piezo pickups, high-end hybrid systems like the Seymour Duncan Mag Mic I use in the video can sound warm and naturalistic through a good P.A. or a quality acoustic guitar amp. (These are generally “P.A.s in a box” designed for maximum clean headroom and minimal distortion, a concept pioneered in the ’80s by Seymour Duncan’s influential TARA amp.)
Like its name suggests, the Mag Mic combines a magnetic pickup and an internal microphone, which are blended to taste via a a dial on the pickup. The mag side provides warmth and body, while the mic captures all the high-end detail. Most leading acoustic players perform through some variant of this system.
But when playing through an electric guitar amp, I turn the microphone completely off — even a touch introduces feedback (a horrible, high-pitched squeal, not cool, musical-sounding stuff). The Mag Mic works great for this lo-fi approach. So do simple mag-only soundhole pickups such as the Seymour Duncan Woody.
But you need one other crucial component: a good clean boost between the guitar and the amp. In the video, I used a Seymour Duncan Pickup Booster, which works great, but you can try pretty much any clean boost. I’ve gotten great results with a Z. Vex Super Hard-On, those little A.R.T. tube preamps, and yes, the Booster/Buffer project from Tonefiend DIY Club. Without a hefty boost, the sound is disappointingly thin.
My affection for this technique stems from childhood: Desperately wishing I had an electric guitar, I shoved a cheap mic between the strings of my mom’s classical guitar and plugged into my dad’s ancient Wollensack tape recorder set to input monitoring. It howled and howled. Total awesomeness.
I’d like to hear from folks who’ve tried similar techniques. And if you haven’t, well, I hope this post inspires you to experiment with transforming your mild-mannered acoustic into a raging electric beast. 
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