PG contributor Tom Butwin highlights 7 preamp options for your acoustic guitar. Wherever you’re looking to plug in your acoustic, these stomps have you covered with a wide range of functionality, sounds, and applications.
LR Baggs Venue DI Acoustic Guitar Preamp / DI / EQ / Tuner Pedal
Radial PZ-Pro 2-channel Acoustic Preamp Pedal
Grace Design ALiX Acoustic Instrument Preamp / EQ / DI / Boost Pedal
Neutrik’s Timbre plug, made for toggling between capacitors.
Let’s begin with some typical additional capacitance values that certain lengths of cable (or capacitors) can bring to your system:
• 10’ vintage coiled cable (approx. 3 meters) -> 1 nF
• 15’ vintage coiled cable (approx. 4.5 meters) -> 1.5 nF
• 20’ vintage coiled cable (approx. 6 meters) -> 2.2 nF
• 30’ vintage coiled cable (approx. 9 meters) -> 3.3 nF
• Ritchie Blackmore-style, ultra-long vintage coiled cable -> 4.7 nF
I listed standard values here, so you should have no problem getting caps to match them in any local electronics store or online; the type of cap doesn’t really matter and will mostly be dominated by size, but I’ll share more about this in a minute.
Let’s quickly summarize the first installment of this column from last month’s issue: From a technical point of view, added capacitance shifts down the resonance frequency of the pickups, so they sound fatter, especially when using overdrive. This is exactly the reason why a lot of distortion and fuzz boxes with a vintage voicing use an additional cap at the input section; the resulting overdriven tone is fat and warm.
This month’s mod, which involves adding a capacitor to your signal, works best with vintage-flavored single-coil pickups (approximately 2.4 H inductance) or a typical old-school PAF-style pickup (approximately 3.8 H inductance). Modern high-output pickups are often sporting inductances of 6 H to 8 H, and don’t sound very good with this mod—when adding more cable capacitance to such pickups, the result is a dull and wooly tone without any clearness and definition. If you want to make your single-coil guitar sound more Les Paul-ish, you should try a 4.7n capacitor. It will shift the resonance frequency of your single-coil pickups down to the typical PAF ballpark, making for a very cool and usable old-fashioned guitar tone. It might feel a little muffled when playing clean, but ultra fat and punchy when using overdrive! In general, values higher than 4.7n are not recommended.
We have two options for where to install our cap.
On the Guitar Cable
This is the easiest location to add additional capacitance to your system, with several mod options:
1. The lightest mod ever isn’t a mod at all—it’s to simply buy a vintage guitar cable and plug it in whenever you need it! I don’t know of any company that offers modern guitar cables with intentionally high capacitance.
2. The Neutrik company offers a special angled plug, called the Timbre Plug, that you can solder to any guitar cable of your choice. The plug has a 4-way rotary knob on top to toggle between different capacitors. In addition to a bypass setting, the plug offers capacitances of 1nF, 2.2nF, and 3.3nF, letting you simulate different cable lengths on the fly.
3. You can add an additional capacitor to any guitar cable of your choice to convert it into a “longer-sounding” cable. You simply open one of the plugs to solder the cap between the hot and ground—that’s it. Small, 2.5 mm contact spacing ceramic caps are easy to put into a standard plug and are your weapon of choice here. It’s essential to only add the additional cap to one of the two plugs, but it doesn’t matter if you plug this side into your guitar, an effect, or your amp. This method allows you to build yourself some cables that simulate their older, longer relatives.
You can add an additional capacitor to any guitar cable of your choice to convert it into a “longer-sounding” cable.
Photo courtesy SINGLECOIL (https://singlecoil.com)
Inside the Guitar
You can also add a cap (or several) inside your guitar if you only need this mod for one instrument. If you’re looking for added capacitance with all your guitars, you’d be better off choosing one of the techniques mentioned above.
1. The easiest way is to solder your additional capacitor directly to your volume pot; this way it has a fixed value that can’t be changed and is always engaged. This operation is very simple to do, and you can use regular-sized caps for this.
You can add a cap (or several) inside your guitar if you only need this mod for one instrument.
Illustration courtesy SINGLECOIL (https://singlecoil.com)
2. If you want to make the cap switchable, such that you can run it either bypassed or engaged, you can install a SPST mini toggle switch or use half of a push-pull or push-push pot, which usually sport a DPDT switch underneath.
This drawing shows how to make your additional cap switchable.
Illustration courtesy SINGLECOIL (https://singlecoil.com)
3. If you want to use more than one cap to simulate different cable lengths, your weapon of choice is a rotary switch, setting up a kind of Gibson Varitone wiring without the inductor. Because we are switching capacitances, it is essential to run an additional 10 meg resistor in parallel to each of the caps, and to use a make-before-break, not a break-before-make, rotary switch to prevent loud popping noises when using the switch while your guitar is plugged into an amp. Leave the first lug of the rotary switch open for the bypass position without an additional cap.
If you want to use more than one cap to simulate different cable lengths, use a rotary switch.
Illustration courtesy SINGLECOIL (https://singlecoil.com)
4. If you want to make this mod even more flexible, you can add an additional “cable simulator pot” to your system. The pot should have the same resistance as your volume pot, and should be wired to your volume pot. This way, for example, you can add a 3.3nF or 4.7nF cap to the extra pot, and dial in as much cable capacitance as you like.
On the Pedalboard
The idea of putting a rotary switch or cable-simulator-pot solution into an external unit to create a kind of extra-capacitance stompbox to use with all of your instruments is just around the corner, and yes, it’s possible! However, I don’t recommend this, because it’s physically located after the volume pot in the guitar, which means less volume (no unity gain) and less high end. But don’t worry: If you are looking for a pedalboard solution to simulate different cable lengths (which, as we defined earlier, means to shift the resonance frequency of the pickups), there are some active solutions on the market offering such a feature, usually in combination with a boost or buffer functionality. To name just a few, you should look into the Seymour Duncan Pickup Booster, Stellartone Micro Pedal, or the i2e Audio AG1.0 The PURR. Along with some other brands, these pedals will do the trick, and they’re not difficult to build if you are looking for a DIY solution.
So far, I’ve received several emails from readers asking for some more DIY guitar tools, so next month, we will look into some sustainable and environmentally friendly DIY guitar helpers—all of which you can build yourself easily by upcycling things you already have at home. Stay tuned!
Until then... keep on modding!
Vox’s Valvenergy Tone Sculptor
I spent a day workshopping ideas in my studio using just the Vox Valvenergy Smooth Impact compressor and Tone Sculptor EQ, and a dash of amp tremolo and reverb to taste. In the process, I produced more arresting sounds than I had heard from my guitars in many days. There were radical direct-to-desk-style Jimmy Page/Beatles distortion tones, sun-sized, cosmic electric 12-string, Bakersfield twang that could burn through crude, and many other sweet and nasty colors. Most decent EQ and compressor combinations can achieve variations on all those themes. But the Smooth Impact and Tone Sculptor also reveal interesting personalities in unexpected places.
The individuality and energy in the Vox Valvenergy pedals is attributable, in part, to the Nutube vacuum tube used in the circuit. Though it looks little like a vacuum tube as most guitarists know them, the thin, wafer-like Nutube is, in fact, a real vacuum tube like those used in fluorescent displays. Fluorescent display tubes have limitations. A maximum operating voltage of around 40 volts means they aren’t useful for bigger power tube applications like a 6L6, which has an operating voltage of about 400 volts. But it can work quite well as a preamp tube in concert with an op amp power section, which is how the Nutube is used in the new Valvenergy pedals, as well as older Vox products like the Vox MV50 and Superbeetle amps.
Valvenergy Tone Sculptor
When you think about “cinematic” effects, you likely imagine big reverb or modulation sounds that create a vivid picture and feeling of space or motion. But narrow, hyper-focused EQ profiles can evoke very different and equally powerful images. Radical EQ settings can add aggression, claustrophobic intimacy, and stark, explosive dark-and-light contrasts more evocative of Hitchcock’s Psycho than Ridley Scott’s Blade Runner.
Any of these moods can be summoned from the Valvenergy Tone Sculptor. Six sliders cut or boost 10 dB frequency bands spanning 100 Hz to 5.6 kHz. A seventh slider cuts or boosts the master output by 12 dB. This platter of options might not sound like much. But you can use these seven controls together to very specific ends.
“Radical EQ settings can add aggression, near-claustrophobic intimacy, and stark, explosive dark-and-light contrasts.”
For example, bumping the high-midrange and the master output produces narrow cocked-wah-like filter sounds with enough push to produce extra amp overdrive—effectively turning the Tone Sculptor into a buzzy, almost fuzz-like filter effect. But unlike a wah, you can carefully scoop high end or add a spoonful of bass to blunt harsh frequencies or give the tone a bit more weight. You can also broaden the palette of an amp/guitar pairing. I matched a particularly trebly Jazzmaster bridge pickup with a very hot and toppy Vox AC15-flavored amp for this test—a recipe that can be spiky on the best days. But with the Tone Sculptor in the line, I could utilize the same sharp, fuzzy, and filtered Mick Ronson wah tones while shaving some of the most piercing frequencies.
EQ pedals exist on many points along the cost spectrum. And at $219, the Tone Sculptor lives on the high side of the affordable range. Does it offer something less expensive models can’t deliver? Well, for one thing, I found it relatively quiet, which is nice whether you’re shaping toppy high-contrast effects or performing more surgical adjustments. And the sliders feel nuanced and nicely tapered rather than like a dull axe with a few basic frequency notches. But in many situations I also liked the color imparted by the circuit—generated, presumably, by the Nutube. “Color,” in audio terms, is a broad and subjective thing, and one should not necessarily expect the warm, tube-y glow of a vintage tube Pultec. Still, the Tone Sculptor has many forgiving, flattering qualities—typical of studio EQs—that enable fine tuning and experimentation with more radical and creative applications of the effect.
Valvenergy Smooth Impact
As with the Tone Sculptor, the Smooth Impact’s use of Nutube engenders certain expectations. It’s easy to surmise that because Smooth Impact has a vacuum tube in the circuit that it will behave like a little Teletronix LA-2A leveling amplifier. That’s a big ask for a $219 stompbox. On the other hand, the Smooth Impact exhibits some appealing characteristics of studio tube compression. At lower compression levels, it works well as a thickening agent—adding mass without much additional noise. And at higher compression levels it can sound snappy, crisp, and tight without feeling like you’ve bled every trace of overtone from your signal.
The Smooth Impact’s controls aren’t totally atypical. But because it lacks some familiar features like variable attack and release, yet is more complicated than a 1-knob DynaComp, you have to trust your ear to navigate interactions among the controls. The most unfamiliar of these is the 3-way vintage/natural/sag toggle. The first two are defined by preset attack and release settings: Vintage is slow attack and long release, and natural is the opposite. The sag mode’s compression is more like what you get from tube saturation, and it’s useful for adding thickness and complexity to a thin amp tone at modest compression levels.
Though the vintage and natural modes certainly have a different feel, they don’t always sound worlds apart. And like the sag mode, the thing they have in common is the way they enrich lifeless amp output at low to medium compression, with a bit of grind from the tube gain and a little extra makeup gain from the output. At the most aggressive settings, the tube gain can get a little crispy. And really crushing the compression can flatline your tone without adding much in the way of extra sustain. These are limitations common to many compressors with similar features. But unless I was chasing very ultra-snappy Prince and Nile Rodgers fast-funk caricatures, I enjoyed the Smooth Impact most in its in-between ranges, where mass, mild, harmonious drive, and low noise showcase the pedal’s sometimes studio-like personality.
Boss’ firstWaza Tube Amp Expander, built with an integrated power amp that enables boosted signal as well as attenuated sounds, was and remains the OX’s main competition. Both products have copious merits but, at $1,299 (Boss) and $1,499 (Universal Audio), each is expensive. And while both units are relatively compact, they aren’t gear most folks casually toss in a backpack on the way out the door. The new Waza Tube Expander Core, however, just might be. And though it sacrifices some refinements for smaller size, its much-more accessible price and strong, streamlined fundamental capabilities make it a load-box alternative that could sway skeptics.
Micro Manager
The TAE Core is around 7 1/2" wide, just over 7 " long, and fewer than 4 " tall, including the rubber feet. That’s about half the width of an original TAE or OX. The practical upside of this size reduction is obvious and will probably compel a lot of players to use the unit in situations in which they’d leave a full-size TAE at home. The streamlined design is another source of comfort. With just five knobs on its face, the TAE Core has fewer controls and is easier to use than many stompboxes. In fact, the most complicated part of integrating the TAE Core to your rig might be downloading the necessary drivers and related apps.
Connectivity is straightforward, though there are some limitations. You can use TAE Core wirelessly with an iOS or Windows tablet or smartphone, as long as you have the BT-DUAL adaptor (which is not included and sets you back around 40 bucks). However, while desktop computers recognize the TAE Core as a Bluetooth-enabled device, you cannot use the unit wirelessly with those machines. Instead, you have to connect the TAE Core via USB. In a perfectly ordered world, that’s not a big problem. But if you use the TAE Core in a small studio—where one less cable is one less headache—or you prefer to interface with the TAE Core app on a desktop where you can toggle fast and easily between large, multi-track sessions and the app, the inability to work wirelessly on a desktop can be a distraction. The upside is that the TAE Core app itself is, functionally and visually, almost identical in mobile and desktop versions, enabling you to select and drag and drop virtual microphones into position, add delay, reverb, compression, and EQ effects, choose various cabinets with different speaker configurations and sizes, and introduce new rigs and impulse responses to a tone recipe in a flash. And though the TAE Core app lacks some of the photorealistic panache and configuration options in the OX app, the TAE Core’s app is just as intuitive.Less Is More
One nice thing about the TAE Core’s more approachable $699 price is that you don’t have to feel too bad on nights that you “underutilize” the unit and employ it as an attenuator alone. In this role, the TAE Core excels. Even significantly attenuated sounds retain the color and essence of the source tone. Like any attenuator-type device, you will sacrifice touch sensitivity and dynamics at a certain volume level, yielding a sense of disconnection between fingers, gut, guitar, and amp. But if you’re tracking “big” sounds in a small space, you can generate massive-sounding ones without interfacing with an amp modeler and flat-response monitors, which is a joy in my book. And again, there’s the TAE Core’s ability to “expand” as well as attenuate, which means you can use the TAE Core’s 30-watt onboard power amp to amplify the signal from, say, a 5-watt Fender Champion 600 with a 6" speaker, route it to a 2x12, 4x12, or virtual equivalent in the app, and leave your bandmate with the Twin Reverb and bad attitude utterly perplexed.
The Verdict
Opting for the simpler, thriftier TAE Core requires a few sacrifices. Power users that grew accustomed to the original TAE’s super-tunable “resonance-Z” and “presence-Z” controls, which aped signal-chain impedance relationships with sharp precision, will have to make do with the simpler but still very effective stack and combo options and the “air feel level” spatial ambience control.The DC power jack is less robust. It features only MIDI-in rather than MIDI-in/-through/-out jacks, and, significantly, 70 watts less power in the onboard power amp. But from my perspective, the Core is no less “professional” in terms of what it can achieve on a stage or in a studio of any size. Its more modest feature set and dimensions are, in my estimation, utility enhancements as much as limitations. If greater power and MIDI connectivity are essentials, then the extra 600 bones for the original TAE will be worth the price. For many of us, though, the mix of value, operational efficiencies, and the less-encumbered path to sound creation built into the TAE Core will represent a welcome sweet spot that makes dabbling in this very useful technology an appealing, practical proposition.
