October 20, 2010
Interested in plugging a flattop into your favorite silver- or black-panel beauty? Here’s what you need to know.
Have you ever tried to plug your acoustic guitar into a classic-style Fender amp? There are some hurdles to overcome, and this month I’ll provide some advice on how to get past them. But first, some background.
Amps made for electric guitars are carefully designed and matched to the voltages and frequency profiles of signals delivered by electromagnetic pickups. An amp sounds best when it does a good job at amplifying or filtering out certain frequencies. So many of us have stumbled upon challenges when the input signal—say from an acoustic guitar or other instrument—is way different than what the amp expects.
A guitar signal is initially created by moving the strings. The more vibrating metal mass closer to the pickup’s magnet, the more magnetic pull and more current is induced inside the coil wire in the pickups. More windings and stronger magnets induce more current, but also reduce brightness and clarity. The coil-wire thickness, wire material, and coating material and thickness also play a role in signal strength and frequency response. The signal voltage produced by a pickup is low—typically between 0.1 and 1V—and contains frequencies between 80 and 1200 Hz.
On the amp side, there are even more factors that amplify or weaken certain frequencies—so-called frequency filtering. Take a vintage Fender Deluxe Reverb. It is designed with specific tubes, resistors, and caps in the preamp stage to amplify a weak input signal and shape it through EQ, mix in some reverb, and transport the result to the power amp circuit, which does three things. First, it splits and duplicates that result into an inverted signal, then it amplifies the two signals as much as possible, and then feeds them into each side of a power transformer that alters the resulting voltage to a suitable level for a loudspeaker. That’s typically 30 to 50V. The speaker cabinet and loudspeaker itself are the final stage in delivering a filtered and amplified guitar tone.
For acoustic guitars I prefer modern American-style speakers that can handle high power and both a firm bass response and a crisp top end.
If you hook up other instruments, like an acoustic guitar or a harmonica with a microphone, and feed an electric guitar amp their signals, you will get totally different results throughout the circuit. You may not get the tone you expect, or, in the worst case, you might damage the amp. But generally, all passive sources with electromagnetic coil pickups are safe to use. This includes piezo pickups mounted to the bridge of an acoustic guitar and vocal microphones. Since they are not powered by an external source like a 9V battery, they are passive and create a weak signal.
You should be careful using electrically powered sources like an acoustic guitar with a battery-powered preamp and EQ. Also, electric pianos, synthesizers, or Bluetooth speakers with mini-jack outputs are dangerous, too, since they can easily blow the loudspeakers due to a wrong volume or EQ setting. Electric pianos can sound very good through a vintage Fender amp. I’ve seen Fender Rhodes keyboards played through Twin Reverbs, and we’ve all heard organs through Leslie/Vibratone speakers, which can be run by Fender guitar amps.
Acoustic guitars with active pickups can be difficult. With typical default amp settings for electric guitar, the tone is narrow and focused around certain mid frequencies. It lacks fullness, top-end clarity, and overall balance. So, I have some tricks you should try if you’re experimenting with this option. First, set all the EQ knobs to 10. This allows the guitar signal to travel through the preamp section with minimum change of tone. Be very careful with volume and start low—at around 1.5—and increase from there. I find big, powerful Fender amps are best for this, since they have plenty of clean headroom and wide EQ possibilities with a full set of bass, mid, treble, and bright-switch controls. And that makes them less prone to howling feedback.
A big speaker cabinet will enhance the low end, allowing the preamp and power amp to relax more without maxing out clean headroom. Remember that the power and energy lie in the bass. I suggest the silver-panel 40-watt Bandmaster Reverb and 85-watt Showman Reverb as practical amp heads for acoustic purposes. I use my Bandmaster Reverb with a 1x12 extension cabinet loaded with an Eminence Maverick. For acoustic guitars, I prefer modern American-style speakers that can handle high power and both a firm bass response and a crisp top end. Speakers are very important for your tone. The guitar’s pickups are also important, together with a correct setup, so the action permits the optimum proximity of the pickups.
Acoustic pickups don’t have to be expensive. They just need to be balanced and clear. A good guitar amp and some careful adjustments of the controls will do the rest.
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A lightweight, portable amp series developed after months of forensic examination of vintage valve amps.
The St. James series offers amps in two formats: an EL34 design creating classic British rock tones and a 6L6 model with crystal clean tones and higher gain, both available as Celestion-equipped combo or amplifier head with matching vertical 212 cabinet. Designed to be simple to use but highly versatile, these amps offer an intuitive two-channel setup that delivers Blackstar’s best-ever clean and overdrive tones.
These amps are ideal for gigging players in search of a great-sounding valve amp at less than half the weight of traditional valve-driven amplifiers, as well as studio players looking for elite tone with the convenience of built-in tools used for recording applications. The models’ light weight is attributable to several factors in construction and design, namely the candlenut wood cabinet and custom Celestion Zephyr speaker, all without sacrificing the all-valve signal path creating the sound and feel of a traditional valve amplifier.
All four amp models feature two-channel 12AX7 preamp tube circuitry, along with three power switch options to fit the user’s need:
- the 50W full power setting, offering the loudest clean headroom;
- the SAG setting, proving the softer, vintage-feeling dynamic compression of a power supply ‘”sag,” most noticeable on the loud transients (attack) of the sweetest tube amps;
- and a 2W low power setting for recording or smaller gigs, delivering a more overdriven power amp tone by controlling HT (high voltage) and bias in the power stage, delivering a more natural tone than the usual “power soak” load resistor method often used.
See How These Players Reacted to St. James | St. James | Blackstar
For more information, visit: www.blackstaramps.com. Blackstar will be exhibiting at Booth 5723 (Hall D) at The NAMM Show, June 3-5, 2022, in Anaheim, CA.
U.S. MAP pricing is as follows:
- St James 50 Watt 6L6 Combo Amp: $1299.99
- St James 50 Watt 6L6 Amp Head: $1199.99
- St James 50 Watt EL34 Combo Amp: $1299.99
- St James 50 Watt EL34 Amp Head: $1199.99
- St James Vertical 212 Cabinet Black: $749.99
- St James Vertical 212 Cabinet Fawn: $749.99
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Need an affordable distortion pedal? Look no further.
We live in the golden age of boutique pedals that are loaded with advanced features—many of which were nearly unthinkable a decade or so ago. But there’s something that will always be valuable about a rock-solid dirt box that won’t break your wallet. Here’s a collection of old classics and newly designed stomps that cost less than an average concert ticket.
JHS Series 3 Overdrive
This OD is part of the company’s Series 3 line which offers affordable stomps with simple control setups. Along with volume and drive controls, it offers a body knob that tweaks the EQ and a gain switch that moves between more saturated and crunchier sounds.
Thanks to an extremely dedicated following among Nashville session cats, the other green stomp is now offered in a downsized setup. It can run up to 18V for increased headroom and sports glow-in-the-dark knobs for those extremely dark stages.
TC Electronic MojoMojo
This all-analog distortion offers classic, vintage-inspired tones with a familiar control setup of volume, gain, bass, and treble. The real secret sauce is in the voice switch, which allows you to move between a more natural sound and a bass cut.
Since 1978, the DS-1 has been a go-to for generations of guitarists. It offers a scooped sound that can take you from grunge to shred and has been affordable for decades.
EarthQuaker Devices Plumes
Although loosely based on a classic circuit, EQD has replaced the 4558 IC with a JFET op-amp for a more mid-focused sound. In addition to the standard controls, the toggle switch moves between two different clipping options or no clipping at all for a wide-open clean boost.
Electro-Harmonix East River Drive
A JRC4558 IC-loaded circuit that creates the classic symmetrical overdrive sound, this is an all-analog affair that is true bypass, housed in a rock-solid chassis, and can run on a 9-volt battery—which is included.
Fender Hammerstone Overdrive
One of the newest entries on this list is a retro-looking stomp that offers some interesting features under the hood. The original circuit allows you to control the mids before the gain stage, plus there’s an internal trim pot to wrangle the high end.
Ibanez Tube Screamer Mini
One of the most popular stompboxes of all time has been shrunk down to a mini-sized wonder. With an oversized drive knob and two smaller tone and level controls, this green monster aims to cop all the classic midrange tones of the original.
Pro Co Rat 2
Is it a fuzz? Or a distortion? Or an overdrive? Well, thanks to the famous filter control, you can blur the lines between all the different flavors of dirt. It offers a totally analog signal path, glow-in-the-dark graphics, and the trademark heavy-duty enclosure.
There’s no mistaking that shade of yellow. This dead-simple setup offers output and distortion controls along with a vintage-sounding germanium clipping circuit that does everything in its power to blur the line between overdrive and fuzz.
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