The Ultra Tonic Pickup - Onboard Feedback Suppression

December 2017

Acoustic Guitar Pickup Discussion DISCLAIMER I: I love the un-amplified sound of an acoustic guitar.

Acoustic Guitar Pickup Discussion DISCLAIMER II: When amplifying an acoustic guitar, my first choice is to use a microphone.

Acoustic Guitar Pickup Discussion DISCLAIMER III: I believe that microphones, while offering the closest representation of an un-amplified acoustic guitar, are the most prone to feedback in a live setting. Thus, my quest continues for a pickup solution that sounds like an un-amplified acoustic guitar, only louder, and is feedback resistant.

Ultra Tonic Pickup
The Ultra Tonic Pickup from James May Engineering

I recently received my first shipment of Ultra Tonic pickups from James May Engineering. James is also a partner in Audio Sprockets, creators of the ToneDexter (see my article on Pickups and Gamechanging Technology). The Ultra Tonic for steel string guitars is a passive, brideplate-mounted, 5-transducer pickup with on-board feedback suppression. A nylon string version is also available.

Soundboard Transducers (SBT’s), piezo-electric crystals often embedded in rectangular, triangular, or disc-shaped modules, are offered in several flavors (JJB Soundboard Transducer, Trance Audio Amulet Acoustic Lens, Dazzo, etc) and are highly regarded for their ability to represent the sound of an acoustic guitar in an amplified setting. They are, however, more prone to feedback than their siblings, the Under Saddle Transducers (UST’s), and can be notorious for co-mingling lower frequencies resulting in a muddy or boomy overall sound. Another shortcoming that plagues many a SBT or UST install on a 6 string guitar is the quiet high E, where the 1st string produces less volume than the other 5 strings.

The Ultra Tonic pickup addresses the two common drawbacks associated with UST’s and SBT’s:

  • An additional transducer is supplied to double-up on the 1st string
  • A small, endpin jack-attached, user configurable circuit board in conjunction with a (larger) 5th disc supplies onboard feedback suppression

How does it sound?

Here are three back-to-back recordings of my 1976 Guild F-512. The first clip is recorded through a Shure KSM141 microphone alone, as a reference. The second clip is recorded (directly) through an LR Baggs Anthem pickup. The third clip is recorded using a (newly installed) Ultra Tonic pickup from James May Engineering, the signal ran through an Audio Sprockets ToneDexter trained with that same Shure KSM141 microphone.

Perspective

I have played the guitar since 1968, having been classically trained on nylon stringed instruments. I became enamored with the steel string guitar in my ’teens and performed professionally for many years, in many venues. I happen to enjoy an amplified sound that most accurately represents the sound of my un-amplified instrument. I also have had to face the pragmatism of controlling feedback, and understood any acoustic guitar amplification system to be a compromise, at best. I have subsequently encountered and/or pursued (nearly) every pickup system available, investing much in time and money, and am convinced of the following fundamentals:

  • There can be a world of difference between a plugged in sound and the elusive my guitar, only louder
  • Pursuit of the latter is extremely costly and may yield less-than-desirable results (more prone to feedback, lots of outboard gear, etc)
  • While I may, not everyone prefers the my guitar, only louder sound
  • Amplifying an acoustic guitar will always involve some form of compromise

Installation

I selected the 12 string as my test guitar thinking that if the new pickup could address the cacophony occurring within the soundbox (aka "lush overtones") that tend to overwhelm most pickups, it could handle anything.

Guild F-512
Guild F-512

I recorded my 1976 Guild F-512 using only a microphone. I re-recorded that same musical piece using the trusty LR Baggs Anthem pickup that I had installed years earlier (when they first came out). The Anthem combines an UST with a soundboard-mounted near-field microphone. An onboard preamplifier gives the UST the responsibility for handling the (otherwise boomy) lower frequencies, while the mids and highs are assigned to the microphone.

The guitar then visited the bench where the strings came off and the Anthem was completely un-installed.

LR Baggs Anthem
LR Baggs Anthem

The Anthem includes an Under Saddle Transducer. When removed, the saddle sits lower in the slot. In my case, it sat too low. While a shim would certainly work, I made a new bone saddle for the guitar.

I studied the instructions supplied with the Ultra Tonic, and opted to fashion a jig to assist me with placement of the discs. Proper placement of an SBT is much more critical than installing a UST. Think location, location, location. Some installers have chosen to test fit an SBT using a double-sided tape as, once it is secured with glue, it is pretty much there to stay. It had better be in an acceptable, if not optimal, location.

Ultra Tonic Jig
Jig for Installing the Ultra Tonic

Installation is similar to installing K&K Pure pickups, where the disc-shaped transducers are affixed to the bridgeplate beneath the saddle position using gel cyanoacrylate glue.

Where the K&K Pure Mini comes with three (3) discs, the Ultra Tonic supplies two (2) additional discs for a total of five (5), with one disc being intended to bolster the (typically under-represented) 1st string and the other, a much larger disc, used to assist with feedback suppression.

JME Ultra Tonic
JME Ultra Tonic

Three (3) of the four (4) smaller discs are attached in a similar way as you would attach a K&K Pure Mini, spaced appropriately below the saddle position. The fourth disc is attached as close to the 1st string as is practical, in line with the other three (3) discs, if possible. In my case, due to the proximity of the X-brace, I had to locate the fourth disc behind the saddle, behind the string hole.

The large suppression disc is intended to be attached toward the back of the bridgeplate on the bass strings side, well away from the saddle or strings. Inadvertently, I allowed the disc to drift a bit too far back and the glue "seized" in a position where the disc was overhanging the bridgeplate. I obtained an additional disc from James and replaced my mistake, attaching the new disc in the correct position.

The endpin jack and circuit board are left outside of the soundhole until testing is complete. I rested the jack on a folded paper towel, and taped it securely to the top.

String-to-string balance

With the jumper that is provided for the feedback suppression options removed, I plugged the guitar in and tested the string-to-string balance. Being a 12 string, it performed as I expected a 12 string would, with the 11th string prominently featured. I was impressed to hear the 1st and 2nd strings at a balanced volume, proving the need for the additional (fourth) disc. The "quiet high E" issue is resolved! Otherwise, the pickup produced a sound much like any other SBT pickup I have heard, where the low end is boomy, the mids are throaty, and the highs are harsh, not articulate.

Should the 1st string (or, in may case, the 1st and 2nd strings) be too loud, James recommends removing the fourth disc (simply clipping the wire would also do). If that thought is off-putting, this factor may make the case for using a double-sided tape for testing the positioning prior to gluing the discs on.

Feedback Suppression

The debut of user-configurable feedback suppression arrived without any real fanfare, and that is bit of a shame. What the Ultra Tonic has introduced is a pretty big deal. Perhaps a little explanation of what is going on will help others understand why I think so. (Oversimplified,) the body of each and every guitar has a resonant frequency, a place at which the instrument is most alive. This will also be the frequency at which the instrument will be the most prone to feedback. Conventional wisdom calls for reigning in, or notching out the offending frequency. As every guitar is different, providing a one-size-fits-all notch filter along with a preamp is helpful, but not near as effective as a guitar-specific solution.

The Ultra Tonic DIP switch selection process finds the best ratio or proportion for mixing in the larger, deliberately out of phase, suppression disc with the smaller, main discs so as to minimize many potential resonances of the top plate (soundboard), not merely the primary resonant frequency that you are using to make your decision with. It typically works on several resonances equally well, so we should be able to expect consistent performance on guitars of various builds.

The resonant frequency is hunted down with the aid of a tone generator (capable of producing a sine wave between 80 and 250Hz), an exciter, and a voltage meter (capable of reading single digit millivolts). Tone generators can be sophisticated standalone boxes or software applications (I happen to like the free, aptly-named AudioTest by Katsura Shareware). An exciter is a speaker that is both capable of reproducing the needed tone (audio frequency) and is able to be put in contact with the soundboard of the guitar without damage. James May Engineering makes a simple exciter that works just fine.

JME Exciter
JME Exciter

The tone is generated. The exciter vibrates the guitar (audibly). A (milli) voltage meter, connected to the endpin jack, reads the output voltage of the pickup (created by the kinetic energy of the vibrating top). Locating the resonant frequency is a matter of altering the frequency of the sine wave (using the tone generator) and watching for the highest voltage reading on the meter. My 12 string happened to really move at 100Hz. Both 99 and 101Hz saw significantly lower output.

JME Feedback Suppression
JME Feedback Suppression

With a shorting jumper (supplied with the pickup) in place, a series of 12 DIP switches attached to the endpin jack are then switched ON and OFF, one at a time, watching the meter for the lowest output. These DIP switches are associated with that fifth (larger) disc, the one that was installed away from the saddle location. The DIP switch that produces the lowest output on meter wins, and gets set to ON for the rest of it’s life.

As with most tests, altering the parameters will affect the outcome. Changing the location of the pickups would necessitate a new test. While I have not done it (yet), I think it would be advisable to retest a double-stick tape installation after gluing the transducers in place, as things could change.

Re-testing the audio output of the pickup in this new condition was eye opening. The predominant 11th string volume was quieter. The boominess was gone! The highs were clean and the mids no longer sounded like a piezo-electric pickup. Pretty impressive! But, in my quest for "my guitar, only louder", I knew I could do even better by processing the signal through the ToneDexter. That signal is what you are hearing in the supplied recording.

Once you are happy with the results, the endpin jack can be installed and the wires secured using any number of methods.

Assessment

This pickup changes things. I am impressed with the ingenuity behind it’s simple design. Paired with the ToneDexter, I believe I possess the closest representation to a mic’d guitar I have ever encountered. To date.

You can read more about the Ultra Tonic pickup on the James May Engineering website