Sustaining the Experience
controllable feedback and sustain for the guitar with the Sustainiac
® model-C
last update: Mar 4, 2011

Copyright 2010-2020 by H. Gragger. All Rights Reserved. All information provided herein is destined for educational and D.I.Y. purposes only. Commercial re-sale, distribution or usage of artwork without explicit written permission of the author is strictly prohibited.The original units  with their associated  trade-names are subject to the copyright of the individual copyright owner. The Author is by no means affiliated with any of those companies. References to trade names are made for educational purposes only. By reading the information provided here you agree to the Terms of Use.
MAIN PAGE>MUSIC STUFF>SUSTAINING THE EXPERIENCE

Index

Sound ingredients for a vintage live stage tone
Types of  Sustain
The Sustainiac® Model-C
Power Supply Issues
Understanding the model-C´s controls
Excursion: creating feedback the organic way with a  guitar amplifier
Sound Samples
Hands-on Experience

Sound ingredients for a vintage live stage tone

Avowed Hendrix- (and sixties-) aficionados always try to explore more and better ways of approaching their idol. Fortunately, there is no magic in the gear he used at least, although there is magic in the way he used it.
Hendrix was no doubt a pioneer in exploiting what was available at the time. Unlike today´s cats, he reportedly used stock equipment throughout, and he was not even affixed to any piece of equipment in particular. He could reproduce his sound with any type of gear.



"But you know, Hendrix would have sounded like Hendrix if he’d played some no-name archtop with add-on pickup through a small Silvertone amp all his career… and we’d all probably be out there trying to score the exact same rig. And before you go buying that left-handed neck and vibrato bridge to add on to your right-handed Strat to “get the Hendrix sound,” consider this: Hendrix borrowed bassist Noel Redding’s Telecaster to record both “Hey Joe” and “Purple Haze”—a sobering revelation for anyone who ever quoted those tracks as classic examples of Jimi’s great Stratocaster tone. [...]"

"Before you spend the mortgage in an effort to acquire “the Hendrix set up,” it’s also worth considering that most of the sounds you have heard on record were produced with far more creative, spontaneous, and impenetrable signal chains than exhibited by his simple live rig."


While the above holds true, some pieces of equipment worked out as Jimi´s favorites.

Fail safe recipe for a basic Hendrix stage tone:

  • use a single coil guitar Stratocaster style
  • use a Marshall tube amp sixties style with 4x12 cabinet
  • use a low gain fuzz face clone
  • use a wah-pedal with discretion
  • maybe add a univibe clone
  • add a little plate reverb with discretion


"Throw all of these into the pot, stir, and simmer gently, and it’s not a stew you are easily going to replicate just by assembling the various bits of hardware and plugging them in. That said, hey, this is all great sounding gear, and if you acquire something anywhere close to it, and get your chops down, you can manage a pretty good approximation of “the tone” … and while you’re at it, maybe even work toward crafting your own soon-to-be legendary voice."


Now this seems pretty costly, and it is. Let alone the hernia you may be inviting upon hauling this stuff.
For myself, I use a Digitech® RP-500 multieffects-processor that has all that built into it. Dial in whatever you imagine.
Don´t forget, the ear changes, and  what you may find appealing one evening may sound disgusting to your ears next morning. I can hear the purists tearing their hair upon the thought of employing a digital device like that. This has been discussed at length elsewhere.

(The above "recipe" does by the way coincide roughly with the tone recipes provided by the famous, but now discontinued Hendrix Pedal by  Digitech® from their signature series.)
May I point out that Hendrix used equipment that, by today´s technical standards, was far less than perfect, and he created signature sounds with them. Don´t get lost in illusions of sound voodoo so much, that it distracts it from your musical growth.

See what can be done with a
simple setup like the one above as demonstrated by
James Santiago and how flexible you are in achieving a certain sound.
This all worked out fine, but one piece was still missing: long sustain on solo playing.

Back To Index

Types of  Sustain

 
I realized that most of the user submitted "Hendrix patches" for the RP-500 contain way too much distortion.



"Listen closely to Hendrix’s tone, however, and you realize a lot of it really is fairly clean, while very dynamic and touch sensitive."


This is very likely caused by the quest for a long, sustained tone. Sustain is the reciprocate so to speak of the natural decay of a guitar´s string. After being plucked, it continually looses vibrational energy in a way that is peculiar to every guitar.

A dying tone
during a guitar solo is exactly the least thing a player wants, so several means to compensate for that have been devised:



"SUSTAIN FROM COMPRESSORS: A compressor makes the instrument pickup signal stay at a constant level for a few seconds, while the string vibrations actually die out. While the string vibration is dying out, the compressor gain automatically gets higher and higher. [...]"

"SUSTAIN FROM DISTORTION EFFECTS: Distortion effects achieve sustain of played notes in much the same way that compressors do: They keep the signal at the same level even though the string vibrations are dying out. Instead of keeping the signal out of the distortion (clipping) range as compressors do, distortion effects simply increase the signal amplitude by very large amounts, and in the process "cut off" or "clip" the positive and negative portions of the signal.
[...]"

"SUSTAIN FROM AMP FEEDBACK: Many players achieve sustain by turning the amplifier up to a loud volume, and by holding their instrument near the amplifier speakers. 
[...]"

-Maniac Music (Sustainiac): real sustain vs. fake sustain

Both compression created by dedicated compressor devices and by signal clipping do mutilate dynamics. They make all signals equally loud. This is not what you want and this is not what those guys did centuries back in time. By all means, try a compressor and wind up distortion, and if this is not what you want, read on.

I personally came to the conclusion: this cannot be remedied electronically by means of a simple stomp box that manipulates the guitar´s signal. And since I do not want to lose either hearing, family nor mortgage, standing close to a cranked amp for that organic feedback was not an option either.

Before doing any internet research, I tried several things out of my own invention, such as proximate speakers; they all failed catastrophically.
I finally searched the web and found that a device is commercially available, that does the trick. This devices applies mechanical vibrations that are sympathetic with the strings vibrations to the headstock of your guitar. Similar devices install in the place of a pickup and apply sympathetic magnetic vibrations directly to the metal strings. This is a more efficient method, s
ince energy has to be converted only once from electric to magnetic. (An electro-acoustic transducer has to convert once more, namely from electric to magnetic to mechanical energy.) Unfortunately installing this device this requires re-working the guitar body and sacrificing one pickup position and has other drawbacks. This option phased out too.

As usual (being an electronics head) I looked for a D.I.Y. solution. There are some patents available, one that gained commercial success is marketed by Maniac Music, Inc., the model-C. It is pretty well documented in the underlying U.S. patent US20050081703A1, while the electronics part is probably more similar to the one depicted in patent 5932827. Those writings are interesting to read in order to understand the function of such a device better, but are not sufficient (with intention probably) to replicate the device. Moreover, I am sure some more development work has gone into that machinery since the patent has been issued.

There is a huge collection of D.I.Y. projects on the subject on http://www.diyguitarist.com, unfortunately this thread has become unreadable, and by browsing through those pages randomly, this has apparently not gone anywhere near a usable project such as the stomp box projects have in some guitar fora.

One half of such an apparatus hinges upon a well-functioning electro-mechanical transducer that is constructed in a way that it does not produce stray magnetic field. It has much of a humbucking pickup, just reversed in action.

It may be easy to replicate an electronic circuit even by a layman, but it appears much more difficult to make an electro-mechanical device (such as pickups and loudspeakers, or, indeed, string driver transducers) by a non-expert, since this requires experience, maybe exotic materials and machinery. I cannot see how this can be done successfully on a cook-book level.

Re-inventing the wheel would thus have been cumbersome, and as outlined already in the
stompbox forum, does not pay in this case. So with all respect and love to D.I.Y., D.I.Y. phased out.

Back To Index

The Sustainiac® Model-C

What remains is the model-C clamp-on electro-mechanical transducer by Maniac Music. I ordered one and had it here in a week. The device is built like a tank. One thing appeared (possibly) damaged, which was the transducer mounting mechanism.
The clamp is mounted to the transducer´s iron core via rubber pads. These have arrived apart, but appear to have been glued at some point, although the two pieces hold together by strong magnetism anyways. I repeatedly wrote to Mr. Hoover but never received a reply on that. It does not matter.  So let´s look at the  thing.

Back To Index

Power Supply Issues

The first small problem arose when the parcel landed - I ordered it without a power supply, since the stock transformer would not be of much use to me. As the website teaches us, they only supply the stock domestic wall-wart transformer. Foreign users will have to either use a cumbersome step-down (resp. step-up) transformer, or get themselves a wall wart supply. This proved to be not easy, since 24 Vac @ 1A wall wart transformers are very uncommon. The only company that stocks one in Europe asks for prohibitively high transport fees to foreign countries.

Fortunately, naked transformers abound, so I happened to have a 230 V to 24V @ 1A toroidal lying around, fused it with 200mA SB primary and 1.2A SB secondary.

The moment of first plugging in was kind of thrilling. Transformer ratings are specified for full load. On low load or off-load conditions the voltage may rise slightly due to the transformer´s inherent regulation characteristics. Hard to say how wall-wart transformers behave in this respect, and impossible to anticipate how the sustainiamp™ would react. I wrote to Mr. Hoover from Maniac Music several times over that, but he never replied. He did, however, reply quickly upon my order request.

I counted two and two together. If at all possible, OPA´s (operational amplifiers) are powered by symmetrical voltages, meaning + and - supplies of equal magnitude, such as +/- 12-15 Vdc, or they are operated from a single supply, such as 30-40 Vdc for a generic OPA, where an arbitrary center voltage is generated.

With a single AC source one can use both methods and remain within the specs. I measured some 27Vac off-load, which in either case is fine for OPA´s.


Also, the actual current demand of the sustainiamp™ is not specified. All the web-site says, a 1Aac power supply is needed.
Now if a transformer is asked to supply its rated current (in my case 1A) for a prolonged time, it will heat up - not a good thing in a closed environment. You usually take a transformer with a somewhat higher current rating, but it turned out that the sustainiamp™ does not consume more than 500 mA at average, some excursions to 700 mA. It does not appear to heat up even after prolonged sessions.

Conclusion is, the sustainiamp™ feels well with a self-made power supply, so don´t spend your money on exotic wall warts.

Back To Index

Understanding the model-C´s controls

What do all the controls do? A sound understanding of their operation allows you to explore their application better.

Harmonics control

From the handbook (not more than a two page flyer) we learn, that the "harmonics" switch alters the way the model-c excites harmonics, and that it is some sort of equalizer. From the usage I deduct that it is some sort of big muff pi tonestack similar to the AMZ Double Tone. This would probably mean a bassy signal on the left and a trebly signal to the right if it were a guitar amplifier, and this coincides with my observations. Since the control has a fixed center frequency it is not a "tracking" filter, as a DSP would probably make one. A tracking filter would adapt its center frequency to the note played and thus remain consistent behavior over a big fret range. Again, this may not be of too much concern if you are just trying to emulate direct amplifier feedback.

The knob nevertheless lets you control if your sustained tone breaks up to harmonics rather than sustaining the base note and how quick. As mentioned, this may not be consistent over the whole fretboard range, in so far the claim of "predictable" feedback is made relative again.

Effects loop

This is very likely placed after an initial gain block. However, the employed effect is only "heard" by the sustainiamp™
.

Gain and String Drive

Some customers mention in their reviews, that they are confused by the usage of Gain vs. String Drive. This stems from a lack of understanding of what the whole system does. Unfortunately the user´s manual leaves you alone with the task of finding out. Also, you are not driving the strings per se, the knob governs the amount of power the sustainiamp™´s output stage
pumps into the transducer. This may all seem pretty confusing.


Back To Index


Excursion: creating feedback the organic way with a  guitar amplifier

An analogy will help shedding more light on the device´s function: treat the model-C as if it were a combo amplifier that is in proximity to your guitar. Don´t forget, it is made to emulate one for its acoustical feedback behavior in the first place!


ecke
rahmenrahmenrahmenrahmenrahmenrahmenrahmenrahmenrahmenrahmenrahmenrahmenrahmen rahmen
rahmen
rahmen
rahmen
stecker knopf knopf stecker stecker knopf stecker lampe
Guitar
Input
Preamp
Volume
Boost
<Bass Trbl>
FXLoop
Out
FXLoop
In
Master Volume
Power
Output

rahmen
rahmen
rahmen
rahmen eckeeckeeckeeckeeckeeckeeckeeckeeckeeckeeckeeckeecke ecke




Fig. 1: fictive high gain high power combo amplifier

Our fictive combo guitar amplifier is of simple nature. It sports a preamp volume control that determines preamp gain, a simple passive "equalizer" stack similar to a big muff tonestack, that makes tone more bassy if rotated counterclockwise and more trebly if rotated clockwise.

A passive tonestack like most vintage amplifiers incorporate it is an all cut control, meaning it has no amplification. So the term "boost" is not quite correct, but makes it more logical to use. In reality it cuts bass to the left and treble to the right with a mixture in the center.

Our virtual amplifier is equipped with a send and return loop, which allows to insert a guitar level effects device such as an equalizer, a delay or a wah-wah pedal after initial preamplification. If unused, the signal is routed through directly.
A master volume control sets gain in the power stage and the absolute power level that is pumped into the (voice) coil.

Loudness resp. the level of power going into the transducer are dependent on two factors:
  1. Preamp volume (PV) setting
  2. Master volume  (MV) setting
A low PV setting will keep preamp gain low and ask for a high MV setting to achieve substantial loudness. A higher PV setting will ask for a reduced MV setting to achieve the same loudness. However,  in traditional tube amps, this will encourage
signal distortion, spectral coloration (signals compressed  by clipping will also be enriched in high frequency content) and compression as described earlier. This yields reduced dynamic behavior, meaning small input signals and loud input signals will eventually produce the same loudness levels to a point.
There is always gain in an amplifier enlarging a guitar´s signal, but PV and MV set the balance between preamp gain and power stage gain and thus affect the aforementioned parameters.

The tone control will shift the tonal balance from bassy to a trebly tone and thus either encourage or discourage the creation of harmonics.

Using a device such as a wah-wah in the FX loop of our virtual amp will mean a high gain in a small frequency band due to its high Q filter nature. This is described on the geofex site well. A wah-wah may overdrive and compress certain frequency bands, if you are already running on elevated gain. A equalizer, particularly a parametric equalizer set to small bandwidth and big amplification, might do something similar.

Finally, a medium (in this case air) transports mechanical energy from a transducer (in this case the loudspeaker) back to the originating source, namely the guitar´s strings. Both of those energies are strongly related frequency-wise, but not necessarily in phase. Air is a bad carrier for mechanical (vibrational) energy compared to denser material such as wood, therefore bigger energies are needed to achieve the same effect.

Both a typical musical instrument loudspeaker and the transducer of the model-C are coil driven and therefore form second order acoustical low-pass filters. This is another striking similarity, although the model-C´s transducer will, due to its smaller size, cut off much at much higher frequencies.

Enough of the theory. Now imagine standing in front of your virtual combo with your guitar, trying to achieve feedback from sympathetic acoustic energy. As mentioned, the MV control sets the absolute loudness level, and it will require a minimum loudness level (or system gain) at a given distance between loudspeaker and guitar to achieve feedback at all.
  1. Wear virtual ear protection ;-)
  2. Start with the PV control low. After finding a sweet spot for the MV loudness where feedback starts to happen, experiment with that setting. Much more, and you will hear permanent squeal, a little less, and nothing happens.
  3. Turn up PV and turn down MV to the perceived same loudness. Experiment with that setting. You may encounter increasing compression effects and perceived sustain. You may feel that you may be able to evoke feedback more persistently (increased compression due to limiting).
  4. Insert one of the aforementioned effect devices and observe its influence. A wah-wah for example will on certain pedal positions (amplification of a certain frequency band) produce severe feedback.
  5. Change the distance between guitar and loudspeaker and observe the effect on sustain feedback due to diminishing vibrational energy. Change gain and see how this behavior varies.
  6. Move your guitar in front of the amplifier sideways or move your body at a small angle and observe the effect on sustain feedback due to changes in phase.
  7. At any given posture, observe the feedback effect on different positions on the neck. Some positions will not easily develop feedback sustain. This may change after a posture change (phase relationship between original vibrational energy and fed back vibrational energy
  8. Rotate the tone-knob clockwise (increase in treble) and notice the tonal shift in feedback sustain notes from base note to harmonics. Observe a possible increase of harmonics due to clipping after excessive gain has been applied.
The model-C is actually working exactly the same as our fictive amplifier. Map our fictive amplifier´s controls to the model-C´s controls and you have understood the sustainiamp™. The only difference being, that the amplified vibrational energy is transferred to the strings by a vibratory element mounted directly to the guitar rather than through air from a loudspeaker cone.

Acute readers may have noted, that there is one thing the model-C does not take account of: a master of feedback, such as Hendrix, would change his body position slightly to fine-tune phase and/or gain, on performance level so to speak. There is no built-in solution for that, but provision has been made by the loop circuit: try an external volume pedal or performance-tunable small delay. The sustainiamp™ just provides a 0 or 180 deg phaseshift, whatever this may translate to, once mechanical energy is sent down the neck. The automatic phase change function is explained further down in more detail. There are more paths to be explored as far as inserting external effects goes.

If you were trying to emulate the feedback coming from a vintage setup with rather low gain settings throughout, you may decide to keep gain low. Remember, you really have a separate little amplifier that is just "heard" by your guitar, and it does not manipulate your tone, it affects sustain. You may run your guitar into your amp clean, in fact you may turn your amp off entirely. But for a vintage stage situation, keep the gain of sustainiamp™ in a range comparable to your amplifier´s gain.

For a more contemporary set-up with high gain employed, such as heavy metal or grunge, you may work with high gain on the sustainiamp™, too. This can typically be heard on the metal players fraternity recordings where all tones on guitar solos eventually end up on harmonics with endless sustain. Well...
But this is entirely up to your taste.

I hope this little excursion has aided to clarify what the model-C does.

Back To Index

Sound Samples

The following sound samples are nothing fancy. Don´t expect screaming solos. Just a few single note exercises to create an impression of how the sustainer would react in different situations and with different settings.
My focus was on demonstrating the device, not on demonstrating virtuosity.

I suggest listening with headphones or pretty loud to catch the fine nuances. The sustainiac´s effect is unobtrusive.

The subsequent recordings have been done using the following setup:
  • Stratocaster with singlecoils, center pickup
  • J-FET buffer directly after the guitar
  • Jazz Chorus with Jazz Chorus 2x12 cab simulation on  Digitech RP-500 for clean recordings
  • Marshall JTM-45, Guyatone OD1, EMT Plate reverb and 4x12 cab simulation on Digitech RP-500
    for overdrive recordings.
  • PC hard disk recording straight into sound card.
Setting: clean; ascending single note single string riff played, all other strings muted by right hand.
(click on the symbols to invoke player)

Tone
Exmpl.
String
Harm.
Gain
String
Drive
Remarks

2
2
7
Low preamp gain setting, low compression. on lowest string.
Sustained note does not build up easy with upper harmonics discouraged.
Note how sustain develops easier towards fret7, decreasing towards 12 again.
Note interesting fret buzz effect.

9
2
7
Same gain setting, harmonics encouraged, sustain builds up easier

9
2
7
Low preamp gain setting, low compression. on G-string.
Note how much easier sustain develops due to a more prominent pole piece on the staggered pickup (= higher starting volume). Noticeable dependency on the distance to the pole pieces.

9
2
7
"Special technique", release fret pressure slightly for fret buzz and make the note change to even higher harmonics. Takes training.
Note that tones were not picked again, what you hear is fret buzz.

Setting: overdrive; small rock riff played with right hand muting á la steel guitar playing where possible.
(click on the symbols to invoke player)

Tone
Exmpl.
String
Harm.
Gain
String
Drive
Remarks

-
-
-
riff without sustainer
 
1
2
7
riff with low preamp gain setting, low compression. harmonics discouraged
 
10
2
7
dto. with harmonics encouraged

1
8
2
high preamp gain setting, higher compression. harmonics discouraged
 
10
2
8
dto. with harmonics encouraged

Back To Index

Hands-on Experience (the Experience lives on...)

This device works as promised generally. As some users have put it on harmony-central, "the instrument becomes alive" in your hands. An interesting experience. Also, you may find yourself winding down distortion, because you don´t need a lot of clipping compression to achieve sustain.



"Achieving feedback sustain becomes predictable and reliable."
"...to give you controllable, reliable feedback sustain every time."


-Maniac Music (Sustainiac): real sustain vs. fake sustain

Now that is a bit big-mouthed and I cannot concur with that unrestrictedly.

To fully understand the problem we have to delve deeper into the matter. In the
patent US20050081703A1 under [0087] we can read:



[0087]
The vibration energy is coupled into the strings at the points where the strings are pressed against the frets. [...]
The vibration energy travels to the upper string end at the speed of sound for that particular neck, so the farther down the neck that notes are fretted, the longer it takes for vibration energy to travel there. This causes phase shift of the transducer driver signal relative to the string vibration. [...]
For some notes, the phase shift of the sustainer out put signal arrives [...] precisely out-of phase with the string vibration.[...]

For these notes, the musician must quickly change the sustainer phase by tapping on the appropriate foot-pedal, or memorize the particular notes where this happens and refrain from using them.

  -US patent US20050081703A1

The sustainiamp™ also has an automatic mode, that provides phase-reversal in case such a condition is detected.  Of course this does not happen instantaneously, the electronics needs some time to react, letting alone the fact that vibrational energy must be built up and out-of-phase mechanical energy has to be counteracted first.

This means, that you find sweet spots on your fretboard, that obviously evoke feedback easier than others, to which for some conditions neither 0 deg phase shift nor 180 deg phase shift fit well. You may find you play a nice tone with plenty of sustain, pull the string up, next phase shift becomes excessive, the sustainiamp™ decides to toggle phase and your tone comes to a dead stop. You may stomp on the footswitch to force a phase change again, but for your tone it may be too late. They claim that the automatic mode counteracts this, but since it only shifts 180 degrees or zero and nothing inbetween it can not possibly cater for all cases. See earlier how our fictive amplifier handles this.

For unconditionally correct phase shift you would need a bloody fast DSP (digital signal processor), which  is yet another story. It has been done by Edgar Berdahl, but this may be over the top for our purposes. Jimi encountered the same problems in direct amp feedback, by the way. Turning the body a little or changing the distance, and tone comes to a grinding halt. He was a master in controlled feedback too.

So, "controllable, reliable feedback sustain every time"... maybe for a particular setup, certain strings and certain frets -yes. But for all frets and all strings, letting alone string bends - not in my experience. But it certainly evokes sustain very similar to direct amp feedback - too similar maybe as we have seen. Read more on the manufacturer´s site: Performing with the MODEL C.

The extra cable dangling down from the headstock does indeed get in the way, as some reviewer stated. I decided to route it on the back of the guitar as they have outlined it on the drawing for the cord routing system. It then teams with the guitar cable that is already there. I might later decide to build a routing box as they sell one. I might also cut the transducer cable and insert an additional plug approximately where the cord routing box would come to reside (if I had one), which would enable me to leave the transducer mounted all the time with its cord fastened to the guitar´s body or to the strap and without meters of cable to tame.

I have read somebody was concerned about the optics of the extra cable hanging down - hey, innovations seldomly fit into a picture of tradition, folks.

Negotiation with the site owner (Mr. Alan A. Hoover from Maniac Music, Inc.) does not appear fruitful, unlike most of the abroad contacts I had in the past. Although processing my order quickly and flawlessly, he did not respond to a few technical inquiries I made. In the case a very specific question on the power supply, his answer was vague and not really to the point, in short: not helping. Thank god, all worked out fine anyways. And, with all respect, the website formatting leaves room for improvement to put it mildly.

I have not made any of the dramatic experience with the device reviewers have written about on harmony-central. All in all,
the device works well and my newly gained tone shades were attested 20-20 vintage coolness by the other band members. Any reader experience is gladly welcome.

Back To Index

Update History
  • Dec 26, 2010: corrected layout error
  • Nov 3, 2010: added flash mp3 player
  • May 9, 2010: first release
Back To Index
MAIN PAGE>MUSIC STUFF>SUSTAINING THE EXPERIENCE
MAIN PAGE | MUSIC STUFF | IMPRESSUM

© 2010-2020 AQUATAUR Musik & Elektronik