| Sustaining the Experience controllable feedback and sustain for the guitar with the Sustainiac® model-C last update: June 9, 2022 Copyright 2010-2022
by H. Gragger. All Rights Reserved. All
information provided herein is destined for
educational and D.I.Y. purposes only. Commercial
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The Author is by no means affiliated with any of
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MAIN PAGE>MUSIC STUFF>SUSTAINING THE
EXPERIENCE
Index  Sound
ingredients
for a vintage live stage toneTypes of
SustainThe
Sustainiac®
Model-CPower
Supply
IssuesUnderstanding the
model-C´s controlsExcursion: creating
feedback the organic way with a guitar
amplifierSound
SamplesHands-on
ExperienceSound 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.
While the above holds true, some pieces of equipment worked out as Jimi´s favorites. Fail safe recipe for a basic Hendrix stage tone:
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.) 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.
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:
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, since 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 when I waved dollar bills at him). 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. 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 electro-acoustical feedback behavior in the first place!
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. Maybe the term "tilt control" would be more descriptive. 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:
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. A 12" guitar speaker has a typical high end roll-off around 5 kHz. The sustainiamp, if it is behaved, will have to force complement this roll-of in some way. A typical (unaltered) speaker (technically called a driver) exhibits strong beaming for higher frequencies, relative to its cone diameter. Higher frequent sound components will form a small sonic beam of high energy very much focused on the center axis, whereas lower components will radiate more spherically. It has been observed that those musicians using controlled feedback as an expressive element walk around the stage beforehand to track and mark those spots. In electrical terms this will be akin to a high Q high mid (boost) filter, or according to the yin-yang of sound, a suppression other frequencies. In the sustainiamp, this may have been realised with something as simple as a high pass filter together with some sort of automatic gain control (AGC). The subject of phase relation on the other hand raises some questionmarks in my head. Phase on a multi-frequency signal can only refer to a lower frequency component of dominant magnitude. Does the unit extract the fundamental frequency out of the signal brew? On a relatively simple analog unit this can only be as complex as a higher order low pass filter. More investigation is necessary. 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.
The model-C is actually
working exactly the
same as our fictivous 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. Sound Samples Note: This section won´t work any longer since Adobe has disabled Flash content. Maybe one day I overhaul it. 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:
(click on the symbols to invoke player)
Setting: overdrive; small rock riff played with right hand muting á la steel guitar playing where possible. (click
on
the symbols to invoke player)
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.
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:
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 twenty-twenty vintage coolness by the other band members. Any reader experience is gladly welcome. 2022 update, or The Experience Never Dies Unfortunately I did not get on well with the unit. It felt it was kind of ... stubborn and not cooperating and so I parted with it. Maybe too early as it turns out. My guitar always lacked sustain on the upper frets, the notes were just dying. After installing a new vibrato system (colloquially called tremolo) I found that my neck had been shimmed the traditional (lousy) way, and after curing this, the situation improved vastly. The maker of the Model-C did not address this subject (and he likely is not aware of it anyway), that transferring sonic energy via the neck into the body will only work if their junction allows for that, in other words, if the guitar has good sustain in the first place. Think about it, this is logical. This may have been the main reason for the sustainer having great problems in conjunction with my guitar, but alas... Just recently I stumbled upon a further interesting facet that may further improve the neck-body coupling, namely by force-fitting the neck in the pocket before final fastening of the bolts. It has been explained in the video Luthier Trick: Increase Sustain On Bolt-Neck Guitars. Note that if the neck moves changes its relation to the bridge, this will invariably call for revisiting intonation settings. Conclusion: a guitar lacking sustain will not cooperate eagerly with the Model-C. It might not be an issue with real amp feedback, but it certainly will be if vibrational energy is imparted via the headstock. Fix the guitar first. Back To Index Update History
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