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Spin Doctor's primary structure is a non-electronic matrix. An analogue of an acoustic space with alternative size settings.
Alpha Orbiter, © our proprietory sound projector, conveys audio signals around this space. These are collected at suitable nodes for amplification.
The first design has two nodes, creating a stereophonic system.
Implementing four nodes produces a true quadraphonic system.
'Space' damping is adjustable. A critically damped setting, together with an orbiting speed from 4 to 7 C/S (HZ), gives Stereo Vibrato. 4 C/S suits a Rhodes, 6.8 C/S for a Hammond.
An undamped setting gives a lively, 'atmospheric' space, creating Spatial Vibrato. From under 1 through 7 C/S, it bears some resemblance to a rotary speaker. With orbiter disengaged the stereo image is retained, stationary at whatever point it has reached.
Perceived acoustic size depends on speaker spacing & the matrix Size setting.
Chorus projects a stationary signal image, central in the stereo field. This also works in mono, with Vibrato at 6.8 C/S it is then like a tone wheel Hammond's C1 & C2 settings.
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A matrix variation creates Tremulant, in stereo with a two node system. More atmospheric than the Stereo Suitcase Rhodes Tremolo, even more so with 'Spatial' setting.
Mono uses one node, producing Vibrato & Chorus close to those of a tone wheel Hammond. Suitable for updating early tone wheel models or the L series. Stereo, whilst not traditional, is unique. Mono Tremulant is strong & undistorted.
A Rhodes shows another matrix aspect. Complex phase interaction 'wakes up' the piano without spoiling its unique character. Attack & dynamic range increase. Treble is clear & bright. Bass is strong & clear. This change applies at any Orbiter speed, even stationary.
Contour projects selected frequency bands to the stereo field's centre. A response from 20 C/S to 20 KC/S is available.
Provision for connecting a spring reverb allows simulation of a large room's ambiance. Accepting a rotating signal from the matrix, its output amplified straight. Greater realism than reverb into a rotating speaker.
A dual Orbiter model separates bass from treble, with differing acceleration & braking rates. A throttle pedal assembly provides an alternative speed control.
Building will begin in earnest, when current restorations are complete.
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A little History.
When we took on a 1937 Hammond model E, it was decided to restore the beast, to original condition or better. The heaviest, most complex & most expensive model of its time. Ours, a 240 Volt, 50 Cycle, British specification version, is one of an increasingly rare breed.
Fitting vibrato & percussion is part of the plan. The first idea for vibrato used a delay line, with electronic scanning, built to accurately match the Hammond type. Since the E is a two channel instrument, unlike other early models, selective vibrato is possible.
Pressure of service work delayed a start. Meanwhile the vibrato design was refined, simplified & became optical. We also had requests for Stereo Tremolo on Rhodes Stage pianos, to emulate the Suitcase models. Similiar to devices I made years ago.
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The Rhodes' tremolo was incorrectly called 'vibrato' by the makers, I decided to create true stereo vibrato. It was obvious that two utterly different instruments could share a common design. Shortly after, the newly developed opto-electronic system was shelved in favour of a mechanical approach. In keeping with our modern design philosophy.
Maybe inspiration produced what seemed a practical idea. Around Christmas 2001 a prototype was started & produced sound early in January 2002. Bearing no resemblence to anything that had gone before, it worked first time. Spin Doctor was born. That original is still spinning, after a year & a half of continuous testing. No sign of wear & working well.
No design changes or development required. It was correct from the start. Initially called Orbiter, due to its characteristic mechanical action. The 'Spin Doctor' name was chosen by my wife, a genuine flash of inspiration. So she holds the copyright to the name for this application. Published on these pages in April 2002, after orbiting for 3 months.
Our government probably holds the rights to the political version.
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Test Results, Potential Uses.
Firstly, Spin Doctor is not a replacement for rotary speakers & was not conceived as such. Many electronic devices have been & are being produced for that purpose. None so far has succeeded convincingly. We have no intention of going down that stony road.
This machine is new & can stand on its own. It is not an emulator or replacement for anything. Comparisons are for the purpose of illustration & to convey an idea of the type of sound produced by Spatial Vibrato. Some uses will clearly show its individuallity.
The test prototype is specifically designed as a lead model. For melody rather than bass. Dependent on settings, it does however smoothly handle the entire musical spectrum.
We have tested it with a number of musical instruments & sound sources. An attempt has been made to determine suitability, or otherwise of features for each. Some results were expected but some rather less so. Not all settings suit all instruments.
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The Hammond organ. This proved a success, no surprise here, as this was the original intent. Mono Vibrato & Chorus improve on the poor effects of the L100 series. They also update early models, best speed is 6.8 C/S. Stereo Vibrato is an alternative for all models.
Spatial Vibrato has been found suitable for all Hammonds, Tone Wheel or clone. The dual Orbiter version may be considered better, using slow or fast with bass 'run up' & 'run down'.
The Rhodes Piano is another unsurprising success. Stereo or Spatial Vibrato @ around 4 C/S sounds ethereal. Less expected is the increase in dynamic response. Bass Contour strengthens the bottom end.
Guitars, both electric & miked acoustic are definitely a strong point. All speeds & settings suit. Contour works well with a bass, maintaining depth, with animated overtones.
Clavinet D6, very effective, a cutting & dynamic sound. However the instruments high background hiss is emphasised, especially with Chorus & Treble Contour.
Wurlitzer EP200A, best with Contour & Chorus off. To avoid emphasising the piano's already high background noise & hum.
No great increase in dynamics, more laid back, instead of its supposedly 'angry' nature. Stereo Vibrato & tremulant improve on the original tremolo (labelled Vibrato).
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| Further Tests.
On acoustic sources, via a microphone.
A Grand Piano is interesting. Not for the purists, it is different, enhancing harmonic character. With slow orbiting an almost 'honky tonk' sound. Apparent dynamic response is increased. Not everyones taste, but what is?
A Drum Kit is also interesting. Contour with Chorus or Phase Mix. On slow phase or with the Orbiter disengaged, sound is crisp & clean. Electronic phasers have been used to good effect with drums in the past. The non-electronic clarity is new.
The Human Voice produced unexpected results, almost accidentally. Electronic effects usually spoil clarity & character. Even reverberation, although useful, especially with poor singers, blurs enunciation.
Character is maintained, with a distinct edge to consonants. Stereo Vibrato, especially with small setting, may be useful, certainly different, likewise with Slow Phase or Chorus. Voice is not however our choice of an ideal source.
A Flute, Saxophone & Violins have been tried. Useful to create a different sound but possibly not for classical music.
To sum up, due to its clarity, it can be used with more sound sources than many effects. Stationary can produce very musical results. However it is all too easy to overdo use & dilute potential impact. This has often happened before with something new.
Hammonds, Rhodes & Guitars remain its intended use.
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Customer test,
Spin Doctor has been tested by a musician, using one of the better digital pianos, a Yamaha P100, internally combined with a Roland Sound Canvas, SC-55. Comments follow.
The sonic quality is inherently musical, inspiring one to play the piano & experiment with styles not previously contemplated. Harmonic development is enhanced.
Piano presets are woken up, overcoming a somewhat 'one dimensional' aspect. Musical qualities of the instrument are brought out, always there but not previously heard. Whilst stationary it is in some ways reminiscent of certain 'high end' studio sound processors.
One useful addition would be a player defined Orbiter stopping point.
Bass Contour, with Spatial, is probably the best setting overall. All Yamaha presets & many Roland sounds benefit. On a 'Rhodes' preset, slow stereo tremulant is uniquely satisfying.
A criticism is that the perceived increase in brightness is not always desirable. Also Chorus in particular can emphasise excessive instrument noise. Treble roll off works here.
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Application note
Spin Doctor is a low impedance machine, requiring around 50 to 100 milliWatts of drive power. Thus for high impedance signal sources a built in pre-amp is required. Some instruments have a proper headphone output, including the P100, Wurlitzer EP200 & various others. These give sufficient power for direct drive, allowing the pre-amp to be by-passed.
A truly non-electronic installation is possible. Tone Wheel Hammonds' G terminals can also provide this. These are around 600 Ohms, so a matching transformer is required.
Using Spin Doctor via a mixer's or amplifier's effects loop is far from ideal. They usually have a high inherent noise level & this will be emphasised. In addition they are not usually stereo. It is best to use two input channels of a mixer, with one panned left & one right.
Noise will be lower & full by-pass is provided. Using only one of Spin Doctor's outputs is better, if just a single amplifier is available. Both channels fed into a mono system will cause a 'doubling' effect, probably undesirable.
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Our reaction
We take customer feedback, including criticisms, seriously & will address suggestions.The points had been noted during previous tests, independent confirmation was valuable.
An E.Q. system was sketched into early concept proposals & then deleted. This may now be reinstated. Due to the absence of electronic noise from the machine it can be on the input or outputs. Further tests will determine which sounds best.
In many applications the perceived increase in brilliance is a benefit, especially with a Rhodes or guitar. Bass Contour uses no electronic tone forming & is often enough to extend the low end response. So any E.Q. needs to be switchable.
Chorus extends the high end response to 20 KC/S & beyond. Most electronic instruments have no useful signal in this region, only noise. This is the problem from the SC-55. Passive high cut may benefit, although added phase shifts can adversely affect the natural response.
A programmable stopping point, when the Orbiter is disengaged, complicates the inherent simplicity. This we try to avoid.
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Principle of Operation.
The Spin Doctor's principle of operation is straightforward. A matrix generates the dimensions of a space, these can be changed. Two alternative values are currently available, the larger producing a greater vibrato or acoustic pattern.
The projector orbits around this space, creating a spatial anomaly. Audio energy is conveyed to points in space. The orbiter uses conventional impulse drive. Warp technology is not employed at present, requiring no anti-matter or scarce di-lithium crystals.
Sub-space signals are received at designated nodes on the matrix. Two nodes are used for a stereo system. As signals travel in relation to nodes, varying delays & reflections occur.
A Critical Damping field can be engaged, supressing reflections, resulting in the creation of Stereo Vibrato. When disengaged, complex rotating sound patterns form, (Spatial Vibrato).
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Further Details.
Stereo Vibrato may be easiest to think of as a rotating sound field with rising & falling frequencies 'chasing' one another round it.
Spatial Vibrato is similiar. The removal of damping however, allows reflections, creating a pattern of standing waves. The same basic mechanism as in a lively room. The rotation causes these standing waves to shift & interact in complex ways.
Chorus projects a signal directly into the matrix. In Mono this is added to the shifted signal, as with Hammond chorus vibrato, which it resembles. In Stereo it appears across the stereo field, creating a third, stationary, sound. It may thus be better called 'Ensemble'.
Chorus with Spatial is even more an ensemble, underlining this machine's unique character. |
| Contour is a variation on Chorus. With Bass Contour signals below the lower midrange are progressively projected directly into the matrix. This reinforces the bottom end with a stationary third signal, ideal for a bass instrument or pedal tones.
Treble Contour handles a selective band of mid-upper frequencies in a similiar way. This gives a clean bite to percussion etc.
A second model is designed specifically for bass & also forms one half of the dual version. Contour with these models is handled in a different manner.
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Phasing uses a different mechanism to Chorus. An unaltered (dry) signal, in mono or stereo is mixed with the matrix outputs. Addition & cancellation takes place at varying frequencies. This is covered in greater detail in the Technology page, Effects section.
An electronic phaser uses phase advance & a flanger uses time delay. Spin Doctor's matrix outputs are both phase & time shifted. This is both more complex & more subtle.
Another trick is using Phase Mix with Contour or Chorus. Gently graduating bass and/or extreme treble provides a subtly interesting response. Effective with a bass guitar or piano.
Inverting Orbiter drive changes the pattern of addition & subtraction. A different sound is created, Chorus is also affected.
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Tremulant is obtained with a central damping field in the acoustic space. Frequency shift is reduced during mid travel, creating more of an amplitude movement in this region. Changing progressively to time & phase shift towards each node.
This is more complex & atmospheric than simple stereo tremolo or auto-pan.
Chorus may be used with Tremulant, for a mild vibrato / tremulant hybrid.
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Spin Doctor, analysis.
Comparing sound with test figures shows an apparent paradox.
With a Rhodes, obviously increased dynamic range. Sound is dramatically brighter, or is it?
Frequency response analysis using a sine wave, gives no answer. A gentle increase in the mid range, falling at both audio extremes. With Chorus the curve is substantially flat, from 20 C/S to 20 KC/S. Using Bass Contour the high treble rolls off. So why is it so bright?
Careful tests show little added brightness when the piano is played very softly. Switching the Spin Doctor out of circuit then makes less difference. Does this give a clue?
Results are different with a Wurlitzer EP200 piano. A sweeter tone than usual, brightness & dynamic range only slightly increased.
Analysing what is actually happening takes some thought. Spin Doctor, when stationary, does not add anything to the sound of an instrument. It simply emphasises what is already there, including timbral changes, but not volume level changes.
The Rhodes has a strong timbral response to velocitiy, the Wurlitzer does not, although it has a greater amplitude response. It is as simple as that, or is it?
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We work together with The Hammond Hire Company @
Service <
 > Hire
Classic & Modern Instruments or Equipment. Stage, Studio & Broadcast
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For information on the Hammond Hire Company and the Zoo visit their Web Site
E-Mail: info@alphaentek.com , For Design Work
For Service call Tiny:
Telephone: +44 (0)207 288 0037 |
Spin Doctor. Last updated on the 3rd of February 2009. © Ron Lebar, Author.
