Continuum Audio Labs - Caliburn Turntable With Cobra Arm, Stand, and Minus K Platform

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Arguably one of the most sophisticated and important turntables ever made.

Stereophile's "Overall Product of The Year" & "Analog Source Component".

Feature Highlights Include:
• Vacuum Driven Record Hold Down System - See our Video.
• Turntable Weight Alone is 160 lbs.
• Platter Weight is 84 lbs. of Magnesium Alloy, Metal Powder and Resin Composite.
• Magnetically Levitated Bearing Reduces Weight to 6 lbs.
• Massive 5" x 1" Bearing Pressurized by Pump to Increase Oil Circulation.
• Stand is Made of Chromed Aircraft Grade Aluminum 176 lbs. 
• Stand is Cross-Braced with Nautical Turnbuckles for Rigidity.
• Turntable Chassis is Made of 1" Thick Magnesium Alloy.
• Computer-Controlled Motor Drive System - Battery Powered and Software Driven. 
• Carbon Fiber Monocoque Construction Tonearm.
• Sapphire Central and Vertical Pivots.
• VTA Adjustable on the Fly.
• Copper Litz Tonearm Cable. 

Package Includes:
• Caliburn Turntable
• Cobra Carbon Fiber Tonearm
• Continuum "Castellon" Stand in a Satin Finish (+$25k Option)
• Upgraded Minus K 250-BM-1C Technology Isolation Platform (Optional) - See our Video
• Shipping Crates for the Turntable (Crates must be returned after delivery)
• Owner's Manual
• Facilities for Two Tonearms - We can Install Second on Request 
• Suction Cup and Screw Down Record Clamp
• New Batteries for Drive System
• Extra Drawer
• Included Delivery and Installation up to 100 miles from Zip 07452 (Two Man Crew)
• On-Site Calibration by Industry Guru Michael Fremer - If Within 100 miles.
• If Turntable is Shipped You Can Provide Your Phono Cartridge for Calibration in-house at SkyFi by Mr. Fremer. (Tonearm Design Allows Cartridge to Retain Calibration in Shipping)

Every aspect of this turntable has been fully tested by us and works as it should.

Physical condition is an 8 with very few signs of use or wear.

This model is no longer avaialble and is quickly becoming scarce as most collectors are holding on to them. Last available MSRP was $150k - $200K

Flat Rate Shipping to the Contiguous 48 US States for $1200.
Shipping Also Available Worldwide with Payment Via Bank Wire.

Please click here to read Mr. Fremer's in-depth Stereophile review to learn more about how this turntable works and sounds.

Link to Continuum Caliburn Owner's Manual

Link to Cobra Carbon Fiber Tonearm Manual

Link to Minus K Technology

Link to Caliburn Website

Individual Component Specifics from Caliburn:

1) Cobra Tonearm - Dig That Groove!

Take any concept that you had about what makes a great turntable, throw the idea of having a conventional tonearm right out of the window, runs it over with a truck... twice. A complex shape and choice of materials demonstrates a departure from the norm in the commercially available alternatives.

Just as Caliburn, the turntable, revolutionised turntable design by use of FEA software and shape optimisation, so too Continuum Audio Laboratories has used the same software technology to derive the new shape and performance parameters of the potent Cobra tonearm.

By taking the design and aesthetic constraints off the prototype modelling, we instructed the software to achieve infinite stiffness with lowest mass.

Ideal parameters in a virtual world not limited by manufacturing constraints.

The resulting Cobra-like shape appears counter-intuitive at first glance. Yes the shape appears large and heavy but it isn’t.

When one considers that every increase in width or height increases stiffness by a factor of close to 8 times then the size of the arm becomes a design requirement.

Materials

Choice of materials was also left open and we evaluated commonly available materials including aluminium oxide (“ceramic”) fuel cell tubes used in the fuel industry.

Problems included how to make a one-piece assembly from headshell to counterweight.

The result is a single unitary piece of arm technology which is lightweight but extremely stiff.

The force required to bend the Cobra would deform most commercially available arms, including titanium and magnesium arms, and would seriously damage multi piece arms.

The key to the Cobra’s arm stiffness is its shape and choice of materials.

Technical Details

Now for the pivot technology. We recognise linear tracking is the ultimate solution but see some designs have issues with “crabbing” where the arm “wiggles” its way across the linear path in a series of short arcs.

Our choice was to use a jewel pivot as found in the finest of aircraft instruments, which offer the lowest friction possible via mechanical means.

Stabilisation is via outrigger pivot, which allows for precise azimuth adjustment.

VTA is adjustable on the fly using a 40TPI microscope fine pitch thread vertical adjustment mechanism.

Clamping is by a triangulated locking system which avoids the common problem of using a “grub” screw to tighten against a shaft, which leaves micro movement to blur the information processing.

The Cobra will accept cartridges of 4 grams to 20 grams (wide range to accept any cartridge currently available) weight by means of a mass loading counterweight that does not shift forward and aft.

It uses a simple weight addition or subtraction method to keep the effective mass at the optimum for the arm.

The Antiskate mechanism, which is currently undergoing patent application, represents a unique solution to the skating force problem, by increasing the anti-skating force from 8% (of VTF) at the inrun groove to 12% (of VTF) at the innermost groove.

Technical Specifications

Pivot to Spindle Distance 221.7 mm

Accepts standard Cartridge centers of 12.7mm and 14mm long slot allows for correct overhang adjustment of any currently available cartridge.

VTA adjustment – on the fly

Azimuth - Adjustable

Antiskate – Adjustable

2) Castellon - World Class Stand Design

**Includes Integrated Minus K 250-BM-1C Isolation Platform

Completing the Caliburn-Cobra analogue playback system, the Castellon was built to defend the Caliburn from external vibrations.

Continuum Audio Labs developed a scientifically designed "floating platform" which uses a combination of magnetic and pneumatic isolation technologies.

Two heavy opposing magnetic plates isolate the Caliburn from external vibrations with no hard flanking paths.

During the research and development phase Continuum Audio Labs invested a considerable sum in purchasing a number of well proven isolation technologies.

These included active and passive systems from some of the leading manufacturers of isolation technologies used for atomic force microscopes and other sensitive applications.

There are many definitions of the term "active", and these include piezo and voice-coil computer-controlled cancellation devices, pendulum based systems, vibration modifiers such as elliptical cup and ball systems, oil and fluid damped spring systems, c-shaped elliptical spring systems and self-levelling pneumatic systems.

Suffice to say, one could fill several hundred pages describing various methods of tackling the problem of isolating an actively vibrating object (ie. a turntable) from external vibration, whilst coping with self-generated vibrations caused by the spinning mass of platter and motor combination.

Isolation

The basic formula used to describe an isolation system is Omega (W) = Sq root of K over M where W is the resonant frequency and K is the stiffness of the spring system and M is the mass of the object being isolated.

Damping is an additional consideration into this mix and is a critical part of developing a working solution.

Undamped springs are in our opinion a non-ideal isolation solution.

Damping is required. Imagine driving a car with a spring suspension and no shock absorbers. It is quickly apparent that a damping mechanism such as a shock absorber is critical to reducing the amount of cycles of the suspension system experiences when exposed to external stimuli.

So the properties of the damping mechanism are important as are parasitic effects of combinations of materials. These must be taken into account when designing a solution. Parasitic effects are caused by things such as bellows, fluid seals and other necessary engineering details to move from the purely theoretical to the real world.

Listening Tests

In listening tests we confirmed correlations between the predicted isolation and the sonic results. This led us to question the prior art and forge new approaches to tackling the unique issues associated with turntable isolation.

For example if the motor and platter are connected by a belt and the motor is sitting on separate plane to the suspended chassis and platter then the suspension of the platter and chassis would be constantly excited by the reaction to bearing friction and Young's Modulus constraints of the suspension system.

The Castellon was designed to isolate the Caliburn Motor and Chassis from external sources of vibration but keep the MOTOR and CHASSIS on the same plane. This stops bobbing, twisting, yawing, pitching and flexural modes visible under the Finite Element Method and audible to experienced audiophiles.

The Design

The Castellon was designed using the finite element method for both the mechanical and magnetic spring damper elements.

The Castellon is designed as a complete system when used with the Caliburn. Whilst other isolation solutions are completely valid, in our experience none offered the sonic advancements achieved by the Castellon-Caliburn combination.

There is a significant amount of sophisticated engineering in this stand. For an isolation system to work, the ideal support structure must be infinitely stiff, otherwise the movement of the stand will interfere with the isolation system.

To achieve the best possible result the Castellon uses a nautical turnbuckle system which exerts a significant amount of force to cross-brace the vertical legs and resist rocking motions.

Additionally, the rear of the stand is braced to resist sideways movement. Each shelf is structurally braced to resist torsional and buckling modes.

This results in a structurally rigid platform which raises the eigen modes into a zone where purpose-made elastomers are used in a constrained layer to damp the remaining vibrations.

Finally, the top shelf is an over-damped magnetic spring where the magnetic field is constrained close to a point of collapse, resulting in a very low resonant frequency ideally focussed to work in harmony with the Caliburn.

The system is passive and does not require complex air compression and filtering solutions.

The system can not be driven into over-compensation where the source of vibration exceedes the fine tolerances of a sensor which can then cause an active solution to get confused with the source vibration and its own self-generated counter-vibration.

This state is not ideal, but has been observed in some commercial isolation solutions.

The Castellon is precision-machined in aircraft-grade aluminum.

3) Caliburn Chassis - Unique Magnesium Alloy
The Caliburn uses a unique Magnesium Alloy chassis.

The distinctive positioning of the mounting feet has been calculated to allow the bearing to dissipate energy.

In our computer modelling we predicted that placing the feet at the edge of the plinth would encourage severe vibrational modes to propagate through the chassis. This highlighted flaws in the prior art.

An example is walking along a suspension or rope bridge. You feel the reflected energy of your footsteps coming back as the energy waves are reflected back at you.

In contrast if you walk on a more solid bridge each footstep is dissipated into the infrastructure. Using the right shape and materials you can absorb this energy.

By placing the feet under the chassis to support the bearing we were able to minimize the spring force (Youngs Modulus) being reflected back into the platter from the chassis reacting to the up/down vibration modes.

Computer Modelling

The placement of the feet has been further optimized by the use of advanced computer modelling so that the remaining reflections that still occur do not refocus near the bearing.

To find these points without computer assistance is extremely time consuming (but possible) but would require many holes to be drilled into a chassis eventually compromising the integrity of the material.

Using computer-modelling software, we could bypass these traditional experimental approaches to get it right first time.

Damping

Other features of the chassis include critical applications of damping compounds and the ability to isolate the armboard even further in both the vertical and horizontal planes.

Almost every spring or elastomer-based design has significantly better vertical than horizontal isolation. Without nearly equal isolation in both planes, serious compromise is inevitable for any turntable system.

As a result, “flanking paths” can be created, allowing horizontal resonance to impair the overall isolation effectiveness of a suspension. The reactive damping that is inherent in most spring and elastomer systems can also exacerbate “Flanking”.

The Audiophile Result

The audiophile result was a platter support platform that works in harmony with the platter whilst minimizing the affects of floor borne and airborne vibrations.

This resulted in a significant improvement in depth of field and soundstage height (one can hear into the cavernous expanse of Carnegie Hall or the Palais Theatre with such realism it is frightening). Side to side and up and down motion in a cartridge generates signals, which are trying to reproduce stage width and depth of field.

A platter/chassis that bounces (even microscopically) in these modes blurs the definition of these audible cues and lowers the resolution of the system.

5) Platter - Unique Nested Platter

It may be a surprise to some but a big source of noise in a turntable is the platter itself!

No bearing is perfect, even with ultra fine tolerances; the bearing must still have clearance for rotation.

This tolerance creates vibration when a bearing is required to support a platter spinning at 33 or 45 or 78RPM.

The Wobble

The spinning mass then precesses or "wobbles" and creates modes of vibration at a range of frequencies.

One of these modes is an up and down bobbing motion in the audible range.

This creates interrelationships with the chassis and highlights the need to place the mounting feet at an optimal position. (see Chassis Design)

Other modes a platter generates are twisting modes. The energy transmitted to the platter from a belt or direct drive are also interacting.

Using three motors to drive a platter would add vibration sources and transmission paths.

Belts are also too weak to prevent platter wobble from this perspective.

The Nested Platter

The nested platter design of the Caliburn allows for superior isolation from external and internal resonant modes of vibration that have been shown by FEA modelling to be at the surface of the platter in the critical area adjacent to the record.

In contrast other platters exhibit significant audible vibrations through the bass and midrange which can be characterized by audio terms such as "dark", "bright", "muddy", "analytical" etc.

These modes of vibration have been reduced by clever design and shape optimization as well as choice of materials.

The Vibration diagrams (click the + below to view) are from msc software NASTRAN FEA, and illustrate how we can see problem resonances. Using Shape Optimisation we move these out of the audible band into areas which can be more effectively controlled.

Vacuum Hold Down

The platter is designed for vacuum hold down and uses a washable ultrathin (0.30mm) layer of damping material under the LP to prevent dust impregnation.

We have built a database of properties and measurements which now allows us to "virtually" model any platter design and determine the sonic signature by matching it to similar signatures from prior listening tests.

The Audiophile Result

The audiophile result is an incredibly low noise floor and the ability of the platter to release every last nuance of recorded information without adding additional artefacts. You will be shocked! 

6) Caliburn Bearing - A World First

Caliburn uses a world first turntable bearing engineering design.

In pursuit of the ultimate bearing for the Caliburn, we evaluated all respected bearing design alternatives, and proto-typed several Caliburn platter/bearing combinations.

The Caliburn Bearing has been chosen for its ultimate musicality.

THe Caliburn bearing operates on a hydrostatic principle where oil provides the interface between bearing surfaces for ultra-low friction and high damping.

Due to the superior damping over comparable air bearing systems, this principle is preferred in ultra-precision tooling machines used to manufacture aerospace components and optical systems.

Vacuum Hold Down

Prior art using vacuum required special pumps to be isolated into adjacent rooms or held in cumbersome cabinets to minimize playback noise.

Additionally, pulsing vibration caused by pumps had to be countered with lengthy hoses and adjustment mechanisms.

The pump pressure using “lossy” bearing designs also meant the spindle shape and size were influenced.

So the advantages of vacuum hold down were being held back by engineering challenges.

Alternate gravity based heavy metal rings that are placed around the LP once it has been put on the platter were in our opinion seriously flawed, as they can never be balanced and if they dislodge during playback the potential for serious damage to expensive cartridge arm combinations let alone the underlying turntable is high.

It features a fully sealed vacuum rotary feedthrough, which allows for the LP to be held down under vacuum without the pump having to run during extended playback.

Research and Design

We researched the nuclear and high tech industries to evaluate magnetic ferrofluid seals for rotary feedthrough but these devices were not viable due to the size and assembly requirements.

Our engineers then went back to the drawing board and designed a miniature rotary seal, which creates a vacuum tight low-friction seal in a size not much bigger than a roll of 35mm film.

This option for sealing allows for vacuum pressure to be held whilst the turntable is in operation without the pump running.

Sensors and complex computer logic monitors the pressure and delivers additional vacuum in controlled “doses” to maintain the hold down.

The pressure settings are very low, as the bearing does not lose pressure during playback.

Pulsing vibration is also removed as the system is quiet – “there’s no pump like NO PUMP!”

Bearing Design

The thickness of the bearing shaft also has a critical effect on the resonance of the platter and we have optimized this to keep all the wobble resonances below 10Hz.

The relationship between platter mass and the spindle diameter is critical to the resonance of the platter and we recognise this fact is understood by a handful of turntable designers.

Other features include the use of a ball/thrust pad configuration for vertical motion, and bronze alloy for the axial motion.

The bronze alloy contains higher than normal tin compounds, which fill any micro asperities in the shaft over time to create an ultra silent bearing.

We chose not to use magnetic vertical bearings as the VTA is constantly changing due to the rotational effects of the platter, which results in a loss of depth and soundstage.

Oils Ain’t Oils

Bearing design is not just about how fine the tolerances are or how accurate your CNC process is.

Continuum Audio Laboratories researched the oils used in bearings and worked with tribologists to arrive at a formulation, which “sounds” better than any other oil we have tried.

The reason for this is under pressure different oils exhibit different responses. We required an oil that didn’t outgas (evaporate), remained stable under extreme pressure and worked with the design of the bearing to minimize precession (or “wobble”).

The Audiophile Result

The audiophile result was a bearing that solved the ergonomic issues of a vacuum holddown design and created the most silent bearing/pump combination yet realised in analogue playback.

This breakthrough in engineering has resulted in a significant improvement in micro detail, tonal accuracy and timbre, focus and musicality.

Ease of use and computer controlled and adjustable logic ensure that no skills are required to operate the turntable other than on and off and speed selection.

The user cannot over pressure or create an environment which harms the LP.

7) Caliburn Motor - About Motors

Continuum Audio Laboratories sampled several well-respected brands of motors and concluded off the shelf motors limited the audible potential of the turntable primarily through cogging or hysteresis.

We trialled AC synchronous motors, DC Brushless, DC brushed, and a number of very advanced solutions costing many thousands of dollars.

Our conclusion – It is all to no avail unless you can solve the cogging or hysteresis issue found in most motor designs.

We also evaluated multi-motor designs and concluded having two or three motors only increases the vibration problem no matter how configured.

Multi motors with belt pulleys also do not “stabilise” platters - example of 3 rubber o-rings trying to “stabilise” a 10-15Kg platter is a fair stretch (pun intended) in engineering terms.

They are used primarily to add torque to start platters. But multiple sources of cogging vibration are still felt at the platter no matter how massive the motor housing is made.

Belt Choice

Choice of belts is also critical and the method of mounting pulleys.
Whilst it is important to damp motor vibration by correctly designed housings the cogging vibration of the motor is still transferring itself to the belt and platter.

One has to tackle both the housing and the motor to raise performance to the next level.

Several attempts using DC Brushless motors (which are in fact AC motors!) with ever-smaller motors with low torque and different helical coil windings all failed to pass the “zero cogging” test.

The belt just transmitted these pulses to the platter and caused audible resonances.

Caliburn Motor Design

The Caliburn motor uses the most advanced technology currently available, which has been selected by the US military for select advanced motion control systems.

The Caliburn uses a patented motor coil technology similar in principle to a voice coil.

By working with the underlying technology we reduced the mechanical and RF noise to a minimum resulting in a super quiet motor which does not pulse or cog.

Housed in a solid block of damped alloy with precision-engineered bearings the motor delivers new benchmark levels of performance and motion control.

When compared to the most expensive turntable motors the “true zero cogging” technology we employed delivers superior audio results.

Features and Specifications

Key features:

Powerful enough to drive a 80Lb platter and bearing.
Computer controlled startup cycle launches the platter in a gradual smooth fashion.
Precise speed adjustment
High torque with no cogging – Gives the platter “authority” to handle the most demanding passages and delivers bass control.
Battery powered with trickle charge during down cycle times.
Specifications:

Zero Cogging
High Torque
High efficiency
12–48 VDC

8) Caliburn Control Unit - Computer Controlled

The Caliburn Control Unit is fully computerized motion control solution, able to manage all the parameters for speed, vacuum and hydrostatic bearing management.

It allows for precise adjustment of platter speed selectable at, 33, 45 and 78rpm (range from 68 to 84rpm manual).

The advanced motion control computer system monitors the motor spindle velocity and via specialized software algorithms maintains the platter speed constant per revolution and ensures there is no jitter between each revolution. This inter-revolution jitter is the cause of many sonic anomalies such as an overly etched/ analytical reproduction.

Belt Drive

It is a common misconception that a belt-drive system is less accurate than a direct-drive system.

However, a correctly designed motion control servo loop can harness the ratio of a small high-speed pulley driving a larger, higher platter mass to increase the precision of inter-revolution speed variations by a factor of 10:1 or greater.

In simple terms, a sensor that reads an encoded disk with 5000 lines, if placed on a platter spinning at 33rpm, will "see" less lines go by in one revolution of the platter than the same sensor, with 5000 lines, placed on a motor pulley which spins 300 times to achieve one platter revolution.

The simple math is, a higher speed pulley will use the magnification factor of the platter size to spindle size ratio to offer a much finer resolution of inter-revolution speed variations.

The Control Unit

The Caliburn Control Unit has the horse-power in computing terms to deliver the ultimate sonic performance by taking the guess work out of motion control.

It intelligently delivering smooth, jitter-free, power to the Caliburn's advanced motor technology.

The Audiophile Result

In musical terms, such obsession to motion control pays dividends in rendering pitch sensitive instruments, such as piano with stunning realism.

It also releases the musical cues which convey the sense of "being there".

The Caliburn Control Unit also controls the vacuum unit parameters and oil pressure system ensuring smooth bearing operation.

9) Caliburn Vacuum - Computer Controlled

The Caliburn Vacuum Unit is a super quiet pump with a "stealth-mode" operation during playback.

It is a computer controlled negative pressure mechanism that maintains correct vacuum for record playback.

Because of the "stealth mode" quietness, the Vacuum Unit sits on the lowest shelf of the Castellon, with no impact what so ever on sound quality.

The Vacuum Control Unit also provides the positive pressure required to lubricate the hydrostatic bearing.

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.