Friday, 15 November 2019

ETF 2019

Arrival Thursday evening in lovely Belleme

What is this?

A Magnetizer - get your magnets energized right here.

Test gear

Now that is a triode.

And some steampunk...

Plaster horns and amazing woodwork

And this is a platter...
The cork is 12” LP size.

Greetings from Belleme with more to come...

Saturday, 27 July 2019

The Foundation Turntable

Foundation Turntable

Bolt up - this is ad copy...

The concept for our new turntable has been a natural evolution over the years of experience, observation, and experimentation with LP playback. These distilled into a desire to have the best elements combined in a single unit. Garrard, Lenco, Walker, Kuzma, Galibier, Scheu, Micro Seiki, Verdier, Linn, Thorens were some of the brands which passed through. The best aspects were noted, explored and remembered. Myths were plentiful, good performance less so. With time it became clear what worked and what did not. These insights were an opportunity to combine the best elements and create a turntable which stands out.

The Verdier turntable is highly regarded primarily because its original “Granito” plinth. Among the experienced vinyl cognoscenti there are two turntables which are considered to be classics at the top of the game. The first is the Micro Seiki 8000 and the second is the Platine Verdier with Granito base. As a result of not being able to find a Granito version of the Verdier I approached M. Verdier in 2012 and requested to produce the original "Granito" plinth with his guidance and approval. He was kind enough to provide his mentorship, drawings and specifications as well as awarding my little company dealership of his products in the UAE where I was then resident. 

The original was fabricated in Italy and so one of the historical Terrazzo providers in Italy was selected. Even with detailed specifications it took three iterations over a period of two years before M. Verdier was satisfied. The final approved version utilises an uncommon, super hard concrete with Venetian finish and stones from all parts of Italy in various sizes and colours. Once it was finished and implemented all doubt concerning this plinth's roll in acoustics was dispelled. After trying slate, stainless steel, wood, panzerholz, bronze, brass, Baltic birch, resin encased MDF, steel and combinations of the these, it was quite clear that this unusual concrete and stone mixture had a more neutral and comprehensively powerful presentation than any of the others by a wide margin.

To earth this high mass plinth Stillpoint Ultra SS filters are employed to create a solid and easily levelled platform. This footing is not only for the plinth, bearing and arm but also the motor pulley and platter which is relieved of any suspension movement which causes tension and traction variations.

One of the most copied platters and bearings of any turntable was developed by Thomas Scheu. His enterprise not only provided bearings and platters for famous brands of turntables but also created one of the best sounding, ingenious and no-nonsense turntable designs of its own. Since he also kindly provided parts for DIY’ers, many of these took his concepts and created companies such as Feickert, Teres, Red Point and Galibier with them. Even as they deviated from his original concepts there is no question he inspired them all. His bearing, like the Verdier, utilises an inverted configuration but with modern materials and understandings of oil cohesion, adhesion, surface tension and capillary action. It is a simple and ingenious design which re-lubricates itself after initial servicing and is relatively maintenance free. 

The Scheu platter employs an acrylic of special character. It is harder than the larger part of the acrylic material family to achieve a speed of sound through this solid to be precisely that of vinyl. I have observed this measurement with the appropriate equipment personally. The result is like playing an 80mm thick, 7.5kg LP milled to German, high precision standards. Great solidity along with an inner natural life that is unique.

Not last is the arm pillar. Made of fibre reinforced concrete to marry plinth, platter and arm in rigid geometry while maintaining excellent acoustic properties. The result is a resolute and steadfast loop between groove and stylus which reads microns into macros.

This bearing and platter combine with the Granito plinth through a precision, inverted, alumina, ceramic core bearing, floating in a dynamic oil bath. The result, quite simply, stands out. 

Any readers of my old blog will know that I believe the heart of the turntable is the most overlooked component. While there are endless discussion of tonearms, tonearm cable, cartridges, platter mats and supports the motor is often overlooked and plays as an important a role, or more so, than any of the above. It is the primary active component which not only provides motive force, but also the reactive element to stylus drag. The motor's reaction to this ever-changing load is an interaction which fundamentally influences how a turntable sounds. 

The idler turntable proponents often attribute this influence to the drive mechanism however idler drive turntables use, almost exclusively, very large, shaded pole motors which compensate for the changing load with inductive inertia. Belt drive turntables most often use small ac synchronous motors which look like peanuts when compared to these idler juggernauts.

Thus, the different versions of motors and how they sound are commonly labelled as “idler" or "belt drive" really meaning high or low torque, rigid or loose coupling, associated high or low noise and high or low energy. The Verdier uses a powerful precision DC motor and idler enthusiasts say is the one "belt drive" motor that has any soul. M. Verdier kindly points out its merits in a Sound Practices article - issue 11. 

The grip, heart and slam of the “idler” as well as the fine detail, harmonic decay and ambient information of the best of “belt drive” is found with this motor. A completely new controller has been implemented which not only provides rapid and high current delivery but is also not thrown out of regulation by the EMI coming off the motor (as most DC regulators are). Additionally, this controller senses motor load and prevents resulting sag to maintain speed as the load varies. This is a simple but elegant solution which behaves much like the inductive stability of idler wheel shaded pole motors. A knob allows tuning this electronic inertia. The control provides adjustable degrees of immunity to the load changes of transient attacks without adding noise. One can readily find the desired presentation between “idler” and that of a “belt drive” without giving up the low-level detail idlers often do. 

The high degree of mechanical integrity provided by the plinth, bearing and platter combine with a notoriously good motor and elegantly managed speed stability provides a real foundation for music with all of its power as well as nuance.

Appearance is a simple, subdued, mid-century modern to fit any decor.

To accompany the Foundation we provide Dynavector XV-1S and Kuzma Stogi Reference 313 VTA Tonearms / Cardas Clear wire, on request, for a proven, optimum combination. no-No-nonsense vinylista tools of world class performance.

For orders send us an email. We committed to a small production run and half have already been booked.

Thursday, 11 July 2019

Life in the time of Hay...

A cool and rainy spring gave way to a ferocious beginning of summer. The hottest days ever recorded in France. As a result of this sudden change the farmers came out in synchronisation on the same day to get the hay in before it was lost.

While the farmers have been out in the heat cutting, drying and bailing the hay it has been a busy time indoors as well.

Mojo the mad is a constant companion...

constantly chasing everything (real or imagined) ... 

In trying to stay with the real let's get on with business then, shall we?

Our Field coil design has moved forward.

What started as a simplified way to improve on the historic Tungar battery chargers and Selenium rectified supplies and solve the requirement with a sober design created an avenue of discovery. 

It began with a Schottky rectified, choke loaded design which eliminates noise and its harmonics and provides current stability and storage.

Voltage regulation was tried and was the wrong direction.

Current regulation and turned out to be an excellent solution for field coils, improving sonics considerably.

The difference in the type of AC transformers was more pronounced than anticipated. Split bobbin types were used initially to decouple line noise. R - Cores were tested and were quieter in operation. When toroidal types were tested they demonstrated clear superiority in current delivery. While the other steps forward were solid and clear, the difference of the toroid was pronounced. Quite a treat to experience how much better the music moved and flowed with greater weight and agility above the other steps forward.

Field coils deserve better supplies because they make a field coil more of a field coil - meaning the increased stability of the magnetic field in the face of constantly varying load. The difference in quality of supply is easy to hear. 

 The supplies pictured above are heading to the Island of Crete to power WE555 6-7 volts / 1.5 amps with plenty of headroom. 

For those who would like to update their supplies please contact us by email.

Sunday, 23 June 2019

More Mojo

It has been a busy first half of the year with orders and new projects. Here is a pair of Mojo III heading for delivery. 

The main driver has been updated with new CNC wound field coils and improved magnetic pole pieces and magnetic design. One of the issues with these field coils is that they only open up after 24 hours of power up. No matter how much we tell people this they don't really believe it until after the first 24 hours, after which, they excitedly inform us of how essential this is. 

Dampening plate details... to handle the extra energy and preventing the aluminium from running away with it. 

Mr. Slagle's excellent nickel core magnetics.

The crossover has been updated to very good effect. This has created a new version of Mojo.

The paint work is evocotive of a dust storm with its varied colouration. This pair is heading for West Texas. Run in material will probably include some Thunderbirds and Stevie Ray Vaughn - just because....

In the background is some foreshadowing of a new project - the Foundation Turntable. More on that in a following post.

So here is the new Mojo version 2, looks the same, sounds significantly better.

We have been busy and will post again soon. 

Until then, burning the midnight oil and making lots of noise.

Tuesday, 23 April 2019

Field Coil Power Supply 2

The beginning of a well engineered field coil power supply steps around the audio fashionable - both the vintage Tungar types and the commercial and cheaply made capacitor loaded variants. Experimentation and experience reveal that a split bobbin AC transformer, Schottky rectification with an input choke load lead the way to best performance. A tuned reverse recovery spike filter (snubber) and a 220nF cap to soften dynamics in the choke improve performance further. Rod Coleman’s well designed and evolved constant current sources on the output ensure a constant and stable magnetic field for the voice coil. Not as poetic as museum caliber vintage but performance offsets the collectable caché.

Split bobbin AC transformer prevents coupling line noise to the secondary. 

Schottky diodes into a choke load follow as an excellent and well documented rectification solution:

"... a properly designed choke-based supply's ripple is a perfect sine wave, with no high frequency noise.

Silicon diode types except Schottkys emit a burst of ultrasonic noise as they turn off. This noise can go forward into the load circuit and back into the AC line where it can also excite transformer resonance. The "slow" diodes still have this ultrasonic noise. Schottkys are the only type which do not. Schottkys also have half the voltage drop of other diode types and are usually faster. 

... With the choke there is no steep high current pulse, so no disadvantage to Schottky diodes. You get the advantage of no ultrasonic noise, lower voltage drop (so lower power consumption in the diode) and no big massive current pulses."  - J. Swenson

The superior voltage stability and regulation of an ICPS (input choke power supply) is well documented.

In summary there is nothing rare or esoteric used to achieve better sonic result only sound attention to what the energy is doing and what devices work best regardless of mythology or cost.

It could be said that building these in the springtime of the French countryside adds a certain "Je ne sais quoi" or that the local wines mellow the impression...

... but, in fact, it can be discerned quite easily without augmentation as the magnetic field is more stable, with ample, dynamic and clean power, and this provides a smoother, more nuanced presentation. 

It was then left to be discovered if two could be fit into one…

And so it was done - two into one.

Half the chassis + twice the time = same cost.

Provide the voltage and current requirements and we can build one for your field coils - vintage or new. Just send us an email.

Saturday, 13 April 2019

The virtue of a Field Coil

I am often asked what the field coil magnet does that other magnets do not in a loudspeaker. The question of magnet type concerns the degree of steadiness against which the voice coil reacts in the process of making music.

Different magnet types have different field characteristics. The motion of the speaker system is determined by two magnetic fields interacting with each other. One is the magnet's field and the other is the voice coil's field when current flows though it. The amplifier only provides the current which the speaker must then turn into music. Without the loudspeaker there is no music.

In theory the magnet's field is constant and the voice coil's field is variable. As the voice coil field varies with the music signal it causes motion by attracting and repulsing the magnet's field. This is theory.

In reality the magnet's field is not constant but behaves like a spring as the two fields interact. The stiffness of this spring is determined, in part, by magnet type. The majority of your expensive amplifiers electrical output does not make it into music - instead it is lost as heat in the voice coil. More than 90% of your amplifier's output does nothing but make heat. This why the loudspeaker is the most critical element in a playback system. This is also why efficiency in a loudspeaker is so important. It should be evident that minimising the over 90% loss of energy is critical to fidelity. 
The best of permanent magnets in regard to a stable field is Alnico. While the Alnico and other permanent magnets have finite magnetic resource the field coil is constantly replenished by the current source feeding it and is adjustable but the amount and type of current provided.

The heat factor also explains why speaker magnets can loose strength over time if they are driven hard and get hot. Heat causes loss of magnetism in permanent magnets. A field coil does not suffer similarly.

The voice coil moves with increasing accuracy in direct proportion to the stability and stiffness of the magnetic field provided for it to work against.

The four classes of permanent magnets are:

    Neodymium Iron Boron (NdFeB or NIB)
    Samarium Cobalt (SmCo)
    Ceramic or Ferrite

This table gives us some of the special characteristics of the four classes of magnets. 
Tcoef of Br
Ceramic or Ferrite

Br is the measure of its residual magnetic flux density in Gauss, which is the maximum flux the magnet is able to produce. (1 Gauss is like 6.45 lines/sq in)

Hc is the measure of the coercive magnetic field strength in Oersted, or the point at which the magnet becomes demagnetized by an external field. (1O ersted is like 2.02 ampere-turns/inch)

BHmax is a term of overall energy density. The higher the number, the more powerful the magnet.

Tcoef of Br is the temperature coefficient of Br in terms of % per degree Centigrade.  This tells you how the magnetic flux changes with respect to temperature. -0.20 means that if the temperature increases by 100 degrees Centigrade, its magnetic flux will decrease by 20%!

Tmax is the maximum temperature the magnet should be operated at.   After the temperature drops below this value, it will still behave as it did before it reached that temperature (it is recoverable).  (degrees Centigrade)

Tcurie is the Curie temperature at which the magnet will become demagnetized.  After the temperature drops below this value, it will not behave as it did before it reached that temperature.  If the magnet is heated between Tmax and Tcurie, it will recover somewhat, but not fully (it is not recoverable).  (degrees Centigrade)

This chart does not directly address the "stiffness" of the field. Tcoef of Br gives a clue as it indicates the stability of field in regard to temperature which can be indirectly correlated to overall stability.

The field coil or electromagnet is not as susceptible to field variations as permanent magnets. When we look at the high degree of loss involved in transducing electrical current into sound it is evident that any minimising of loss is critical to the degree of fidelity.