[Arizona Dan]

Let me start off by saying that I read and enjoy this sight on a daily basis.  I have only made a few post, but I learn a great deal from all of the experts at AudioCircle.

I have been thinking about tonearms lately, and was wondering if it is even possible to describe what a perfect tonearm should do.  For now, let's not discuss how this perfect tonearm would be designed or how it would be made, but let's start at the basics - what is it suppose to do.  Let me start.

1.  What is the perfect path for the cartridge:  Is tangetial best? - but what about the vertical direction.  Should the cartridge travel exactly vertical, or is sweeping an angle about the vertical O.K.

2.  The cartridge should be held as ridged as possible to allow the microsopic displacements of the stylus to register as a voltage.  If the stylus moves and the cartridge also moves, then there will be a voltage lost.

3.  O.K.  somebody elses turn.

Dan   

[JCarney]

As close to perfect as both myself and my significant other have ever heard, and she has the ears in the family.

Jcarney

http://www.durand-tonearms.com/

[thunderbrick]

 

[Arizona Dan]

The Durand tonearm looks stunning.  Which I had one.

O.K.  So what does it do that other tonearms don't do.  What should a perfect tonearm do? 

Let me through out another thought.  If the tonearm and cartridge had zero mass and zero friction, I suppose it would make zero music.  Every time the stylus moved, the cartridge would move away.  So, how much mass, momentum and friction is ideal. 

Dan

[*Scotty*]

For starters the phono cartridge cantilever is pivoted,the stylus does not move up and down perpendicularly but also swings through an arc while tracking. That being established I don't see an advantage to having the cartridge's vertical motion remaining perfectly perpendicular to the horizontal plane of the record while tracking a groove. A suitably long tonearm will minimize this error. I don't see huge problem with having the cartridge's orientation relative to the plane of the record deviate few degrees from the horizontal plane of the record when the cartridge encounters a warp on the surface of the record. I think having an exact match of tonearm mass to the vertical and horizontal compliance of the phono-cartridge would be very beneficial.
  I am a firm believer in having the cartridge move in a tangential fashion while tracking the records groove. It lowers record wear,allows for accurate tracing of the small groove modulations that contain the highest frequencies on the record resulting in lower distortion during playback. It also eliminates anti-skate errors from the playback equation.
  A theoretically perfect tonearm should also have zero vertical and horizontal friction. Its resistance to vertical or horizontal motion should be that due to the inertia resulting from the arms mass alone. A perfect tonearm would also exhibit no resonances other than the fundamental vertical and horizontal resonant frequencies that are a product of the compliance of the cartridge combined with the mass of the arm,there should be no other resonances that can be excited either from air-born vibrations or those resulting from the action of tracking the grooves on the record.
  I use an air-bearing tonearm because it approximates some of the performance characteristics of an Ideal tonearm,its vertical and horizontal friction is near zero and it tracks the recording in a tangential fashion thus embodying those engineering aspects of near zero anti-skate error and lower tracing distortion due to the elimination of tracking angle error and better high frequency fidelity. On the subjective side, I like the lower coloration and better highs I get from the tangential design.
Scotty

 

[jazdoc]

As with everything in audio, execution of design is critical.  I have heard excellent linear tracking arms, unipivots, etc.  I currently use two Durand Talea tonearms; one for stereo, the other for mono.  It is the best tonearm I have ever heard. 

I am fortunate to know the designer, Joel Durand and had a front row seat during the product development. Joel possess a terrific ear, which is a byproduct of his chosen profession; contemporary classical music composition.  Joel has an encyclopedic knowledge of the classical genre but owns and enjoys all types of music.  I even helped him track down an original pressing of "London Calling" by the Clash!  Unusually, Joel also trained in Mathematics.  I believe this unique background was critical to the tonearm design.  As a Professor of Music at the University of Washington, Joel had access to expertise and machining equipment that facilitated product development and testing.  He was able to test his working prototypes in several high end systems here in Seattle and use this field experience to further refine his design.

The results were readily audible from the first prototype (when I committed to buy).  Joel has continued to refine the design by testing different materials and wand configurations.  The sound is extraordinary; dynamic but refined, with dead silent backgrounds that reveal previously unheard low level details.  Pitch and timbre are spot on.  I know nothing about audio design but my theory is that the Talea optimizes a cartridge's ability to retrieve information from the record grooves and then transmits the cartridge data highly efficiently to the preamp.

[neobop]

I think you might find this interview with Pierre Lurne' interesting. He designed the T3/5 linear tracking arm. This is the one Goldmund had on their turntables. He sold the arm for awhile through his own company Audiomeca. He has since abandoned linear tracking in favor of unipivots.

http://www.tnt-audio.com/intervis/lurne_e.html

neo

[*Scotty*]

Andy Payor's Rockport Sirius V was the example of a closer approach to an ideal tonearm that I had in mind.
He has virtually solved the problem of imbalance between horizontal mass and vertical mass in the tonearm and the accompanying inertial resistance in the horizontal plane that used typify the older designs.
Link below to Rockport Technologies
Scotty 

http://www.rockporttechnologies.com/

[Arizona Dan]

Thanks for the responses to my post. 

Jazdoc - Very interesting information about Joel Durand and the development of his Talea tonearm.  And you have two of his tonearms  - bet they sound great.  Too bad they are so expensive.

The information on the tnt-audio sight is excellent.  I think I need to get my physics or dynamics book out and do some studying about Ellipsoid of inertia in order to understand it though.  I also looked at the rockport sight - they sure do make beautiful speakers and turntables.  I could not find the Sirius V on the websight.  Scotty - do you know how the design is made to have the same inertial resistance in the horizontal and vertical.

Can anyone explain inertial resistance?  I remember that momentum is Mass X Velocity.  Also, Force = Mass X Acceleration.  But I am a little rusty on inertia.

The part that is difficulty to wrap my brain around is the fact that the stylus moves up and down but the cartridge is not suppose to move.  The stylus is attached to a cantileverd beam.  The cantilevered beam has a spring rate.  Therefore it takes force to deflect the stylus a given distance.  But when force is applied to the stylus and the stylus moves up, the cartridge that is attached to a frictionless arm is not supposed to move.  I think this is related to the natural frequency of the tonearm and the inertia of the tonearm.  Does anybody understand this well enough to explain it?      

Dan

[*Scotty*]

The idea is that the very low mass at the stylus tip will be capable of accelerating fast enough to stay in contact with the microscopic groove modulations which occur when signals of 20kHz. or higher are cut by the mastering lathe. The mass of the cartridge body provides an inertial frame of reference for the motion of the stylus. The ratio of mass in the stylus tip to the mass in the cartridge body insures that the microscopic motion of the stylus is not lost by accommodating motion of the cartridge body.
  Obviously in the real world the entire mass of the cartridge and tonearm are induced to microscopically vibrate by the action of tracking the record grooves. The spurious vibration in the system results in intermodulation distortion of the original signal vibration from the stylus resulting in a loss of fine detail in the best cases and pure mud in the worst case scenarios.
  Successful design lies in suppressing the tendency of the cartridge body and the arm to vibrate at any frequency but that of the fundamental frequency established by the compliance of cartridge and the mass of cartridge/tonearm system. 
  If the arm resists motion in either the x or y plane due to friction this impedes the cartridges ability to go along for the ride and follow the macro- motion necessary to follow the path of the groove walls defined by the spiral cut into the record. A constant radial velocity towards the center of the record is imparted to the tonearm by the spiral and the lateral inertia of motion present means once the arm starts moving towards the center of the record it wants to remain in motion on the same vector. Inertia is a function of mass,the more mass you have the more inertia of rest and inertia of motion you have.
  By way of illustration you can push a semi-rig and if you push long enough and there is no friction to resist the truck's motion eventually the semi will start to move. Once it starts to move it won't take anymore energy input to keep it moving in the same direction. You can now dance a jig while touching the truck and impart very little vibration to it,this is analogous to the stylus tracking the groove in the record while attached to the cartridge body and traveling towards the center of the record. If you are attached to the truck you will be able to resist gross changes in motion from outside forces because the truck wants to keep on going.
   Of course if your foot gets stuck in a pothole or a crack in the road while dancing a jig you will break your leg because the truck won't stop and wait for you to get your foot out of the crack. This is what used to anecdotally happen to some cartridges attempting to track the TELARC recording of Tchaichovsky's 1812 Overture. This is equivalent to the Grand Canyon on the surface of the record.
  This analogy is not perfect but I hope it helps you towards understanding some of what happens when the stylus meets the groove on your record.
Scotty
 

[*Scotty*]

Dan, that was the series 6000/7000 Rockport tonearm I referenced that was last used on the Sirius V turntable. The key to having the same inertial resistance in both the x and y axis is as simple as have the same mass in the horizontal plane as you have in the vertical plane. Real world engineering dictates that some compromises be made.
  The hollow tube that rides on the horizontal manifold needs to be made of as light a material as possible and of a length that is sufficient to achieve a "stiff" bearing at the pressure used in the system but no longer than is absolutely necessary. I don't know by what percentage the horizontal mass in the tonearm exceeds that of the vertical mass but I expect the two are close enough to one another to be a more than satisfactory engineering compromise to realize the benefits of the tangential tracking air-bearing tonearm concept.
Scotty

[neobop]

Here's a review of the Sirius turntable from 2000. The reviewer is none other than Mr Analogue himself, MF.
http://www.stereophile.com/turntables/258/

There have been a few turntables since (even pricier), that have earned similar accolades with pivoted arms. These are a little out of my league, and to be honest, I wouldn't mind having any of them. 

neo