2. analog
  3. 191224-33932

Straight tonearms without offset angle

In the October issue of Stereiphile, there was an article on a tonearm that had no offset angle and therefore had no skating force. The disadvantage of this is at the beginning and end of the record, the tracking angle error was much greater than what you get with an offset angle. For conventional tonearms that have an offset, and require anti-skating, which can never be perfect, the typical tracking error has a supremum of about 2 degrees, and according to online Lofgren calculators, this imposes a second-order harmonic distortion less than 2%. 

I have a single-ended triode amplifier consisting of vintage globe 45 triodes transformer coupled to 833A SETs which drives Magnepans. Such SETs typically have second-order harmonic distortion as high as 10% which does not hurt the sound. A straight tonearm without an offset would have a maximum, or supremum tracking error of just under 10 degrees. If this causes a second-order harmonic distortion of less than 10%, would not this be irrelevant in a SET system? Is there any way of calculating this, or has this ever been studied? 

drbarney1

Showing 3 responses by larryi

larryi
4,277 posts
 

Even with a straight arm with no offset angle, the tracking angle error could have been lessened by making the arm longer and not underhung.  The reason for this design is not only to minimize skating force, it is designed to be extremely rigid by being short.

I have to say I was surprised, but it does sound good.

larryi
4,277 posts
 

The Viv arm causes a deviation from tangency of up to 10 degrees at the start of a record and this declines to zero before again increasing to 2 degrees.  This means FAR less skating than the skating force of an arm with an offset angle of 22 degrees or so.  The lower level of skating might argue in favor of no skating compensation.  

The Reed T 5 approach to tangency, with no offset angle to the headshell is a great approach, at least theoretically.  The same goes for the Schroeder LT arm. Parallel tracking arms using a conventional pivot and a servo mechanism to move the pivot to maintain tangency are also theoretically good.  Air bearing arms, and other low friction approaches that drag the arm back into tangency imposes forces on the stylus/cantilever that is sort of akin to skating forces.

I would like to try the Reed arm, but, it is quite expensive and I mostly listen to digital anyway.

larryi
4,277 posts
 

Wow! That talk by J. Carr covers a lot of topics in a very informative manner.  The explanations are terrific and balanced, with pluses and minuses of various design choices explained very well.  This is one of the few long discussions worth the viewing effort.

Thank you all for these links.

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