Turntable advice / opinion on setup / sound.

Not all LT tonearms are created equal. But certainly the Holbo cum LT tonearm is not the only game in town.

RB, you wrote, 

"Seems to me the arguments for under-hung are quite, well, under-done!

Try this.  Imagine a reference line between the tonearm pivot and the stylus. The primary friction force is along the reference line.  But any time the groove at the stylus point is not completely aligned with the reference line, there will also be a sideways component, the skating force.  This is regardless of the shape of the arm and any offset of the cartridge.  It is also regardless of the amount of under- or over-hang.  It is simply because the friction force always has a sideways component, except when the groove and reference line are in perfect alignment."

Are you actually trying to explain the origin of the skating force to me?  If so, here are some of the issues you leave out that make for a big difference between underhung and overhung pivoted tonearms as regards the skating force. These may not concern you of course, as you are using an LT tonearm.  First, in order to achieve a TAE or HTA or LTA error of only 2 degrees (assuming no zenith error), an overhung pivoted tonearm must have its headshell offset at an angle with respect to a straight line through the cantilever and pivot point (the same angle you refer to above).  This offset angle ranges from about 20 to 22 degrees for a 9 or 10 inch arm, less for a longer arm.  That automatically results in an angular error equal to headshell offset and causes a skating force that is always directed inward.  Any TAE along the way simply adds to the headshell offset angle as a further cause of inward skating force.  For an underhung tonearm with zero headshell offset, it is true that TAE at the extremes of travel (innermost or outermost grooves, if you set up the underhung tonearm such that its single null point occurs close to the midpoint of the grooved surface, or actually about one-third of the distance from the innermost grooves) can develop about 10 degrees of TAE (less for longer than 9 inches), all of which does contribute to a skating force, BUT the skating force of an underhung pivoted tonearm changes direction before vs after the stylus reaches the single null point.  So there is no constant unidirectional skating force.  Moreover, for a large fraction of the playable surface of an LP, before and after the stylus reaches the null point, the angular error is small and only very gradually reaches maxima.  Because the force vector changes direction around the null point, it is not feasible to apply an AS device on an underhung tonearm. But this may be a good thing.  An AS device applies a force near the pivot to counteract skating that occurs at the stylus tip.  This puts a constant tension on the cantilever.  That tension cannot be a good thing, as the real job of the cantilever is to transmit the unadulterated undulations of the groove wall from stylus to the transducing mechanism in the cartridge body. So it’s a question of which is worse for the job of the cartridge, high TAE as it affects the profile of the stylus in the groove in an underhung tonearm or high unidirectlonal skating force as in an overhung tonearm. In my opinion, one has to listen to both.

@elliottbnewcombjr 

I wonder if I could put a linear tracking arm on my setup?

You'd just have to find some space and some dollars!

But I agree with @lewm - there are many designs of linear tracking tonearms and they will likely be as different from each other as pivoting tonearms are, and maybe more so!  Some cost more than a complete Holbo system and none, in my opinion, is better than the Holbo's tonearm from a design and engineering viewpoint.

@lewm 

This offset angle ranges from about 20 to 22 degrees for a 9 or 10 inch arm, less for a longer arm.  That automatically results in an angular error equal to headshell offset and causes a skating force that is always directed inward

I do have a 9-inch SME Series II improved tonearm with fixed headshell and thread-and-weight anti-skating device in addition to the Holbo, so this topic is of practical as well as theoretical interest to me.  If the SME thread falls off its wheel and runs on the axle, the result is very audible!

It bothers me when you refer to the headshell offset angle as an angular error. In fact, it is designed to reduce the angular error between groove and cartridge to as close to zero as possible, within the geometrical constraints of a pivoting system.  Properly set up, there are two points during play where the angular error is zero, Outside these points, the error is under 2-degrees, not around 20-degrees as you imply.

The original calculations were set out by Percy Wilson, then the technical editor of The Gramophone magazine, about 100 years ago.  Before then, Percy invented and I believe patented a linear tracking ’tonearm’.  About 6 feet long, and floating on two mercury baths, the arm directly carried a 6-foot horn loudspeaker made of lightweight papier mache.

The physics is straightforward if you concentrate of the line between the pivot and the stylus - skating forces arise when the record groove moving under the stylus does not align with the line.

An A(nti) S(kating) device applies a force near the pivot to counteract skating that occurs at the stylus tip.  This puts a constant tension on the cantilever.  That tension cannot be a good thing

The ideal antiskating force exactly balances the skating force at the stylus, so the overall suspension is unstressed (surely a good thing).  The stylus experiences exactly opposite skating and anti-skating forces (also a good thing).  The cantilever during play experiences stretching tension from the friction between stylus and record groove which, being made of rigid aluminium, boron, diamond or whatever, it is designed to handle.

There is a continuum for pivoting tonearms from ideal overhang (minimises maximum tracking error) to reduced overhang all the way through various degrees of under-hang.  

The Stereophile review suggests that under-hung tonearms significantly increase distortions which may please some ears.

That’s why I would like you to experience a Holbo, which gets the geometry right and uses the friction-free principle pioneered by Percy’s mercury bearings!

@richardbrand 

I do have a 9-inch SME Series II improved tonearm with fixed headshell and thread-and-weight anti-skating device in addition to the Holbo

I assume you realise that because the SME series II has non offset vertical bearings, whenever the arm is not parallel to the record the azimuth is out and you are probably damaging your records.

With any arm that has non offset vertical bearings and an offset cartridge ( this covers most vintage tonearms ), any time you adjust VTA the azimuth goes out.  ( cartridge is now leaning to one side.  ).

To see this for your own eyes put a bubble level on the headshell and then adjust the VTA - you will be shocked at how much the cartridge rolls and leaves the azimuth out by some margin.

@dover 

You'll have to help me with some terminology here!  What do you mean by vertical bearings?  I don't think you mean the bearings in the pivot that allow the arm to rotate in the horizontal plane?  The other bearing is a knife edge bearing where the knife edge itself is horizontal, allowing the cartridge to lift vertically.

In reality, I have only adjusted the arm height when changing cartridges, or when I changed the thickness of the platter mat.  Changing the arm height is not the best feature of the SME.  I use a reticulated scale to get the arm parallel to the record surface.

The azimuth roll you describe should also be obvious when lifting the arm to cue it.  I'll have a look next time I am home, but my instinct is that the knife-edge bearing is parallel to the cartridge face?  In that case, my brain is not wired to understand how the cartridge rolls