“ SUPATRAC.....everything is elastic at a microscopic level.....”

[TransFi]

Beautiful Adelmo.....but too complicated for me ....

[behind the rock]

Peter

Hmm.....maybe something like this?



 

TBH, having a lot of fun with the SUPA, especially in underhung mode!

Definitely not like that. I reckon the total moving mass including cartridge could be under 100 grams.

Andy


Cheers

Vic

[TransFi]

Happy New Year to all!

Video of anti-skate working with underhung SupaPunk arm:

I have balanced the weight of the antiskate to remain stationary throughout its travel on the blank acrylic disc. The antiskate device, which consists of a delrin barrel skewered by a bar suspending a pair of weights (on ceramic bearings), needed to be increased in diameter to keep reduce the travel of the weights to keep the pull even along it travel. With the offset version of the arm I used a smaller diameter so the pull would reduce as the weights became more vertical.



Need to point out when playing a record, I have to increase the antiskate slightly as the stylus skews when set up for blank disc.

[low pitch]

Ingenious!  certainly seems to work.   But for an UH TA that is neutral (ie not a supa)  I cannot see there being any deflection of the cantilever whatever the skating force caused by non tangency.  The  sidewall reaction force acts on the stylus and the cantilever and TA just follow along behind.  (unlike an offset arm with no antiskating).

[TransFi]

Martin...I only know my experience of what I am working with. Have not  tried this on a non-Supa TA, but I take your word for it!

[low pitch]

It's been making me think, though really it's far to hot here for that.  I figured out that on an offset arm with no antiskating, the stylus, cantilever pivot point and TA pivot point must all fall in a straight line.  If you pull hard enough.  Which gives you cantilever deflection.   On a straight arm it doesn't.

So it follows that variations of drag force on an offset TA produce variations in cantilever deflection, regardless of whether the antiskate force is set right.  And that contributes to music signal. Not necessarily in a bad way.

[TransFi]

It's been making me think, though really it's far to hot here for that.  I figured out that on an offset arm with no antiskating, the stylus, cantilever pivot point and TA pivot point must all fall in a straight line.  If you pull hard enough.  Which gives you cantilever deflection.   On a straight arm it doesn't.

So it follows that variations of drag force on an offset TA produce variations in cantilever deflection, regardless of whether the antiskate force is set right.  And that contributes to music signal. Not necessarily in a bad way.

Jeez.....send some heat over here.

I think compared to an non-offset arm, it contributes to the music in a bad way. I have a spare offset wand I have been swapping with, but keep going back to the underhung wand. It just sounds more lively for whatever reason.....

My take on it:

[low pitch]

There must be good reasons why a straight arm sounds that way ... if only at one point on the arc haha! Tracing distortion being something else.   With 2 manual shifts of pivot position that can be reduced to about 2.5 degrees which is my plan.   Or you can just set it in the middle and get 7 degrees max. Looks terrible but...  Not commercial but who cares, I like fiddling. Boring listening to a whole side

[TransFi]

Yeh....I have not taken the 'distortion' into account. May be my age, but I cant hear anything untoward in this regard.

[low pitch]

Same here.  It concerns me more if it does damage the grooves.  From Graeme F Dennes  'AN ANALYSIS OF SIX MAJOR ARTICLES ON TONEARM ALIGNMENT OPTIMISATION AND A SUMMARY OF OPTIMUM DESIGN EQUATIONS
>>
Record Wear
Very few phonograph needles at the time possessed a point fine enough to reach the bottom of
the record grooves, so the needle would usually ride up on the groove walls. As the (round)
needle tip follows the groove during play, the wear from the groove walls produces facets on the
sides of the needle, resulting in the creation of a chisel-shaped tip along the line of the groove.
As the arm traverses the record during play, the tracking angle is slowly but continually changing
due to the geometrical arrangements. The chisel-like shape of the needle, which is continually
being reground due to the continuing change in the tracking angle across the playing surface,
produces extra wear on the record, due primarily to the leading edge of the needle’s chisel tip
being continually driven into the groove walls, causing the facets to be reground to "fit" the
groove walls. This process is ongoing and relentless during play and the groove walls become
damaged and worn from the chisel-like shape of the needle tip and the surface noise increases.

The Doubly-Good Solution
To maximise the sound quality and minimise the record wear, the method devised by Harsanyi
was firstly to apply an overhang which minimises the change in tracking angle so as to minimise
the angular "rotation" of the needle in the groove across the playing surface, which in turn
minimises the reshaping of the needle tip and the subsequent damage to the groove walls from
the chisel front edge of the needle, which in turn minimises record wear. Then secondly, to apply
an offset angle which minimises the tracking error and so maximises sound quality by minimising
distortion.  <<

[TransFi]

If I could hear any mistracking or distortion, I might worry about wear....but everything sounds fine to me.

These discussions tend to get rather theoretical, and I am sure there are more factors involved. I have read that the diamond alignment within the cantilever is never perfect, and many cantilevers have a skew. The first AT-OC9 I owned was slightly off. The current one I am using is better...but who knows?

I think the Decca Reference I used to own chewed up my records considerably, and that was used in a Terminator linear tracking air arm. After a few plays, the record became noticeably spitty. I went back to a conventional stylus.

[low pitch]

It's a good point, if the stylus was causing damage surely you would hear it....   

Also you wonder about the chisel thing... are there any microscope photos that show this ?  You might even say rotating the stylus in the groove a little would even out or distribute the wear.

[TransFi]

I haven't really gone into it in any depth. Not gonna get too concerned about it....just enjoy the music!

[mred]

I haven't really gone into it in any depth. Not gonna get too concerned about it....just enjoy the music!

A,worthy statement 

[pde2000]

It's a good point, if the stylus was causing damage surely you would hear it....   

Also you wonder about the chisel thing... are there any microscope photos that show this ?  You might even say rotating the stylus in the groove a little would even out or distribute the wear.

I think this more a marketing ploy when it comes to diamonds. Sapphire will wear down to a chisel on a cheap crosley and do damage.  Using a microscope I can see the large polished flats on old styli but they just sound dull. I did fit a line contact stylus that had worn and was offset from being on a bent cantilever. This was able to shave the groove a little bit. Microline diamonds loose their major radius quickly and continue sounding great and last a long time after with two straight edges (smooth and polished)