Tracking Alignment Adaptor for the Exhibition Soundbox

[Marco Gilardetti]

To the best of my knowledge, tracking error can't be zeroed throughout a record with a pivoted arm, whichever the length of the tonearm. It can only be zeroed locally in two points, and kept to an acceptable minimum in all others.

What's the purpose of that blueish cord wrapped around the tonearm?

[audioengr]

To the best of my knowledge, tracking error can't be zeroed throughout a record with a pivoted arm, whichever the length of the tonearm. It can only be zeroed locally in two points, and kept to an acceptable minimum in all others.

I measured the angle of the tonearm and the center of the record for outer, half-way and inner part of the track using the CAD tool and they are all 90 degrees. Perfect tracking across the entire record.

What's the purpose of that blueish cord wrapped around the tonearm?

This is parachute cord with lead shot inside. It adds mass and dampens the tone arm so it does not vibrate.

[jamiegramo]

I measured the angle of the tonearm and the center of the record for outer, half-way and inner part of the track using the CAD tool and they are all 90 degrees. Perfect tracking across the entire record.

Marco is correct, unlike a tangential tonearm, perfect tracking can not be achieved with a pivoting tonearm. Tracking error can, however, be improved by either making the tonearm impractically long, moving the tonearm bracket sideways to approximately half the radius point of the record (playing half) or introducing an offset angle at the soundbox (or pick-up) as with most post 1925 machines.

The 90 degree upright angle of the soundbox does not normally change throughout the course of playing a record. Tracking alignment angle does change.

[audioengr]

I measured the angle of the tonearm and the center of the record for outer, half-way and inner part of the track using the CAD tool and they are all 90 degrees. Perfect tracking across the entire record.

Marco is correct, unlike a tangential tonearm, perfect tracking can not be achieved with a pivoting tonearm. Tracking error can, however, be improved by either making the tonearm impractically long, moving the tonearm bracket sideways to approximately half the radius point of the record (playing half) or introducing an offset angle at the soundbox (or pick-up) as with most post 1925 machines.

The 90 degree upright angle of the soundbox does not normally change throughout the course of playing a record. Of course the tracking alignment angle does.

Well, if the ~39 inch tonearm is not exactly on-track for the entire record, it is within a fraction of a degree, less than 1 degree off, not that this is practical. Just an interesting analysis.

[jamiegramo]

It is interesting, I often wondered what the minimum length of the tonearm would need to be to achieve near perfect tracking.

[audioengr]

It is interesting, I often wondered what the minimum length of the tonearm would need to be to achieve near perfect tracking.

I don't think it is a minimum length. I think it is an exact length. I tried longer and shorter and there is no solution I can find. Notice that the outer and inner points on the record are not on a line with the hub.

[Henry]

It is interesting, I often wondered what the minimum length of the tonearm would need to be to achieve near perfect tracking.

Infinity. Theoretically speaking, of course.

[jamiegramo]

It is interesting, I often wondered what the minimum length of the tonearm would need to be to achieve near perfect tracking.

Infinity. Theoretically speaking, of course.

True but if the tonearm stretched from here to Australia I guess the error would be very difficult to determine!

[audioengr]

It is interesting, I often wondered what the minimum length of the tonearm would need to be to achieve near perfect tracking.

Infinity. Theoretically speaking, of course.

True but if the tonearm stretched from here to Australia I guess the error would be very difficult to determine!

The Greeks determined the size and moon and the distance between them in the second century BC BTW. The tone arm is an easy problem.

If you can get it exactly with ~39", basically one meter, why go further and have any error?

[emgcr]

The man who originally worked out optimal tracking in the nineteen-twenties was Percy Wilson. His findings, together with those of his co-author G W Webb, are incorporated into their definitive 1929 publication "Modern gramophones and electrical reproducers". We are extremely fortunate that this extremely valuable knowledge can now be viewed at nil cost on the internet. Page 121 initiates the discussion of tone-arms from the three viewpoints---geometrical, acoustical and mechanical :

https://archive.org/details/ModernGramo ... /page/n141