TWISTING CARTRIDGE FOR ALIGNMENT.

[A K Bhattacharjee]

Distance between the arm pivot to spindle is 207mm. Therefore, effective length comes to 225 mm & overhang 18.9mm. Now none of the headshell I have can be adjusted to a length of 225mm. Without headshell arm length is 180mm. When I push the cartridge to extreme back of the headshell even then the effective length is more than 225mm. Result, I have to twist the cartridge towards the spindle slightly for alignment according to Stevension Protractor. Twisting varies from cartridge to cartridge. I have Technics, Audio technica & universal headshells. Is it possible to have headshell with wider gaps? I have tried number of times & also with different protractors but In any case alignment could not be done without twisting. In all the cases twisting was towards the spindle. For this specific turntable I am unable to come to a conclusion that whether shall I twist the cartridge or keep it parallel to the headshell. Any help?
Thanks in advance.

AK B

 

[jls001]

Please explain more clearly what you mean by "twisting towards spindle". Are you trying to achieve the desired offset angle? If yes, it's perfectly okay for the cartridge body not to be in line with the headshell length as long as you're achieving correct offset.

Using Conrad Hoffman Arc Template Generator 1.16, I tried generating using your pivot to spindle distance of 207 mm. The numbers it generated for Stevenson A (one can generate Löfgren A or B too) are:

Inner groove radius: 57.5 mm (as per DIN standard, but one can generate as per IEC standard, or use custom numbers)
Outer groove radius: 146.05 mm (DIN)
Pivot to spindle distance: 207 mm
Inner null radius: 57.5 mm
Outer null radius: 115.522 mm
Effective length: 222.467 mm
Overhang: 15.467 mm
Offset angle: 22.884°

 

[A K Bhattacharjee]

Please explain more clearly what you mean by "twisting towards spindle". Are you trying to achieve the desired offset angle? If yes, it's perfectly okay for the cartridge body not to be in line with the headshell length as long as you're achieving correct offset.

Using Conrad Hoffman Arc Template Generator 1.16, I tried generating using your pivot to spindle distance of 207 mm. The numbers it generated for Stevenson A (one can generate Löfgren A or B too) are:

Inner groove radius: 57.5 mm (as per DIN standard, but one can generate as per IEC standard, or use custom numbers)
Outer groove radius: 146.05 mm (DIN)
Pivot to spindle distance: 207 mm
Inner null radius: 57.5 mm
Outer null radius: 115.522 mm
Effective length: 222.467 mm
Overhang: 15.467 mm
Offset angle: 22.884°

According to Lofgren B specifications are what I mentioned. In this case, overhang is 18.930 but how to achieve this because as I mentioned even when the cartridge is at the extreme rear end of the headshell, overhang is more than 18.9. In both the cases either Lofgren B or Stevension universal protractor, I had to twist the cartridge for perfect alignment. In that case cartridge is not square to the headshell. Thanks jls. I want to align the cartridge in the given parameters.

 

[jls001]

According to Lofgren B specifications are what I mentioned. In this case, overhang is 18.930 but how to achieve this because as I mentioned even when the cartridge is at the extreme rear end of the headshell, overhang is more than 18.9. In both the cases either Lofgren B or Stevension universal protractor, I had to twist the cartridge for perfect alignment. In that case cartridge is not square to the headshell. Thanks jls. I want to align the cartridge in the given parameters.

If you want the cartridge to be square to the headshell, you can do so. Just make sure you set overhang correctly. You'll be aligned as per the tonearm's geometry. But it's perfectly okay not to be square as long as your cartridge is aligned correctly to the two null points in a two-point protractor. Being correctly aligned to the two nulls is obviously more important than being square.

Which tonearm are you using? And do you have the original protractor for it? Use a regular 1 foot ruler to re-measure the pivot to spindle distance and verify that it is indeed 207 mm. This is the primary measurement from which all other numbers we're discussing are derived.

 

[sunder]

Instead of using any protractor, you can try with Overhang Gauge which is specially made for Technics TT & Specially made for Audio Technica TT. Both TTs have their own Overhang spec.

 

[Fiftyfifty]

Hi,

If your tone arm is 180mm, then you need around 40mm as the headshell length measured upto the cartridge mounting position. This should be possible with most universal headshells unless your cartridge protrudes way forward. I'm using a Stanton Universal headshell which measures around 40mm upto the midpoint of the mounting position, so it should work in your setup without the need to twist.

Best wishes