For years I have aligned cartridges on my 9” and 12” PU7 arms (both use Linn-type mounts) using the handy single-point universal cartridge protractor that comes with them.
However convenient, universal single-point (or even 2-point) alignment protractors work by simplifying the arm’s actual tracking geometry, and are therefore a bit hit-and-miss.
Arc protractors, on the other hand, are in theory more accurate because they specify a made-to-measure arc for any arm with a given pivot-to-spindle distance, with bespoke alignment grids calculated specifically for that arm.
I therefore invested some time this BH weekend to find a simple way to create and use arc protractors for cartridge alignment, with simple DIY tools. This post is to share my experience in the hope that others will find it useful. (I haven’t searched the forum – it may be that I’m repeating what’s already covered elsewhere). This note only covers the steps I took for cartridge alignment; it assumes that you already have adjusted azimuth, VTA and VTF correctly.
I used the latest version of Conrad Hoffman’s free Arc Protractor template generating programme – link here http://www.conradhoffman.com/chsw.htm
Choose “Custom arc template generator …..”. I found it extremely easy to use, and very accurate. The download comes with detailed instructions.
All I had to do was to measure the pivot-to-spindle distance for each arm accurate to 0.5mm or better, choose the alignment algorithm (the programme calculates Lofgren A (Baerwald) or Lofgren B or Stevenson) and print out the calculated arc protractor on photo paper using my cheap home inkjet. The printout comes with alignment marks at 100 and 200mm – I checked them with a steel ruler to make sure the printout was at exactly the right scale. It was, without any printer adjustment whatsoever.
Alignment using the included instructions was equally simple. Interestingly – for both arms and two different cartridges with quite different construction – the arc protractor’s optimal alignment had about 3-5mm difference to the universal protractor I used to use. It took about 20 min to complete.
Did it make a difference? Yes – particularly on records with grooves stamped closer to the spindle. There was a clearly audible decrease in end distortion, particularly on the 12” arm, and background noise was lower right through the records.
Very well worth trying IMO!
However convenient, universal single-point (or even 2-point) alignment protractors work by simplifying the arm’s actual tracking geometry, and are therefore a bit hit-and-miss.
Arc protractors, on the other hand, are in theory more accurate because they specify a made-to-measure arc for any arm with a given pivot-to-spindle distance, with bespoke alignment grids calculated specifically for that arm.
I therefore invested some time this BH weekend to find a simple way to create and use arc protractors for cartridge alignment, with simple DIY tools. This post is to share my experience in the hope that others will find it useful. (I haven’t searched the forum – it may be that I’m repeating what’s already covered elsewhere). This note only covers the steps I took for cartridge alignment; it assumes that you already have adjusted azimuth, VTA and VTF correctly.
I used the latest version of Conrad Hoffman’s free Arc Protractor template generating programme – link here http://www.conradhoffman.com/chsw.htm
Choose “Custom arc template generator …..”. I found it extremely easy to use, and very accurate. The download comes with detailed instructions.
All I had to do was to measure the pivot-to-spindle distance for each arm accurate to 0.5mm or better, choose the alignment algorithm (the programme calculates Lofgren A (Baerwald) or Lofgren B or Stevenson) and print out the calculated arc protractor on photo paper using my cheap home inkjet. The printout comes with alignment marks at 100 and 200mm – I checked them with a steel ruler to make sure the printout was at exactly the right scale. It was, without any printer adjustment whatsoever.
Alignment using the included instructions was equally simple. Interestingly – for both arms and two different cartridges with quite different construction – the arc protractor’s optimal alignment had about 3-5mm difference to the universal protractor I used to use. It took about 20 min to complete.
Did it make a difference? Yes – particularly on records with grooves stamped closer to the spindle. There was a clearly audible decrease in end distortion, particularly on the 12” arm, and background noise was lower right through the records.
Very well worth trying IMO!
