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Technics SL-1200 tonearm alignment for once and for all!

Posted by B.K. (A) on April 25, 2007 at 11:58:35

Technics SL-1200 tonearm alignment for once and for all!

There was a rather unpleasant discussion here about a week ago regarding the alignment of a cartridge on the tonearm of the Technics SL1200: unpleasant because of the potty mouthed contributions from one unregistered poster.

I’ve been busy lately; however, yesterday I found this link to the Panasonic website which gives the dimensions of the tonearm of the SL1200 mkII and the SL1200 mkV, the most common in this series of turntables (the mkI was a substantially different turntable, the mkIII was only available for a few years in the US, and the mkIV, which was unique in offering a 78RPM option, was only ever released in Japan).

http://www.panasonic.com/consumer_electronics/technics_dj/prod_specs_sl1200mk5.asp

As you can see, the tonearm dimensions are given in the above link as follows: effective length, 230 mm; overhang, 15 mm (corresponding to a mounting distance of 215 mm); offset angle, 22 degrees. The dimensions are the same for both the SL-1200 mkII and the SL-1200 mkV models, so it is reasonable to assume that the tonearms on the mkIII and mkIV models also had the same dimensions.

Several years ago, I prepared an excel file which allows the calculation of null radii from tonearm parameters, and vice versa. Steve of the analog dept kindly hosted this excel file, and you can find this on line here:

http://www.theanalogdept.com/images/spp6_pics/Alignment Spreadsheet/Arm Data Calculator.xls

By entering the tonearm parameters from Panasonic website in the cells highlighted in red in the top box of the first worksheet, the null radii of the Technics tonearm when a cartridge is aligned according to the manufacturer’s recommendations are produced. It can be seen that the Technics recommended null radii are 58.8 mm and 113.5 mm. These null radii are not unusual for a Japanese made tonearm.

If a user wishes to use an alignment protractor which is designed to give null radii at 66.0 mm and 120.9 mm (the so-called Baerwald alignment), then, since the mounting distance is fixed, the effective length and the offset angle of the cartridge have to be changed.

The same link above allows the calculation of the new tonearm parameters: just click on the worksheet tab marked “Null Radii+Mounting Distance”, enter 66.0 mm and 120.9 mm for the null radii, and 215 mm for the mounting distance in the cells highlighted in red in the top box. The resulting effective length is produced in the second box down the page, the answer is 232.8 mm which means that the cartridge must be moved forward about 3mm in the headshell compared to the manufacturer’s alignment.

The offset angle is also produced in the second box down the page and it can be seen that this has increased to 23.7 degrees. These results are in line with the observations of most users (myself included) who have aligned a cartridge on the tonearm of a Technics SL-1200 using a standard protractor with grid centres at distances of 66.0 mm and 120.9 mm from the centre of the spindle hole, i.e. that the cartridge must be advanced to the front of the headshell, and skewed clockwise relative to the headshell when viewed for above.

The unpleasant discussion mentioned above can be found here:

http://www.audioasylum.com/audio/vinyl/messages/648979.html

IT is interesting because the picture posted by Ralph NLD verifies the results predicted above.

I hope this post clarifies the matter.

Best regards,

BK

• Tonearm Data Calculator   (Open in New Window)

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