This Project is to see If I can improve the Stock Technics Arm from an SL-1200 II/V.
This "S" shaped arm is typical of the type. If you draw a line through
the balance weight stub the "S" bend straddles this line. The weight of
the headshell/cartridge roughly balances the bent part of the tube and
presents the weight evenly balanced for the bearing, as per top
picture. You can see that the stylus is positioned a considerable
distance from the centreline. When I first got my Technics deck, I had
problems with Inner Groove Distortion (IGD) and had to change my
cartridge alignment from my preferred Baerwald to the one Technics
devised themselves, which is very similar to Stevenson alignment but
not exactly the same. This arm seems prone to problems with IGD and
there are lots of posts on the Forums regarding this. I have a
suspicion that a combination of different headshell/cartridge weights
is contributing to this by changing the centre of gravity relative to
this centreline and producing an element of built in anti skate bias
regardless of the setting of the anti skate control. This bias is
contributing to the IGD - that's my theory anyway.
If you look at a typical straight arm from Rega or Linn for instance,
the stylus sits on or very close to the centreline as per the bottom
picture.
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