VPI-JMW 12.5 tonearm

Mounting Distance Adjustment


Often I come across user request on a Best Tractor for the VPI JMW-12 series.

The problem is I cannot find any official figures published on its Effective Length and Mounting Distance. From time to time I get quotes from users, but I cannot agree with the specification and hence I have to tell them I cannot be of any help.

One of my most important objective is to ensure my users would get a Best Tractor that I am fully confident that it would give good results. If in doubt I would rather turn down a case request. Please do not treat this as a negative comment on the user equipment. It is just that I do not have good working knowledge to help.

When this tonearm is installed on a TNT or HR-x turntable, the users report to me that the Mounting Distance is fixed in advance and there is no way to alter it. Comes a deadlock and I do not have any advice to offer.

A couple of months ago I discussed this same problem with another user. And he offers his way of adjusting the Mounting Distance of the JMW-12.5 tonearm:

  Remove the Main arm assembly from arm base
  Loosen the two set screws at the bottom and you can rotate the main elbow.
  Loosen the 3 screws on base and rotate to the inner most position.
  Put arm assembly back onto the base. Notice how you need to rotate the arm assembly to line up with the base.
  Arm assembly now realigned with base.
  Arm Base at its original position as set by the Factory
  Arm assembly removed again and the base rotated to it's outer most position.
  Arm assembly put back on. Now it needs to be rotated again to line up with the base.
  Arm assembly now lined up with the base again.
  Arm in it's new outer position. This would increase the Mounting Distance.

Compare this picture with the one below and you can tell the difference.

  Original Position

WE work together and come up with a Best Tractor.

After alignment job with the Best Tractor here is his comments:

"Yes the JMW 12.5 is performing really well.  Resolution, soundstage and focus are all greatly improved, much better than with the standard VPI jig.  I couldn’t be more happy with the result."


Note: This Mounting Distance adjustment is not a Factory recommended method. You do this at your own risk.



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