ODYSSEY RP1 - xg
Mounting Dimensions
The RP1 has an adjustable base, which allows the distance from the centre of the turntable spindle to the horizontal arm pivot axis to be varied. This compensates for variations in cartridge cantilever length and position, which change the effective length, and thus the offset angle, which necessitates an adjustment of mounting distance.
The notional geometry is Lofgren A DIN, (nulls at 63.5mm and 119.5mm) but Lofgren A IEC (nulls at 66mm and 121mm) or Stevenson can be accommodated. The difference in angle is tiny, and so, due to the clearance between the cartridge screws and the mounting holes in the headshell and cartridge, there is normally enough adjustment to get the appropriate offset angle. If the new headshell is fitted, then setting the offset to any angle is simplified.
When mounting the arms, a 35mm diameter hole should be drilled in the arm board such that its centre is approximately 215mm (for the standard arm) or 295mm (for the long arm) from the centre of the turntable spindle. A spacer made from card can also be used: it should be 200mm long and placed between the spindle and the arm pillar. This 200mm distance is not critical as there is ample adjustment to
obtain the appropriate pivot to spindle distance for any cartridge. The base can then be orientated
The base plate can then be positioned to suit the arm board position and also to allow for the maximum
adjustment range of the offset pillar mount together with easiest access
to the adjustment screws, either facing towards the centre as per SME, or parallel to the arm-rest. The 3mm diameter holes for the mounting screws can then be marked for drilling.
Alternatively, a standard SME arm board can be used, or any SME template, centred at 215mm (for the 9" arm), or 295mm (for a 12" arm), and rotated to the desired alignment. The slot can be replaced by a 35mm diameter hole.
Because the arm has the facility to adjust pivot to spindle distance at the base, the initial positioning is non-critical. See the article on SME geometry for more information. An arc protractor should not be used, as the effective length is nominal and depends on the distance from the cartridge mounting holes to the stylus. Adjustment at the base allows for this.
The standard arm:
The standard arm is designed as a nominal 9" (230mm) effective length arm.
The long arm:
The long arm-tube options are now usually at a nominal effective length of 12"
(308mm) with a mounting distance of around 295mm and an offset of around 17.5 degrees. Custom effective lengths can also be made to order, and will require appropriate mounting distances.
