Ammonite Audio Improved Jelco Mounting Collar
Our custom improved mounting collars for Jelco tonearms have been developed continuously over the years and are now even better and easier to use. Key improvements introduced over time include:
- The main improvement is that the central pillar hole has a sharp side-cutout. This means that the arm pillar is now held gently, but firmly, against two vertical’knife edges’, so there is no longer any possibility of the arm pillar leaning to one side. If your armboard and platter are aligned to the same level plane, this new collar will guarantee that the Jelco arm pillar will be truly vertical to that plane.
- The standard grub screw is a large 6mm stainless steel item, now with a nylon tip as standard that grips the arm pillar better than a flat steel screw, meaning that the arm height can be set using minimum force. Jelco’s original collar has a small hard ended grub screw that literally ‘mashes’ the soft arm pillar.
- The overall diameter of the collar is the same as the standard Jelco collar – our very first design (prior to 2010) was larger. This means our improved Jelco collar is fully compatible with any armboard cut correctly for a standard Jelco arm.
Why do I need a different collar for my Jelco tonearm?
Have you ever tried to set the azimuth of a Jelco tonearm correctly? Just when you think you’ve got it sorted, it’s off again! That’s because the standard collar, while beautifully machined, provides very poor vertical support of the arm pillar; and the tiny set screw typically pushes the top part of the arm to one side, almost guaranteeing that the arm will not be properly set up. The azimuth actually varies as the arm traverses the record, which matters a great deal with modern cartridges and stylus profiles. The custom collar gets around that problem by ensuring that the arm pillar will always be secured properly vertical, so setup becomes easy and repeatable. That means better musical reproduction.
Is the collar compatible with other tonearms?
The collar is fully compatible with standard Jelco collar mounting templates, and all Jelco manufactured derivatives with 18mm diameter pillars, including Audioquest, LAD, Ortofon, Roksan. Some Sumiko variants have a smaller 16mm pillar, so are not compatible.
- The Improved collar is 2mm taller than the standard collar, and longer underneath for much better support of the arm pillar:
- It is fitted as standard with a large stainless steel M6 grub screw, with flat end stub to protect the soft metal of the arm pillar.
- A nylon-tipped grub screw is now standard. The nylon tip grips the arm pillar better than the flat steel version, meaning that the arm height can be set with minimum force. These nylon tipped screws are expensive for us, but worthwhile.
- Supplied with a hex key for grub screw adjustment, and stainless steel fixings consisting of 25mm long M4 bolts with nuts and washers and hex key for arm height adjustment. If you have a thick armboard and need longer mounting bolts (40mm, 50mm and 60mm bolts are available), these can be supplied at no additional cost
The custom collar is 2mm taller above the armboard, and longer underneath than the Jelco original, as shown in the images below. All the mounting points, angular positions of the grub screw and front cutout are the same. The grub screw on our collar is positioned 1mm higher than the original Jelco. Look carefully at your tonearm as it’s currently fitted to the turntable – if there is less than 2mm clearance between the top of the standard Jelco collar and the base of the arm rest plate as currently fitted to your record deck, it may not be possible to set the arm low enough with the custom collar, to achieve correct VTA, without recourse to a thicker platter mat or headshell spacers. It is possible to use thin metal shims between the cartridge and headshell to tilt the rear of the cartridge down a touch, thereby achieving the correct VTA without using different mats or spacers. Please ask us if you are unsure about this. In practice, the potential problem only applies to turntables with very low-profile platters, eg the Technics SL-1200; however suitable and compatible armboards are available for the SL-1200 from us and other sellers which allow the whole arm to be sunk low enough to ensure that correct VTA is achievable without any difficulty.
A matching 10mm spacer ring is available immediately – it is designed to raise the whole tonearm higher to accommodate really tall turntable platters, such as stacked platter Lencos. The spacer ring is fully compatible with the standard Jelco collar.
Our collars have the same mounting pattern as a standard Jelco collar. Please note that some compatible Jelco-derived arms may have original collars with different mounting patterns, so to fit a standard Jelco collar, or our improved collar, may require alterations to the arm board opening and arrangement of bolt holes.
Overall diameter: 56mm
Height above armboard: 12mm
Bolt Holes: 3 x M4 arranged at 48mm diameter
Centre Bore: 18mm
Armboard Hole: 30mm
Design Change Summary
Mk1 (Up to 2010): Diameter 60mm, height above armboard 15mm, bottom part length 20mm, centre bore 18mm plain. Hole fixing, front cutout and grub screw angular positions as standard Jelco Collar
Mk2 (September 2010): All fixing points as Mk1. Diameter reduced to 56mm to match a standard Jelco collar, height above armboard reduced to 12mm, side cutout introduced to centre bore, bevelled top edge.
Mk3 (January 2016): Cosmetic change – upper edge changed to 5mm radius instead of bevel. No change to fixing points nor overall dimensions.
Mk4 (June 2017): Front cutout for the arm’s lift/lower device widened; grub screw centre lifted upwards by 1mm. No change to fixing points nor overall dimensions.
What Length Bolts Do I Need to Mount a Collar On My Deck?
Please note that only 25mm bolts have full threads – please refer to the product images above, and choose the optimum bolt length carefully using this table:
|Depth (Thickness) of Armboard|
Collar + Spacer Rings
|Up to 12mm Depth|
*we don’t supply bolts longer than 60mm