DIY 12 inch Wood Unipivot tonearm

Using the unipivot bearing from my previous DIY Balsa Wood tonearm, I wanted to make a 12 inch (305mm) long tonearm.

I already had some solid wood, a locally available hardwood from the Pacific region called Kwila (Merbau).

This timber is dense (around 850 kg/cu m) – but importantly, this wood is stiff, it has a solid tone and ‘fast’ response when tested.

Wood in general has good energy ‘damping’ characteristics – but there are many varieties of wood.  Some are light & soft, some are dull & ‘slow’.

Here is the design:

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Here is the wood:

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Shaping the wood:

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(A ‘slot’ underneath for wiring)

The tonearm finished shape:

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With the brass Unipivot bearing housing (from the Balsa Wood tonearm)

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(Furniture-wax finish)

Tonearm wiring – Cardas 33awg with Eichmann Bullet Plugs – well proven:

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Screw fixing the wood arm onto the brass unipivot bearing housing:

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(It looks like a U-boat  😉 )

Finished!…..

The Counterweight is a plastic film cannister with lead-shot, suspended using waxed thread (from bicycle tubular tyre repairs).

A hanging counterweight does not change distance from pivot if the tonearm rises up or down.

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(Shown on Aura turntable with Fidelity Research FR64 tonearm.)

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Headshell ‘outrigger’ weights are also a convenient finger-lift.  (Koetsu Rosewood cartridge)

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This 12 inch wood tonearm has good low frequency control and power.  Good percussion and rhythm.  Good ‘separation’ and clarity, especially at the LF end.  These are its strengths.

Of course, we know that peak tracking distortion is lower with a 12 inch tonearm (40% less, compared with a 9 inch tonearm).  So, we have a more consistent, slightly more ‘relaxed’ sound across the record.

For comparison, the stainless steel FR64 tonearm (9.5 inch/245mm Effective Length) has a legendary ‘punchy’, ‘forceful’ sound in the mid-band, but is rather harsh, ‘coloured’ and restricted in bandwidth, in comparison.

The Analog Instruments Apparition 12″ tonearm (superseded by the Siggwan) is an overall better performer, but this DIY tonearm will still give musical satisfaction.

 

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