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cactuscowboy 27th September 2010 09:23 PM

DIY oak unipivot tonearm
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Greetings from Wyoming,

I just completed my first DIY tonearm/turntable project. I'll put this up in multiple posts, since there's a fair number of photos.

The platter and motor used were scavenged from a Marantz 6170 yard sale find. The Marantz tonearm had issues and I was not impressed with the cheesy plastic and MDF plinth, so I set out to build a 'better' turntable... or at least have fun trying. :)

Stripping the 'good parts' out of the Marantz.

Glueing up pieces of scrap 2x4. The pieces were rough-sized and squared up with my table saw and planer prior to laminating.

cactuscowboy 27th September 2010 09:27 PM

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I have a well-equipped shop, but lack a metal lathe. So I opted for a wood tonearm, using oak, since I had some scrap material at hand.

Tonearm wand halves were grooved using a router, prior to laminating. This creates a hollow tonearm, reducing weight and providing a channel for tonearm wires.

cactuscowboy 27th September 2010 09:29 PM

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Creating slots in the headshell using a pocketknife and needle file.

Looking good so far.

cactuscowboy 27th September 2010 09:34 PM

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Plinth with platter and tonearm wand resting on it, for a quick visual perspective.

Five coats of Tung Oil finish applied.

Motor/platter and controls in place. Works great! On/off switch to left. The strobe light is housed in a common copper plumbing fitting. 33/45 speed adjust and selector to the right.

cactuscowboy 27th September 2010 09:36 PM

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Detail shots of plinth.

cactuscowboy 27th September 2010 09:43 PM

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Most parts and materials were either scrap laying around the shop or common parts from the local Radio Shack & hardware store. The exceptions being Cardas tonearm wire and a jewel quality stainless steel pivot and matching sapphire vee bearing.

The pivot is securely attached to the tonearm. Pivot point and stylus tip are the same distance from tonearm tube centerline.

The vee bearing was epoxied into the head of an 8-32 socket head bolt. I drilled a deep pilot hole into the head of the monster lag screw and tapped it for 8-32 threads. Using the jam nut, the two bolts are firmly attached together.

cactuscowboy 27th September 2010 09:52 PM

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Tonearm in place.

The large lag screw driven into the plinth is very secure. The vee jewel bearing is adjustable up-down, allowing for variable VTA.

Brass thumbscrews on the outriggers can be adjusted to fine-tune azimuth setting.

The wire brad behind the pivot will provide an anchor point for string-and-weight for an antiskate device, yet to be installed.

The counterweight came from the Marantz tonearm. Note that it can be moved up or down, allowing for precise adjustment of center of gravity (COG). COG was adjusted to be slightly under the pivot point, providing stability without unduly affecting ability to track warped records.

Tonearm has an effective length of 12".

The small board with RCA jacks can be easily removed. A nice feature since my tonearm wires are soldered directly to the jacks.

3GGG 27th September 2010 10:00 PM

Looks great cactuscowboy! How does it sound

cactuscowboy 27th September 2010 10:10 PM

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Grado platinum reference cartridge in place and spinning vinyl!

As soon as the needle hit the groove, I knew I had a winner. Excellent clarity and detail to the sound. How does it compare to a 'known quantity?'

I had done vinyl to WAV transfers from two 45 rpm 12" singles by The Cult, and a Classical piano solo LP, using my fully-modded KAB Technics SL-1200 w/Grado cartridge a few days ago. I made the same transfers using the DIY turntable. IMO, the transfers from the DIY turntable exhibit a bit more sharpness or precision to the sound compared to the Technics. Both sound very good. That my DIY tonearm can produce results equalling my Technics thrills me to no end. :)

I also had my wife, her friend, and our six-year-old great niece sit in for a 'blind' A:B test of the WAV files. They could not detect any difference between the classical piano selections. With The Cult's single "Lil' Devil" they preferred the Technics, citing 'a bit smoother'.

I'm very happy overall with the project, but became aware of a design flaw well into the process. That being the configuration of the headshell. I realized that ideally, the stylus should be positioned precisely in line with the center of the tonearm (COG). In theory, as it was actually built, riding warped records could produce a side-to-side rocking motion, altering azimuth angle. However, in actual practice that is not the case, as the mass of the tonearm is sufficient to resist this effect.

A fun project that was completed within three weeks time.

The Space Egg Corp 27th September 2010 11:06 PM

Nniiccee Job
Hi Cactus

Love the TT and unipivot.
Am doing a TT refurb myself at the moment.
I have an arm to use on it, but would love to have a go at one of my own.
Great photos, have saved them in my gallery.
Very inspiring.

Cheers Simon...:)

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