Turntable Plinth (Base)

Originally posted on April 21, 2014 (personal website) and then on January 18, 2016 (LumberJocks).
 
Here are some photos of the custom plinth (base) I designed and built for my Thorens TD 166 MkII turntable way back in 2014. The sides are maple with cherry accents (dowels). The base plate is 1/2" oak plywood with birch edge banding, inset by 1/4".

I used a three-step finish. First, I used Watco danish oil to warm the maple and accentuate the little grain it has, and to darken the cherry dowels. Then I used spray shellac to build the finish and add gloss. Finally, I applied paste wax with #0000 steel wool to smooth the shellac and soften the gloss to create a smooth satin finish. I stained the edges of the base plate a very dark brown (almost black).

Around back, I added phono jacks (Dayton RCA-CHRB from Parts Express), power supply jack, and a binding post for the ground wire. I also routed slots for the dust cover hinges.

I wasn't in the habit of taking in-progress photos back then, but I do have have some old (and unfortunately low-resolution) renderings that show how the design evolved and the sides are constructed.

Design Concepts

I bought the maple hardwood for the plinth before I designed the plinth. The maple boards were plain, so I knew I had to use either contrasting tones, grooves, or accents to add visual interest.

It took me well over a year to finalize the design. I explored numerous designs. You can't beat CAD (I use MicroStation) for this type of iterative design process.

I started by considering horizontal cuts or stripes. I've seen similar designs on the web.

I considered vertical segments.

I considered a two-tone variation of the vertical segments.

I considered a V-waist design with an aluminum dowel "belt." I came very close to building this design.

While trying to decide about the V-waist design, I started thinking about slightly curved or contoured shapes.

The final design combines elements of the V-waist and contoured designs. I'm very pleased with it; it doesn't look like any other plinth design I've seen. (I later learned that a company named Voyd used plinths that are similar, just without the accent dowel in the center channel.)

Construction Notes

To sculpt the sides, I used a table saw and three router bits: a 1/2" cove bit, a 3/4" roundover bit, and a 1/4" round nose bit.

1. Start with 2-3/4" x 3/4" maple board.

2. Cut the board into two 1-1/8" wide sections.

3. Scoop out the inside edge of each section with the cove bit.

4. Glue the two sections back together.

5. Route the recess for the dowel accent using the round nose bit.

6. Contour the outer edges with the roundover bit raised to make a partial cut instead of a full quarter-round cut.

I glued the dowel accents to the sides before making the miter cuts so the accents so the corners matched up.

I did not create detailed drawings for the various parts inside the plinth (the corner braces and blocks for the transport screws). I just used the original plinth as a guide and duplicated those parts as closely as I could.

Because the plinth is shallow (short), the three posts for the suspension springs contacted the top of the bottom plate, as did the underside of the tonearm mount. To eliminate those contact points, I drilled 1/2" clearance holes for the suspension posts and routed a clearance recess for the tonearm mount.