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Plinths by the webmaster

examples below:

 

 

In the "heavy weight" category I have this massive slate plinth for the TD124:

After trying several different plinth designs which are noted below, and including open box plywood plinths which I have not yet described, I'm back into the slate.  And you know what.....the TD124 sounds great in slate.

For the story about how I came into this heavy slate plinth here's a link:  LINK

For theTD124: 3 minimal light designs as follows: ML1, ML2 and ML2-F

 

A foam core minimal light plinth with a slightly larger foot print

The ML2-F plinth design for the TD124

Above:  Cad render. The ML2-F waiting for its TD124 to be installed.

Above is a cad render of the core material within the ML2-F. 

Properties:

Density: 2 lbs per cu ft. (not very dense)
compressive strength: 25-30 psi
tensile strength: 30 - 40 psi
shear strength: 25 - 30 psi

It is a rigid, yet lossy, material that is cast into a proprietary mold. The mold tool, in addition to being a casting tool, is also used to assemble and adhere the plinth structure that holds it.  The object is to cast this material into a partially built plinth so that the material expands tightly against all surfaces which contain it. When the material is cured after casting, the top mold piece is removed.  Then the cavity mold tools are removed. After this a plinth top plate is carefully fit and adhered into its mating parts to form an outer 'shell' that slightly bulges from the pressure of the cast material within it.  Shell materials can vary.  In this instance, the lower and outer side panels are cut from baltic birch multi-ply.  The top piece of the plinth is cut from mdf. Once cast, and with the top plinth piece adhered, the entire structure is; first sealed per the needs of the material, then coated in a texture black enamel. Footers can vary.  The first iteration makes use of heavy duty rubber feet.  Hard cones can also be substituted.

Commonly used in surf boards as a composite core, Poly Urethane expanding foam is used in the ML2-F plinth as its core..

DSC_3105.jpg (204431 bytes) left: td124 sn#13943 stands within the first ML2-F undergoing initial trials.

above: getting more serious. The rubber feet have been replaced with Golden Sound Large ceramic cones.  The Neuance platform beneath. Above, the ML2-F polyurethane foam core plinth.  This plinth does pass the 'knock' test.  That is, with the sound turned up, stylus in groove, record not turning, knock on the chassis with one knuckle.  No noise through speakers.  Knock on plinth with one knuckle; no noise through speakers.  This is dramatically different when the TD124 is mounted in an open box plywood plinth (with mushrooms). 

Another concern: static electricity.  It is Winter.  The carpet is nylon.  As pictured, I see no more static than is normal for this time of year.  Fwiw, to reduce static when changing record, a chassis ground to building is often the solution.  As it has been in my listening room.

Record playback.  The Graham tonearm /Shelter 501-II combo is sensitive to vtf, overhang and zenith angle.  Vta, --- not so much -- but best sound is with cartridge body slightly tail down. Vtf works best at between 1.7 and 1.8g. Additionally, the Shelter works better in a high mass tonearm.  Hence the 'head weight' seen mounted in the photo between cartridge and headshell.  With the headweight the arm/cartridge system resonates at 10 - 11 hz using test record # hfn001.

I'm going to try a different armboard.  The ebony board pictured transmits drive train vibes more readily than does the metal chassis of this player.

1/16/2016

while this plinth does offer good isolation from external vibration, both surface borne and air borne, I have noticed some low frequency rumble while playing classical records that have quiet passages. Which led me to try this:

My trusty old heavy slate plinth.  Guess what?!.  The rumble went almost entirely away.   A very dramatic difference..!  That should tell me something.  The ML2-F wasn't such a good idea after all.  For now I'm back in slate and will attempt to "re-think" my foam plinth idea.  Perhaps it isn't just as simple as a single type of foam that serves as a core within a wood plinth.  Perhaps I need to consider using multiple density foams in the build with the 'lossy-est' foam at center and the denser, least lossy foam at the outer layers.  Mean time, TD124 #13943 is sounding quite awesome within the slate plinth I have had since 2007.  Maybe I'll shelve the foam plinth idea for a while.

ML-2:  For the TD124.  below

Minimal Light plinth #2.  (ML-2) This is a variation on the theme set by ML-1 with a few detail differences. 

It is light on mass and high on rigidity.  

Its stance is firm.  Its footprint is no larger than it needs to be.  Area dimensions: 16-3/8 inches wide x 13-3/4 inches deep.  Exterior finish is to be a high texture matte black or matte charcoal enamel.

Below are 3d renders showing the build with a TD124 chassis mounted.  

  with a SME 3012 S2 mounted

from virtual reality to....reality.

Design goals: Light rigid support system for the Thorens TD124 that will dampen drive-train vibrations while maintaining a stance that takes up no more space than it needs.Build: Constrained layer with Two material types as follows: bottom 4 layers Baltic Birch Multi-Ply, top 3 layers MDF.  Adhesive is hide glue. The finish is highly textured black enamel. The very large rubber feet are chosen to provide a firm stance as well as significant isolation from the supporting surface.  The plinth is drilled to accept #14 pan-head phillips stainless steel screws to attach each heavy foot.  

DSC_1377.jpg (244647 bytes) DSC_1366.jpg (210303 bytes)  DSC_1367.jpg (161975 bytes) DSC_1368.jpg (192119 bytes) DSC_1369.jpg (176755 bytes)

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In chassis sn# 13943

DSC_1379.jpg (257709 bytes) For reference.

Above: Looking in from underneath...:-)

ML1 below

 ML-1 (minimal light #1). A light/rigid philosophy for supporting the TD124 

Dimensions: plinth with feet only.  16-3/8 inches wide x 13-3/4 inches deep x 3-15/16 inches high.

goals: 

To maximize rigidity of stance while minimizing mass and area requirements.
This design follows the light/rigid philosophy.  Vibration transfer is meant to be quick as is the dissipation of it.  Other words; design means to avoid vibration energy retention.

Design sketches in 3D cad.

 

DSC_1061.jpg (187221 bytes) DSC_1062.jpg (140144 bytes) DSC_1063.jpg (263258 bytes) DSC_1065.jpg (186872 bytes) DSC_1067.jpg (193969 bytes)

As well as implementing a light/rigid design, there was a desire to create a somewhat rough-cut looking plinth to match with the brushed bare metal chassis of the TD124 pictured above; sn 13932.

build materials:

baltic birch multi-ply
hide glue
multiple coats of lacquer sealer
primer
texture black

 

 

The Mule plinth (for the Technics SP10 mkII)

Above: concept sketch "The Mule"

exploded mule_1.jpg (199264 bytes) exploded Mule plinth assembly view.  Material: baltic birch multi-ply .  Adhesive: hide glue

below: 1st Mule prototype

TMbuild_27.jpg (318742 bytes) TMbuild_28.jpg (360082 bytes) TMbuild_30.jpg (234066 bytes) TMbuild_31.jpg (254859 bytes) 

The idea of this shape was conceived with two goals in mind.  One goal was to minimize the area footprint of the SP10 mkII  motor unit. The other was to alter the visual impact of the rather large rectangular chassis in relation to the tonearm mounted to it.  In particular, to reduce the visual mismatch that occurs when mounting a 9 inch tonearm next to the chassis, which from its inception was always intended to be matched to a 10 inch tonearm.  

There was some curiosity on my part to find out if a high mass plinth was really necessary in order to extract the maximum available sound quality from this motor unit, or if a minimum mass plinth might work just as well.  With that in mind, this plinth was designed and built light.

I expect to produce some variations on this theme in the months to come.

sp10 mkII project page

Mule#2 (aka Bob's Mule)

DSC_2438.jpg (261802 bytes) 

DSC_2430.jpg (431410 bytes) DSC_2431.jpg (289215 bytes) DSC_2432.jpg (187084 bytes) DSC_2433.jpg (182825 bytes)

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Bespoke version built for client.  It differs from the first version in that the uppermost layer is MDF.  The layers below are Baltic Birch multi-ply as in the first version.  Like the first version it uses the Stillpoint cone footers.  (Stillpoints to be installed by the client).  Three armboards were constructed per order. (in purpleheart)  One for a Graham tonearm.  One for an SME V and one (left blank) for a Dynavector DV-505 tonearm. 

Damage Report re: Bob's Mule and the follow-up response.

 

 

R7........a custom plinth for the Thorens TD150

R7 iso 6.jpg (97746 bytes)concept render

The actual thing

 

Detailed information and the story behind this TD150 project:  No. 34259

R7_2

details: No. 79209

 

Above: an alternate plinth design for the original Teres kit turntable.

link to more info on this project: TeresR1

Below Some early concept sketches for belt drive designs

Plinth Concept Drawings by the webmaster

 

150plnth2e.gif (94870 bytes) New plinth ideas R2

150skel_3.jpg (71794 bytes) Skeleton Plinth R3    J.J. Jimmink builds the R3

R4_4a.jpg (26681 bytes) R4

TD150_R5_4.jpg (58528 bytes) R5

TD150_R6_1a.jpg (43194 bytes) R6

Comments:

From time to time I will receive a request to build a custom plinth for a turntable.  I do consider these.

Comments and inquiries can be made to: webmaster@theanalogdept.com  (aka Steve Clarke)