-edible zone-
No.6435
Overview
Starting Line Arrival
Deconstruction
Beneath Decks
First Night's Spin
Listening to Plinths
Motor
System:The Tonearm Tweaks Articles
Bookshelf Transit
"It has been said that idler wheel turntables
easily cause rumble, but the problem lies in the plinth rather than the
motor itself. Our plinth is made of solid laminated cherry wood designed
to deaden outer vibrations. Unlike conventional plinths, this plinth
allows only minimum space for the motor and arm base. The construction
of the plinth virtually demolishes any vibrations caused by the motor
but not by deadening the overall sound, which often happens with other
plinths that are also designed to eliminate vibrations caused by the
motor vibration. Once I designed a plinth that killed vibrations without
killing the life of the table, I stopped experimenting and have been
making this plinth ever since.
The plinth is the key." - Shindo
Design Phase, Build Phase
It's been over a year now since starting work on my 301 project,
and more than two since setting out to find one. In the meantime, small
parts have been bought, sold & flown across both Atlantic and Pacific; a
second greasebearing 301 has been purchased; a search for the right
tonearm has turned up a period-correct SME series-one 3012; and three
plinths have been built.
This is titled a 'Listening' project,
because the turntable plinth has an enormous effect on the sound, and
the design of plinths is as much about the tinkering and evaluating as
it is about the build.
However, it must be said that, well, I'm
listening, but I still can't hear any records playing. Yet.
The
secondary 301, several critical years newer, is to allow the original
No.6435 to spin with optimal parts, fittings, and motor, as close to the
Garrard level of spec as possible. When it's all together this will be a
fully-optimized 'ultra' 301, and the secondary one will still be
suitable as a mono deck. And thereafter lots of record playing will
ensue ...
The three plinths are : first, what has become the
servicing jig plinth, which provides any-angle access or positioning of
the deck for adjustment. Sidepanels are tall to protect switch-levers
when the deck is inverted on jig.
Second, a more high-mass
plinth, a shot-in-the-dark idea prompted by the discovery of a massive,
free-for-the-taking segment of roof-beam in my construction-obsessed
neighborhood. For novelty's sake, this was fashioned by manually
chiselling out the closely-conforming shape of the 301's under-carriage
from solid, ala Shindo. With a sliding armboard block. Considerably
quieter and much more resolving than the open-frame jig, this
high-center-of-gravity design pointed the way, by default, to the
resvised shape.
A very much lower drive-motor position and much
wider base ..... The third plinth, a slight rethink of the classic
stacked baltic birch-ply plinth ---this one is much lower, leaner, and
yet still very high-mass.
And laminated, very tightly indeed,
with the Tomb-Of-The-Pharaohs adhesive compound, known in Egyptian times
as The Only Glue There Is. Today known as "hot hide-glue", it is a
really ancient means to bond wood for furniture, comprised of
boiled-down animal hides, as gelatin. Luthiers and pianomakers still use
it to construct musical instruments, due to it's ability to shrink in
volume as it cures, and to draw the adjoining layers together while
doing so. An internet source describes what happens thus :
As the
moisture evaporates from curing hide-glue, the polymer chain bonding the
wood shrinks to less than a third of it's original size.
If the
objective is to closely bond the layers of birch-ply, so as to
effectively transfer a wide band of resonance artifacts through the
plinth, hot hide-glue's "death-grip and disappearance" characteristic is
absolutely perfect.
However.
Because the hide-glue
has a very fast set-up time--- really little more than a minute given
wide areas to cover--- the clamping procedure must be really quick, and
critically accurate.
Designing the clamping press consumed the
lion's share of the effort with this plinth. After the overall scheme
was sorted out, the whole ordeal was reduced to nine glue-ups, over ten
days, to bond ten layers of birch.
The press itself is a little
like a massive Easel--- one that kneels like a praying mantis. The way
it works is that the ply layers are loaded--- one layer is glued at a
time-- into the folded-down table with legs on the front edge in the
kneeling position. The front edges of the ply layers rest against the
spines of the bottom-most furniture clamps, which are firmly seated in
Jorgensen Bar-Clamp Saddles, to maintain a straight & square line-up for
the successive layers, courtesy Gravity.
A heavy press-cover is
placed over the birch layers, and the edges are double-checked, all
around. Then the clamps are tightened, in order front-to-back, slowly so
as to allow the glue to spread, cover, and if necessary bleed out. But
by tightening in order, the bleed will go harmlessly out the back of the
ply-stack.
Then the easel is up-righted, legs locked out, and the
plinth is now level for final cure. At this point, bottom clamps can be
detached from their 'saddle' fittings (by unfastening small thumbscrews)
and, with all clamps still in place, the layer-stack can actually now
slide out and along the table-surface for all-sides glue mop-up.
Which will be necessary, given the chaotic fury of aligning,
hot-glue spreading, fixing, and clamping down each layer, since the glue
is always cooling ... while the clock ticks.
Even in this
phase--- Time. It is always Time that sets the rules of the game.
Photos can be found at The Analog Department site:
https://www.theanalogdept.com/jds-301.html
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Notes On The Glue
Use of hot hideglue in a stacked plinth
requires a little research on methodology, as well as several practice
runs with the actual materials. This isn't overly difficult, but it is
very easy to get wrong if not well acquainted with the process; trial
runs with wide areas of sample material are highly recommended. I made
various platforms and shelves to get up to speed before attempting a
plinth.
To condense the information, the following will tend to slow
down the quick set of the hideglue : High room temperature, high object
temperature, high room humidity, low room ventilation all keep the bond
from setting too quickly. It's an organic, non-toxic glue, so those
conditions aren't impossible to work with. Also, more water in the
mixture, a less absorbent surface (ie fine-sanded and / or sized), and a
thicker overall layer will promote a slower set.
The best single tip
for hideglue work is that a common everyday kitchen Coffeemaker, on US
voltage at least, will provide a carafe of constantly-maintained 140
degree hot water in which to immerse the jar of hideglue gel. Double
check with a thermometer. ....
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