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AN
OBJECT OF ART
According
to various reviews at the time when the SP10 mkii was launched,
many stated that the problem with the SL1000 (SP10 in the obsidian
base plus feet) is that they measured some mechanical feedback
when playing music relatively loud.
Hi-Fi
Choice from Great Britain reported that the bass was somewhat
slender and there was some shallowness in the mid and upper mid
frequency region. This is certainly caused by the amorphous "structure"
of volcanic glass (and any other glass often used for platters).
This
criticism does not make the complete SL-1000, as the Technics
engineers designed it as an entity, less desirable, less unique.
In this way it can be considered as an example of industrial design
as it was achieved in the nineteen seventies of the last century.
Thus seen it is an object of art. But for sound reasons...
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OBSIDIAN
BASE FOR MK3
The Technics
SP-10Mk3 is a completely different turntable. The opening for
the motor in the obsidian base for the Mk3 is a round hole and
it can not accomodate Mk2.
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KANETA
BASE FOR SP-10 MK3
It
seems that the motor unit alone, which is the SP-10 Mk2, was sold
in higher quantities. No wonder many audiophiles and designers
construct plinths from wood which makes a sonic difference if
wood is chosen with specific sound porperties: propagation and
speed of sound, density of the material, and stiffness. That is
why Akito Kaneta chose layers of a specific wood for his base
of the Technics SP-10Mk3. In the picture
at left (courtesy Richard Huxley from France), the Kaneta philosophy
was applied, although in the original Kaneta version the SP-10
is stripped and just the motor unit with platter is mounted on
the layered wooden plinth. Also the power supply was altered.
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MANY
ROADS LEAD TO ROME
In
case you come accross an SP-10 Mk2 or Mk3 without the SH-10B3,
there are several options to construct a base/plinth. You either
can go the Cotter way and make the suspended type, or construct
a solid plinth of several layers of wood, or even add thin layers
of aluminum or sheets of steel in between the wooden pannels,
and then place this plinth on rubber feet. Such a base or a similar
construction can give a harmonious sound and better dynamics in
the lower register and a firmer mid band. You know that if the
bass is not firm, full and controlled, the rest of the spectrum
suffers.
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Material |
Density |
Speed
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Aluminum |
2.6989 |
6.36 |
Carbon |
2.26 |
18.1 |
Copper |
8.94 |
|
Iron |
7.8733 |
5.95 |
Lead |
11.34 |
3.83 |
Zinc |
7.133 |
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Acryl |
1.2 |
<
3.83 |
Brass |
8.3 |
|
Boron |
2.34 |
|
Beryllium |
1.85 |
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Titanium |
4.507 |
|
Magnesium |
1.74 |
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Rubber |
|
<
1.45 |
Felt |
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<
0.98 |
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If you do
not own the obsidian base you will have to construct a solid and
relatively heavy base and de-couple it from its environment by
means of insulating rubber feet. Various materials can be used
for the base:
- multiple
layers of particle board (chip board)
- plywood
covered or combined with a thin sheet of aluminum (1 mm)
- layers
of thin wood glued together
- serpentino
(thin plate of stone, about 10 mm, with a sort of grainy and
not too dense structure), andmbine it with a wooden panel, and
there is - as some people suggest -
- corian.
Better
not use corian as it has a frequency curve with emphasis on high
frequencies, depending on the thickness.
I have tried it for arm base and for a 5 mm thick turntable mat
shaped according to the drawing on my page about .
The properties of corian are not always as desired because the
percentages of aluminum varies (large or small flakes, more or
less flakes).
And
better not use MDF, or sparingly because of its odd frequency
characteristic which shows uneven sonic qualities with emphasis
in the lower mid area. This anomaly may disappear when you use
many layers and construct a very heavy base. But then the fact
remains that it is in fact "dust", the dust particals
pressed and bonded.
I myself am
not an advocate of too heavy plinths made of materials with a
high density. Better choose the material and the volume in
accordance with speed of sound and an even frequency characteristic
without abrupt filtering of the signal. In that case the sound
dissipates gradually.
The data for
stiffness, density and soundpropagation are important in order
to get an idea of what the best combination of materials is. Look
for the data of sound propagation in materials. A few data in
the table at left are taken from The Practising Scientist's Handbook,
written and compiled by Alfred J. Moses (Van Nostrand Reinhold
Company, New York, 1978).
It is obvious
that carbon has almost 3 times the speed of aluminum. Hence it
is preferred by cartridge builders for the material of the cantilever.
See also the difference between aluminum and acrylic. These materials
have a significant effect on the measure of tangibility of the
sound.
If certain
materials are used in alternate layers, they team up very well
for arm boards and chassis, whereas acrylic alone gives less definition
and detail.
A wooden plinth
coated with a thick, shiny layer of lacquer may influence the
frequency characteristic in a negative way.
The frequency
of the isolating rubber feet or springs supporting the
base plate (the SP10mk2 unit included) should preferably be in
the region of 2 to 4 Hz.
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LIGHT
floating, relative light weight chassis de-coupled by springs
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HEAVY
solid, relative heavy plinth on rubber feet, cones or specific
points
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lively,
speed, slam, good transient
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>
<
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restrictive,
controlled, may be less engaging
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risk
for colouration
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>
<
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neutrality
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empirical
search for best materials in relation to sound
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>
<
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choice
of materials
and combination
seem less critical
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precise
combination of materials eliminates resonances
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>
<
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unwanted effects generally cancelled by sheer weight
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tonearm
and arm board become part of the construction
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>
<
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base
/ plinth does have a less critical effect on tonearm
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adding
a second tonearm will alter the performance of the total
system somewhat
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>
<
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the heavy plinth/base allows more tonearms to be mounted
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distortion
prone if not critically and emperically damped
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>
<
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damping
is critrical to eliminate mechanical feed back
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poor
tonearm quality
influences the sound
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>
<
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a
low quality tonearm can sound better than it actually is
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choice
of cartridge is very critical as it easily interacts with
arm/ board / plinth
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>
<
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cartridge will naturally show its actual quality in relation
to a specific tonearm
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measures
have to be taken to prevent swinging (wow) in the horizontal
plane
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>
<
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heavy plinths (and platters) add to stability of the nominal
speed
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in case of a belt drive turntable, the motor should be located
in a heavy housing to prevent transmitting vibrations
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>
<
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in case of a direct drive turntable, the motor benefits
from the heavy plinth
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VARIATIONS
The choice
of materials, the amounts used, and the position in the total
concept determine the quality of a turntable, loudspeaker, amplifier,
cd-player, cable, etc. In short: choice, amounts and topology
can make or break the quality of the reproduction, deteriorate
or improve the sound.
Most high-end components have been designed accordingly on the
basis of a quasi unlimited budget. While in cheap, mass marketed
audio systems the budget is the restrictive factor, the best solutions
for the dollar have been sought by the engineers.
This adage naturally applies to the Technics SL-1000 Mk2 (SP-10Mk2
on plinth with cover) and though considered high end, it was produced
in relative large quantities. Some reservations exist concerning
the use of volcanic glass (obsidian) for the plinth and maybe
the EPA 100 tonearm, but at the same time the system was optimized
in other details, for example the addition of plywood to the small
arm board which would have a somewhat counteracting, positive
effect.
Shape and
damping of the suspension in a light floating chassis turntable
are extremely important. They are as important as size, contact
area, and design (shape) of the feet for a turntable system mounted
on a heavy plinth - be it of slate, volcanic glass or massive
wood.
Diminishing mechanical feed back coming from external sources
may seem the main objective, but springs and feet do play a role
in damping vibrations in the chassis or plinth itself, as I found
out.
Some time
ago I obtained a second and perfectly working SP-10 Mk2 unit with
the high quality EPA-A501 tonearm with exchangeable arm tubes
(wands). The unit had previously been in use in a studio. It is
mounted on a stone plinth made of slate measuring 550 x 440 x
28 mm. When installing the table it soon became clear that the
top area of the rubber isolating feet influences the frequency
characteristic significantly. The smaller the contact area of
the top of the feet touching the underside of this slate plinth,
the better the sound reproduction is (B). 
But that is
because this slate plinth of 2.8 cm thick can pick up vibrations.
Therefor it is necessary to have a heavier plinth that will be
inert to externl influences.
No matter
how well the turntable system works, it will always be the result
of a compromise. The lesser the compromise the better the sound.
At left a
list of choices which will have a greater or lesser effect when
designing a complete turntable system or when building just a
plinth for an existing motor. Just for you to contemplate and
decide what the plinth you want to construct should be like. Going
heavy is a less complicated way if compared to designing/composing
a plinth by using various materials which have their effect on
increasing the harmonics and the transient.
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ALBERT
PORTER'S MK-2
BASE
The
following pictures were send to me by professional photographer
Albert Porter. They show the solid base he constructed for his
SP-10 mkII with SME SME 312S (Magnesium), and Air Tight PC1 Moving
Coil cartridge.
He made the plinth thicker and heavier than 30 mm to 35 mm (1-11/64
inch to 1-3/8 inch) which is the minimum, indicated on the original
Technics mounting template of which he bought a real size copy
from me.
He used multiple layers of Baltic Birch plywood, an aluminum sheet
and Bass wood.
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The
massiveness of the plinth can be seen in the opening of the arm
board and the room the tonearm base needs. The arm board has about
the same thicknes as the top panel of plywood. The arm board is
attached to two rectangular strips of thick brass. There are three
threaded holes in each strip for mounting the arm board. This
solution is very practical. It not only provides a secure and
firm connection of arm base and platter (no bending mode), in
this way various arms can easily be mounted.
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This
picture gives an idea of how the panels were cut out according to
the instructions on the template, and how they were arranged. This
picture shows that the aluminum sheet has not been cut out (yet?).
You can contact Albert Porter to get more details.
In front lays the heavy piece of iron which is incorporated in the
bottom of the base. It weighs 20 pound and guides a threaded brass
rod to the spindle (underside) of the motorand touches it to drain
any motor/spindle noise. |
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This is the
unfinished base with the SP-10 Mk2 mounted on it. It shows that
the height of the base is substantial.
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The
exterior is wrapped in black African Wenge, a dense, hard wood. |
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The plinth
Albert Potter constructed does not rest on feet, spikes, rubber
dampers, cones, or whatever is generally used for coupling such
an important component to the environment. Albert states: "There
is no need for suspension with this Technics as there is no feedback
problem. The plinth as shown weighs 85 pounds (38 kg., Ed.)
and sits in my equipment and software bookcase on a 2.5"
(6,35 cm., Ed.) Maple butcher block shelf, approximately
20 feet (6 m., Ed.) from the speakers."
Well, how
does it sound?
Albert writes: "My other turntable is a Walker Proscenium,
which is one of the best turntables in the world. The Walker is
fitted with the Koetsu Jade Platinum Signature. I would classify
the two tables as somewhat equal and at the same time, different.
The Technics seems to be as quiet and speed accurate as possible,
but it is much more dynamic than the more expensive table. I am
almost 100% sure that's due to the cartridge difference but plan
on doing testing soon, I've asked Air Tight to loan me another
cartridge for my Walker so I can do an exact comparison."
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And
he continues: "The Air Tight PC1, which many reviewers are
calling "the best cartridge in the world" is truly superb.
Much faster, lower distortion and higher output than my Koetsu.
The Koetsu is more beautiful in the midrange and more musical but
at the expense of speed and resolution. Like all things, also in
audio it is impossible to have it all. I do know some of this is
due to the Air Tight PC1 being 0.6 mV and the Koetsu has 0.2 mV
output. That probably accounts for the gain and dynamic differences
and (of course) increases the apparent signal to noise ratio in
my all tube phono stage. Larger input voltage means less gain required
from tubes to achieve equal SPLs from my preamp, amps and speakers." |
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This plinth and the plinth Albert Porter designed for the Mk3
motor deck and the way they are constructed may well inspire
any owner of an SP-10 Mk2 or Mk3 turntable. But certainly also
those who want to make a beautiful base for their respective
high grade turntables in order to gain excellent physical and
frequency related sound properties.
Albert
Porter is a reviewer for Positive Feedback Online. You can view
Albert
Porter's audio system there.
And
you can visit his
Albert
Porter's Audio Website.
For
comments you can reach him there per email:
Albert Porter.
Anyone
who has a similar or different proposal for a plinth (eventually
to be published on this page), is welcome to e-mail
me too.
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ALBERT
PORTER'S
BASE FOR MK-3
At
left you see a different concept for a plinth. It is the Ebony
plinth Albert Porter devised for his Technics SP-10 Mk3
motor deck.
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The
core of the plinth is a construction of thicker panels than in
the original SP-10 Mk2 plinth. Shown here are the two Panzerholz
sections bonded and milled plus basswood panel and 6061 aluminum
plate. There is also the iron block and brass rod, but the iron
block is not yet driilled or threaded.
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Here
you see the assembled core of the plinth.
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"Core"
assembly shown with one of Albert Porters Technics SP-10 Mk2 tables.
The plinth may also be used with the Technics SP-10Mk2 as both turntables
need the same cut out. The plinth can be built to many quality levels
from strip down to deluxe. This is the most strip down version with
just clear lacquer but works good. |
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Layers in
proper sequence for MK2, filler panels must be added for MK3
and deluxe exterior parts if wanted.
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Note that
there are four circular filler inserts only for the MK3. They
may be removed to accommodate the MK2 in the same same plinth.
The inserts do not touch the Technics or outer plinth construction
except by two stainless steel screws on each, which fasten to
the Basswood panel in center. There are two brass mount rails
with brass screws to mount the arm board.
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Bottom view
showing iron block and rod in final position with brass secure
nut. Note that bottom is 3/8" hard Maple, stained to match
the Ebony lumber. Four corners have been tapped for brass studs
and StillPoints are installed. Albert Porter likes the esthetics
of Stillpoints but the plinth resting on Stillpoints will have
to be tested yet.
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Here
is a rear view of Ebony plinth, showing split grommet + plate
system for cables.
Albert
Porter adds: I also designed a platform for my MK3 to rest on,
it's 9 layers, including a layer of Texas Instruments FerriShield
with dedicated ground plane. It's finished in Piano Black and
is a mirror design of the MK3 plinth, with same angles, corners
and shape.
You
can read various posts on AudiogoN. Albert Porter tells about
the quality achieved. He also relates about the cost of the total
project. 
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BACK
TO THE SP-10 PAGE
FOR
DUTCH AND FLEMISH READERS AND THOSE WHO HAVE SOME UNDERSTANDING
OF THE DUTCH LANGUAGE:
THE
ABUNDANTLY ILLUSTRATED SERIES OF ARTICLES ORIGINALLY PUBLISHED
FROM 1986 UNTIL 1995 ABOUT BUILDING A DIY HIGH END TURNTABLE.
Zelf
een Draaitafel Ontwerpen en Bouwen?
Dat kan heel goed!
Het
is de normaalste zaak van de wereld dat hobbyisten luidspekerkasten
bouwen in alle soorten, kwaliteiten en maten. Maar wat komt
er voor kijken als je een draaitafel wilt bouwen?
Lees
in deze gebundelde artikelenserie van meer dan 55 interessante
pagina's over de materialen, het gewicht en de massa, de ontkoppeling
en de vering, de aandrijving en de gelijkloop, de akoestische
terugkoppeling en de resonanties.
Deze
serie geeft inzicht en inspireert tot het zelf bouwen van een
draaitafel, uitgaande van bestaande onderdelen of aan de hand
van het zelf ontwerpen en laten vervaardigen van plateau, sokkel
of andere onderdelen.
Euro
20 inclusief
verpakking en verzending.
(Euro
25 voor België en andere EU en niet EU landen.)
Klik
hier
om een email te sturen om de serie te bestellen.
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