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Improving a TD160 MK II
Rolf writes:
Today I did the first assembling of several TD 160 parts, prepared over the last
weeks.
Some basic information about the table:
01. RDC ground plate
02. Double walled lead ball filled outer frame
03. Sub-chassis with wooden lead ball filled under construction
04. Leaf spring sub-chassis suspension
05. RDC bearing flange
06. Mirror polished hard metal bearing
07. Acrylic outer platter with cork matt
08. Stabilizer
09. Low voltage AC synchronous motor
10. Extern High End power supply
Total weight : 30 Kg
The combination of sub-chassis and suspension construction allows a mass center
far below the center points of the suspension. Platter and stabilizer included.
A
mass stabilization of the sub-chassis could be realized this way - like the
Reference II. The springs are adjustable in x/y/z direction so the sub-chassis.
So the sub-chassis can be forbidden to do any lateral movement - to any tone arm
weight the cassis can be adjusted to swing perfectly vertical.
The mass of sub-chassis and outer frame are well balanced and into the the same
center, so the system will became independent from outer influence as noise and
vibrations.
Pulled out of storage, the almost standard TD160 II is examined. Almost standard... Previously, an RDC bottom plate had been added. Otherwise, a very stock and normal appearing TD160. Note the standard issue TP16 ISO-Track tonearm.
TD2001 bearing with RDC damping collar. Inside the bearing housing is a Widia thrust bearing to carry the vertical loading of the platter assembly. Increasing mass, weight and stiffness, the standard sub-chassis plate becomes the top portion of lead shot loaded structure. MDF is the favored construction material for the lower portion.
Original cabinet forms the inner structure of the lead shot loaded cabinetry.
Note the spiral pattern to the RDC application in this bottom plate.
Dustcover appears similar to a TD2001. Tonearm in photos is identified only as an Audioquest. More details to come later.
Notes and conversation between Rolf and myself while Rolf is doing all the work, (and much other work) to transform this once humble TD160 MK II.
About lead shot loaded plinths, drive motors and power supplies
Rolf writes: The
outer frame of the TD 160/ II has been completed today. Now I´m working on it's
surface. Pics tomorrow....
In parallel I'm thinking about the technical layout. The motor must be replaced
by a low voltage type, ready to use an external power supply. But I don´t want
a mains frequency driven motor, so I search for an "internal
oscillator" solution like 2001 etc.
Steve writes: People I know
of on this side of the pond are interested in high quality DC motors with low
moments of inertia and precious metal brushes. Like out of the Maxon motor
catalog. Instead of expensive AC power conditioner, they substitute 12v battery
for quiet running motor. A suitable motor controller then becomes the issue.
Over my head, but there are circuit designs in the public domain being used
effectively.
Rolf writes: I know about that, but
my personal choice is an AC motor. Two reasons. Any DC motor has direct contact
between still and rotating masses. Brush fire will cause high frequently noise
and will damage the motor over the years.
Akku power supplies are another point. I thought of them for a long time. A high
dimensioned akku ( minimum 5 hours runtime ) for driving the table. Loaded when
the table is not in use, or two akkus, one in use and one loaded,
interchangeable automatic by the system. My favorite power supply.....
Steve writes: It
seems logical / possible that with a massive and heavily damped sub-chassis
platform, less spring compliance will be needed to isolate from motor plate.
Possibly even no springs. Perhaps just semi-compliant rubber donuts...? Lots of
room for experimentation.
Rolf writes: You spoke out my
thoughts, I think more systems have to be tested.
Steve writes: Q. Why must the
spring be of a conical design...? This design allows easy movement in the
lateral. Wouldn't it be better to restrict motion to the vertical....?
Rolf writes: I prefer a mass
stabilization, realized in the Reference II. The mass center of
the sub-chassis must be placed (far) under (below) spring level.
Steve writes: I too
like the idea of hanging from above rather than supporting from below. (re
floating sub-chassis). The challenge becomes fitting a suitable apparatus within
the package. I look forward to your solutions. I'm thinking about cantilevers as
springs. But that's a guess.
Rolf writes: I think about
cantilevers, but the first solution will be 524 konical springs, working on a
hanging high weight sub-chassis with a very low mass center.
Tonearms
Rolf writes: I
don´t want to exchange the tonearm. The TP 16 should been upgraded. I'm
thinking of precision ball bearings and a new arm wand. Several materials are in
disussion.
 |
Light wood |
|
RDC |
|
Carbon |
Steve writes: I
always did like the look of the TP16 gimbal. Some mods I've considered: 1)
bearings upgrade, but which bearing...?
Rolf writes: Ball
bearings are normed parts. Precision by list. We have a world-wide known
specialist here in Lahr - I took a contact...
Steve writes: 2) remove
spring loaded vtf adjuster assembly entirely. 3) replace counterweight
with offset weight that puts center of mass at stylus elevation
Rolf Writes:
My thought is the same. It should have been made an eccentric counterweight to
bring the mass center on cartridge level.
Steve writes: 4) plastic
armboard has to go, but replacement armboard must also have a close tolerance
bore to receive tonearm body.
Rolf writes: I want to use
RDC material. A contact to Clearlight Audio has been made this afternoon. Close
tolerances are obligate..
Steve writes: 5) magnetic
anti-skate assembly on the TP16 is not precision gear. It is a nice bit of work
for being all injection cast polystyrene, but there has to be something better.
Rolf writes: I did not think
very much about points 2 and 5 in the past. I think the vtf and anti-skating are
not elementary problems of the TP 16.
Steve writes: Arm tubes.
Tubes, regardless of material, form an effective acoustic conduit. The arm tube
has to be damped somehow. SME style silicon trough and paddle...? Greater
stiffness would be a plus. More mass would allow use of modern MC cart.
Rolf writes: The arm
tube has not to be damped with silicon. The only problem is to interrupt noise
signals between stylus and platter and on the way back over the sub-chassis
through the arm-board, arm and stylus. These noise signals will damage precision
in sound. You an hear them with a stethoscope all over the table. The secret of
the Reference II is very simple. He has a calm sub-chassis. Stable conditions
for anything mounted on it. So I wanted to do with the TD 160 / II.
Platter Bearings
Steve writes:
Hi Rolf. The pics are very good and show the method clearly. I'm sure this will
be very useful to the many TD160 fans out there.
Rolf writes: Thank You, I
only want to transform improved components from greater tables to this little
160....
Steve writes:
I've been able to determine, from my own experiments, that there is significant
noise coming off the platter bearing of the TD160. Otherwise, simple damping of
the sub-platter would have had no audible benefit for me.
Rolf writes:
I did very much work on bearings in any way. Two
things are important.
1. The bearing tube. Thorens tubes are anything but perfect. I polished
them to get a better result. Surface mechanical noise is the main problem. And
the oil...I use van den Hul's silicon oil, containing ceramic nano balls,
working as a microscopic ball bearing.
Steve writes: What I don't
know is where, within the bearing, the most noise is generated. I assume the
vertical thrust pad is a likely candidate. In either of my two tables, there is
no rocking of the sub-platter. This indicates a good fit between spindle shaft
and bushings. The body of the standard bearing is solid steel but seems a bit
light, for what it does, and should tend to resonate. The bronze bearing in your
pictures look, to me, like a really substantial upgrade.
Rolf writes: 2. The
bearing base plate. It must be absolutely flat. Every abrasive worked
material has a very little bulb in its' center - where the spindle rotates.
Spindles center and bulbs center have not the same center-point, unless they are
selected together. So the spindle has to go up and down the bulb, causing some
low frequency noise.
Rolf writes: (re:
bronze bearing housing)
Drive Pulleys
Steve writes: I also
have read a recent article at TNT, by Hartmut Q., about upgrading a TD125. The
thing about that article that caught my interest was his pulley replacement. He
chose to toss out the plastic clutch pulley and replace it with a solid steel
pulley. This assumes that the standard pulley might be prone to flexing,
resonance and shape distortion during it's normal operation. Just looking at the
pulley used on the TD160, this seems possible. It is a light piece. It appears
to be damped for resonance by way of a soft pad mounted under the pulley. With a
motor that locks on to the frequency of the power supply, pulley diameter
becomes an important factor. With a motor that is controlled, by electronics
that senses platter speed and then regulates it, pulley diameter becomes not a
size issue, but one of choosing optimum rpm with regard to the torque curve and
quiet running of the motor.
Rolf writes: A metal motor
pulley will perform with more mechanical precision, but more resonance too. It's
the difference between a "pinnnnng" and a "tock". So I
prefer plastic pulleys in the past, they do a wonderful "tock"
At last, I like to watching ideas crossing the big pond (we say in german "großer
Teich" with the same meaning) in both directions.
Best analog regards
Rolf
comments to: rolf.kelch@t-online.de