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Old 26th February 2004, 11:08 PM   #1
Sid-W is offline Sid-W  United Kingdom
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Join Date: Feb 2004
Location: Derbys
Default Systemdek IIX tweaks

I've bought a Rega 250 arm to replace the AT fitted on my Systemdek and I'm wondering if there are any other tweaks I can perform while I'm machining up a new armboard and VTA adjuster.

The metal base looks like it might benefit from some damping for a start.... all ideas welcome
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Old 27th February 2004, 12:07 PM   #2
sreten is offline sreten  United Kingdom
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Some simple tips for the IIX :

1) oil the motor, few drops where the spindle enters the housing,
top and bottom. Check the motor angle is correct, the belt should
be running in the centre of the pulley.

2) check arm leading dressing is free, I find a single twist before
the clamp works well, often moving the clamp to the back surface
helps.
The angle of the lead should be ~ tangential to a circle centred
on the main bearing. (Purpose here is to damp any rotational
modes of the subchassis whilst free in other planes)

3) Clean out and re-oil the main bearing.

4) Remove main bearing from subchassis and then replace but
using Araldite to lock it in place.

5) the MDF armboard should fit directly to the subchassis, no
spacers should be used. Use PVA wood glue to semi-permanently
bond the armboard to the subchassis.

6) The deck proper needs to be level to get a really good bounce
from a correctly adjusted suspension, adjust the suspension with
a record in place. Try to get the clearance below the top-plate
and above the motor nearly equal for a clean bounce.

7) I used a layer of felt on the subplatter for fine hieght
adjustment of the RB250.

On my IIX I sprayed the subchassis and the bottom board
with car underbody anti-chip type type stuff.
Mask off the area where the main bearing and armboard seat.

Allthough not necessary to prevent feedback, a light rigidly
mounted shelf / table, prefarably to a solid wall or on a solid
floor is still required for the cleanest resolution.

I made a acrylic mat out of 3 thin layers of acrylic, one layer
with the label cutout. They where glued together with black
car paint and the whole top sprayed black.
Was better than the felt mat, but not as good as an old hard
rubber mat the Disk SE2.2 (1Kg/2.2lbs).
There where a few 1Kg or 500g hard rubber mats sold.

sreten.





sreten.
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Old 27th February 2004, 12:28 PM   #3
Sid-W is offline Sid-W  United Kingdom
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Cheers Sreten, plenty of things to do there

I may make the armboard from carbon fibre, it's stiff and light and more importantly I have a 6mm thick sheet of it laying around in my workshop that I haven't yet found a use for

While the deck is in pieces I am going to machine and fit adjustable feet for levelling.

Does anyone think that adding heavy damping material inside the plinth would be a step forward ?
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Old 28th February 2004, 12:05 AM   #4
sreten is offline sreten  United Kingdom
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For the spaces left in the plinth foam damping
will prevent acoustic resonances, this will also
damp the base board.

But given the suspension design high mass
loading of the plinth will have minimal effect.

I can't comment on the armboard, if I had
6mm carbon fibre sheeting I'd be going for
a multilayer replacement subchassis,
not the arm board on its own.

But I obviously haven't done it, and can't see
any real advantage of a carbon fibre armboard.
(not that there might be)

sreten.
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Old 4th March 2004, 01:45 AM   #5
Sid-W is offline Sid-W  United Kingdom
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Interesting... the RB-250 arm arrived yesterday and I just had to try it.

Looking inside the Systemdek for the first time I found that the metal base was already damped, as was the sub-platter.
The main bearing is worn out - at least I think it is worn out - once upon a time I built engines for exotic cars and racing motorcycles and if I had found that sort of play in a camshaft bearing then it would have gone in the bin. Every bearing needs some clearance for the lubricant, but this seems excessive considering the RPM and load. It doesn't make any noise though. I put some moly grease on it after cleaning and decided to worry about it later.

The RB-250 went onto the armboard at something approaching the right height courtesy of my current method of scratching a living - spacers and shims robbed from the night vision equipment that I make, repair and service. I'm going to machine the VTA adjuster some time soon
VTA is currently dealt with by cardboard 'sub platters' under the mat

The final audition result after setting everything up is....mmmmm....no difference at all over the AT arm.
The Rega one looks nicer, but that's all for now. New cartridge on the way soon, we'll see what difference that makes.

Not that I am unhappy with my Systemdek, it sounds excellent to me, and I get a lot of pleasure from it....I just like tweaking stuff

One thing I have noticed when setting up the Systemdek to work at it's best ( according to my limited knowledge ) is that the sonic improvements come in small increments, but the reduction in surface noise from LP's has been dramatic. I'd love to know why this is....
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Old 4th March 2004, 11:25 AM   #6
sreten is offline sreten  United Kingdom
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Hmmm....... no difference at all ?

Surface noise can be exaggerated by resonances that do not
sound as such whilst playing music, low surface noise IMO is
a sign of good resonance control.

There no difference in surface noise between arms ?

I have a IIX fitted with a Rega RB250 and compared it extensively
with a IIX fitted with a Linn LVX+(fixed headshell) I rebuilt for a
friend of mine.

IMO is terms of cost performance (the deck and arm were 90
as the motor was making horrible grinding noises - easily fixed
with a little oil) changing the arm was out of the question.

The LVX+ and a Grado Black or Ortofon 510 held up remarkably
well against my Rega RB250 and Ortofon MC15mkII Super.

After all the tweaking the only major difference between the two
decks was the precision of the top octave, minor differences
being the consistency of dynamics across the frequency range
and a difference in the solidity of stereo staging.

But I did feel that these limitations were due to both the arm
and cartridge. A better tipped cartridge would help for sure,
but I didn't feel the LVX+ would work as well as the Rega if
a good MC was going to be used.

sreten.

P.S. I'd be very surprised if the bearing is worn out if it still had
some oil in it. The well at the top for oil reserve is tiny, and you
have to overfill it and mop up the overspill to make sure the
bearing is full of oil.
My IIX has a plain bearing and MDF sub-platter. I suspect your
subplatter is the damped plastic version - and has the spiral cut
bearing - which needs some clearance to prevent it lifting itself
out of the bearing.
(The shaft may have a slight step at the top such
that only this part matches the top bushing, the
rest of the shaft matching the bottom bushing.)
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Old 4th March 2004, 11:27 PM   #7
Sid-W is offline Sid-W  United Kingdom
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Thanks for more excellent input

I think that maybe the difference between arms isn't audible because of a 'bottleneck' somewhere else ( my guess is the Linn cartridge of unknown history - it's what is usually called a K-9 on Ebay auctions, has a bright yellow stylus holder )

Also it may well be my cloth ears.....

I had another listen tonight and the sound is really pleasing - one further issue to explore once I have built the new armboard with VTA adjuster will be mats. If someone had told me that a TT mat could alter the sound two years ago then I would have laughed in their face But I have proved it to my own satisfaction now and I'm eating humble pie

As soon as I can source a 12X1mm die then I'll make a new stub and counterweight for the arm - maybe it'll improve the sound, maybe not - but it'll only cost me a few hours to machine up.

You are spot on about the sub platter by the way, plastic and damped.
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Old 6th March 2004, 02:08 AM   #8
KBK is offline KBK  Canada
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In Britan, find out who carries the TRI-ART brand of artist coatings.

Get a bottle of the Acrylic-Urethane TOPCOAT.

A bottle of the Micacous-Iron-oxide.

And finally a bottle of the Nephaline-Gel-Coarse.

Mix all three together.

(We have 4800 different coating formulations possible in the factory. I'm trying to figure out which of the items I use in the factory that can be used in their finished form. Off the top of my head, it is the three mentioned items. I use the raw ingredients.)

A very effective damping compound is the result. Highly absorptive, stiff as can be.

Coat the inside of any loudspeaker cabinet.... maybe the inside of the MDF body of that there systemdek, for example!

Try something other than the turntable first, like a speaker cabinet interior. Make sure to slop it in the corners when you do so.
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Old 6th March 2004, 12:42 PM   #9
sreten is offline sreten  United Kingdom
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My favourite all purpose damping is the cheapest and thinnest
industrial style self adhesive vinyl floor tiles you can find.

Easy to fit, easy to check it fits before hand, easy to control
the amount of damping by the number of layers, and it works
very cost effectively well.

They do add some stiffness, but not much (if they were very
stiff then by definition they would not be effective damping).
The use of thin layers increases the damping effect.


sreten.
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Old 12th March 2004, 09:40 AM   #10
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Not sure which version of the IIX you have but a few of the later ones had a power supply board for the motor (along the same lines as the Linn valhalla). As I remember, this made a significant improvement to the sound so maybe worth checking out if you don't already have one.
In blind listening tests, quite a few of our customers preferred the systemdek (acrylic platter and psu) over the roksan xerxes which was not bad considering the price differential. I had good results with the rega arm and the roksan tabriz worked well too. I have tried both with the Linn K9 style mm cartridges as well as the old Audio Technica AT 0C9.
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