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Roksan Sara tonearm

The two points I am thinking of are; 1/ how the effective mass of the arm is altered and, 2/ the change to the moment of inertia as the arm tracks records that not entirely flat, which is pretty much every record. I suspect the biggest influence on the sound with the heavier Naim weight is actually down to the alteration of the overall effective mass but this is just supposition on my part. The SKale is a slightly different issue though as this uses additional decoupling between the counterweight and the counterweight support stub and this will have its own impact (you can also adjust the weight by adding/removing additional shims).
 
The moment of inertia alters essentially not at all as the deflection, in terms of angle is all but nothing. The horizontal distances involved do not change by anything like any significant % - it is truly less than minute in terms of % - we are talking differences in the cosine of angles between 0 and a couple of degrees or so - about 0.06%. Moment of inertia is simply a force multiplied by the square of the, in this case horizontal, distance at which it acts.

A 2 degree deflection over a 9 inch arm represents around 0.3 inch warp - HUGE.

Decoupling is something that would need experiment to discover, but the resonant frequency of a great big lump of metal??????????? As an educated guess, I would have thought that coupling the pin and weight would be better as it would then act as one huge lump of metal. Far too complicated for any normal mortal to get their head around in reality - show me some analysis about resonant frequencies involved. (A great shame that I do not know anyone in turbine or compressor design at work as it would all be a piece of cake for their software to do the number-crunching - now that WOULD be interesting.)
 
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I have just had a Roksan Sara fitted, my previous post about my faulty phono stage has necessitated a nasty and quite expensive fit of upgrade-itis. This is a classic tonearm. Lovely natural balance. Helps the needle track like a tracky beasty thing. Huge improvement on the Tabriz I had on there. Don't know how it would compare to an SME but worth what I paid - they're not cheap obviously.
 
Bouncing this thread to ask a question…

I’ve recently acquired a Xerxes 20 plus with a Sara arm. I don’t currently have a cart - other than an Ortofon 2M Black, which I was going to resell to part fund an MC cart. The situation has changed as I need to pick the Black up anyway. I’ve also now read that the DX2 I plan to add phono cards to does actually cater for MM/MC (switchable) - I had thought it was either/or.

Soooo… it’s been suggested that the cabling in the Sara is only well suited to an MC cart. I’m a bit sceptical, but do understand that tonearm cabling is likely far more significant than most interconnects! Has anyone run a Sara (with standard cabling) with an MM cart? If I can get up and running using the Black it would be great as I’m otherwise likely saving for an MC for a little while!
 
Whaleblue said:
Bouncing this thread to ask a question…

I’ve recently acquired a Xerxes 20 plus with a Sara arm. I don’t currently have a cart - other than an Ortofon 2M Black, which I was going to resell to part fund an MC cart. The situation has changed as I need to pick the Black up anyway. I’ve also now read that the DX2 I plan to add phono cards to does actually cater for MM/MC (switchable) - I had thought it was either/or.

Soooo… it’s been suggested that the cabling in the Sara is only well suited to an MC cart. I’m a bit sceptical, but do understand that tonearm cabling is likely far more significant than most interconnects! Has anyone run a Sara (with standard cabling) with an MM cart? If I can get up and running using the Black it would be great as I’m otherwise likely saving for an MC for a little while!
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There is nothing about tonearm wiring and/or cable that would make a particular tonearm favour one particular phono cartridge type vs. another. Roksan mention silver-plated OFC and the pictures indicate a pretty standard wiring configuration all the way through.

If DX2 has no specific load selected then the default is 47kΩ//47pF, an excellent starting point for use with 2M Black. You'll still want to have DIP switches 1 and 6 on, with the others off (i.e. 5mV gain setting for MM cartridges). What is less clear is whether having switch 2 on adds 100pF to the 47pF, or changes the load to 100pF; regardless, this might be worth experimenting with.
 
Thanks chaps, appreciate the input. Looks like the Black (which I’ve had before and really admire) will work fine for a while. I’ll get the stage cards added to the DX2…
 
Craig B said:
There is nothing about tonearm wiring and/or cable that would make a particular tonearm favour one particular phono cartridge type vs. another. Roksan mention silver-plated OFC and the pictures indicate a pretty standard wiring configuration all the way through.

If DX2 has no specific load selected then the default is 47kΩ//47pF, an excellent starting point for use with 2M Black. You'll still want to have DIP switches 1 and 6 on, with the others off (i.e. 5mV gain setting for MM cartridges). What is less clear is whether having switch 2 on adds 100pF to the 47pF, or changes the load to 100pF; regardless, this might be worth experimenting with.
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A bit of thread necromancy here, but I have just asked Roksan about this and I got this information (edited for clarity):

The capacitance of the tonearm cable, inside the tonearm, is 38-44pF. The capacitance to ground was 20pF.

However the HDC cable that is supplied with the Sara to connect the tonearm to the phono stage is not suitable for MM applications as its capacitance is very high at 340pF – it was designed to maximise noise rejection for use with MC cartridges, such as the Shiraz, which are much less sensitive to load capacitance due to their lower impedance. Therefore I’d recommend if you buy a MM cart to also get a new cable with suitably low capacitance.
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This means that the external cable has far too much capacitance to be used with a typical MM cart and typical MM stage. Many carts, like the Goldring 1042 or the Roksan Corus2 and others have recommended load capacitances of 100-200 pF or 150-200 pF. Typical phono stages have 100 pF or perhaps 220 pF.

If the internal cable is 40 pF and the stage is 100 pF, there is only a budget of about 60 pF left before you go outside the recommended load for most carts. And with the Sara's HDC cable, you reach more than double the recommended load for those example carts. So it really is a bad match for most MM carts and best used with MC or MI(*.

*) Even some MI carts can be affected, as not all MIs have equally low inductance so YMMV.
 
Chefren said:
A bit of thread necromancy here, but I have just asked Roksan about this and I got this information (edited for clarity):



This means that the external cable has far too much capacitance to be used with a typical MM cart and typical MM stage. Many carts, like the Goldring 1042 or the Roksan Corus2 and others have recommended load capacitances of 100-200 pF or 150-200 pF. Typical phono stages have 100 pF or perhaps 220 pF.

If the internal cable is 40 pF and the stage is 100 pF, there is only a budget of about 60 pF left before you go outside the recommended load for most carts. And with the Sara's HDC cable, you reach more than double the recommended load for those example carts. So it really is a bad match for most MM carts and best used with MC or MI(*.

*) Even some MI carts can be affected, as not all MIs have equally low inductance so YMMV.
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Thanks, that’s useful input.

I’ve ended up with an AT-OC9XML on mine.
 
Chefren said:
This means that the external cable has far too much capacitance to be used with a typical MM cart...
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I was talking to Johnnie about this arm not that long after he sold it to Roxsan. It is not identical to the Uniarm. Roxsan have increased the mass and the compliance is no longer well suited to MM carts.

All I can tell you but it might be useful.
 
Mr Pig said:
I was talking to Johnnie about this arm not that long after he sold it to Roxsan. It is not identical to the Uniarm. Roxsan have increased the mass and the compliance is no longer well suited to MM carts.
All I can tell you but it might be useful.
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It has been very useful for my 'peace of mind' :)
I've just (2 days ago) mounted an A.O 'UniArm' which I purchased s/hand some time ago, onto my Lenco/PTP6 in conjunction with a RigB 500 re-bodied A.T. VM740ML cartridge. It replaced a Roksan Tabriz with a RigB 500 re-bodied A.T. VM540ML.
All I can add at this point in time, is that the 'UniArm' / A.T. VM740ML combination tracks 'Babylon Sisters' without the mistracking experienced with the former pairing - however I must add that the 'set-up' of the Tabriz / A.T. VM540ML might not be perfect, as I have inadvertantly managed to damage my 'SMARTractor'. I therefore I set-up the 'UniArm' using the supplied A.O. alignment protractor (Baerwald) whereas I used the Roksan protractor (?) for the Tabriz, that plus my now deteriorated eyesight doesn't make cartridge alignment easy :(
I also have both a Nima / Heed Zene and an Acoustic Signature (RB 250?) / Goldring Elite M.C. combinations available to try, but as that also involves swapping phono stages etc., I'm not sure that at this point I can the summon the necessary motivation. :)
Regards
Mike K.
 
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david ellwood said:
"Hearable" Is that science based terminology?
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I guess it can be measured. Hearable means something that can be heard. So if you allow for an implicitly added "by humans", you can say that every sound above 0 db is hearable, since that is how the decibel scale is defined.
But for sure it doesn't carry the same level of scientific heft as the word "thingy".
 
Roksan came back to me again and recommended an alternative tonearm cable for use with MM carts : https://www.atlascables.com/ic-element-achromatic-tonearm.html
This has 83.34 pF/m so with a 100 pF phono stage input, a 0.5m length of this cable with the Sara gets one below 200 pF.

I can't help but to wonder why we are in this situation that most MM carts require 200 pF or less capacitance and most phono stages take up half or more of that. It seems there is not much overall consideration for that you need a cable too anymore.

I also read while researching this that the internal "natural" (internal cabling and such) capacitance of phono stages is normally not included in the rated value, so in practice the cartridge will be loaded slightly higher than specced.
 
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