diy Morsiani antiskating questions - Page 2 - diyAudio
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Old 21st February 2006, 03:26 PM   #11
diyAudio Member
 
Join Date: Jan 2005
Location: Scandiano-Reggio Emilia-ITALY
Default drawings

I see that there is only one drawing in my previous reply,in this I post the missing one.
The ALNICO magnets are these:
n° 2 diameter mm 6,lenght mm 20 for the arm turret(rotor)
n° 2 diameter mm10,lenght mm 30,for the arm base (stator).
Answering to FERGS 1 question,the idea came from the DECCA international arm,it ws the only one with unipivot bearing and magnetic antiskating.But the magnets do not allow to be adjusted separately,because are tied toghether.
I did not invented the unipivot arm with magnetic antiskating , I invented a new magnets displacement and the method of adjusting the antiskating force.
The cutted groove has two sides, it is very important that the pressure of the stylus is balanced on these two sides.
In my previous mail I described how it is possible to demonstrate that the skating force is diminishing toward the centre of the disc.
So it is useful to adjust the antiskating accordingly.

If this does not happens,mistraking occurs,and this means distortion.My method allows to keep balanced the stlus pressure on the two sides of the groove from the beginning to the end of the disc,
giving less distortion,more stable and focused stereo image.
The mono discs play in the middle of the speakers, and the sound does not floats from one speaker to the other.

Then with my design,the mono cartridge for mono discs is not necessary,if you have a stereo system.
So You do not need to depress that damned "mono "button,which parallels the two channels,and causes high frquencies losses and worser sound.

Best regards,Carlo Morsiani.
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Old 25th February 2006, 12:38 AM   #12
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Join Date: May 2003
Location: Berlin Germany
Dear Mr. Morsiani,
Great to see you participating in this forum. Just for your information, there was at least one more unipivot arm that featured magnetic skating force compensation: The KMAL(Keith Monks Audio Labs) arm, mostly remembered for the use of Mercury as a conductive element(in the true sense of the word:-) between armwand wiring and tonearm base wiring. In this design, the skating compensation is higher at the outer edge of the record too, but it is preset for a VTF of ~ 1,5gr.

Greetings from Berlin,

Frank Schröder
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Old 25th February 2006, 01:23 PM   #13
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Location: Scandiano-Reggio Emilia-ITALY
Dear Mr Schroder,
you are right.
I remember the Kmal arm .This unusual Kmal arm was dedicated to high compliance cartridges .
I have the original brochure ,wich I collected in Milan hifi show when Kmal products were introduced in Italy in the end of the seventies.
But I never purchased it , and never I had one in my hands,it is a rare item to find.
I remember also the other product of Keith Monks,the vinyl washing machine .
But this arm was not so inspiring for me like the Decca international arm,so I forgot to mention it.
This is a thing of more than 35 years ago.
Over fifty years old audiophiles only can remember this.
Best regards,Carlo Morsiani
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Old 25th February 2006, 01:32 PM   #14
AndrewT is online now AndrewT  Scotland
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Hi Nem,
your joking.
Once we get over that age we forget most things.
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Old 26th February 2006, 11:24 AM   #15
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Join Date: May 2003
Location: Berlin Germany
Hello Mr. Morsiani,
Seven more years left, sigh.....

But if you'd ever feel the urge to try the KMAL arm, I would gladly send it to you so you could inspect it/play with it for a couple of months. It's been sitting in a drawer for several years anyway. Just let me know off list.

Best,

Frank Schröder
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Old 26th February 2006, 12:42 PM   #16
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Thank you Mr Schroder,
You are very generous ,but the Kmal antiskating arm is pre-set for 1,5 grams stylus pressure.
I have MC cartridges ,a Denon DL 103 requiring gr 2,5 and a Koetsu Red requiring the same.
Really I can not employ the Kmal arm.
Best regrads,Carlo Morsiani.
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Old 28th February 2006, 04:51 PM   #17
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Dear Mr Morsiani

Great thanks for providing this information! You are very generous with your knowledge. I was wondering, given a fixed distance between magnets, in what range would the attractive force between magnets need to be in order to provide the proper antiskating force?

I understand since unipivot arms have such low friction, this force must be reasonably small...

Regards,

Zach
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Old 28th February 2006, 08:19 PM   #18
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Join Date: Jan 2005
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Dear Capt Zach,
it is useless to know how much strong the antiskating force is,
this value is different for each set up,depending on the stylus pressure,the cartridge mass,the arm lenght.
Instead it is useful to know the effect of this force, is the pressure of the stylus balanced on the two sides of the groove?
When you know that this happens,the antiskating force is right.
How to know this?
An empyrical way is to look at the cantilever ,the force is balanced when the cantilever stays in centre of the cartridge body.
The best method is to have a dual trace oscilloscope,and a test disc with fixed frequency.
The pressure is balanced when the vawes of the two channel have the same amplitude.
When the antiskating force is too scarce,you will see distortion in the right channell.
The problem is that many test disc do not have a fixed frequency for all the disc side,so you can adjust correctly the antiskating for the zone in wich che arm is playing the test track.
And you can not know what will happen in other zones.
I have old Decca test disc with a fixed frequecy in all the side.
But in the real life it is not possible to adjust the antiskating with rare test disc and oscilloscope.
A flat uncutted disc can be used,adjusting the arm not to stay stopped,because the skate force in the cutted grooves is greater than in a flat disc,it is enough to adjust the antiskating to obtain a slow arm motion toward the outer of the disc.
Playing the vinyls,look at the cantilever if it is in the centre.
What will show you that the antiskating is right is that after 10 hours of playing the cantilever will be in centre as after 100 hours.
In too much cases I see cartridges with cantilver out of the centre,
generally toward right looking from the front side.
This is the condition of cartridges playing without antiskating,or with a too scarce antiskating.
In these cases the distortion rises up to 10%,this means mistraking,the life of the cartrige is shorter,and remeber that the diamond is harder than vinyl,the mistraking damages the cutted grooves irreversibly.
My method is empyrical,but with some pratice it is possible to obtain a satisfactory sound.
It is like to adjust the heads of a tape recorder by ears with a good heaphone ,I used to align the play head for pre-recorded tapes.

Best regards,Carlo Morsiani
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Old 16th March 2006, 07:09 PM   #19
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Dear Carlo,
I understand what you are saying about the variable in antiskate forces. However, my question is about the magnetic force that you utilized in your design. Given an arm of similar geometry, a certain magnetic force would need to be chosen in order to offer and acceptable range of adjustibility, and have the overall anstiskating force be appropriate to the arm and cartridge. If for instance, one utilized powerful rare earth magnets, the force might be too strong, and no amount of adjustability could get it into the appropriate range. BTW, where are you in Italy. Are you close to Tuscany. Im currently studying in Florence right now.

Thanks,
Zach
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Old 16th March 2006, 08:02 PM   #20
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Dear Capt Zach,
the sizie and the placement of the magnets in my arm is described in my previous posts.
But you can find the right magnets by experiments,exactly in the same way I manufactured my first arm .
You need an uncutted disc for rough adjustment,then a test disc with fixed frequency and a dual trace oscilloscope.
If you want to see and hear my arm working ,I have one customer in Florence .
We can arrange a meeting.
Write to my mail info@morsiani.it
Best regards,Carlo Morsiani.
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