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Retrofit Anti-Skate to Older Unipivot Tonearm?

Sort of doing a little thread hi-jack here, hope it's ok.
Just wondering if there are any kits available for a retrofitted antiskate that will fit any tonearm?
Also interested in DIY solutions so links to manuals and instructions would be appreciated.
Looking into adding as to a Lenco B52 stock tonearm.
 
T68 said:
Sort of doing a little thread hi-jack here, hope it's ok.
Just wondering if there are any kits available for a retrofitted antiskate that will fit any tonearm?
Looking into adding as to a Lenco B52 stock tonearm.
Click to expand...

I don't think there are any universal kits. But you may be able to modify to make it similar to the L75 tonearm.
 
Decca unipivots use magnets to apply antiskating (as does the Rega, but its a conventional gimballed arm). I haven't be able to figure out how it functions since it is adjusted by moving a collar around the pivot up and down. I assume this move a magnet closer to either another fixed magnet on the arm, or simply attracts the metal arm tube, but why doesn't moving it up and down make the arm tilt?
 
Nat said:
Decca unipivots use magnets to apply antiskating (as does the Rega, but its a conventional gimballed arm). I haven't be able to figure out how it functions since it is adjusted by moving a collar around the pivot up and down. I assume this move a magnet closer to either another fixed magnet on the arm, or simply attracts the metal arm tube, but why doesn't moving it up and down make the arm tilt?
Click to expand...

Wow. That Decca is impressive. The anti-skate magnet ring is at the pivot point but I don't know if it is a tapered ring type or not. But if it is, the mag force would keep it level I imagine. But what really got my attention were the opposing magnets at the base. Mag Lev?

PS: One just turned up on the Bay at a reasonable price.

decca-int-pivot_700.gif
 
I had an earlier version of this arm that I bought in 1973. It was the same unipivot design but had a much longer base with detachable cable/connector, and a low mass skeleton headshell.

Decca Intl Arm_Top 258K 753x1153.jpg
Decca Intl Arm_Side 71K 661x308.jpg

It is an excellent arm. The bias collar has two magnets, symmetrically placed one on each side, and I can attest to the fact that adjusting the antiskate by moving the magnet ring/collar up and down on the pillar has no observable effect on tilting the arm and/or disturbing the azimuth. The magnet ring/collar is at or below the pivot point, depending on the bias setting used. The azimuth is adjusted solely by tweaking the eccentric counterweight. The entire arm and pivot assembly does indeed float mag-lev on the two opposing ring magnets down in the pillar.

I don't advocate arbitrarily re-wiring tonearms but this link shows one of these arms taken apart so you can see what the internal components look like:

https://www.tnt-audio.com/sorgenti/decca_arm_e.html

BTW the silicone damping on a brand new arm is user-installed optional and, from what I could see in the photos of the one currently 'on the bay', it looks like the capsule that contains the silicone damping fluid is missing. The fluid damping in a used arm will leak out when it lays on its side or gets turned upside down during shipping. If you buy a used one, it's no longer damped and you have to re-plenish the silicone fluid in the bearing cup. That's what the hole in the top is for.

Ray K
 
magnets close to the carts wires make me think about distortion. for sure the engineers considered it, but still.
nice Tonearm anyway.
AG.
 
Andre Garcia said:
magnets close to the carts wires make me think about distortion. for sure the engineers considered it, but still.
nice Tonearm anyway.
AG.
Click to expand...

The magnets used for anti-skate are very weak and far away from the cartridge anyway. It is a very common method. Their field cannot reach the cart.
 
Andre Garcia said:
magnets close to the carts wires make me think about distortion. for sure the engineers considered it, but still.
nice Tonearm anyway.
AG.
Click to expand...
Faraday's law:
"when the magnetic flux linking a circuit changes, an electromotive force is induced in the circuit proportional to the rate of change of the flux linkage."

It's the relative movement between a conductor and the magnetic field that induces a voltage or, in this case, distortion. The tonearm wiring and bias/suspension magnets are fixed in place while playing the record so not to worry. Our entire audio systems are bathed in the earth's magnetic field, but there haven't been too many reports of equipment sounding different depending on whether you're in the Northern or Southern hemisphere due to the polarity change. Motors can be problematic because their stray magnetic fields vary with your AC mains frequency, which can induce hum.

Ray K
 
Antiskate is a calculated outward force bias applied to the arm, damping schemes are something entirely different.
The best way to use this arm as-is with a cart that matches its characteristics, tracking at the higher end of the stylus' recommended vtf range.
 
Pio1980 said:
Antiskate is a calculated outward force bias applied to the arm, damping schemes are something entirely different.
The best way to use this arm as-is with a cart that matches its characteristics, tracking at the higher end of the stylus' recommended vtf range.
Click to expand...

Correct. But even with an anti-skate, the 43.1 effective mass is still an issue. I acquired a NOS Shure M44C today that 'should' work well at the recommendation of KentT over on VE.
 
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Update. The tonearm mount for the string anti-skate is done. It clips on and can be rotated to precisely adjust it to the exact pivot point. It also can be mounted on either side. Now I need to design the sub-chassis mount that will have vertical adjustment. So far so good.

20191129_134933-X3.jpg


20191129_141650-X3.jpg
 
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John Berard said:
Update. The tonearm mount for the string anti-skate is done. It clips on and can be rotated to precisely adjust it to the exact pivot point. It also can be mounted on either side. Now I need to design the sub-chassis mount that will have vertical adjustment. So far so good.

20191129_134933-X3.jpg


20191129_141650-X3.jpg
Click to expand...
Nice! Is the plastic clip that supports the thread rod 3d printed?
 
JB,

I am totally impressed with how you finessed this. The aesthetics are first class, it's scientifically designed, 100% reversible mod, and to anyone not familiar with the arm it looks factory OEM. Well done!

Ray K
 
vinylrayk said:
JB,

I am totally impressed with how you finessed this. The aesthetics are first class, it's scientifically designed, 100% reversible mod, and to anyone not familiar with the arm it looks factory OEM. Well done!

Ray K
Click to expand...

Thanks Ray. Yes, I am attempting to make it look OEM and not change any of the original hardware. I have been struggling to figure out the next mount but I think I have it solved now. One more 3D printed piece, some 2mm stainless rod and a Thorens motor shaft collar should do it.
 
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