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Buddha
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Need vocabulary assistance.

Hola,

Question: In a unipivot tonearm, what do you call the deviation from the "vertical plane" that can occur with cartridge motion?

Is it 'rotational azimuth?'

'Vertical azimuth?'

This seems to be a phenomenon much at the heart of unipivot performance, but I'm blocking on vocabulary.

Did that even make sense?

I'm trying to put a name on the ability of the cartridge to rotate around an axis 'described' by the tonearm itself.

The reason I ask is that I was just playing with a Well Tempered arm, and it does this like crazy!

Thanks for remediating me.

Jan Vigne
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Re: Need vocabulary assistance.

How about "wobble"? "Rotational Azimuth" sounds good but I don't believe that's the correct term.

When the WTT is set up correctly there shouldn't be any azimuth wobble once the stylus is in the groove.

Ergonaut
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Re: Need vocabulary assistance.

As I remember it -- this arm was wierd and had NO pivots - it hung from little tiny suspension threads and the movement would be entirely in sympathy with the record as it is near frictionless. Perhaps the deviation is just that, and is perfectly normal.....just a wild waving arm guess....oops ....pardon the pun

Jan Vigne
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Re: Need vocabulary assistance.

The WT arm is "bearingless" but, not being a linear tracker, it does have a pivot point. It is suspended by a single piece of monofilament which passes through an adjustment screw/nut. Making corrections on this screw/nut adjusts and ensures proper azimuth - though any cartridge worth putting on this arm in today's marketplace shouldn't have azimuth problems from the factory. At the pivot end of the WT arm, there is a paddle with holes in it sitting in a cup of light weight silicone damping fluid. (If you buy the full WT table, you get a syringe of lightweight silicone for the arm and a syringe of heavyweight silicone for the platter's main bearing, such as it is.) Just as with a fluid damped unipivot, the WT arm should have sufficient friction in the vertical plane to resist excessive wobble or reaction to warps. The flat Teflon(?) pivot paddle, however, has virtually no friction in the horizontal plane and tracks through the disc effortlessly by presenting a very small face to the silicone fluid. The larger dimension of the paddle is what controls the vertical movement and the holes allow fluid to seep through the paddle's face when the arm tracks a warp or you cue the arm up or down. The arm can react to fairly swift, small actions but resists large, long terms actions. The idea is to have the arm stable in the vertical plane and yet free to move with minimal friction in both planes. As the arm traverses the groove the monofilament twists and provides an anti-skating effect proportional to the position of the arm across the disc surface.

http://www.welltemperedlab.com/frameset2.html

If the arm you played with was not set up properly or didn't have the correct amount of fluid in the arm cup (which would be almost zilch), the arm wouldn't have the correct amount of damping and could react to warps and other problems. Like any unipivot arm the WT arm feels like it's going to fall apart when you handle it but settles into the groove and performs quite well.

dbowker
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Re: Need vocabulary assistance.

I have a WTT and have set it up a few times so could you detail a little more what the issue is? IF all things are set up to spec. and the the WTT cart gauge you should have very stable everything. BUT- here's the thing: you pretty much have to do all adjustments about 3 times over the course of a day or so because that silicon stuff in the cup takes so long to settle. Kinda tedious, but as I said, once set you're good to go for practically until you need a new cartridge! I still check every six months or so JUST in case...The key to the whole process is ever so GENTLY doing anything in the setup so as to minimize how you push that goop around in the cup. In the end, one of the best designs ever though 'cause you can't get any quieter than no bear at all!

Oh yeah- one more thing- in pretty much all WTT setups I've seen you should set the anti-skate to zero or nearly so. It's the two metal arms up top that spread out the monofiliments. Rotate the wheel in between them so they come together and make contact- that's technically zero but almost never is the case. Try that setup for a week and see what you think and if you feel it needs it gradually give it more (like one turn at a time). Of course you'll have to re-check all you settings when change this one...

Another thing- the paddle should be covered by the silicon but not liek halkf way down the cup- less is more so maybe it would be 80% up the cup with 20% covering it. Otherwise you get too much damping. Come to think opf it that could be your problem. Check that first!

Buddha
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Re: Need vocabulary assistance.

Hi,

I guess I am having a hard time describing it.

With the WT arm, I can see side to side "wobble" as the LP moves the stylus around, as though the arm allows some 'rotation' of the cartridge to take place. To try to make a visual, picture a boat from head on, and as it moves, it has some side to side motion.

The pivot does not seem to totally prevent this "leaning" from port to starboard, so to speak.

It also seems to have a little forward and back play.

I could almost picture an acceleration/deceleration thing happening depending on the 'drag' of the LP groove on the stylus.

So, some fore and aft motion as well as some rolling from port to starboard, I guess.

dbowker
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Re: Need vocabulary assistance.

It's sounds like something's off-center. Have you checked your stylus alignment gauge again? If it were just one record I'd say that it's center hole was the issue. Also- make sure you have the proper horizontal alignment with the cart- it will actually be ever so slightly tilted since it run parallel to the dish shape of the platter. Again, also make sure your anti-skate is set as low as possible.

Jan Vigne
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Re: Need vocabulary assistance.

Is this a new arm? If so, then you must be using the correct silicone for the arm, right? Have you contacted WT?

dbowker
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Re: Need vocabulary assistance.

Any luck fixing your problem Buddha? Can you hear the issue you are seeing BTW? Just curious.

Buddha
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Re: Need vocabulary assistance.

Hi,

It's a friend's arm, and the silicone was the stuff supplied with the arm, and we set it up and double checked all the things for setting up arms, but the dang thing has some sway/roll to it.

The cool thing about that type of 'bearing' set up with that arm is that while you 'can' move the arm slowly and easily, it should present itself as being very stiff with regard to small rapid motions.

That's why I am perplexed by the quickness with which it can sway - or 'rotate' around the long axis of the arm.

Very curious.

The silicone seems right, the monofilament is not "stretchy," I can't figure out where the motion/play comes from.

It almost seems as if the center of gravity of the arm's bearing is well above its center of gravity. I know it ain't, but that's the way it moves.

It seems to have some fore and back play, too, like a gimble arm with loose bearings.

My friend is going to rewire it (which I will happily volunteer not to help with!) Maybe when we set it up AGAIN, it will make more sense.

The fluid cup is about 80% full, perhaps after he does the wiring, we'll experiment with a slightly higher fill level.

Thanks for the thoughts, I don't have a definitive outcome to report yet.

When it plays a record, it gives me the creeps, watching how the cartridge moves is like watching a speed boat travel through stormy seas.

dbowker
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Re: Need vocabulary assistance.

Unfortunately we're nearly a continent apart or I'd volunteer to come over and take a look. That's the down side of the Well Tempered series at this point- no service. It's fallen to the few original owners who actually have had them for a while to keep the fire buring and help out newer owners. The one other thing is: what cartridge is he using? Any way that's aport of the issue? And the painfully obvious question: this isn't about record warp right? Flat record, clamped down, level 'table, and you're getting all this weird movement?

KBK
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Re: Need vocabulary assistance.

Sounds like the cartridge stylus tip is not centered on the arms longitudinally oriented mass (rotational center). So it rolls to one side, as seen from the front of the arm. that, combined with record warp.

Sounds like the silicone fluid has hardened up (outgassed), and the viscosity is now off. Might need new fluid.

dbowker
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Re: Need vocabulary assistance.


Quote:
Sounds like the cartridge stylus tip is not centered on the arms longitudinally oriented mass (rotational center). So it rolls to one side, as seen from the front of the arm. that, combined with record warp.

Sounds like the silicone fluid has hardened up (outgassed), and the viscosity is now off. Might need new fluid.

I'd say of the two ideas posted, it's almost certainly the former than the latter. The silicone fluid in my tables was not replaced for over 12 years and it never changed a bit. The only reason I changed it all was it got dirty from years of dust, pollen etc. The cartridge could definitely be the issue though.

Another question- the fluid in the cup is the original, or factory shipped, replacement fluid for the bearing cup, right? Nothing added or substituted that would at all thin it's viscosity?

Wait a minute- maybe that paddle is too far up in the cup? If someone strung it wrong and the paddle is too far up it might be messing things up in the way you describe. In my experience the paddle should be at least half way down into the cup with the fluid about 75-85% to the top.

piinob
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Re: Need vocabulary assistance.

Buddha, did you solve this mystery? Got me curious now.

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