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Need a AR-XA measurement please...

jimreeves

jimreeves

Poopy & Me
I'm in need of a confirmation of a measurement from those of you with a AR-XA. The sub-platter spindle to motor spindle centerline. I'm getting 117mm but the springs are a mess on this one.
Maybe this is flexible + or - since the platter is sprung while the motor is not?
 
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jimreeves said:
I'm in need of a confirmation of a measurement from those of you with a AR-XA. The sub-platter spindle to motor spindle centerline. I'm getting 117mm but the springs are a mess on this one.
Maybe this is flexible + or - since the platter is sprung while the motor is not?
Click to expand...

Hi, 117-118mm is a good number. That applies to all single motor XA's up through the line to ES-1.

What's up with your springs?
 
Thanks Mark! The springs are fine, just did the Fedex boogie cross country, and I've never set one up before. Bought one in rough shape for the innards, the arm, deck and plinth won't be reused. I'll make them available cheap to an AKer that can use them. Here's the plan, in its infancy...

ARburlXA.jpg


...waiting for the arm (Luxman) to show up next week. Lots of planning, measuring, drilling, routering etc before this one is done. I may pester you again before I'm done!
 
Tell me if there's a best way to separate the arm bearing well from the t-bar so it can be salvaged for someone else?
 
jimreeves said:
Tell me if there's a best way to separate the arm bearing well from the t-bar so it can be salvaged for someone else?
Click to expand...

Nothing to salvage. Try not to lose the subchassis ground screw hole. Are you going to suspend this table in the burl I see, or are you making this a "solid" suspension table? In either case, the more rigid you can attach the new arm mount to the existing subchassis the better the arm energy drain will be. If suspended, the arm end spring rate will need to be changed. Make sure you sum total all the difference in mass to get an idea of the spring rate you need, or how to mass load the whole to equalize the spring rate should you go to the Linn black springs.
 
My intention is to suspend it in the burl once I've routered it out for the t-bar. Spring rate-ing is way above my pay grade, but I can easily weigh the existing arm, arm well with extraneous metal and compare to the new arm and mount extension. I don't have the AR headshell so I'll have to allow for it.
It would be much easier to rigid mount it, but that defeats the purpose doesn't it?

I'm happy to report that the existing Haydon motor is very quiet and seems to spin true. Waiting for a new belt as well.
 
jimreeves said:
I told Ben this would be a fun project! Thanks Ben.
Click to expand...

Indeed! It looks like one :D The arm looked like it is in very good condition apart from the broken arm rest! It seems to have no bearing wobble, et cetera. I want myself an AR XA someday. Someday.....somewhere.......


Ben aka MacKat
 
mackat said:
Indeed! It looks like one :D The arm looked like it is in very good condition apart from the broken arm rest! It seems to have no bearing wobble, et cetera. I want myself an AR XA someday. Someday.....somewhere.......


Ben aka MacKat
Click to expand...

Would an XB suffice? :D
 
jimreeves said:
My intention is to suspend it in the burl once I've routered it out for the t-bar. Spring rate-ing is way above my pay grade, but I can easily weigh the existing arm, arm well with extraneous metal and compare to the new arm and mount extension. I don't have the AR headshell so I'll have to allow for it.
It would be much easier to rigid mount it, but that defeats the purpose doesn't it?

I'm happy to report that the existing Haydon motor is very quiet and seems to spin true. Waiting for a new belt as well.
Click to expand...

I actually wrote an extended reply to this yesterday, but got pulled away from the 'puter before I could post it.

Mass loading, and or tuning the springs takes no more than basic 4th grade math once you understand what really is involved. If the arm and its parts you plan to install are considerably heavier than the stock arm and amount of T bar you remove, a heavier spring will be needed. I can walk you through that.......and it's probably easier via e-mail since i have some photos to help explain it. The goo on the bottom of the Tbar where the springs sat need cleaned off......goo-gone works for this. You need to (regardless of spring(s) used) to square the springs top and bottom. Some come this way (linn) . Are you planning to rout this burl to accept a top plate big enough to hold the suspension studs and motor mount? As the subchassis has about 1/8-1/4" airspace between the top plate when tuned in its normal state.
 
marcmorin said:
I actually wrote an extended reply to this yesterday, but got pulled away from the 'puter before I could post it.

Mass loading, and or tuning the springs takes no more than basic 4th grade math once you understand what really is involved. If the arm and its parts you plan to install are considerably heavier than the stock arm and amount of T bar you remove, a heavier spring will be needed. I can walk you through that.......and it's probably easier via e-mail since i have some photos to help explain it. The goo on the bottom of the Tbar where the springs sat need cleaned off......goo-gone works for this. You need to (regardless of spring(s) used) to square the springs top and bottom. Some come this way (linn) . Are you planning to rout this burl to accept a top plate big enough to hold the suspension studs and motor mount? As the subchassis has about 1/8-1/4" airspace between the top plate when tuned in its normal state.
Click to expand...

Thanks again Marc, but after some more work I'm finding that a properly sprung subchassis is going to be tough for this project due to the constraints of the burl plank I'm using. I can't align the arm location with the t-bar, so the arm mount will be off to one side. I realized that this would add a torsional force to the springs that I don't expect could be compensated with the 3-point springs. (correct me if I'm wrong about this) I was wrong about this!

Nevertheless, I've forged ahead and have made more progress than I expected to at this point. Rather than scrap the whole t-bar arrangement, I've inset it into the burl as you can see in the following photos.

burl1.jpg


Burl2.jpg


The motor will mount from the top in the hole to the left...

Burl3.jpg


If hard mounting the motor introduces any noise I've left enough room to wrap it in 1/8" sorbothane and soft mount it with silicone.

The t-bar is held in with 2 1/2" ss screws with shorter springs stolen from my previously suspended Integra 1057 turntable. Later changed to 3" screws with Linn Springs. The top surface of the t-bar rests against sorbothane sheet the entire area of the routered 'trough'.
Here's a dry fit photo...

Burl4.jpg


top view...

Burl5.jpg


With approx. half compression of the springs I've gotten the platter to level with some spring, though I expect it will have to be more rigid than originally intended if the arm is hard mounted. The arm is sprung on the T Bar, jump ahead to post #39

Burl6.jpg


Burl7.jpg


Burl8.jpg


I realize this is turning into AR heresy. :sigh:
The outcome could be good or not so good, either way it isn't true to the original XA. I'm having a great time working on it though! :thmbsp:
 
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No heresy at all. :thmbsp: I still love the burl. Taming the motor noise will be easier done with mass than with compliant material. Think lead. The motor being 24 pole and spining 300 rpm creates a 12.5hz fundamental frequency.
Compliant material doesn't damp low frequency well, but mass will. Since you won't be mounting the arm to the subchassis, you still need to mass load the Tbar (at the tonearm end) so all three springs are compressed an equal amount. Provided all three springs are of the same rate. If not, the various frequencies the springs respond to will be additive.

marc

BaMorin@AOL.com
 
Not to be a killjoy but I do not see how this is successful without a common mount for the platter spindle and the arm pillar on the suspended substructure. The only desirable differential forces between arm/cart/stylus and platter/record would be for groove advancement/modulation.
 
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