AR XA tonearm reveals its secrets

american simplicity
oztayls
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AR XA tonearm reveals its secrets

Post by oztayls » 25 Jul 2019 06:11

I used to have a nice AR XB1 which I stupidly sold it after fixing it up and rewiring the tonearm. A few weeks ago I came by a nice 1969 XAU model which is slowly being sorted out. Last week I had the tonearm apart and the wires all look great, so I've decided they don't need replacing. The bearing was full of muck so after cleaning that out, I saw that the coupling parts were also pretty grubby with baked-on black stuff which looked like dried grease, so I released the pivot pins and pulled everything apart. A pretty easy job really as this arm is as simple as they come. I cleaned everything up with a Scotchbrite pad and after lubricating the bits, inspected those pivot pins. One of them looked blunt and I could see that someone had probably tightened the pin against the brass housing while dislocated from its Delrin bearing. It wasn't too bad and I was able to reprofile the pin by working it on some 1500-grit wet n dry paper. A quick lube and it went back together and I played a few records. I wasn't quite happy with the bit of play in the coupling parts so I decided to read up on the arm to see how this could be corrected.

The first revelation was that the arm had a "butterfingers" mode, where you twist the post to adjust the drop. There is also meant to be a foam washer below the plastic washer of the arm post where it screws into the coupling, so mine had probably disintegrated and it had formed part of the muck I had cleaned off the threads. I made a new foam washer from one of those self-stick surface protection pads that you fix to the bottom of ornaments etc. It's just polyurethane foam and it works well!
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However, in my readings of old AR files, the words that really got my attention were "viscous coupling". Ha, it all suddenly made sense as I continued to read about a high viscosity grease that was used in the arm. The article went on to describe that the arm-drop should be adjusted for a fall rate of 3 seconds. I first applied some 300k CST, but the arm-drop was too fast. I had some 500K CST silicone grease which I use for arm set down mechanisms and this proved to be the winner as I suddenly had full control of the arm. With the post screw adjustment, I found I could put the needle over the lead-in grove and let it drop down by itself. 3-seconds....perfect!

Suddenly, the arm and pivot bearings felt like an arm should. Listening tests also confirmed a clear leap in performance. It just sounds so much better across the frequency spectrum, but the bass extension is the standout for me. I must be due to the extra damping of the arm. Wow, this arm rocks! It sounds just wonderful! But, I was about to be impressed some more!

AR reckoned this arm could track as low as 0.5g, so clearly, it can cope with high compliance carts. However, AR does qualify that statement by suggesting most carts will track better at 1g and above. I would agree there. I put my Shure V15 III into the spare headshell, set it at 1g and put on the 1812 Overture. The canons didn't phase it one bit and it tracked beautifully when they went off! There was however a niggle...

No anti-skate on the arm means that I'm having some issues with channel balance. Some records are better than others, and even some tracks on the same record vary, but in general, it's a royal PITA. I'm beginning to be impressed with this arm but if the XA is to win my heart completely, it has to have anti-skate, so I made one. It only took 2 hours of my time to cobble one together. What took some fiddling was to get the mass of the weight on the string right. I kept taking it to the grinder and eventually found that 1.4g is spot on. It works very well, as well as the AS on any other arm, and I'm now completely happy with this arm!
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For now, the anti-skate is simply fixed on with BluTac, but once I'm sure that I won't have any more mods, I'll glue it on with a spot of acrylate.

I just used scraps from the shed to make it. The base of the post is a metal grommet from an old injector harness from my Land Rover. The wire is just stainless steel welding wire and it's held in the post with metal epoxy putty. There is a magnet under the post so that it can be moved around and its position fine-tuned. I made the little weight from a brass bolt which I put into my drill and ground off the threads with a file while it was spinning. The hole for the string is 1.5mm. I used a piece of light fishing line but next time my daughter visits I'll ask her for a donation of hair which will work even better than the line.

fscl
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Re: AR XA tonearm reveals its secrets

Post by fscl » 05 Aug 2019 20:22

oztayls wrote:
25 Jul 2019 06:11
.....major snippage......I first applied some 300k CST, but the arm-drop was too fast. I had some 500K CST silicone grease which I use for arm set down mechanisms and this proved to be the winner as I suddenly had full control of the arm. With the post screw adjustment, I found I could put the needle over the lead-in grove and let it drop down by itself. 3-seconds....perfect!

Suddenly, the arm and pivot bearings felt like an arm should. Listening tests also confirmed a clear leap in performance. It just sounds so much better across the frequency spectrum, but the bass extension is the standout for me. I must be due to the extra damping of the arm. Wow, this arm rocks! It sounds just wonderful! But, I was about to be impressed some more!

AR reckoned this arm could track as low as 0.5g, so clearly, it can cope with high compliance carts. However, AR does qualify that statement by suggesting most carts will track better at 1g and above. I would agree there. I put my Shure V15 III into the spare headshell, set it at 1g and put on the 1812 Overture. The canons didn't phase it one bit and it tracked beautifully when they went off! There was however a niggle...

No anti-skate on the arm means that I'm having some issues with channel balance. Some records are better than others, and even some tracks on the same record vary, but in general, it's a royal PITA. I'm beginning to be impressed with this arm but if the XA is to win my heart completely, it has to have anti-skate, so I made one. It only took 2 hours of my time to cobble one together. What took some fiddling was to get the mass of the weight on the string right. I kept taking it to the grinder and eventually found that 1.4g is spot on. It works very well, as well as the AS on any other arm, and I'm now completely happy with this arm!

IMG_4630.JPG

For now, the anti-skate is simply fixed on with BluTac, but once I'm sure that I won't have any more mods, I'll glue it on with a spot of acrylate.

I just used scraps from the shed to make it. The base of the post is a metal grommet from an old injector harness from my Land Rover. The wire is just stainless steel welding wire and it's held in the post with metal epoxy putty. There is a magnet under the post so that it can be moved around and its position fine-tuned. I made the little weight from a brass bolt which I put into my drill and ground off the threads with a file while it was spinning. The hole for the string is 1.5mm. I used a piece of light fishing line but next time my daughter visits I'll ask her for a donation of hair which will work even better than the line.
Have wanted to restore the AR arm to it's original state thanks for the idea using the polyurethane washer.

The AS is quite ingenious.

Thanks again

Fred

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Re: AR XA tonearm reveals its secrets

Post by lenjack » 05 Aug 2019 20:34

The original had no problems tracking at 1 gram or less with the new, then, ADC 1 cart. That was my first setup. If I had an XA now, I would certainly work up an antiskate mechanism for it. While I think Ed Villchur was a genius, I think he and Roy Allison missed the boat re antiskate. Great work fsci, on an often denigrated arm. =D>

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Re: AR XA tonearm reveals its secrets

Post by 1200y3 » 06 Aug 2019 06:45

Its gotta make you wonder why a seemingly archaic tonearm that appears to built by bored machinists can be so great.

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Re: AR XA tonearm reveals its secrets

Post by oztayls » 06 Aug 2019 10:22

I wouldn’t say it was archaic, just brilliant engineering that has been glossed over and not properly analysed or understood.

Since posting the above, I’ve been fiddling with the arm a bit and I’m now in two minds whether to do a video. There is more engineering sorcery in this arm than I had oringinally thought. Back in the 60s, there were no long-lasting silicon greases with CST ratings, so we don’t know what they used in the XA’s viscous clutch, nor do we know what oil they supplied for use for the tonearm post bearing. After some experimentation, I now have some idea. I’m not done yet, but I now have an XA arm that is almost completely neutral in both horizontal and vertical planes. The astounding thing is, centripetal forces are almost completely neutralised, meaning no anti-skate is actually required! I’m now beginning to “get” what Villchur was on about. I have an arm with a Stanton 618EEE Shibata (brush off) tracking perfectly at 1.25g and almost perfect channel balance. It’s sounding fricken amazing, and I’m realising too that there is some arm damping going on as well that is contributing. I’ve seen some complex arm damping solutions on some arms which are crazy complex and costly, yet this arm has it built in! Wow, who knew?! I can see Villchur chuckling to himself and saying “Duh!”

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Re: AR XA tonearm reveals its secrets

Post by lenjack » 06 Aug 2019 15:59

Go herehttps://www.americanradiohistory.com/Ar ... 62-oct.pdf, for the article on page 34, for Ed Villchur's explanation of how he designed the arm. It's part of a two part article explaining how he designed the turntable.

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Re: AR XA tonearm reveals its secrets

Post by oztayls » 06 Aug 2019 23:51

lenjack wrote:
06 Aug 2019 15:59
Go herehttps://www.americanradiohistory.com/Ar ... 62-oct.pdf, for the article on page 34, for Ed Villchur's explanation of how he designed the arm. It's part of a two part article explaining how he designed the turntable.
There's some good stuff in there. This Part 2 article deals with the motor so perhaps the arm is discussed in Part 1? Will have a look for it. Thanks for sharing.

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Re: AR XA tonearm reveals its secrets

Post by oztayls » 07 Aug 2019 00:21

Here we go, Part 1 talks about the arm and importantly, the principles of the types of arm balance. The AR's arm uses "neutral balance".
https://www.americanradiohistory.com/Ar ... 62-Sep.pdf

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Re: AR XA tonearm reveals its secrets

Post by lenjack » 07 Aug 2019 14:41

Sorry, I got part i and part 2 mixed up. Villchur was also the inventor of the acoustic suspension speaker.

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Re: AR XA tonearm reveals its secrets

Post by noisefreq » 07 Aug 2019 16:04

There's much to be admired from Villchur's design.

I'm impressed by your addition of anti-skateing to the XA arm, but my thoughts while reading this thread are 'it's impossible to improve on perfection'.

But you don't know if you don't try and I applaud your experimentation.

I'm guessing the AR was never taken seriously I the 60s and early 70s because of the inexpensive price tag but I'm hypothesising.

Truth is, the AX arm is very versatile because of being in "neutral balance" and accounts for anti-skate being unnecessary.
It also makes the arm very adaptable to most cartridge weights with the addition of the appropriate counter weight.

A huge improvement can be made by polishing the tapered pivot pins and replacing the delrin bearings with Ruby bearings.

I am currently running a XV 15 on mine and loving it. Excellent combination.

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Re: AR XA tonearm reveals its secrets

Post by lenjack » 07 Aug 2019 16:25

Actually, it was taken very seriously, as it remained in production for 17 years! :!: =D> 8)

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Re: AR XA tonearm reveals its secrets

Post by fscl » 11 Aug 2019 16:47

lnjk,

Thanks for the links to the original writings of E. Villchur in Audio magazine....... =D> =D> =D>

Fred

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Re: AR XA tonearm reveals its secrets

Post by oztayls » 19 Aug 2019 01:13

I've just fitted an AT-VM95ML to the XA headshell. It's a little tricky because there are two threads to contend with on each screw. The trick is to hold the cart flat to the headshell when doing up the screw so that you get the screw "synced" with the two threads. Start with the end of the screw flush with the top of the cartridge. It works well and is held tightly to the shell.
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Re: AR XA tonearm reveals its secrets

Post by lenjack » 19 Aug 2019 02:06

Those headshells are extremely rare and expensive. The key here is to take your time, and maybe use up all your 4 letter words.

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Re: AR XA tonearm reveals its secrets

Post by oztayls » 19 Aug 2019 02:22

lenjack wrote:
19 Aug 2019 02:06
Those headshells are extremely rare and expensive. The key here is to take your time, and maybe use up all your 4 letter words.
You are not wrong there! The aftermarket ones are just as expensive especially with $20 shipping to Australia on top.

By the way, there seem to be two main aftermarket suppliers of AR headshells, ie. "Pat's Audio" and "Best Audio". Is there anything to choose from between these, or are they roughly the same quality?

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