DIY linear tonearm

On my most recent arm I've attached 6 thumb screws on 3 bolts.
The bolts heads are epoxy set and countersunk on the bottom of
the thicker plate. The thinner plate is moved slightly in four directions
by adjusting the thumb screws. The tubes are fixed to the thinner
plate. Both plates are secured by the main column. This gives a very easy and precise method of leveling the tubes.

This is my version using 2 bearings on 2 tubes....works very well and
weighs 20 grams with the cart and the counter weight. I want to
build a lighter wand and carriage, hopefully this weekend, if I have time.

This arm is mounted to a Rega P3



 
Show of hands......who would of bought a Cantus but because of this thread
wont? Probably none of us....

The people here are hands on, thats why they come here, they read, they're
inspired, they build. Maybe in the course of it they might even improve upon it.

My final build is different than both Colins and the Cantus.
It works spectacularly, am very happy with it, if it wasnt for this thread
I'd have a much lesser system.

I look forward to any off shoot threads this one produces.

PDRCan,

Great job! I would expect it to work spectacularly! When I started experimenting with LT arms my first build was a rather crude model using 2 precision ground steel rods and 2 bearings. Proved the idea but was impossible to use for sticking and skipping etc, etc. So I went on to build successful versions using window glass V tracks which then became Colin's 4 bearing single tube type. So when you posted the pic of your 2 rod/2 bearing model I was delighted to see it and pleased with your report on its performance.

I've been testing various schemes to eliminate or diminish a low bass frequency ringing of the track tube on my arm. It shows when I finger tap the tube with the volume turned up. I really don't know if this resonance is excited by music or other mechanicals and getting into the audio signal. As near as I can tell you cant hear any problem when playing records. So the question is, to ignore it or push on working the issue. Holding on to the free end of the tube pretty much kills the ringing. So I had a spare tube assembly with an easily removable track tube. It is filled with fine sand and plugged on the ends.

Then your arm pics brought my early experiments back to mind. Yesterday, already, I modified my arm to be a 2 bearing/2tube arm. Removed 2 of the 4 bearings, repositioned the other 2 on their shafts and attached the spare track tube along side, touching, the single tube. Held it together with super glue. My hope was that it would provide some solution to the resonance problem. It did, killed the bass ringing and gave some new ones an octave or two higher. Other than that it tracks flawlessly and sounds great. Mechanically it is far less prone to flying of the handle when treated roughly. Sound is not changed from the previous model.

Would you please do the finger tap test with the stylus resting on a non-rotating record, both with and without the record mat and report back what you find. I think you mentioned that the mat is the non-slip carpet underlayment variety. That type mat looks like it would be really effective.

Thanks in advance and enjoy your new linear tracker.

BillG

P.S. If there are any real Cantus users reading this post, Would you please do the same test and get back to me.

BillG
 
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I have no intention to hijack the topic, so, ignore this question if you think it's way too OT:
If only the "C" shaped (cut glass tube) and two roller bearings on the carriage are used, but everything else is different than the original Opus 3 Cantus tonearm, does it count as a copy/clone (I don't think it does since Clearaudio did sometnig like that as well)?
The dimensions of the tube and the bearings are not the same as the Opus Cantus...
 
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It would be interesting to see if it's possible to design and build an arm (LT) with a small paddle submerged into a small reservoir of thick silicone oil - the reservoir would of course have to be paralell to the shaft/glass tube and long enough... Works for the WT arms as a resonance killer... Just a thought...
 
I had a Cantus until I sold it last year. They have no damping whatsoever with the tube simply epoxied in to the carrier-it rang like hell when tapped! Seems that Bo wasn't too bothered about this aspect!
ChrisG,

So I guess I should adopt the "If it only hurts when you touch it, stop touching it" approach.. Thanks for the info. This is the only part of the Cantus, all flavours, arm that bothers me. The 2 bearing/2 tube I now have has the ringing controlled a good bit better than the single tube. I'll leave it there for now. Still think it is the best arm I have ever heard or used.

Thanks again,

BillG
 
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Hi Bill
I've been toying with the two tube idea-what diameter are you using please? Looks like the 10mm diameter?

Chris and Arch, Get ready for a blast! One tube is the 10m that is epoxied into the carrier block. The second tube is a piece of 8mm (7.9xxxmm , a fractional inch size)that I had lying around. The difference in diameters matters not a whit. Actually might help with the resonance issue. The bearings are well used hybrid ceramics running with a light oil FILM. If you glue or clamp the tubes they will be parallel and if you clamp them to a board or table top, upside down on the board, the up side of the tubes will be aligned also. I'm toying with the idea of sealing one end of the tubes, filling them with viscous fluid and sealing the other end. How much resonating can a liquid filled tube do???

BillG
 
It would be interesting to see if it's possible to design and build an arm (LT) with a small paddle submerged into a small reservoir of thick silicone oil - the reservoir would of course have to be paralell to the shaft/glass tube and long enough... Works for the WT arms as a resonance killer... Just a thought...

Stein, Tried the oil bath back when I was doing window glass tracks. Made a reservoir attached to the V track and deep enough to accommodate a short wire drag attached to the carriage. Bottom end of the wire was coiled into a flat spiral about 1/8" in diameter and bent 90 deg to be parallel to the plane of the track. Yes it worked but was messy enough and I was having other problems with the arm so I discontinued the test.

BillG
 
Stein, Tried the oil bath back when I was doing window glass tracks. Made a reservoir attached to the V track and deep enough to accommodate a short wire drag attached to the carriage. Bottom end of the wire was coiled into a flat spiral about 1/8" in diameter and bent 90 deg to be parallel to the plane of the track. Yes it worked but was messy enough and I was having other problems with the arm so I discontinued the test.

BillG

Thank you for sharing the experience. :)
 
PDR,

Out of curiosity how is the movement on a long runout groove, completely smooth or minor stick slip?. When I tried the two tube it worked, and much easier to set tracking weight, you can take the arm, set it level and bounce it with a finger tap that kept it bouncing a number of times like a pendulum. For vertical resonance I don't know that this is ideal but deifinately it will bring the vertical and horizontal mass further apart. Of course pay alot of attention to those woofers, and their precious voice coils :).



Colin
 
Works exceptionally well on long run out grooves. I have an album with one, I'll video it and pop it here so you can see just how nicely tracks.

I've been running the 2 tube since November. I have a lot of hours on
it now, enough to take it from prototype to a finished arm. The first
version was on my DD table, this new one on the Rega was just finished
after X-mas, I only have maybe 40 hrs on it.

I found that if I drop the wand on to my scale that I get consistent
reading every time, I wasnt getting that with my single tube.
I would think thats because there is less weight above the tubes
so it settles better? Dont know why, just know its better.
The total weight of the arm including 6 gram cart and 5 gram counter
is now a just over 19 grams, I trimmed some fat yesterday.

I have 8pc of 12" woofers in my system...dont want to wreck any of them.
Just a note, I'm not a bass junky, I have 2 dual subs behind for smoothing.

Like Bill I have also found that its almost impossible to have
an accidental falling off, thats just a convenience thing though.

I would think the next step of this riding the tubes system would be using smaller tubes and smaller bearings.....I'm going to try that in the near future.
Maybe damp the bottom valley with some liquid rubber, or even a small sheet
of rubber glued to the underneath of the tubes?.......just thinking out loud.

Bill, I havnt had time to do what youve asked, but should have time tonite....I'll report back.

Heres a short vid of the prototype:
double tube linear - YouTube
 
Works exceptionally well on long run out grooves. I have an album with one, I'll video it and pop it here so you can see just how nicely tracks.

I've been running the 2 tube since November. I have a lot of hours on
it now, enough to take it from prototype to a finished arm. The first
version was on my DD table, this new one on the Rega was just finished
after X-mas, I only have maybe 40 hrs on it.

I found that if I drop the wand on to my scale that I get consistent
reading every time, I wasnt getting that with my single tube.
I would think thats because there is less weight above the tubes
so it settles better? Dont know why, just know its better.
The total weight of the arm including 6 gram cart and 5 gram counter
is now a just over 19 grams, I trimmed some fat yesterday.

I have 8pc of 12" woofers in my system...dont want to wreck any of them.
Just a note, I'm not a bass junky, I have 2 dual subs behind for smoothing.

Like Bill I have also found that its almost impossible to have
an accidental falling off, thats just a convenience thing though.

I would think the next step of this riding the tubes system would be using smaller tubes and smaller bearings.....I'm going to try that in the near future.
Maybe damp the bottom valley with some liquid rubber, or even a small sheet
of rubber glued to the underneath of the tubes?.......just thinking out loud.

Bill, I havnt had time to do what youve asked, but should have time tonite....I'll report back.



PDR, Good information! It was snowing here this afternoon so I pplayed around with damping in the bottom valley. Rolled some plumbers putty between my hands to get a thin snake and plastered that in the valley. The insides of the tubes already were filled with fine sand which was not doing very much at all. The combination seems to quieted things down a lot. I'm not aware of the damping doing anything to degrade the sound/music. Still interested in how your arm does with the tap-ring test. ChrisG's information re Bo's Cantus ringing like hell really is what I was after and gives me some encouragement with what I've done so far. My total weight is 28 grams. Weight isn't bothering the tracking at all, but I will be building a lighter one soon.
 
PDR,

Out of curiosity how is the movement on a long runout groove, completely smooth or minor stick slip?. When I tried the two tube it worked, and much easier to set tracking weight, you can take the arm, set it level and bounce it with a finger tap that kept it bouncing a number of times like a pendulum. For vertical resonance I don't know that this is ideal but deifinately it will bring the vertical and horizontal mass further apart. Of course pay alot of attention to those woofers, and their precious voice coils :).



Colin

Hi Colin,
Checked out the Beethoven symphony #4 which uses only half the recorded side. Rest is one long runout groove. Absolutely smooth, no stick-slip. Checked it for stylus hunting and also monitored the rotation of the outer race. Only smooth and constant motion.

BillG
 
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