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DIY Tonearm

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Sumanta

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Another two question or can be called ideas too.

1) What will happen if we support the arm by hanging it with thread to reduce friction and ease DIY effort?

2) What if we use a glass surface as contact point for the refill tip and use Mseal as guiding block. We need to fix the block with Mseal with the refill tip inserted and then removed earliy before the Mseal dries. Before taking out the tip, we can rotate the refill to smoothen Mseal surface.

Dear JLS001, you have taken full interest of mine. Thanks for gifting such a wonderful idea to us.
 

jls001

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Another two question or can be called ideas too.

1) What will happen if we support the arm by hanging it with thread to reduce friction and ease DIY effort?

2) What if we use a glass surface as contact point for the refill tip and use Mseal as guiding block. We need to fix the block with Mseal with the refill tip inserted and then removed earliy before the Mseal dries. Before taking out the tip, we can rotate the refill to smoothen Mseal surface.

Dear JLS001, you have taken full interest of mine. Thanks for gifting such a wonderful idea to us.
I have not seen a purely thread bearing, but the Well Tempered Arm (WTA) uses a golf ball suspended in a vessel filled with high density silicon oil, the arm tube rigidly attached to the top of the golf ball either through a groove or hole cut into the golf ball, AND suspended from top on its two sides by thread. I think the threads provide azimuth stability and azimuth adjustability. Pls google for pictures and DIY WTA efforts. It is perhaps another very easily do-able tonearm. The thick oil serves as the pivot cum dampening fluid. The inventor claims that it is not a bearing in the traditional sense of the tonearm usage.

Another "thread" arm is the famous Frank Schroeder tonearm. It uses two very strong neodymium magnets, one permanently attached to the base of the arm (fixed) and another fixed to the bottom surface of the tonearm tube where it normally pivots. Then the arm tube is suspended from a bracket above using a kevlar thread exactly at its pivot point, with arrangement to adjust height. Adjust the separation between the magnets to adjust amount of damping. Adjust angle of offset counterweight to adjust azimuth. Very, very clever. Works fabulously. Many have cloned it. In my thinking, the principle of the Schroeder arm is unipivot, though there is no actual bearing contact area. Also, the "bearing" area is not single point as in an unipivot, but it displays the characteristic sideways wobble and instability of the typical unipivot. Very good arm. Very costly arm. If you have the patience, you can clone it too:)

Glass may not have the compressive strength needed for unipivots. If you calculate the force acting on the tip of the ballpoint refill, it is tremendous. In my case a rough estimate - 25 grams weight of arm tube and headshell and lift clip, 106 grams of counterweight, about 10 grams of cartridge weight, totalling about 142 grams concentrated on a point. I think the force will be of the order of thousands of kg per sq cm. Glass will work but will be susceptible to shattering in case of accidents. May be a simple piece of smooth metal plate is more suitable.

Jewel bearing like ruby or sapphire have been used by others. Also M-Seal type glues have been used by others to make female bearing, very similar to your suggestion.
 

jls001

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How to calculate this resonant frequency? I am finding answers to many problems by your way of design and can easily follow your design. But effective resonance of my selected arm and cartridge assembly may vary.
What exactly "compliance" mean here? Compliance to its specification? Is it written in spec of cartridges?
Some reading material here: Cartridge / Arm Matching
 

jls001

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Did a test spin of the tonearm. It's sounding good.

Using a Shure M44-7 cart right now. It's an old cart, and the stylus can slip out, so I have used some heatshrinks to secure it in place. Bass is real tight. Very M44-7 like:)

Tonearm wire is cannibalised from a cheap and nasty headphone that I dug out from my junk pile. The wire is surprisingly good. It is coaxial, very thin and fairly flexible. I tried a mouse too but find the insulation of the individual wires quite rigid. Another headphone yielded similarly hard insulation. I think I need to find better wire.

Arm lift is still a work in progress. The one I made works during testing but on final fitment it mysteriously failed to reach the appropriate height:) I don't want to cannibalise an arm lift from another TT. Can someone suggest a DIY-able arm lift? Mine works with a strong spring to hold down the lift lever but doesn't provide the gentle hydraulic-like lift/drop. I want it to be a gentle lift/drop mechanism.

The plywood base is made of three different boards of 18 mm + 12 mm + 12 mm. Will glue them together so that they don't slide around with every lifting of the arm.

Will do proper alignment and try a better cart this weekend.

Will post pics later.
 

jls001

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Some more pics:

In action on the Lenco L75:










Denon DL 160 cartridge and clone of the Catridgeman Isolator:







Catridge pins are made from gold plated female pins cannibalised from a D-sub data connector. The slit on the pin needs to be carefully spread and the tip bent by inserting a screw blade or pin. Tonearm wire is cannibalised from a cheap and nasty headphone, but it is surprisingly good (coax construction), but could be thinner and more flexible.

I swapped out the "learner" Shure M44-7 cartridge to a sparingly used Denon DL 160 HOMC. This is a medium compliance cart with 14x10^-6 cm/dyne compliance rating. Did the usual alignment and balancing rigmarole. The arm tube is still tied together with three nylon cable ties. Gluing will happen only after it has been tried and further changes carried out to it, as required. It is also still operating with a borrowed counterweight. The base is now sanded down and the three layers finally glued to have a secure and heavy base but they will need screwing down onto the plinth.

How does it play?

The sound with this cartridge is nothing less than stunning!

It doesn't have any right to sound even half this good!

There is very clean and clear separation, with a believable sound stage. Fine tonal balance. Agile attack and decay and a relaxed sense of musical flow. It is digging up more details than I've ever heard on any combo of my TTs/arms/cartridges. Barring none, despite the modest cartridge. And I've tried quite a few. It has amazing air and delicateness of sound with an unmistakable musical flow.

I'm not yet clear where the contribution of the foam type isolator between headshell and cartridge (I have cloned the Cartridgeman Isolator) begins or ends. Need to try with the regular headshell later. And a better cartridge as well. A non-rigid coupling between headshell and cartridge goes against the accepted audio wisdom but it seems to work fabulously at least on this arm and the cart.

More people should be making this arm. It makes very good music.
 

Sumanta

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S

I'm not yet clear where the contribution of the foam type isolator between headshell and cartridge (I have cloned the Cartridgeman Isolator) begins or ends. Need to try with the regular headshell later. And a better cartridge as well. A non-rigid coupling between headshell and cartridge goes against the accepted audio wisdom but it seems to work fabulously at least on this arm and the cart.
What is the accepted audio wisdom and its basis? With my common sense, I think if the cartridge can be isolated from the arm then problem of resonance can be avoided.
 

jls001

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What is the accepted audio wisdom and its basis? With my common sense, I think if the cartridge can be isolated from the arm then problem of resonance can be avoided.
There are many methods of damping or isolating tonearm from plinth, but I don't know about any other method of isolating catridge from tonearm.

Older SME arms for example use tiny rubber grommets between the wood screws used to secure the arm base to the plinth. The rubber grommets are placed between baseplate and plinth, threaded through the wood screws. This provides some amount of damping BUT the wood screw that passes from the base plate into the plinth below is still a short circuit and vibration still passes through. It's not an isolation. It only dampens somewhat.

Another unique dampening mechanism is the one used in Townshend Rock. The headshell is given an extension and this extension has a paddle attached to it. This paddle swims in a silicon oil. The container that contains the silicon oil can be swung into position, or away from the top of the spinning record. This damps the extraneous vibration closest to the cartridge. Supposed to work very well.

Others use similar silicon oil near the pivot. For example, KABUSA sells after-market damping devices for Technics SL 1200 arms.

But the above examples are damping of one form or another.

Others use a pod separate from the main plinth for mounting the tonearm so that the vibration from motor to plinth does not directly affect the tonearm. But the plinth and pod, though separate structures, are usually mounted on the same support platform. So the isolation is partial, as in theory some of the vibration would still pass through the support structure to the pod, but it would have been very substantially attenuated. But it's not a cakewalk to maintain correct mounting distance for a separate pod. And there is also the question of stability of the pod itself, besides having to build plinth and pod as independent entities.

Heavy mass plinths are another popular damping mechanism, especially effective with high torque idler drive TTs.

The isolator I cloned is made of three layers - one sheet of steel with a screw threaded through it to attach it to the headshell. One layer of the isolating material is glued onto the surface from which side the screw head is threaded in. Appropriate sized holes are cut at the position of the screw head. One more layer of isolation material is then glued to the first layer. No cutouts done on this later. Third layer is isolation material again, with appropriate holes cut out for screw heads. This is finally glued to the lower steel plate. This plate attaches to cartridge through two screws threaded through it. I have filed down the thickness of the screw heads so that screw heads doesn't protrude and touch the other steel plate. There is no metallic circuit (the screw attaching the headshell does not physically touch the other plate or screws that connects to the cartridge) to pass on the vibration in either direction. The assumption here is that the isolation material is good enough to dissipate all unwanted vibrations without passing it on to the other coupled structure. At least that's the theory:)

We know how cones drain vibrations from cabinets and speakers. Well, people have extended the concept to headshell-cartridge interface. They use a spacer with tiny cones inserted on one surface of the spacer. It needs capability to machine tiny parts. Use three grubs screws on each surface and sharpen the tip of the grub screws to a conical point. That's it! Non-cone surface goes to cartridge top and coned surface goes to headshell. Of course the assumption here is that headshell's bottom surface is flat to be able to mount it properly. Supposed to improve the sound in much the same way a cone under a speaker does.

There are many ideas - ranging from the seemingly foolhardy, or dubious to outright brilliant. How much benefit they actually bring about, considering the cost, time, and difficulty involved - that's the thin line separating wisdom/experience from knowledge/information and general audiophilia (progression usually being in the reverse order). Personally, I believe many small and cheap or free tweaks can bring about substantial improvements in the sound. I have been experimenting a lot with a couple of friends (Hi, fellow loonies:)) on sand and heatlon foam damping on top and below gears. We've come to some conclusions and it has definitely helped sharpen my sound further. We need to experiment further with their setups. And it has been a dirt (literally! pun intended) cheap exercise:)
 
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jls001

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Made some small progresses building a better tonearm base:










If the network of holes and channels looks like a Rube Goldberg contraption, that wasn't really the intention. After trying out hollowing out the space for a regular cabinet-mounted RCA connectors, I realised that I was losing too much mass from the base. A couple of protos had to be discarded. The base will eventually be screwed down to the plinth but I thought that it needs to be able support the arm even free standing. So the current design is to retain as much mass as possible within the small footprint of the base.





Below: Female RCA connectors were friction fitted on the acrylic panel. There is no need to carve out much hole in this arrangement as just wires come out from the back (inside panel) of the RCA female sockets.




Final looks:




I am now happy with the mechanical outcome. Next step is to start gluing tube together and begin oiling. In the meantime, need to work on a proper counterweight.
 

jls001

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And here's a Decca London Super Gold cartridge playing on the arm:




BTW, this is a difficult cartridge to match with tonearms but it plays superbly with this arm. And it is kicking the Denon DL 160's behind all over the place:)
 
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quad

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Superb work!
Did you try Litz wire - it is supposed to be very good for the tonearm wire.
 

jls001

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I made another wire:



Since I didn't know how to braid litz, I just twisted all four strands in a simple twist. I've now found detailed instructions on how to do it, so may be I'll re-do it. BTW, this is Teflon insulated wire, also cannibalised from another head phone.

Edit: the one currently used works very well, so I'm rather afraid to change it and introduce hum. Right now I'm not using any grounding wire, though I've shorted left channel ground to earthing terminal in the panel attached to the new base. In any case, there is no metallic part in the arm so there is no possible point to ground. So I simply followed the way some arms are wired. So far so good:)
 
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kaushik

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i hope the wood resonance dont play a major part .. i modded a electric basic guitar with good pickups due to bad wood never sounded anywhere acceptable ...if just a matter of attaching how about 3dprinted Arm?
 

jls001

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i hope the wood resonance dont play a major part .. i modded a electric basic guitar with good pickups due to bad wood never sounded anywhere acceptable ...if just a matter of attaching how about 3dprinted Arm?
As far as I can hear, there is no unwanted vibration due to lack of rigidity of the wooden arm tube, or due to the resonance nature of the woods. The tube wall is fairly thick and, therefore, rigid. Also, wood has been widely used in this application, and known to work well.

Just this morning I was wondering about 3D printing and was actually browsing for providers of such service. What I found so far is that they won't be able to make my required length (16 inches) and I'm not sure the plastic they use for printing (ABS, I think) would be suitable. It's very interesting, though.
 

Hiten

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I made another wire: Since I didn't know how to braid litz, I just twisted all four strands in a simple twist.
I may be wrong but, tonearm wires should be soft and supple and loosely tied for free movement and flexibility, otherwise it would resist movement of tonearm at pivot point. If possible twist two channels separately.
And here's a Decca London Super Gold cartridge playing on the arm:

if just a matter of attaching how about 3dprinted Arm?
Noob thoughts. Some basic fundamentals required for ideal tonearm I guess are... It should be light weight and move frictionless laterally, less so vertically (to damp tonearm vertical movement) with reducing bias as it moves towards center, with least amount of vibrations reaching to/from cartridge and somewhat less tortional flexing along the length of tonearm. I may be wrong but advantages of 3D printing single stiff body tonearm are not seen in AK designs.
Regards.
 

jls001

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I may be wrong but, tonearm wires should be soft and supple and loosely tied for free movement and flexibility, otherwise it would resist movement of tonearm at pivot point. If possible twist two channels separately.
Yes, Hiten you are very right about suppleness. When the wire exits the arm tube, it should not exert any horizontal force which can act as a skating force on the arm. This is especially true for an unipivot like mine where the wire exits at a point other the pivot.

Regarding whether twisting the two wires of the left pair, and twisting together the two wires of the right pair is superior to litz braiding all four wires together, is something I need to read up on. If anyone can authoritatively advise on why I should be using one over the other, I am ready to execute it. I have only seen the arm wires coming out of the headshell or the bottom of the arm base, and at these points they're no longer twisted/braided (if they were inside the arm tube). Advice/pointers welcome. I don't know what's best. FWIW, on my other DIY arm I had simply twisted all four leads in the same direction (unlike a twisted pair where the two wires cross each other continuously). I haven't been able to make this arm hum free. May be I am doing it wrong, so this one is also prime candidate for improvement.
 

Hiten

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I guess braided separate channel (Twisted pair) will minimize crosstalk and decrease stiffness. I think it will also solve hum problem somewhat. Not Sure. For wooden tonearm hum and static are problem. while stylus is running it will create static and pop sound at roughly regular interval. See if you can connect short wire from one channel ground of your tonearm base to TT metal chassis.
Regards
 

jls001

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Took apart the tonearm and glued the two halves of the arm tube. I preferred using Fevibond rubber glue instead of the usual Fevicol wood glue, as it sets much faster. After it had set, I followed it with another round of sanding to have more uniform seam where the two halves meet.

I applied the first layer of oiling using this oil:




For the first go, I oiled it liberally. It's taking quite a long time to dry. I used cotton wool to apply it, and now that it's getting dry I find lots of cotton wool strands stuck on the oiled surfaces. I guess it's better to use soft cotton cloth. Looks like it's gonna be lots of elbow grease to get (hopefully) a nice shiny finish.

I'm still trying to figure out the best way of implementing a decoupled counterweight. I'm thinking of using a strip of steel sheet shaped around the counterweight stub, wrapping around the stub with a layer of thick-ish foam. The weight will hang (screwed down, actually) from this shaped strip, the weight hanging well below the stub, so that the center of gravity of the weight will be roughly at the level of the stylus tip, so that the weight provides a dynamic balance. At least that's my understanding of it.

I also thought of an offset counterweight with an offset hole, but it looks like it will be quite unwieldy as the arm stub diameter is already fairly large (>11 mm), so the hole itself will have to be even larger to accommodate a damping layer. So this idea is dropped for now.
 
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