DIY TurnTable arm

I've been playing around with a diy tone arm, but haven't really got past the drawing stage. I've half built an arm using balsa wood, and it's light and super stiff. It also looks cool, kinda like a miniature bridge. But the problem of how to connect it to the TT kills me. Anyone know of a good website with some diy arm projects? Anyone able to help here, using this thread?
Thanks.
 
SemperFi,









look on Jeremy Epstein's Teres page and on Roscoe Primrose's airbearing arm page.

Apart from that, i hope diyAudio will be the DIY tonearm site very soon; i hold my DIY tonearm project back until Jason manages to open a TT or analog forum, don't nail him or me on the name.









To your tonearm: at the moment your question is not specific enough and, as always, answers are never better than the triggering questions. If you could post pixes of your draft and tell what you initially planned (linear tracker, gymbal arm, unipivot arm) i see what hints i can give.

Maybe my buddy Hartmut joins us with hints, he has enormous practical experience with pivoted tonearms. Hartmut, are you listening?
 

THOR

Member
2002-03-24 7:10 pm
Ca
Unipivot

How simple or complex , cheap or expensive ? I had a bunch of tone arms and finally built my own. The simplist cheapest and still excellent arm is the Unipivot, built properly these can be very good . Try it out simply and then make it better :) Get a fairly good sized darning needle from wifeys sewing kit and mount it pointing up in a block of wood that u can double sticky tape to the TT. Go to a clock shop or watch repair shop and get a few large "jewel pivot bearings ". Find where u want the pivot by trying the needle directly on the balsa top sheet of ur construction , add weight to the rear and shift it around till its ballanced for tracking force and side to side ballance. Lets say theres a top and botton on that part of the arm . make a hole in the bottom plate that will be only big enough to not interfere with the needle when u are handling the arm. Once u have the pivot point located . glue on the "jewel" to the underside of the top plate , wire it up and go:) U may have to add a small weight on a pin pointing down and put the weight low . Keeps the arm from twisting. Mount the cartridge with as little of the stylus as possible below the bottom of the arm and adjust the height of the unipivot untill the bottom of the arm is close to, and parrallel to the record , This reduces "warp wow " . If ur arm is very light it could "chatter "on the bearing . A small glob of silicone grease on the jewel will stabilize things without harm . HTHs :).
 
SemperFi,





Should the vertical axle be the same height as the pickup needle?




a linear tracker has no vertical axis (on could claim it is in infinite distance), only a horizontal axis. Yes, the horizonatal axis should be as close to record surface lavel as possible. But in real life, #1 cartridge height is not standardized and #2 the height level of the horizontal axis should be adjustable to suit the need for VTA adjustments (Vertical Tracking Angle). Consider the rail is not meant to horizontally tilted against level due to adjustments. You will have to provide some parallelogram mechanism.



With the linear travel this arm will have, how do I figure out the optimum length of the arm?

Geometrically you can choose any length that suits you. But mechanically the arm is more likely to jam the longer the tonearm wand is. Moreover, a longer tonearm is not as stiff as a short one of the same cross-sectional structure and it is more prone to resonances hence the low end reproduction will suffer from a longer tonearm wand.

OTOH one could hang the rail over teh record surfa e in order to have a VERY short tonearm. But then ANY heigt variation of the record surface will cause the tonearm to produce speed varations, wow, if you wish to call it so. I do not recommend this as >70% of real-life records have warps and/or pressing bubbles.

A very reasonable length for a linear tracker is 180-192 mm effective length. If record and platter do not exceed a diameter of 320mm.
 
thanks.
I meant horizontal axis, the one for up/down movement of the arm, thanks for correcting.

man, why aint there no vinyl forum here? espescially now that cds are being watermarked! I hate all this **** the record companis are doing to my music.

JUST SAY NO TO WATERMARKED CDs!!!!
While at it say no to digitally remastered vinyl, how dare they!
 
I think it sounds quite good because it is made of solid wood. Most tonearms are not solid, but tubes.

A tube is a hollow resonator. While you put the arm on the record, the cartridge will stimulate the tube and you will have standing waves inside, with local points of maximum amplitude and total extinction.
The tubes hollow resonances stimulate the cartridge and thus alter the sound, according to the tubes material and mechanical properties.

You should listen to your tonearm while playing a record, with no amplification. I had an Ortofon arm on the TD124 player before. It sounded horrible because of its resonances.

Modern tonearms (like the Rega and SME) also use a tube, but the tube's diameter is not constant. It is large at the bearing and smaller at the headshell. This way, it does not work as a good resonator.

With a solid wooden arm, you have no problems with standing waves.

Happy glueing, Charles :)
 
this is a new 12inch....
 

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An analogue forum! Neat!

I've been on vacation, what a nice surprise upon my return.

Bernhard was good enough to post some links to my site where I discuss the trials and tribulations of my Ladegaard arm experiments. Guys, this thing is really good, is all I can tell you. I keep telling people it is the best project in DIY - it costs little, performs well, and is simple to build. If you love vinyl as much as I do it is quite a treat to really hear what is on it. If you follow the link on my page to the Ladegaard Builder's FAQ you will save yourself some retracing of my mistakes.

I always get very excited when you can remove a problem at its source and linear tracking does this. I was recently discussing linear arms with a friend who just got an ETII set up and he was noticing that his cartridges are less sensitive to VTA adjustment than before - where before it was NECESSARY to get it spot-on, now it is something you can listen through, and the range of adjustment that sounds good seems to be larger.

My contention is that, since distortion is multiplicative, you are just removing a whole term from the equation and that makes the result of any misalignment that much less audible. And the difference between a VTA misadjustment with the stylus square in the groove and one with it skewed is apparently a significant one.

I think the whole thing works the same way - once you get the tracking and antiskating almost perfectly correct all theway across the record surface, you have a whole lot less in the way of good sound.

In my mind, I look at tracking error as a time-misalignment of the two channels, and we all know how important time is to music.

I'd be very happy to help anybody with questions about setting this arm up - I have had it running for about a year I guess so I know a lot of the pitfalls and how they reveal themselves.

-j
 
Hello Jeremy and all,



have to fully agree with what you say about multi-layered distortion.



Now, as linear trackers seem to be the solution to you and me and others (but not to the Swiss guy we both know who is claiming linear trackers are impossible to get working and if not, they are not worth the hassle), let's try both pathes competitively: Ladegaard-type airborne and the purely mechanical idea i recently came up with.



Let's build two linear trackers, one airborne, one mechanical and both based (cheapo-style) on the adjustment facilities of the LT-1 so that we can compare both arms under equal circumstances.



I already acquired from surplus a direct drive looking fine and well-designed and i alraedy have a fitting platter for it which can be modded easily to sound fine. Two LPs epoxied on the top and the bell-shaped platter filled whit "liquid steel" (Devcon, maybe they even have "liquid lead") from the bottom. I will have a test TT very soon with a raw plywood plinth allowing to mount anything anywhere on it.

The direct drive/platter is already tested and provides speeds from 16 to135 rpm which should be sufficient to spin anthing in the black/hole realm at proper speed.



I had discussions about that with Manfred and he ushered me, wrong, pushed me towards mechanical. He is not convinced on Ladegaard at all, to sloppy for his mind.

The longer i muse about the Ladegaard, the more intense i wish to try it out.



In this context: how much hassle do you expect for inverting the Ladegaard bearing i.e. to feed the air to the slider instead to the rail? Would be my preferred version as methinks advantages more than outweigh drawbacks.
 

J Epstein

Member
2002-02-08 7:24 pm
I think the stiffness of the tubing will cause a problem by applying a side force that you can't effectively null out. Getting the cables right to null this force requred using tiny, limp cable - I think an air hose will be difficult to find that will be soft enough, especially under pressure, but I don't have any experience trying that approach. I know you have had ideas about using soft, narrow rubber tubing, this will be a try-it-and-see situation.

If you are trying to solve the problem of audible air hiss, in my experience this has not really been objectionable or even audible provided you have an adjustable pump and adjust it as low as possible. And I don't listen terribly loud.

In any case Roscoe Primrose had a good idea for that which bears exploring: cut a small channel (rebate) in the bottom of the slider and use only a few air holes near the center of the rail that are always covered. I tried to do this but I removed too much material (channel was ~6mm wide and ~1mm deep) from the slider and this apparently left the remaining air bearing surface area too small to support the weight, I need to try again wiith a narrower channel. (Perhaps more pump pressure would work OK with the same channel, I haven't tried that either.)

What does Manfred think is sloppy about the Ladegaard? To my mind it is quite elegant. He wants to design a mechanical system with some precision servos and 3-layer circuit boards, eh?

Not me! My idea of precision tools: a blacksmith's anvil.

That Swiss guy is delusional anyway. Ignore him, he's a dangerous menace to society! ;)

-j
 
Jeremy,













I think the stiffness of the tubing will cause a problem by applying a side force that you can't effectively null out.












I have tis in mind, but think it can be tackled without problem. If Versa and Rockport tackled it, so can i. Remember, these are high-pressure/low flow bearing desings with the air hose considerably stiffer, due to pressure-- no problem with a Ladegaard.











If you are trying to solve the problem of audible air hiss, ...





no, not really, I object having free-blowing nozzles causing instability and reduced bearing stiffness and/or heavily increased nozzle cost due to needing 0.1mm nozzles (much water has still to go down the river until i trust holes punched into adhesive tape).









I want the bearing to behave the bearing constant and i want it to doso independent pf position.









In any case Roscoe Primrose had a good idea for that which bears exploring: cut a small channel ...








Roscoe is here and listening ? No? methinks this is a bad idea, a really bad idea (Roscoe, no offense meant, ok?) I loathed that idea from the start and i said so bach then on the Teres list. Meanwhile i read a huge lot about airbearings and my loathing gets backup from those readings. The slot acts as a nozzle pre-chamber, it stores a compressible medium (air) having a lot of energy stored. As we all know, stored energy is pre-condition for and almost always cause of (unwanted) oscillations. Pheww!! :eek: ... :mad:





I am close-minded on this issue, i do not want to try it out.







I leave your statement about Manfred uncommented as i hope this stirs him up and he answers with his 1st post here (one always can hope :) and praising him did not help so far)







The blacksmith's anvil, well, not really my concept of precision :)







Swiss guy: i quite like him but i guess he would not be well-advised to bring his nay-saying to this forum. Naysayers have been tarred and feathered here and chased thru the streets :)
 

J Epstein

Member
2002-02-08 7:24 pm
I think our Swiss friend would look cute in feathers, with that big beak . . . .

Another way to look at the uncovered nozzles, rather than as a waste, is like a bleeder resistor for a power supply - a constant excess "wasted" draw that improves the regulation/damps the variation of the "useful" portion that is used to float the bearing.

I have no idea if this is true, but it is a thought that occcurs to me.

There is already a certain (small) volume of air trapped between the tape "nozzles" and the underside of the bearing (in the small holes that surround the smaller holes in the tape.) I don't know if removing/reducing this volume is an improvement or not. I poked my holes in some stiff Mylar tape and fastened it to the underside of the surface of the rail, and let's just put it this way - every other piece of the system has been reworked except this one. A non-problem.

-j
 
Jeremy,

did i observe right? U used mm as length unit! Wow! you are light years ahead of your compatriots! :)
Whenever i have to do with American engineers professionally and we established a friendly athmosphere, and it tunrs out the American(s) expose a bit too much pride of American-style engineering, i use to tell (with an utterly, provokingly innocent face expression) that 3 1/2 countries in the world are stuck to the inch/foot unit system, the half one is clear, England, they are struggling to convert to metric units and succedding better every other day, then , well 3 countries, the 1st is Birma, the 2nd is Burundi, the 3rd ..... the 3rd ??? help me which was the 3rd? :)
 
Jeremy,

yes agreed, there is already a pre-chamber. However literature agrees unanimously the pre-chamber has to be there (1 nozzle carries 3 times the load then) but it has to be small.

As to your "bleeder resistor" : nice thought, but it indicates your air supply needs smoothing which should not be the case at all. Oscillations ....

If you want to smoothen your air, better build a CRCRC equivalent: a row of small buffer tanks each separated interceded by a flow control valve adjustend to minimum required pressure. The tank is C, the valve is R.