DIY linear tonearm

Ok, thanks for the explanation. The big question is if the inertia of the rod (be it glass or whatever) and the bearings on its ends would not be larger than the friction of the bearings against the rod. Otherwise stated: would the arm, moving up and down, be able to turn the rod? It would need bearings with very low resistance I think.
It would be worth to make an experiment, imho. Anyone having a 4-bearing arm up for checking this?

Greetings, Hansrudolf

Some are saying that the vertical armwand motion should be as stationary as posssible !! what seems to be the case with this arm ( Colin's design ) . ( at least to a certain degree ) .

It sounds plausible to me that we donot want the armwand to get launched during a warp .. or even at micro scale movements .

another thing : does a record cutter head remains stationary during the cutting process ??? well... make up your mind if that's the case .

Paul
 
Paul: Bo's original design with the rolling knife edge bearing was the extreme case of full and easy motion for the arm with respect to riding a warp as it could rock back and forth (note it is not really up and down but back and forth) easily. When Bo changed to the current version where the only play was that of the bearing race performance improved. The fact that if the arm had to drag the carriage up the wall of the glass tube to play a warp is a good thing. The less free motion the arm has in this plane the better. As for playing severely warped records, I have over a period of time come to understand and agree with Bo's position that this is simply a stupid thing to do and that it should not be a concern as far as arm design goes. No matter how well your arm will track a warm you can not and will not ever make it sound good. Buy a flat copy of the record and enjoy the music. Best regards Moray James.
 
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Paul: Bo's original design with the rolling knife edge bearing was the extreme case of full and easy motion for the arm with respect to riding a warp as it could rock back and forth (note it is not really up and down but back and forth) easily. When Bo changed to the current version where the only play was that of the bearing race performance improved. The fact that if the arm had to drag the carriage up the wall of the glass tube to play a warp is a good thing. The less free motion the arm has in this plane the better. As for playing severely warped records, I have over a period of time come to understand and agree with Bo's position that this is simply a stupid thing to do and that it should not be a concern as far as arm design goes. No matter how well your arm will track a warm you can not and will not ever make it sound good. Buy a flat copy of the record and enjoy the music. Best regards Moray James.
Hi Moray, Bravo! I second your comments almost in full. It is the up/down/forward/back interpretation that I will forever have problems with. Draw a circle or look at the front wheel on your bike. Draw or imagine a horizontal line extending out from the axle to the circumference of the wheel. Let this represent your tone arm. Put a stylus on the end of it and a warped record under it. Along comes the warp which being an inclined plane drives the stylus to assume the new position in space which is vertically displaced from the previous position, aka "up". Now let the arm wand and stylus tip remain located at the horizontal position. Pick a point on the wheel +90 deg from the previous position. Rotate the wheel the same amount that the warp lifted the arm wand in the first case. Now we observe that the point at the top of the wheel has moved ALMOST purely along a horizontal line, or forward or backward. Contrast that with the almost purely vertical displacement of the point on the horizontal axis.

To be fair in this discussion I recognize that these motions do follow a circular path (arc) and can not be taken as pure horizontal/vertical vs up/down motion. What you call them depends on where you look at the wheel. IMHO the motion of the arm wand at the record level is overwhelmingly UP/DOWN. I have the greatest respect for what Bo has created and subsequently how Colin has advanced Bo's work. Kudos to both. But I think that the forward/back, no up/down was a marketing ploy, perhaps even a red herring.
Respectfully submitted,
BillG
 
Hi Moray, Bravo! I second your comments almost in full. It is the up/down/forward/back interpretation that I will forever have problems with. Draw a circle or look at the front wheel on your bike. Draw or imagine a horizontal line extending out from the axle to the circumference of the wheel. Let this represent your tone arm. Put a stylus on the end of it and a warped record under it. Along comes the warp which being an inclined plane drives the stylus to assume the new position in space which is vertically displaced from the previous position, aka "up". Now let the arm wand and stylus tip remain located at the horizontal position. Pick a point on the wheel +90 deg from the previous position. Rotate the wheel the same amount that the warp lifted the arm wand in the first case. Now we observe that the point at the top of the wheel has moved ALMOST purely along a horizontal line, or forward or backward. Contrast that with the almost purely vertical displacement of the point on the horizontal axis.

To be fair in this discussion I recognize that these motions do follow a circular path (arc) and can not be taken as pure horizontal/vertical vs up/down motion. What you call them depends on where you look at the wheel. IMHO the motion of the arm wand at the record level is overwhelmingly UP/DOWN. I have the greatest respect for what Bo has created and subsequently how Colin has advanced Bo's work. Kudos to both. But I think that the forward/back, no up/down was a marketing ploy, perhaps even a red herring.
Respectfully submitted,
BillG

Yep ! I agree with the geometric thingy ;) and it all makes sense and also not that hard to follow when we apply the math . I mentioned up and down motion as that's what the eye can see :bigeyes:

I'm more interesting in what people say about the audible effects ... stationary vs smooth and easy vertical motion ??

THX for the inputs guys !

Paul
 
Bill,


I must say I'm flattered for any sort of reference to any advancement on Bo's work, judging by clearaudios latest offerings it appears it was seminal not to mention not referred to enough, funny enough we share some heritage in my 1/4th swede :). For such a technically imperfect medium I think we have a lot to learn yet on playback of this medium. Pivoed arms didn't do it for me, perhaps it was phase anomalies even so slight, but as muh as there are huge gains in a linear arm there are just as huge gains in a well designed riaa stage, I've tried all active, no likes here. Still the most mmusical sounding was and is passive 2122hz filter followed by an active 50hz 500hz zero filter, of course with the debated 50khz time constant included, my ears tell me this is a must regardless of debate :).



Colin
 
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Hi Colin ,

Perhaps we should not pay too much attention to the technical tonearm subject , just enjoy it and have it tracking our precious record collections !
I fuly agree with you about the sonical superior advantage of the LT vs ordinairy gymbal , although many would like to kill me for saying this :D

As for the signal amplification / riaa etc. much , much more to discover at
that stage indeed . there's an interesting thing going on on this forum .. the salas jfet simple passive phono amp .

I'm using a jfet stage to boost the mc output level only , all the rest is build
up around vacuum tubes .

Paul
 
perseverence

I’ve been a bit quite for a while, some of you may have been wondering what I was up to?
http://www.diyaudio.com/forums/analogue-source/238027-diy-linear-tonearm-105.html#post3692732

I changed the wire to trans-fi’s excellent wire and it still wouldn’t track a single turn.:confused:
My suspicions were the bearings which I had just washed out. Tried washing them out in my WD40 alternative – Inox. Still no joy. Washed out in WD40, spun them slowly in a drill.
3 weeks of stuffing around with changes to the carriage and just a few more grey hair and a sniggering wife. Wasted another $40 on another set of sealed bearings from RS supplies. Went to the same routine of washing and spinning.
I was tempted to give up but that would only upset me even more so I kept going.
Today I decided to increase the spacer between the bearings from 6mm to 8mm (12mm glass tube).
Still no luck. Then went back to the 5mm spacer from when I used a 10mm steel rod.
Hasn’t missed a track since then.
I had the – ½ the diameter in my head from somewhere in the thread.

Just goes to show you can’t take anything for granted with this thing. It all depends on your particular carriage, bearings and rod.
Never give up!!:D
Kffern
 
I’ve been a bit quite for a while, some of you may have been wondering what I was up to?
http://www.diyaudio.com/forums/analogue-source/238027-diy-linear-tonearm-105.html#post3692732

I changed the wire to trans-fi’s excellent wire and it still wouldn’t track a single turn.:confused:
My suspicions were the bearings which I had just washed out. Tried washing them out in my WD40 alternative – Inox. Still no joy. Washed out in WD40, spun them slowly in a drill.
3 weeks of stuffing around with changes to the carriage and just a few more grey hair and a sniggering wife. Wasted another $40 on another set of sealed bearings from RS supplies. Went to the same routine of washing and spinning.
I was tempted to give up but that would only upset me even more so I kept going.
Today I decided to increase the spacer between the bearings from 6mm to 8mm (12mm glass tube).
Still no luck. Then went back to the 5mm spacer from when I used a 10mm steel rod.
Hasn’t missed a track since then.
I had the – ½ the diameter in my head from somewhere in the thread.

Just goes to show you can’t take anything for granted with this thing. It all depends on your particular carriage, bearings and rod.
Never give up!!:D
Kffern

Photos please :D
 
This is an old picture. It's currently disassembled.
I will change the wood dowel to aluminum in a week or so.
It consists of 3x10x4 bearings. using 3mm screws which have a long shank, blank brass standoffs as spacers with a transistor isolating tophat at the end,
3mm plexiglass. Riding on a 12mm glass tube held on a threaded bar with a few o rings and bolts. I will post a picture when finished.
My next attempt will use a Lenco collar with an old japanese arm riser.
Kffern

An externally hosted image should be here but it was not working when we last tested it.
 
This is an old picture. It's currently disassembled.
I will change the wood dowel to aluminum in a week or so.
It consists of 3x10x4 bearings. using 3mm screws which have a long shank, blank brass standoffs as spacers with a transistor isolating tophat at the end,
3mm plexiglass. Riding on a 12mm glass tube held on a threaded bar with a few o rings and bolts. I will post a picture when finished.
My next attempt will use a Lenco collar with an old japanese arm riser.
Kffern

An externally hosted image should be here but it was not working when we last tested it.

:D
 
Kffern,


Glad to see your build, the dimensions as you have noticed are no accident. So much so for any future inquiries you can pm me for info on exacting details :). This arm, turntable design and phono design based on the inverse of the Neumann sab74 cutting amp card is as close to the master as attainable I feel in analog audio, forget tubes, they are a P.I.T.A,besides only the oldest or modified amps are based on this.


Colin
 
solid carrying rods

Although I am really enjoying this arm. I had glued my glass onto the supporting rod with silicon. I have had major problems with vibration ending up at the needle. I finally got round to copying Colin's idea of decoupling the supporting rod and the glass tube with two rubber "o" rings. It has made a massive difference in the amount of vibration reaching the needle. Its a real eye opener to hear how much vibration is cut. When I look at the pro arms which run on a glass tube running straight into the rest of the arm they must have the same problem. I would be wary of using solid rods to carry the carriage assembly.

Further, I bought about 3 meters of 10mm outside diameter pyrex tube on ebay. It came in 4 lengths and yes they were very slightly bent. However the length required for the tone arm is so short that when cut to size there is no bend.
 

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Hi chokesrule,
Would love to see some pictures of your base for the arm. Have you made any changes there?
I'm still trying to figure out how to level the glass tube, how to raise and lower it to get the right VTA and any other adjustments you can make on the fly.
At the moment I'm digesting what other have done and trying to borrow a drill press.
See ya.
 
Chokesrule,

Glad to see that the beauty of minimal contact point yet solid rigidity still rings true. Many test were performed with the decoupling using a frequency sweep record and good ol fingertips :). The turntable I built uses the same principle, better to transfer vibration and prevent getting to, than store it and change its fundamental resonance, though the very base of it all should be its heaviest point.


Colin
 
Although I am really enjoying this arm. I had glued my glass onto the supporting rod with silicon. I have had major problems with vibration ending up at the needle. I finally got round to copying Colin's idea of decoupling the supporting rod and the glass tube with two rubber "o" rings. It has made a massive difference in the amount of vibration reaching the needle. Its a real eye opener to hear how much vibration is cut. When I look at the pro arms which run on a glass tube running straight into the rest of the arm they must have the same problem. I would be wary of using solid rods to carry the carriage assembly.

Further, I bought about 3 meters of 10mm outside diameter pyrex tube on ebay. It came in 4 lengths and yes they were very slightly bent. However the length required for the tone arm is so short that when cut to size there is no bend.

Hi Chokesrule, I'm delighted that you are enjoying the arm. I am still very happy with mine. Would you please go into greater detail describing the "vibration" that was giving you so much trouble. Also a couple of pics showing the base and pillar assembly. My arm is a rather close copy of the Cantus arm with a block of hardwood roughly 1.5 x 1.5 x 3" perched on top of a post. The block has a clearance hole for the glass tube which is simply epoxied into the hole. I did put a rubber O ring on the free end of the tube. As a precaution I filled the tube with very fine sand for damping and sealed the open end with a plug of plumbers putty. I didn't try the arm without the sand so I can't say whether or not it does anything good or bad. I do know that I can tap and bang all over the arm and hear nothing but dull thuds. Another thing is the arm wand itself. My earliest samples of carriages used single tubes of either wood or thin wall aluminum tube. Not hard drawn like arrow shafts but soft aluminum. These single wands gave me lots of trouble with resonances that needed damping and even feedback like you would hear from a PA system turned up. All these problems went away when I built a carriage having 2 thin wall brass tubes from ball point pens. and mounted like the Cantus carriage.

So, I would like to check my design for the problems you had and make sure I'm not overlooking anything or worse yet oblivious to something that may be there. Needless to say it's great that you solved the problem to your satisfaction.

BillG
 
I am seeing lots of good stuff in this thread here, but am wondering if there is a post that kind of gives an essential BOM for this build. Or at least a consolidated list or principles derived from this thread. After 112 pages, a few sleeps and some head scratching, I am a mess of random data.

For anyone who has seen Adaptation, you will remember that principles aren't rules, but rather ideas or concepts that work and have worked over time... Or something like that.

I see that the gap on the two bearings is usually half the tube diameter. Is that usually a safe bet?

What size or range of sizes of bearings have people found the best performance with? I see ceramic, good quality as being preferred type. All of you run lubricated bearings?

The bearings are both loose on a single axle, and spacing between them is maintained by the pressure of the glass tube? Or have some used a spacer on the axle to maintain constant distance?

The carriage weight I have seen in the 25 gram range, including cartridge as well, yes?

What cartridges have people found work best for them on this arm? Is compliance a concern? If so, I guess this is a low mass arm?

I'd like to build a tonearm from a reference point and go from there. So many great experiments and variations popping up, I want to get in on the fun :D

Thanks in advance.
 
I am seeing lots of good stuff in this thread here, but am wondering if there is a post that kind of gives an essential BOM for this build. Or at least a consolidated list or principles derived from this thread. After 112 pages, a few sleeps and some head scratching, I am a mess of random data.

For anyone who has seen Adaptation, you will remember that principles aren't rules, but rather ideas or concepts that work and have worked over time... Or something like that.

I see that the gap on the two bearings is usually half the tube diameter. Is that usually a safe bet?

What size or range of sizes of bearings have people found the best performance with? I see ceramic, good quality as being preferred type. All of you run lubricated bearings?

The bearings are both loose on a single axle, and spacing between them is maintained by the pressure of the glass tube? Or have some used a spacer on the axle to maintain constant distance?

The carriage weight I have seen in the 25 gram range, including cartridge as well, yes?

What cartridges have people found work best for them on this arm? Is compliance a concern? If so, I guess this is a low mass arm?

I'd like to build a tonearm from a reference point and go from there. So many great experiments and variations popping up, I want to get in on the fun :D

Thanks in advance.

Welcome back when you have read to precence.

I wouldn't deal with shortcuts - then youll probably miss the Essentials - Haha
 
Hi,Bob, I have not made any other changes to the rest of it except making sure the supporting metal rod does not touch the channel I had cut in the laminated perspex block carrying the arm. It is held to the block only by the bolts now. I have used fibre washers and I am going to castle cut the washers to minimise surface area contact.

My first set up is so ridiculously bad at transmitting vibration I figured it was best to leave it as it as it will be a hard test for any modification to the arm and carriage. The rubber washers on the metal rod is the onlt success I have yet had in reducing the thud when you tap the assembly, apart from putting the whole table in a bath of sand

The base is a granite block glued on to the bottom half of the turntable chassis. Its rubbish! My next plan is to change the base to either a multi material laminate structure. Or as BillG reports : to simply wood. This time the base will be held only by 3 points to the chassis. Or, I might have it independent.

Colin's idea of using things to absorb vibrational energy has made me wonder if the decoupling fixings etc should have springs on them where possible . I have tried rubber washers but it had no effect.

The only affordable ,small , accurate, level I have ever come across is the Fat Max Extreme Torpedo. I use that to get my levels but you can also level the arm to the table simply by measuring the distance from the platter to the bottom of the arm end/middle/start with some calipers. I get the arm height by eye, I set the counterweight, then adjust the arm height until I see the cartridge running level to the record. To set the carriage's track I scored a fine line in a bad , but flat, record; chock the platter ; then watch the needle track the score line . I set VTA by eye, the arm is held to the carriage by tight fit so its just a matter of twisting. I am going to try a cross line laser level to set up every thing at a later date . With my arm adjusting is very fiddly affair; the church is putting up for the ,position " Alan Saint of Patience ", but its worth the time. I get the feeling that the arm posted by Colin is the result of a lot of time trying 'things' and perhaps this is the set up to copy I did mine like that because I had no angle iron but loads of Perspex and glue. Sorry about the build quality but the whole thing is experimental. When I learn what works best I will try and make it prettier. Final shot also shows where there is loads of super fine enamel wire in every TV set chucked out in the rubbish
 

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