Hi,
Its completely the same as I outlined below, except
your drilling big holes in LP's so you can use a modified
45 rpm adaptor to do the same thing I described.
Commercially my solution fly's better, no LP drilling.
rgds, sreten.
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Plenty of litz wire is made using different insulation methods. Calling a ECW single core litz is just wrong.
I don't care how well its damped 10" from the stylus. If you clamp a ruler to a table with some of it sticking over and whack it, you still get vibrations. A tuning fork still rings if the handle is embedded in concrete. You arm/cartridge combination has a resonant freqency. If you didn't find it with the test record then its above 25Hz and therefore in the audible frequency band. this is bad.
Your arm tube is carbon fibre. They make archery bows and magic feet for paralympians out of it because in certain lay ups it very bendy. Unless you damp both ends, like the townsend arms it will resonate. The fact that you have not found rhe resonant frequency does not mean it is not there.
The dragon TT certainly falls into that category. as does the turntable where the platter moved and the arm was fixed.
Maybe using a USB microscope? Then you need a laptop dedicated to record alignment.
@billshurv (#102),
Look to the image below. It is a cross section of the tonearm. The armtube itself is made of 2 carbon tubes: an outer tube (8 x 7 mm) and an inner tube (4 x 3 mm). The space between both tubes is filled with Styrofoam (no glue). Both tubes are mutual connected near the headshell. There is no other connection between both tubes at the other side of the tonearm. Therefore, every resonance in one tube is damped by the resonance in the other tube (the relation between the dimensions of both tubes is not the cause of the existence of the first harmonic).
It is true, everything resonate. Nevertheless, we only want to avoid peak resonances like self resonance (not the average resonance). The armtube of tonearms with a fixed pivot resonate because the vibrations are locked up between the cartridge and the bearing of the tonearm (like a guitar string). But this is not the only cause; there are more reasons why fixed pivot toneams resonate (e.g. offset angle).
Now look to the carbon tonearm in the image above. It has – of course – a cartridge too. But the other side is not a rigid bearing, it is a damper! (sphere into the water of the bowl). Conclusion: this tonearm cannot resonate by the vibrations of the stylus.
@sreten (#101),
It is nice to hear that you have nearly the same idea about centring eccentric records. But... don’t forget a lot of readers – like me – are not native speakers of the English language. So when you explain your ideas you must keep in mind that people like me don’t understand a bit informal sentences. I only understood your idea a bit when I drew 2 circles with a vertical connection. Therefore, an image that shows the details is very helpful for me and everyone else.
Look to the image below. It is a cross section of the tonearm. The armtube itself is made of 2 carbon tubes: an outer tube (8 x 7 mm) and an inner tube (4 x 3 mm). The space between both tubes is filled with Styrofoam (no glue). Both tubes are mutual connected near the headshell. There is no other connection between both tubes at the other side of the tonearm. Therefore, every resonance in one tube is damped by the resonance in the other tube (the relation between the dimensions of both tubes is not the cause of the existence of the first harmonic).
An externally hosted image should be here but it was not working when we last tested it.
It is true, everything resonate. Nevertheless, we only want to avoid peak resonances like self resonance (not the average resonance). The armtube of tonearms with a fixed pivot resonate because the vibrations are locked up between the cartridge and the bearing of the tonearm (like a guitar string). But this is not the only cause; there are more reasons why fixed pivot toneams resonate (e.g. offset angle).
Now look to the carbon tonearm in the image above. It has – of course – a cartridge too. But the other side is not a rigid bearing, it is a damper! (sphere into the water of the bowl). Conclusion: this tonearm cannot resonate by the vibrations of the stylus.
@sreten (#101),
It is nice to hear that you have nearly the same idea about centring eccentric records. But... don’t forget a lot of readers – like me – are not native speakers of the English language. So when you explain your ideas you must keep in mind that people like me don’t understand a bit informal sentences. I only understood your idea a bit when I drew 2 circles with a vertical connection. Therefore, an image that shows the details is very helpful for me and everyone else.
Tom: You are either deluded or have solved a problem that many minds have tried to address. The resonance is of the cartridge, loaded by the tonearm. It has to exist.
If you look at traditional air bearing linear trackers they have a large bearing and a small silicon damping trough, with a paddle. You have a very small bearing and a very larger water damping trough. But makers of air bearing arms have never claimed they can magically stop a cartridge resonance.
The calculation of resonant frequency has been well known since well before most of us were born and should be in your test record.
If you look at traditional air bearing linear trackers they have a large bearing and a small silicon damping trough, with a paddle. You have a very small bearing and a very larger water damping trough. But makers of air bearing arms have never claimed they can magically stop a cartridge resonance.
The calculation of resonant frequency has been well known since well before most of us were born and should be in your test record.
@billshurv,
Resonances at macro scale have to be excited. A fiddlestick for a violin, etc., etc. So the question is, what is at the level of the cartridge, the cause of peak resonances? Resonances that transpose themselves into the material of the armtube.
The stylus of a cartridge is attached to the cantilever. A tube that has its own pivot inside the cartridge. The movements of this small tube are damped by a little rubber disk at the pivot side of the cantilever. Moreover, the stylus is moving by the pull of the record. So the tip of the stylus is not the actor, it is the follower. The damper controls the amplitudes.
Now think about it. Why there are peak resonances? Caused by the design of the cartridge? That’s really strange! When this is true, all the cartridges were sonically decoupled from the armtube (small fluid dampers, etc.). The argument that the mass of the body of the cartridge is too low to absorb the resonances isn’t sensible. The relation between the mass of the stylus/cantilever and the body of the cartridge is about 1 : 2000. It isn’t caused by the frequencies of the music too, because there are no rules to avoid certain kinds of frequencies when we make a master recording (the RIAA correction is mostly done to get more music on one side of a record).
The cause of the peak resonances is – simple – the rigid construction. Nearly every fixed pivot tonearm and every tangential tonearm has a rigid construction. We force the stylus through the groove and the result is the existence of peak resonances. The stylus is just acting like a groove scraper. (And some tonearm designs increase the peak resonances by overhang, tracking error, offset angle, pulling the mass of the cartridge and tonearm to the centre of the record, etc., etc.)
Nevertheless, the outer carbon armtube is attached at both sides of the sphere (80 mm), so the damping is not restricted to one point. Moreover, the counterweight is attached to the outer tube so the resonances of the inner tube are a-symmetrical damped by the Styrofoam. I have incorporated a lot of little mechanical tricks to avoid possible peak resonances. Just in case off.
Resonances at macro scale have to be excited. A fiddlestick for a violin, etc., etc. So the question is, what is at the level of the cartridge, the cause of peak resonances? Resonances that transpose themselves into the material of the armtube.
The stylus of a cartridge is attached to the cantilever. A tube that has its own pivot inside the cartridge. The movements of this small tube are damped by a little rubber disk at the pivot side of the cantilever. Moreover, the stylus is moving by the pull of the record. So the tip of the stylus is not the actor, it is the follower. The damper controls the amplitudes.
Now think about it. Why there are peak resonances? Caused by the design of the cartridge? That’s really strange! When this is true, all the cartridges were sonically decoupled from the armtube (small fluid dampers, etc.). The argument that the mass of the body of the cartridge is too low to absorb the resonances isn’t sensible. The relation between the mass of the stylus/cantilever and the body of the cartridge is about 1 : 2000. It isn’t caused by the frequencies of the music too, because there are no rules to avoid certain kinds of frequencies when we make a master recording (the RIAA correction is mostly done to get more music on one side of a record).
The cause of the peak resonances is – simple – the rigid construction. Nearly every fixed pivot tonearm and every tangential tonearm has a rigid construction. We force the stylus through the groove and the result is the existence of peak resonances. The stylus is just acting like a groove scraper. (And some tonearm designs increase the peak resonances by overhang, tracking error, offset angle, pulling the mass of the cartridge and tonearm to the centre of the record, etc., etc.)
Nevertheless, the outer carbon armtube is attached at both sides of the sphere (80 mm), so the damping is not restricted to one point. Moreover, the counterweight is attached to the outer tube so the resonances of the inner tube are a-symmetrical damped by the Styrofoam. I have incorporated a lot of little mechanical tricks to avoid possible peak resonances. Just in case off.
You need to understand a bit more how a cartridge works I think. There is a resonance caused by the cartridge compliance and the effective mass of the tonearm. This is a well known mechanical principle and should be measurable with your test record. You cannot change that whatever you do.
@billshurv (#107),
Without a doubt you are right. So don’t worry about crazy tonearms. Fortunately, you have a nice SME and you are content with it. That’s how it has to be.
Without a doubt you are right. So don’t worry about crazy tonearms. Fortunately, you have a nice SME and you are content with it. That’s how it has to be.
Every mass-spring system has a resonance frequency and resonates. You cannot avoid it.
Key word: EVERY. You cannot avoid it. You can lower and broaden the peak with damping or move the resonance frequency to another frequency, but you cannot avoid it.
Jan
@jan.didden,
I haven't said there are no resonances. So I am really pleased when we stop this off-topic discussion.
I haven't said there are no resonances. So I am really pleased when we stop this off-topic discussion.
Tom technically you are mis-using the term Litz. It has to do with making a large gauge up from from individually insulated strands to avoid the skin effect. Litz has nothing to do at all with the individual strands.
I would suggest that you might want to try getting some 1mil gold bond wire. BTW I have never seem anything less than 50 AWG not that I have looked extensively. Less than #40 or so are very difficult to handle and solder to.
I read through your web site, you certainly have a lot of enthusiasm.
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Actually you did say there were no resonances. And i called you on it. Would be very instructive to measure your resonant frequency as that will for one work out your effective arm mass, something I have not seen quoted.
Hi,
Arn resonances have nothing to do with the fundamental
mass/compliance resonance that is usually about 10Hz.
I for one, don't agree that the arm cannot have "arm resonances".
That is is simply wishfull thinking, not a real fact in any sense.
They may be well damped, better than most, but will still exist.
rgds, sreten.
However I'm lost about the 80mm sphere in water, with
a 16" (400mm) long arm, that is inherently vertically
unstable and has no location mechanism that I can see.
Arn resonances have nothing to do with the fundamental
mass/compliance resonance that is usually about 10Hz.
I for one, don't agree that the arm cannot have "arm resonances".
That is is simply wishfull thinking, not a real fact in any sense.
They may be well damped, better than most, but will still exist.
rgds, sreten.
However I'm lost about the 80mm sphere in water, with
a 16" (400mm) long arm, that is inherently vertically
unstable and has no location mechanism that I can see.
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@sreten,
Measuring the resonance of a tonearm with the help of test frequencies is measuring the peak resonance/self resonance (that was the question of @billshurv). To get an armtube into self resonance, the added energy by the vibrating stylus has to be “locked up” so it can accumulate inside the armtube. One side is the stylus – continuously supplying energy – and the other side is the rigid bearing of the tonearm (nontransparent for long frequencies). Of course, the dimensions of the tube and the mass are responsible for the specific self resonance, if the arm tube is absorbing enough energy. This carbon tonearm has no fixed pivot (or other rigid constructions) and all the generated energy is dispatched to the water inside the bowl. And to prevent the rare occurrence that the armtube can get into self resonance by only a very little bit of energy (because of the dimensions), I have incorporated a lot of damping. (The carbon fibre of the tubes is not winded, all are longitudinal.)
The test record supplies a test frequency from 20 Hz, 19 Hz, etc. to 6 Hz and there is no self resonance of the carbon tonearm. So if there is some misunderstanding about “no resonances inside the armtube”, sorry it is “no self resonance inside the armtube”.
The instability of the carbon tonearm because of the spherical floater.
The construction is not like a boat, because the stylus is “at solid ground” (VTF is 2,5 gram). Therefore, the point of gravity can be above the surface of the water, because the instability is decreased by nearly 50%. Therefore, the mass of the cartridge (10,6 gram) and the counterweights (9 gram) hardly influences the point of gravity in relation of the upwards force of the water. The sphere has mass of its own and about 50% is below the surface of the water.
It is a bit confusing. There is a point of gravity that normally has to be below the surface of the water because of the stability of the spherical floater, and, there is a point of gravity that must be near the point of contact between the horizontal bar and the vertical roller bar. Just to prevent the tonearm from “rolling/rotating” to and fro in the vertical plane by the eccentricity of records. Because this “rolling/rotating” is nothing else than a deviation of the azimuth.
The image above shows the tonearm without arm wiring from the end of the armtube to the RCA connectors (a “clean” test). The record is rotating. The counterweights are in the uppermost position and the horizontal bar sticks exactly in the vertical centre of both holes in the transparent sphere. So there is balance, although the centre of mass in the vertical plane is at the point of contact between the horizontal bar and the vertical bar under the armtube (the friction between stylus and groove stabilizes the tonearm too).
I have tried different kind of cartridges – for example 4,5 gram mass and 1,0 gram VTF – and there was not much difference in stability of the sphere. Nevertheless, I prefer low mass cartridges with only a small VTF.
Measuring the resonance of a tonearm with the help of test frequencies is measuring the peak resonance/self resonance (that was the question of @billshurv). To get an armtube into self resonance, the added energy by the vibrating stylus has to be “locked up” so it can accumulate inside the armtube. One side is the stylus – continuously supplying energy – and the other side is the rigid bearing of the tonearm (nontransparent for long frequencies). Of course, the dimensions of the tube and the mass are responsible for the specific self resonance, if the arm tube is absorbing enough energy. This carbon tonearm has no fixed pivot (or other rigid constructions) and all the generated energy is dispatched to the water inside the bowl. And to prevent the rare occurrence that the armtube can get into self resonance by only a very little bit of energy (because of the dimensions), I have incorporated a lot of damping. (The carbon fibre of the tubes is not winded, all are longitudinal.)
The test record supplies a test frequency from 20 Hz, 19 Hz, etc. to 6 Hz and there is no self resonance of the carbon tonearm. So if there is some misunderstanding about “no resonances inside the armtube”, sorry it is “no self resonance inside the armtube”.
The instability of the carbon tonearm because of the spherical floater.
The construction is not like a boat, because the stylus is “at solid ground” (VTF is 2,5 gram). Therefore, the point of gravity can be above the surface of the water, because the instability is decreased by nearly 50%. Therefore, the mass of the cartridge (10,6 gram) and the counterweights (9 gram) hardly influences the point of gravity in relation of the upwards force of the water. The sphere has mass of its own and about 50% is below the surface of the water.
An externally hosted image should be here but it was not working when we last tested it.
It is a bit confusing. There is a point of gravity that normally has to be below the surface of the water because of the stability of the spherical floater, and, there is a point of gravity that must be near the point of contact between the horizontal bar and the vertical roller bar. Just to prevent the tonearm from “rolling/rotating” to and fro in the vertical plane by the eccentricity of records. Because this “rolling/rotating” is nothing else than a deviation of the azimuth.
The image above shows the tonearm without arm wiring from the end of the armtube to the RCA connectors (a “clean” test). The record is rotating. The counterweights are in the uppermost position and the horizontal bar sticks exactly in the vertical centre of both holes in the transparent sphere. So there is balance, although the centre of mass in the vertical plane is at the point of contact between the horizontal bar and the vertical bar under the armtube (the friction between stylus and groove stabilizes the tonearm too).
I have tried different kind of cartridges – for example 4,5 gram mass and 1,0 gram VTF – and there was not much difference in stability of the sphere. Nevertheless, I prefer low mass cartridges with only a small VTF.
So the test bands to check for cartridge resonance don't excite the armtube. I'm astounded. Arm resonances are usually 200Hz and up.
@billshurv,
The only knowledge I have about the self resonance of tonearms is the paper from Bruel & Kjaer. In the past I have tested 2 fixed pivot tonearms with the test record (SME III and a Japanese tonearm). At ~10 Hz both tonearms started intensely shaking (in fact, these tests are very “helpfull” to mangle the stiffness of the cantilever of a cartridge). So I was very relieved the carbon tonearm appeared to be impervious for these low frequencies.
The only knowledge I have about the self resonance of tonearms is the paper from Bruel & Kjaer. In the past I have tested 2 fixed pivot tonearms with the test record (SME III and a Japanese tonearm). At ~10 Hz both tonearms started intensely shaking (in fact, these tests are very “helpfull” to mangle the stiffness of the cantilever of a cartridge). So I was very relieved the carbon tonearm appeared to be impervious for these low frequencies.
Without saying what the cartridge was that really doesn't say much. By SME III I assume you mean 3009 series III. That was a very low mass tonearm designed for high compliance MM cartridges, so its very easy to mismatch the cartridge on that and get to the point where the tail wags the dog. But that is basic arm/cartridge synergy. The 3009 Series 3 also had an optional low cost version without damping trough which made mismatches worse.
Tom, I suspect you have simply damped the primary resonance to a Q well below 1. This is easily achieved on a pivoted design with a reservoir of damping fluid coupled directly to the bearing assembly. The Jelco style of arm had two hemispheres in close contact that had a fluid of just the right viscosity and just the right level to adjust the Q. Others better versed in the details could maybe enlighten us on the pros and cons of damping the primary resonance.
@billshurv, scott wurcer,
The self resonance of the armtube is the frequency of the test record (e.g. 9 Hz). So when the armtube starts vibrating in line with the cantilever – same frequency – the cantilever will show an enormous amplitude. Just because the centreline of the armtube isn’t a stable position any more. It moves in line with the stylus of the cartridge.
The mass of the carbon armtube – without counterweights and cartridge - is 39,3 gram. The mass “before the pivot” is 9,4 gram (headshell and half the armtube). The counterweights have a mass of 9 gram because the cartridge – Ortofon MC Cadenza Red (VTF = 2,6 gram) – has a mass of 10,6 gram (the tonearm is quite symmetrical). When I test these low frequencies, it doesn’t matter I replace the Cadenza red by an MM cartridge (7 or 4,5 gram). Therefore, the well known theoretic about tonearms isn’t totally suitable for this carbon tonearm. For example, when I play a record, every cartridge sounds balanced. No matter what type of cartridge or how many mass and VTF. But of course, a good MC cartridge produces far more detail than a cheap MM cartridge.
Anyway, I have ordered the centre fraise (milling cutter) to experiment a bit. Trying to get perfect centre holes in bad records. If there is no failure, I will start thinking about the way to DIY the tool to centre records (2 non concentring rings).
The self resonance of the armtube is the frequency of the test record (e.g. 9 Hz). So when the armtube starts vibrating in line with the cantilever – same frequency – the cantilever will show an enormous amplitude. Just because the centreline of the armtube isn’t a stable position any more. It moves in line with the stylus of the cartridge.
The mass of the carbon armtube – without counterweights and cartridge - is 39,3 gram. The mass “before the pivot” is 9,4 gram (headshell and half the armtube). The counterweights have a mass of 9 gram because the cartridge – Ortofon MC Cadenza Red (VTF = 2,6 gram) – has a mass of 10,6 gram (the tonearm is quite symmetrical). When I test these low frequencies, it doesn’t matter I replace the Cadenza red by an MM cartridge (7 or 4,5 gram). Therefore, the well known theoretic about tonearms isn’t totally suitable for this carbon tonearm. For example, when I play a record, every cartridge sounds balanced. No matter what type of cartridge or how many mass and VTF. But of course, a good MC cartridge produces far more detail than a cheap MM cartridge.
Anyway, I have ordered the centre fraise (milling cutter) to experiment a bit. Trying to get perfect centre holes in bad records. If there is no failure, I will start thinking about the way to DIY the tool to centre records (2 non concentring rings).
How about this idea: mount the tonearm board on an X-Y slide. Drive the slide with two orthogonal linear motors (could be simple coils over a metal rod).
Get the 0.55Hz excentricity signal with a 0.55Hz bandpass from whatever signal comes off the cartridge. Drive the linear motors with the I- and Q signals from the excentricy.
Should work, any record, no mods, although it might be a somewhat, ehh, eccentric solution. 😉
jan
Get the 0.55Hz excentricity signal with a 0.55Hz bandpass from whatever signal comes off the cartridge. Drive the linear motors with the I- and Q signals from the excentricy.
Should work, any record, no mods, although it might be a somewhat, ehh, eccentric solution. 😉
jan
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