Stealth Mk 3
Hi Folks
I've been a bit quiet lately as other projects have been taking up my time!! Anyway, I keep going back to the unipivot, and, whilst walking our pet Choccy Labrador, came up with this design. It might remind you of another arm-forgot the 'naim'!!
It's quite a re-working-the pivot is much more in control than my other efforts-still one ciontinuous arm tube with no breaks or joins. The ball point nib has been replaced by a 2mm ball bearing-I've used this on other arms and found it very good indeed- and it means I don't have to mess around with that awful ink that gets everywhere when you start to cut up the refill.
I'm currently tidying up the pivot on a second version which doesn't have the protruding set screw and nut on the top and looks a whole lot neater.
Sound quality-I never cease to be impressed- I'm never going the commercial route ever again.
Here are some pictures- I'll post some of the 'refined' version when complete.
Hi Folks
I've been a bit quiet lately as other projects have been taking up my time!! Anyway, I keep going back to the unipivot, and, whilst walking our pet Choccy Labrador, came up with this design. It might remind you of another arm-forgot the 'naim'!!
It's quite a re-working-the pivot is much more in control than my other efforts-still one ciontinuous arm tube with no breaks or joins. The ball point nib has been replaced by a 2mm ball bearing-I've used this on other arms and found it very good indeed- and it means I don't have to mess around with that awful ink that gets everywhere when you start to cut up the refill.
I'm currently tidying up the pivot on a second version which doesn't have the protruding set screw and nut on the top and looks a whole lot neater.
Sound quality-I never cease to be impressed- I'm never going the commercial route ever again.
Here are some pictures- I'll post some of the 'refined' version when complete.
Attachments
This needed a bump!
The most recent issue of LinearAudio has a good article on tone-arm physics. What interested me most was that the subsonic resonant frequency of the arm and cartridge combination is easily excited AND puts inter modulation distortion on the fundamental. The author dug up a lot of material from decades ago. The conclusion -- damping is your friend.
The most recent issue of LinearAudio has a good article on tone-arm physics. What interested me most was that the subsonic resonant frequency of the arm and cartridge combination is easily excited AND puts inter modulation distortion on the fundamental. The author dug up a lot of material from decades ago. The conclusion -- damping is your friend.
This needed a bump!
The most recent issue of LinearAudio has a good article on tone-arm physics. What interested me most was that the subsonic resonant frequency of the arm and cartridge combination is easily excited AND puts inter modulation distortion on the fundamental. The author dug up a lot of material from decades ago. The conclusion -- damping is your friend.
The most recent issue of LinearAudio has a good article on tone-arm physics. What interested me most was that the subsonic resonant frequency of the arm and cartridge combination is easily excited AND puts inter modulation distortion on the fundamental. The author dug up a lot of material from decades ago. The conclusion -- damping is your friend.
Stealth MKIII and bumps....
hi guys,
thought I'd come back in and check things out as I haven't for some time.
Chris:looks very nice. Not what I would do, but different strokes for different folks...it appears that you are using the top bolt has a holder for an "upside down" pivot vs what I do. And the mass about the pivot (a deep cup?) can help with some lateral stability issues, but if carefully done the original style works just fine. There are other means to this end that I think are somewhat more elegant than a typical oversized "cup", although many manufacturers did just that with unipivot type arms.
jackinnj: As I don't have a subscription to Linear Audio I can't really comment. I'll PM you though...
Calvin: I am not against the use of carbon fibre. I just do not have the capability to ensure that any possible airborne particles do not make it into my lungs and thus caution all regarding the risk involved when working with carbon fibre. I also do not believe that it can provide a benefit as it may be much too light when using typical cartridge, mounting screws and wiring.
Now regarding damping:
Ff course there are a few ways that this can be accomplished. External mechanical, fluid and internal mechanical (such as the Funk Firm are but a few. For me when I calculated the effective mass of the tonearm, cartridge, mounting screws and wiring, I ended up with a Fs of something in the order of 8-11 Hz. As is I haven't tried any dampening method, nor any anti-skate. I can say that dampening may help, particularly if the mass of the arm or if the cartridge/mounting screws etc., are much heavier than mine. Now of course in those situations may help. Where minimal damping is required, carefully located O rungs can be added, or pure latex liquid theatrical paint, or even specifically applied heat-shrink tubing.
hi guys,
thought I'd come back in and check things out as I haven't for some time.
Chris:looks very nice. Not what I would do, but different strokes for different folks...it appears that you are using the top bolt has a holder for an "upside down" pivot vs what I do. And the mass about the pivot (a deep cup?) can help with some lateral stability issues, but if carefully done the original style works just fine. There are other means to this end that I think are somewhat more elegant than a typical oversized "cup", although many manufacturers did just that with unipivot type arms.
jackinnj: As I don't have a subscription to Linear Audio I can't really comment. I'll PM you though...
Calvin: I am not against the use of carbon fibre. I just do not have the capability to ensure that any possible airborne particles do not make it into my lungs and thus caution all regarding the risk involved when working with carbon fibre. I also do not believe that it can provide a benefit as it may be much too light when using typical cartridge, mounting screws and wiring.
Now regarding damping:
Ff course there are a few ways that this can be accomplished. External mechanical, fluid and internal mechanical (such as the Funk Firm are but a few. For me when I calculated the effective mass of the tonearm, cartridge, mounting screws and wiring, I ended up with a Fs of something in the order of 8-11 Hz. As is I haven't tried any dampening method, nor any anti-skate. I can say that dampening may help, particularly if the mass of the arm or if the cartridge/mounting screws etc., are much heavier than mine. Now of course in those situations may help. Where minimal damping is required, carefully located O rungs can be added, or pure latex liquid theatrical paint, or even specifically applied heat-shrink tubing.
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Comment on a comment
Hi Stew and Chris,
I did some thinking about de pivot, and came to the conclusion that using a bigger pivot housing, you'll be able to lower the center of gravity, thus creating a more stable arm. IMHO this works the best with and normal ( not upside down) pen nib pivot.
Grtz, Mark
Hi Stew and Chris,
I did some thinking about de pivot, and came to the conclusion that using a bigger pivot housing, you'll be able to lower the center of gravity, thus creating a more stable arm. IMHO this works the best with and normal ( not upside down) pen nib pivot.
Grtz, Mark
Hi Stew and Mark
No-I'm not using the pivot 'upside down. What is protruding from the top of the housing is the grub screw which has the cup-the pivot is attached to the arm pillar as with all my arms. I don't believe the design is adding or taking anything away from the performance compared to my original efforts. What I have been trying to do is improve on the aesthetics.
Regards
Chris
No-I'm not using the pivot 'upside down. What is protruding from the top of the housing is the grub screw which has the cup-the pivot is attached to the arm pillar as with all my arms. I don't believe the design is adding or taking anything away from the performance compared to my original efforts. What I have been trying to do is improve on the aesthetics.
Regards
Chris
hi guys...
Chris: OK so you've got an adjustable height pivot that moves the cup, which within limits is useful in designing and experimenting. with. When I designed the arm (even though it may look like there was no design involved) I conscientiously did a little math and paid attention to a few details that (to my way of thinking) results in something that approaches an inherently balanced tonearm. The manner in which the cartridge is mounted and the location and use of the "hanging" weight is not an accident.
Mark: Using a bigger housing to hold the cup ("right side" or nib pointing up from the stationary postup) is not the only way to accomplish this. As long as one ensures that the cup is above the radius (as seen laterally), the CofG is guaranteed to be lower than the pivot.
To this end I took great pains to set the pivot slightly higher than what I thought was ideal so that the CofG was slightly lower than the pivot. As the arm is then inherently stable. Think of it like a teeter-totter, but with one side slightly heavier than the other.So out of proper balance, but no far gone as to tilt the teeter-totter enough for it to approach the ground. It will then take almost no additional mass to move the slightly heavier side towards the ground. I actually looked at the mass I was using for a counter-weight and calculated where I might like to have the pivot , so as to allow me enough tracking force while still allowing space for the counter-weight. It wasn't all fluke
. If I were to use a lighter counter-weight, then I'd need to make the back end of the arm longer.
Chris: OK so you've got an adjustable height pivot that moves the cup, which within limits is useful in designing and experimenting. with. When I designed the arm (even though it may look like there was no design involved) I conscientiously did a little math and paid attention to a few details that (to my way of thinking) results in something that approaches an inherently balanced tonearm. The manner in which the cartridge is mounted and the location and use of the "hanging" weight is not an accident.
Mark: Using a bigger housing to hold the cup ("right side" or nib pointing up from the stationary postup) is not the only way to accomplish this. As long as one ensures that the cup is above the radius (as seen laterally), the CofG is guaranteed to be lower than the pivot.
To this end I took great pains to set the pivot slightly higher than what I thought was ideal so that the CofG was slightly lower than the pivot. As the arm is then inherently stable. Think of it like a teeter-totter, but with one side slightly heavier than the other.So out of proper balance, but no far gone as to tilt the teeter-totter enough for it to approach the ground. It will then take almost no additional mass to move the slightly heavier side towards the ground. I actually looked at the mass I was using for a counter-weight and calculated where I might like to have the pivot , so as to allow me enough tracking force while still allowing space for the counter-weight. It wasn't all fluke
. If I were to use a lighter counter-weight, then I'd need to make the back end of the arm longer.Hi Stew
Good to hear your thinking on this. You are correct about the ability to experiment with the pivot on my arm.In the configuration I have ended up with, I have achieved more stability than with my other arms-and from experience, more than with arms made by Hadcock, Opera Consonmance (I've been experimenting with their 12" unipivot) etc.I'm currently building a 10" with the grub screw not protruding from the top of the housing and it looks much neater.
As I'm writing this, you have triggered off another thought which I'll experiment with-ah 'Happy Days!!'
Regards
Chris
Good to hear your thinking on this. You are correct about the ability to experiment with the pivot on my arm.In the configuration I have ended up with, I have achieved more stability than with my other arms-and from experience, more than with arms made by Hadcock, Opera Consonmance (I've been experimenting with their 12" unipivot) etc.I'm currently building a 10" with the grub screw not protruding from the top of the housing and it looks much neater.
As I'm writing this, you have triggered off another thought which I'll experiment with-ah 'Happy Days!!'
Regards
Chris
some stories RE:Opera/Consonance and the inverted cup
Chris,
I had worked (a little) with Ian Grant regarding tonearms and turntables prior to his passing. The one (arm) that came with his prototype turntable (he never completed the project or brought the original design to market, it has been marketed as a new "Revolver" turntable in the UK) was pretty bad. The maker (I can't recall who it was but it was a Chinese OEM) had the basics correct, but the details were terrible. The potential was there, it just wasn't right. The arm used very heavy parts and simply looked “clunky”. They tried to design a high performance arm without understanding the design criteria.By comparison the 219 looks svelte and begs to be played. The turntable had flaws too, most notably the bearing and how it coupled to the platter. The platter and plinth are quite nice. The motors were/are nothing special, but they were quiet, Once the issues were taken care of, the tables seemed pretty good. In one instance the bearing was re-machined, in the other I stripped a motor from a DD turntable, gutted the innards and used just the bearing and screwed it to the sub-chassis.This turntable sounded quite excellent using a Rega RB300 and an Ortofon Turbo 3 MC cartridge. I have essentially 2 complete tables (less arms) here. They look wonderful. One issue is the sub chassis is made of MDF. Acrylic would be much better, but the chassis itself would require a complete revamp. The Revolver did receive some very positive reviews in the UK, but I am unsure if the bearing was/is the same as the one that I have here.. I am unsure if it remains in production or on offer for sale in the UK. I don't think any were brought into North America
I provided Ian with what I thought should be a recipe for a killer turntable/arm attainable for a good price. He had been speaking to Opera/Consonance about this. Their response was that they already made a similar turntable (who would have thunk it?), the Consonance Forbidden City Liu. At the time they only offered a typical gimbal bearing styled tonearm at a fairly high price. I suggested a simplified version, where “less is more”. I see now their "988" tonearm is a unipivot (it is not that different from the "219", but I can't say that they copied it in any way, but Ian had seen and heard the "219" several times and knew the details. Apparently Ian had samples of the /Consonance arm and table . I am unsure if Rachael continues with the turntables since Ian's passing.
The 219 does not require additional mass and if built in the same manner as I suggest will give what I feel is optimum performance. I understand that many uni-pivots use an oversized inverted "cup" (or at least a carrier for the female bearing) and that can allow for the pivot to be vertically higher than the centre of the arm tube. To me this is a needless complication. The only benefit is to increase the required rotational inertia to upset the arm. This can be more effectively done as per the "Longhorn" modification at or near the stylus tip. If something must be an engineered solution, it is usually best to resolve the issue at or nearest the problem.
Chris,
I had worked (a little) with Ian Grant regarding tonearms and turntables prior to his passing. The one (arm) that came with his prototype turntable (he never completed the project or brought the original design to market, it has been marketed as a new "Revolver" turntable in the UK) was pretty bad. The maker (I can't recall who it was but it was a Chinese OEM) had the basics correct, but the details were terrible. The potential was there, it just wasn't right. The arm used very heavy parts and simply looked “clunky”. They tried to design a high performance arm without understanding the design criteria.By comparison the 219 looks svelte and begs to be played. The turntable had flaws too, most notably the bearing and how it coupled to the platter. The platter and plinth are quite nice. The motors were/are nothing special, but they were quiet, Once the issues were taken care of, the tables seemed pretty good. In one instance the bearing was re-machined, in the other I stripped a motor from a DD turntable, gutted the innards and used just the bearing and screwed it to the sub-chassis.This turntable sounded quite excellent using a Rega RB300 and an Ortofon Turbo 3 MC cartridge. I have essentially 2 complete tables (less arms) here. They look wonderful. One issue is the sub chassis is made of MDF. Acrylic would be much better, but the chassis itself would require a complete revamp. The Revolver did receive some very positive reviews in the UK, but I am unsure if the bearing was/is the same as the one that I have here.. I am unsure if it remains in production or on offer for sale in the UK. I don't think any were brought into North America
I provided Ian with what I thought should be a recipe for a killer turntable/arm attainable for a good price. He had been speaking to Opera/Consonance about this. Their response was that they already made a similar turntable (who would have thunk it?), the Consonance Forbidden City Liu. At the time they only offered a typical gimbal bearing styled tonearm at a fairly high price. I suggested a simplified version, where “less is more”. I see now their "988" tonearm is a unipivot (it is not that different from the "219", but I can't say that they copied it in any way, but Ian had seen and heard the "219" several times and knew the details. Apparently Ian had samples of the /Consonance arm and table . I am unsure if Rachael continues with the turntables since Ian's passing.
The 219 does not require additional mass and if built in the same manner as I suggest will give what I feel is optimum performance. I understand that many uni-pivots use an oversized inverted "cup" (or at least a carrier for the female bearing) and that can allow for the pivot to be vertically higher than the centre of the arm tube. To me this is a needless complication. The only benefit is to increase the required rotational inertia to upset the arm. This can be more effectively done as per the "Longhorn" modification at or near the stylus tip. If something must be an engineered solution, it is usually best to resolve the issue at or nearest the problem.
Added antiskate to my 219:
I am thinking of refining the anti skate mechanism. I didn't use any science while making mine. The slots are cut at 5 mm intervals, the weight as you can see is from a bolt, hung on the thinnest fishing line I could get (not supple enough). In other words, the weight isn't calibrated.
Any idea how I can have precise calibrated weight when placing the string on slot number 'x'? What are the calculations involved? Spacing of slots? Length of string? Mass of the hanging weight?
Kindly advise. Thanks in advance.
The 219 does not require anti-skating, but a convenient azimuth adjust...
... would be nice.
Okay, if anti skate is required or wanted here's a thought. Usually anti-skate is approximately 1/10th of the tracking force. Most adjustable anti-skate mechanisms use this as a starting point.
Remember that anti-skate is a force and actually acts as torque. So:
T:= F X r [eqn1]
And
F= m ∙ a [eqn2]
Because we can't change [eqn2], that leaves [eqn1]. Keeping the mass constant, that leaves r. Increasing r will result in more anti-skating force, else the mass must be increased.
Your picture actually allows for an azimuth adjust, not anti-skating. I'm attaching a jpg that shows the scheme required.
Regarding string, just use good thread. I often use upholstery thread to good effect
... would be nice.
Okay, if anti skate is required or wanted here's a thought. Usually anti-skate is approximately 1/10th of the tracking force. Most adjustable anti-skate mechanisms use this as a starting point.
Remember that anti-skate is a force and actually acts as torque. So:
T:= F X r [eqn1]
And
F= m ∙ a [eqn2]
Because we can't change [eqn2], that leaves [eqn1]. Keeping the mass constant, that leaves r. Increasing r will result in more anti-skating force, else the mass must be increased.
Your picture actually allows for an azimuth adjust, not anti-skating. I'm attaching a jpg that shows the scheme required.
Regarding string, just use good thread. I often use upholstery thread to good effect
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how moving the string affects anti-skate
jls001,
Moving the string will increase or decrease the length of r. Increasing the mass, m will increase the value of F. But as vectors they don't "add" in the usual way, they follow "vector mathematics".
Anti-skating must be to a pure lateral pull in a uni-pivot such as the 219. If Gimbal bearings are use in a tonearm, then the "anti-skating arm" can be rigidly coupled to the arm in any lengthwise direction (compared to the arm tube). In a uni-pivot, the force must be applied laterally so as to not "twist" the arm towards the "anti-skate arm".
If you like I'll do a very quick sketch that might help you see this more clearly (if need be).
jls001,
Moving the string will increase or decrease the length of r. Increasing the mass, m will increase the value of F. But as vectors they don't "add" in the usual way, they follow "vector mathematics".
Anti-skating must be to a pure lateral pull in a uni-pivot such as the 219. If Gimbal bearings are use in a tonearm, then the "anti-skating arm" can be rigidly coupled to the arm in any lengthwise direction (compared to the arm tube). In a uni-pivot, the force must be applied laterally so as to not "twist" the arm towards the "anti-skate arm".
If you like I'll do a very quick sketch that might help you see this more clearly (if need be).
Hi Chris,
I used my arm which is a 12 incher without any anti skating arrangement, and it works. Recently I read a newsletter written by Mark Baker of Origin Live, which insisted that having anti skating is better than not having it even in longer arms. He gave some good arguments, and I guess I buy it. So I slapped on the agricultural-looking A.S. that you see now Do I hear an improvement? Honestly I can't say I have. But perhaps this is because I haven't got it right. Will try Stew's suggestion to pronounce if it brings improvement.
I used my arm which is a 12 incher without any anti skating arrangement, and it works. Recently I read a newsletter written by Mark Baker of Origin Live, which insisted that having anti skating is better than not having it even in longer arms. He gave some good arguments, and I guess I buy it. So I slapped on the agricultural-looking A.S. that you see now
Do I hear an improvement? Honestly I can't say I have. But perhaps this is because I haven't got it right. Will try Stew's suggestion to pronounce if it brings improvement.The thing about applying bias is that it really isn't an exact science and really a matter of trial and error. With a 12" arm the offset angle is lessened and the arm is therefore getting closer in accuracy of tracking to a parallel tracker. In all my 12" arms and above, I have never applied bias and, when using the HFS75 test record, there has always been secure tracking. I say forget about it whatever MB says-I don't listen to guys who slap a £6.00 transformer in a box and sell it for around £200.00 as an 'upgrade transformer!'
Regards
Chris
Regards
Chris
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