So there are these questions...
It's like seeing a power amplifier with 0.01 percent distortion, and another with the same power rating but at slightly higher cost and distortion (with of course the same harmonic spectrum generated so they are comparable) with 0.001 percent distortion. Some may ask "Few if anyone can actually HEAR 0.01 percent distortion, why spend more for something that offers an inaudible improvement?"
But I've read through the Modulus-86 (an amp claiming remarkably low distortion) threads and many others on DIYAudio and don't see anyone asking that sort of thing.
So what are we doing here? Perhaps trying to push the state of the art.
It appears we want to reduce the vibration created by a bearing as much as possible. This may not be the biggest problem in LP reproduction technology, but ...Hi,
So, this 11 years old thread is trying to tackle what problem exactly ?
Cheers,
It's like seeing a power amplifier with 0.01 percent distortion, and another with the same power rating but at slightly higher cost and distortion (with of course the same harmonic spectrum generated so they are comparable) with 0.001 percent distortion. Some may ask "Few if anyone can actually HEAR 0.01 percent distortion, why spend more for something that offers an inaudible improvement?"
But I've read through the Modulus-86 (an amp claiming remarkably low distortion) threads and many others on DIYAudio and don't see anyone asking that sort of thing.
So what are we doing here? Perhaps trying to push the state of the art.
Metal lathes can move at very low speed (as in cutting screw threads or helical gears), but a small vibration there isn't the problem it is in a turntable. Even a moderate variation in speed isn't a problem for a lathe, because the lathe chuck and cutting tool move together with gearing, and thus are always "in the right place" relative to each other.Frank, you cut right to the bone on this one.
I would simply ask, what unique problems does a TT present not seen/engineered around in other rotational machinery? The biggest one I can think of is the extremely low speed of operation.
I can nothing say about the technic. But i know that in Germany there runs one turntable with a platter bearing you are searching for: http://youtu.be/RFnYrzAecKk It was build by Rainer Horstmann from http://www.avdesignhaus.de
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Certainly not my intent to stifle innovation or be a wet blanket, but I'm wont to think in terms of solid, if not utterly excessive, engineering (e.g. Mod86, as referenced).
Like BenB, I went to precision CNC machinery first and then to turbomolecular pumps (turbines in general) as my first two places to look for innovation. Magnetic levitation bearings are commonly used in the latter since they last so much longer than fluid bearings (low friction/better alignment). They're also quieter, which is a nice bonus (although at 33 1/3 rpm versus, say 25,000 rpm...that advantage is seems lost). Direct drive would be my recommendation as well, and generally a light platter with a very good motion feedback system.
This thread has potential.
Like BenB, I went to precision CNC machinery first and then to turbomolecular pumps (turbines in general) as my first two places to look for innovation. Magnetic levitation bearings are commonly used in the latter since they last so much longer than fluid bearings (low friction/better alignment). They're also quieter, which is a nice bonus (although at 33 1/3 rpm versus, say 25,000 rpm...that advantage is seems lost). Direct drive would be my recommendation as well, and generally a light platter with a very good motion feedback system.
This thread has potential.
Hi,
Could have fooled me.
Floating the platter is the totally wrong approach.
Almost any TT or arm out there is a compromise of some sort or another.
I own and cherish a Anologue Audio TT made by the late Tom Fletcher whom I advised throughout his designs in a gentlemanly way for years.
160lbs platter and it's still not good enough for me. Why?
I can tell you why but will you really listen?
Cheers,
Could have fooled me.
Floating the platter is the totally wrong approach.
Almost any TT or arm out there is a compromise of some sort or another.
I own and cherish a Anologue Audio TT made by the late Tom Fletcher whom I advised throughout his designs in a gentlemanly way for years.
160lbs platter and it's still not good enough for me. Why?
I can tell you why but will you really listen?
Cheers,
Hi,
Could have fooled me.
Floating the platter is the totally wrong approach.
Almost any TT or arm out there is a compromise of some sort or another.
I own and cherish a Anologue Audio TT made by the late Tom Fletcher whom I advised throughout his designs in a gentlemanly way for years.
160lbs platter and it's still not good enough for me. Why?
I can tell you why but will you really listen?
Cheers,
"Advised" but did he ask for that advice and did he listen or had he already even been through those same ideas beforehand but still politely listened as if hearing the idea for the first time?
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If you load a magnetic bearing heavily so that the weight is just supported and the magnetic field highly compressed there's pretty much no reason for it to move in the vertical plane anyway, short of you have an elephant party in the same room.
I have a friend with a mag lev platter on a fully suspended deck, any vertical deflection during play is below our ability to detect. I suspect his use of 3K silicon oil in a close tolerance bearing is beneficial in this case.
I have a friend with a mag lev platter on a fully suspended deck, any vertical deflection during play is below our ability to detect. I suspect his use of 3K silicon oil in a close tolerance bearing is beneficial in this case.
Hi,
Excellent. But you don't need to use a floating platter to achieve that and that's also what I suggested to Tom Fletcher.
Tom's left us so he can no longer defend himself. He was a true gentleman though.
Here's what I suggested to him many years ago in a nutshell:
- Don't run the main bearing axle up to the spindle, separate both physically.
- Use a platter material that has a slightly higher mechanical impedance than vinyl as the top layer of the platter so perceived mass of vinyl record is increased when coupled to it.
- Etc., etc.....
With all due respect to Tom and I can assure you along with him the same engineering mistakes exist throughout quite an amazing amount of designs.
Simple details that make a world of difference. Especially at this level.
One reason that attracted me to Tom (other than his most charming character) was his understanding of tonearms. Uni-pivots in particular.
Which led me to assume that he would be able to implement the same principle to his TT designs.
I was mistaken as it turned out.
Cheers,
Excellent. But you don't need to use a floating platter to achieve that and that's also what I suggested to Tom Fletcher.
Tom's left us so he can no longer defend himself. He was a true gentleman though.
Here's what I suggested to him many years ago in a nutshell:
- Don't run the main bearing axle up to the spindle, separate both physically.
- Use a platter material that has a slightly higher mechanical impedance than vinyl as the top layer of the platter so perceived mass of vinyl record is increased when coupled to it.
- Etc., etc.....
With all due respect to Tom and I can assure you along with him the same engineering mistakes exist throughout quite an amazing amount of designs.
Simple details that make a world of difference. Especially at this level.
One reason that attracted me to Tom (other than his most charming character) was his understanding of tonearms. Uni-pivots in particular.
Which led me to assume that he would be able to implement the same principle to his TT designs.
I was mistaken as it turned out.
Cheers,
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Hi,
reviving an old thread it seems.....
planning for a floating platter- in water or oil
platter acrylic, say 4 kg
float hard polystyrene (roofmate) about 8 cm high- glued to platter
kitchen sink to hold the liquid- no drain
centering of platter/float by belts from motors/pulleys in Y config- which can be adjusted
speed at the edge at 33 rpm is 0,5m/sec (noise?)
please provide your comments and ideas!
Appreciate the help
Thx
Coolerooney
reviving an old thread it seems.....
planning for a floating platter- in water or oil
platter acrylic, say 4 kg
float hard polystyrene (roofmate) about 8 cm high- glued to platter
kitchen sink to hold the liquid- no drain
centering of platter/float by belts from motors/pulleys in Y config- which can be adjusted
speed at the edge at 33 rpm is 0,5m/sec (noise?)
please provide your comments and ideas!
Appreciate the help
Thx
Coolerooney
Have you folks seen this?
tigerpawaudio | Tranquility
Its not meant to float or maglev the platter but to ease off the spindle point off the thrust bearing by some degree. It have a screw ring to adjust the opposing magnet gap to suit the LP12. I've seen this and handled it up close (belonging to a friend) I'm sure this concept can be adapted if its reverse engineered and adapted to your own table. I wish I could do something like this and adapt it to my 20lb VPI platter with inverted bearing. I don't know where to source the magnet disc, possibly these are custom made and incorporated into their design.
tigerpawaudio | Tranquility
Its not meant to float or maglev the platter but to ease off the spindle point off the thrust bearing by some degree. It have a screw ring to adjust the opposing magnet gap to suit the LP12. I've seen this and handled it up close (belonging to a friend) I'm sure this concept can be adapted if its reverse engineered and adapted to your own table. I wish I could do something like this and adapt it to my 20lb VPI platter with inverted bearing. I don't know where to source the magnet disc, possibly these are custom made and incorporated into their design.
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