My DIY turntable had a VPI acrylic platter and Teres motor. The combo had small speed stability problem caused by not enough inertia for Teres speed controller. I managed to eliminate static buildup by covering acrylic with copper foil. The sound was good, but it wouldn’t be a true DIY turntable without home made platter. I came up with the following:
http://gallery.AudioAsylum.com/cgi/gi.mpl?u=21150&f=platter4.jpg
The platter was cast in one operation and consists of 3 layers:
3.5mm solid graphite
3.5mm carbon fiber/metal powder/epoxy composite with gradually increased density
54mm high density fiberglass/metal powder/epoxy composite.
I used fine, heavy powder, about 55%W, 40%Cu and 5% Pb. Lathing was a pain - my universal milling machine is too small for the job. The platter (without center weight and peripheral ring clamp) weighs 11 kg, most of it is supported by 2 neodymium ring magnets. The bearing had to be extended for the new thicker platter; the center of gravity is deliberately raised to bring it closer to bearing support point. The top magnet is set in resin ring which is set in steel ring for shielding (see pictures). The position of steel ring is adjustable to compensate for possible future weakening of magnets. The Teres speed controller works fine now. The shielding is not quite what I’ve expected. The needle of the compass placed on top of the platter bends downward. I need more listening time to comment on the sound.
Fill free to criticize and ask any questions.
Warning!!! Epoxy resin is toxic and allergenic; air born metal powder is toxic. Hardening process of thick composite may run out of control, do not do it indoors.
http://gallery.audioasylum.com/cgi/view.mpl?UserImages=21150&session=
Marek
The system
DIY turntable with Teres motor, DIY tone arms, Shure and Shelter carts
Cary PH302, Moth S2A3; DIY composite Lowther horns
DIY dedicated room; DIY balanced power supply etc.
http://gallery.AudioAsylum.com/cgi/gi.mpl?u=21150&f=platter4.jpg
The platter was cast in one operation and consists of 3 layers:
3.5mm solid graphite
3.5mm carbon fiber/metal powder/epoxy composite with gradually increased density
54mm high density fiberglass/metal powder/epoxy composite.
I used fine, heavy powder, about 55%W, 40%Cu and 5% Pb. Lathing was a pain - my universal milling machine is too small for the job. The platter (without center weight and peripheral ring clamp) weighs 11 kg, most of it is supported by 2 neodymium ring magnets. The bearing had to be extended for the new thicker platter; the center of gravity is deliberately raised to bring it closer to bearing support point. The top magnet is set in resin ring which is set in steel ring for shielding (see pictures). The position of steel ring is adjustable to compensate for possible future weakening of magnets. The Teres speed controller works fine now. The shielding is not quite what I’ve expected. The needle of the compass placed on top of the platter bends downward. I need more listening time to comment on the sound.
Fill free to criticize and ask any questions.
Warning!!! Epoxy resin is toxic and allergenic; air born metal powder is toxic. Hardening process of thick composite may run out of control, do not do it indoors.
http://gallery.audioasylum.com/cgi/view.mpl?UserImages=21150&session=
Marek
The system
DIY turntable with Teres motor, DIY tone arms, Shure and Shelter carts
Cary PH302, Moth S2A3; DIY composite Lowther horns
DIY dedicated room; DIY balanced power supply etc.
Hi Marek,
Nice job indeed! I like your idea of one-piece composite platter, it shall be more inert than multi-layred one, since you are getting rid of inter-layer deflections. Must be great deal of preparation work messing with all this stuff. I just wander how did you manage to distribute the platter mass evenly, especially within the variable density layer. And did you leave bare graphite surface or apply some protective coat on it?
I was also worried with the compass niedle behaviour placed on top of my magnetically levitating platter. It's been working hard for three months, no problem with the cart or unshielded tonearm wires so far...
Looking forward for your listening report. Must beat your previous acrylic platter hands down..
Cheers,
Michael
Nice job indeed! I like your idea of one-piece composite platter, it shall be more inert than multi-layred one, since you are getting rid of inter-layer deflections. Must be great deal of preparation work messing with all this stuff. I just wander how did you manage to distribute the platter mass evenly, especially within the variable density layer. And did you leave bare graphite surface or apply some protective coat on it?
I was also worried with the compass niedle behaviour placed on top of my magnetically levitating platter. It's been working hard for three months, no problem with the cart or unshielded tonearm wires so far...
Looking forward for your listening report. Must beat your previous acrylic platter hands down..
Cheers,
Michael
Thanks Michael,
As far as preparation, more time went into research and planning. All materials were ordered on Internet, and the form was made from MDF. I tested the epoxy for hardening and took the risk of throwing a few hundred dollars worth of material . I was very lucky: the metal powder in the mixture absorbed some heat during the hardening process and stopped it from overheating.
I made a progressive density layer to provide smooth transition from graphite to high density layer without sound waves reflections. The first thick carbon fiber blanket was layered on graphite plate with epoxy, the second with epoxy and powder. Some powder sedimented into the fibers. A thick, heavy mix of powder/epoxy/chopped fiberglass was poured on top of the second blanket. Again, some powder sedimented into the carbon fiber. The form was level so density should be fairly uniform. Because of sedimentation the top layer of cast (bottom of the platter) had less powder - I planned for that and milled it off. After lathing, I statically balanced the platter. Actually, it didn’t take much, it was not bad to start with.
The graphite is not coated, I washed it with acetone and it does not blacken napkins any more. Coating may change the sound and I do not know if it would be good or bad.
What cart do you have on your table MM or MC ? I’m afraid that cart may get magnetized or demagnetized or whatever.
Did you notice any weakening of platter’s magnets ?
Marek
As far as preparation, more time went into research and planning. All materials were ordered on Internet, and the form was made from MDF. I tested the epoxy for hardening and took the risk of throwing a few hundred dollars worth of material . I was very lucky: the metal powder in the mixture absorbed some heat during the hardening process and stopped it from overheating.
I made a progressive density layer to provide smooth transition from graphite to high density layer without sound waves reflections. The first thick carbon fiber blanket was layered on graphite plate with epoxy, the second with epoxy and powder. Some powder sedimented into the fibers. A thick, heavy mix of powder/epoxy/chopped fiberglass was poured on top of the second blanket. Again, some powder sedimented into the carbon fiber. The form was level so density should be fairly uniform. Because of sedimentation the top layer of cast (bottom of the platter) had less powder - I planned for that and milled it off. After lathing, I statically balanced the platter. Actually, it didn’t take much, it was not bad to start with.
The graphite is not coated, I washed it with acetone and it does not blacken napkins any more. Coating may change the sound and I do not know if it would be good or bad.
What cart do you have on your table MM or MC ? I’m afraid that cart may get magnetized or demagnetized or whatever.
Did you notice any weakening of platter’s magnets ?
Marek
Magnets wekening? To some degree, I would say; I feel it trying to lift my plate with fingers. So what? Initially about 3 kilos out of 33 total platter weight was left for the bearing ball to support. Now the load increased say to 4 kilos; still pretty low to bother, and I believe it's pretty much set. This is one of the hybrid bearing advantages above pure magnet levitation: you do not have to worry about constant platter heigth.
I have two MC carts on my TT: D102 and Ortofon SPU RN; no problem observed so far.
If I were you, I would probably consider to add some more mass underneath your platter, like aluminum ring with cavities filled with leadshot (?). Shouldn't cost a fortune. I believe additional rotational mass will not hurt.
Good luck with your project!
Michael
I have two MC carts on my TT: D102 and Ortofon SPU RN; no problem observed so far.
If I were you, I would probably consider to add some more mass underneath your platter, like aluminum ring with cavities filled with leadshot (?). Shouldn't cost a fortune. I believe additional rotational mass will not hurt.
Good luck with your project!
Michael
Thanks Michael,
Lead shots are a good idea but almost halve of my platter mass is distributed on the periphery increasing rotational mass adequately:
http://gallery.AudioAsylum.com/cgi/gi.mpl?u=21150&f=platter1.jpg
Also, I use heavy 13.5” stainless steel periphery ring.
Marek
Lead shots are a good idea but almost halve of my platter mass is distributed on the periphery increasing rotational mass adequately:
http://gallery.AudioAsylum.com/cgi/gi.mpl?u=21150&f=platter1.jpg
Also, I use heavy 13.5” stainless steel periphery ring.
Marek
Periphery ring
What is your experience with outer ring?
I was playing with this idea, but in the end I left it because of fear of damaging needle accidently. But I still have lot of records I cannot fix firmly to the platter surface with central reflex clamp.
Can you provide some details of your ring?
What is your experience with outer ring?
I was playing with this idea, but in the end I left it because of fear of damaging needle accidently. But I still have lot of records I cannot fix firmly to the platter surface with central reflex clamp.
Can you provide some details of your ring?
The ring is from VPI. It weighs over 2kg, diameter 343mm outside, 306mm (without a lip) inside, 15mm high. It has an inside lip 0.5mm thick 3.5mm wide which stays on top of the edge of LP, practically on the same level as LP. There are 4 velvet strips inside the ring that help a snug fit. It has two rubber bands on the outside which ads grip when you start the platter.
The ring flattens waives nicely especially those located close to the edge of LP, but it isn’t 100% effective. Even strait LPs benefit from the ring. The ring does not cover starting groove so damaging a needle is not a problem. Some LPs (about 1%) are too small for the ring, but VPI (and my own) platter has a stepped edge which stops the ring from falling down, so you can use it as peripheral mass. You need professional machine shop to make one.
Marek
The ring flattens waives nicely especially those located close to the edge of LP, but it isn’t 100% effective. Even strait LPs benefit from the ring. The ring does not cover starting groove so damaging a needle is not a problem. Some LPs (about 1%) are too small for the ring, but VPI (and my own) platter has a stepped edge which stops the ring from falling down, so you can use it as peripheral mass. You need professional machine shop to make one.
Marek
Originally, I used 114mm OD magnets. When installed 50mm below top of the platter, they created much stronger than acceptable field near the inner grooves. After experimenting with shield, I noticed that field from those neodymium magnets can easily saturate shielding materials and could also saturate the cartridge.
I stated before that magnetic shield was not quite what I expected, in fact, near the end of LP the sound changed enough to make me disassemble the platter and rebuild it with smaller magnets.
Restricted by dimensions of the bearing and platter, I could only use 56/41/6mm magnets. The horizontal distance from inner grooves increased by 29mm. Because I installed new magnets under the bearing, the vertical distance also increased - the upper magnet is 72mm from top of the platter. I made more effective double layer shield using high saturation magnet shielding material and aluminum rings. http://gallery.AudioAsylum.com/cgi/view.mpl?UserImages=21150&invite=
The new magnets and shield work nicely. However, I noticed that the platter wobbles slightly and has to be corrected on a professional lathe.
Waiting for out of stock magnets I made a major addition to acoustic treatment of my room, which improved the sound considerably, but I will never know the sound difference of the new platter alone.
Regards,
Marek
I stated before that magnetic shield was not quite what I expected, in fact, near the end of LP the sound changed enough to make me disassemble the platter and rebuild it with smaller magnets.
Restricted by dimensions of the bearing and platter, I could only use 56/41/6mm magnets. The horizontal distance from inner grooves increased by 29mm. Because I installed new magnets under the bearing, the vertical distance also increased - the upper magnet is 72mm from top of the platter. I made more effective double layer shield using high saturation magnet shielding material and aluminum rings. http://gallery.AudioAsylum.com/cgi/view.mpl?UserImages=21150&invite=
The new magnets and shield work nicely. However, I noticed that the platter wobbles slightly and has to be corrected on a professional lathe.
Waiting for out of stock magnets I made a major addition to acoustic treatment of my room, which improved the sound considerably, but I will never know the sound difference of the new platter alone.
Regards,
Marek
Magnet field shielding
Hi Marek,
Can you elaborate about your magnet shield design/materials?
To my limited knowledge, it is quite difficult to isolate magnets:
- exotic materials like Mu-metal are used,
- the shield shall form closed (or about closed) box around magnet.
How did you manage to address these issues?
How did you get the indication, the mag field is weakened?
I guess you are right about magnets screwing the sound when cart approaches inner tracks. This is probably the reason why I sometimes hear distortion on inner tracks, when my linear tracker is getting closer to the platter center (which oterwise does not make any sense). My magnets are a bit bigger than yours, and they are placed 95 mm below surface (which I thought is enough). But, the bearing spindle appeared to be made of ferromagnetic stainless steel, which became saturated very strongly with time, and it probably acts like trans core, driving magnetic flux along it. Looks like I have to replace it with non-magnetic material. But, I would like to add magnets shielding anyway.
Hi Marek,
Can you elaborate about your magnet shield design/materials?
To my limited knowledge, it is quite difficult to isolate magnets:
- exotic materials like Mu-metal are used,
- the shield shall form closed (or about closed) box around magnet.
How did you manage to address these issues?
How did you get the indication, the mag field is weakened?
I guess you are right about magnets screwing the sound when cart approaches inner tracks. This is probably the reason why I sometimes hear distortion on inner tracks, when my linear tracker is getting closer to the platter center (which oterwise does not make any sense). My magnets are a bit bigger than yours, and they are placed 95 mm below surface (which I thought is enough). But, the bearing spindle appeared to be made of ferromagnetic stainless steel, which became saturated very strongly with time, and it probably acts like trans core, driving magnetic flux along it. Looks like I have to replace it with non-magnetic material. But, I would like to add magnets shielding anyway.
Hi Michael,
Yes, it is difficult to shield magnets, especially two repulsing each other; I just weakened the field to the level I think and hope is safe.
For the shield, I bought MagnetShield Plate 36x15x0.015” (Cat#274-15) $39 from www.lessemf.com. I used multiple layers of the material separated by aluminum rings - you can see it in one picture. If you count from the outside, there is 1mm shield, 9mm Al, 2mm shield, 5mm Al and 7.5mm magnet. The outside layer covers side only, not the top. The inner layer forms a box, the side is 2mm the top is 3mm thick. The inner shield is separated from magnet by 5mm of aluminum. I cut a 1” hole for 0.5” spindle. The shield covers both magnets but not from the bottom. There is one additional (0.015”) horizontal shield under the platter, above strobe ring: a 9”OD/ 3.5”ID ring. It is separated by vertical distance of 10mm from the side shield. This ring is located about 4cm from top of the platter - you do not want Mu metal close to the cart.
To determine the strength of the field I placed needle compass on top of the platter - at the outside edge of the platter the needle turns towards the center but does not bend down. About 5cm from the center the needle bends down but not rapidly. On my first design the needle bent down like crazy 8cm from the center.
My bearing spindle is ferromagnetic too, but it ends about 20mm below LP. I have no shield between inside of magnets and the spindle.
I do not post any drawings as my design is compromised by restricted dimensions and parts I used.
Yes, it is difficult to shield magnets, especially two repulsing each other; I just weakened the field to the level I think and hope is safe.
For the shield, I bought MagnetShield Plate 36x15x0.015” (Cat#274-15) $39 from www.lessemf.com. I used multiple layers of the material separated by aluminum rings - you can see it in one picture. If you count from the outside, there is 1mm shield, 9mm Al, 2mm shield, 5mm Al and 7.5mm magnet. The outside layer covers side only, not the top. The inner layer forms a box, the side is 2mm the top is 3mm thick. The inner shield is separated from magnet by 5mm of aluminum. I cut a 1” hole for 0.5” spindle. The shield covers both magnets but not from the bottom. There is one additional (0.015”) horizontal shield under the platter, above strobe ring: a 9”OD/ 3.5”ID ring. It is separated by vertical distance of 10mm from the side shield. This ring is located about 4cm from top of the platter - you do not want Mu metal close to the cart.
To determine the strength of the field I placed needle compass on top of the platter - at the outside edge of the platter the needle turns towards the center but does not bend down. About 5cm from the center the needle bends down but not rapidly. On my first design the needle bent down like crazy 8cm from the center.
My bearing spindle is ferromagnetic too, but it ends about 20mm below LP. I have no shield between inside of magnets and the spindle.
I do not post any drawings as my design is compromised by restricted dimensions and parts I used.
marekst said:
When I was seeking info on shielding my magnetic bearing design I spoke with a rep at lessemf.com. He was oblivious as to what I was talking about and basically said none of his products would "shield" the magnetic field at all. I then contacted unitednuclear.com and someone there actually knew something about the magnetic field principle. He basically summed it up for me by saying that if you can come up with a substance that actually shields magnetics, you will become a millionaire. There is no such substance. Mu-metal and other so called shields only REDIRECT the field, that's it. The best way to minimize the field is with DISTANCE. IOW, get the magnets as far away from the critical area as possible.
My bearing completely levitates the 36 pound platter, no thrust bearing at all is used. There is absolutely no rocking or up & down motion of the platter while spinning as proven by a dial indicator positioned at the outer edge of the platter under torque. It could be because the platter is very heavy and the repelling magnetic force generated is approx. 100 pounds. I don't know but the actual proof is in playing records and it performs very well.
Your platter building approach is to be commended, very nice job!
RE the magnetic bearing. I think it is in your best interest to completely levitate the bearing rather than simply relieving pressure. You've already commited yourself to the project, why not go all the way?
Thanks Addict,
“The best way to minimize the field is with DISTANCE”
-sure, if you have it.
I did not know if the idea of home made composite platter would work at all so I used a bearing I had on hand. As a consequence, the distance is limited. In the second design I did what I could to save the project. I am against operating magnetic cartridge in strong magnetic field; I can hear the difference, not to mention I can not effort to damage the cart.
“Mu-metal and other so called shields only REDIRECT the field, that’s it”
Precisely! Redirecting was exactly what I had to do, and that’s what I did. I redirected the strong field away from critical area. Finding a substance that would “eat” magnetic field is a different subject.
I did partial magnetic levitation because the weight of the new platter would damage the bearing. With the original, much lighter platter the bearing was quiet.
As far as going all the way, I went far too far with my vinyl project already.
I am not a vinyl freak. Two years ago I added a turntable to my system because I could get near mint classical LPs for less than a dollar. I was reluctant to invest more into digital because parts to repair CD players are not available. Once I got into vinyl I had to build a turntable and tonearms, I am a DIY addict. Oh, well….
Marek
“The best way to minimize the field is with DISTANCE”
-sure, if you have it.
I did not know if the idea of home made composite platter would work at all so I used a bearing I had on hand. As a consequence, the distance is limited. In the second design I did what I could to save the project. I am against operating magnetic cartridge in strong magnetic field; I can hear the difference, not to mention I can not effort to damage the cart.
“Mu-metal and other so called shields only REDIRECT the field, that’s it”
Precisely! Redirecting was exactly what I had to do, and that’s what I did. I redirected the strong field away from critical area. Finding a substance that would “eat” magnetic field is a different subject.
I did partial magnetic levitation because the weight of the new platter would damage the bearing. With the original, much lighter platter the bearing was quiet.
As far as going all the way, I went far too far with my vinyl project already.
I am not a vinyl freak. Two years ago I added a turntable to my system because I could get near mint classical LPs for less than a dollar. I was reluctant to invest more into digital because parts to repair CD players are not available. Once I got into vinyl I had to build a turntable and tonearms, I am a DIY addict. Oh, well….
Marek
marekst said:
You are to be commended for your ability in building well thought out turntable projects. I see a lot DIY'ers give up with projects when the going gets tough. I too have been guilty of going too far, LOL, however it's worth it most of the time when everything is completed, but then, is it ever completed? 😉
platter questions
I, too, find this platter construction interesting. I am more interested in the platter construction and material choices than I am regarding the issues related to the magnetic interferences. The idea of having variable density layers seems like it would solve a variety of resonance issues.
A few questions for marekst:
1) How/why did you arrive at your material choices (Graphite, Tungsten, Copper, Lead, Fiberglass)?
2) How did you ensure that the densities were evenly applied (i.e. that the platter doesn't come out unevenly balanced)?
3) Where did you buy the various metal powders?
4) How does it sound?
5) If there's anything you'd do differently....?
Thanks in advance,
Chris
I, too, find this platter construction interesting. I am more interested in the platter construction and material choices than I am regarding the issues related to the magnetic interferences. The idea of having variable density layers seems like it would solve a variety of resonance issues.
A few questions for marekst:
1) How/why did you arrive at your material choices (Graphite, Tungsten, Copper, Lead, Fiberglass)?
2) How did you ensure that the densities were evenly applied (i.e. that the platter doesn't come out unevenly balanced)?
3) Where did you buy the various metal powders?
4) How does it sound?
5) If there's anything you'd do differently....?
Thanks in advance,
Chris
Hi Chris, sorry for a delayed answer, I was away.
1) I have chosen Graphite as it bonds very well with my composite and as you may know it is used on some of the best platters.
Metal powder composite is the material I developed and used a couple of years ago to build my horn speakers. When searching for 200lb of Lead powder I was lucky to find a Tungsten powder mixed (contaminated) with Copper and Lead priced at $1 a pound. I bought the same kind of powder for the platter this spring but the price was 5 times higher. I had left over chopped fiberglass and I used it to fortify the composite.
2) I mixed it thoroughly, the form was level and I balanced the platter after machining.
3) As I stated before, I bought a mixed powder. Various powders of pure metals would be too expensive. The source was www.tungstenheavypowder.com San Diego, CA. The name of the mixture is “bargain powder”; it was available but it was not listed on product list.
4) I was away for a couple of months and had no chance to listen to the platter or to deal with the problems. On short listening, in my excessively sensitive system, it sounded crispier but nosier than acrylic. Summer time is bad for sound evaluation; neighbors ACs disturb lines and air. Additionally, after changing the acoustics of the room I have to run my phono and amp a notch higher which makes tube noise audible. What I am trying to say, is: I still do not know how it sounds.
5) I would use chopped carbon fibers not fiberglass. Fiberglass made milling very difficult!!!
I would go to a professional machine shop for final machining.
I would use longer bearing and make the platter taller to keep magnets further from carts.
And finally, I wouldn’t do it at all, it’s been a total pain in the neck. However, the metal powder composite worked extremely well in my speakers which are out of this world…
Marek
1) I have chosen Graphite as it bonds very well with my composite and as you may know it is used on some of the best platters.
Metal powder composite is the material I developed and used a couple of years ago to build my horn speakers. When searching for 200lb of Lead powder I was lucky to find a Tungsten powder mixed (contaminated) with Copper and Lead priced at $1 a pound. I bought the same kind of powder for the platter this spring but the price was 5 times higher. I had left over chopped fiberglass and I used it to fortify the composite.
2) I mixed it thoroughly, the form was level and I balanced the platter after machining.
3) As I stated before, I bought a mixed powder. Various powders of pure metals would be too expensive. The source was www.tungstenheavypowder.com San Diego, CA. The name of the mixture is “bargain powder”; it was available but it was not listed on product list.
4) I was away for a couple of months and had no chance to listen to the platter or to deal with the problems. On short listening, in my excessively sensitive system, it sounded crispier but nosier than acrylic. Summer time is bad for sound evaluation; neighbors ACs disturb lines and air. Additionally, after changing the acoustics of the room I have to run my phono and amp a notch higher which makes tube noise audible. What I am trying to say, is: I still do not know how it sounds.
5) I would use chopped carbon fibers not fiberglass. Fiberglass made milling very difficult!!!
I would go to a professional machine shop for final machining.
I would use longer bearing and make the platter taller to keep magnets further from carts.
And finally, I wouldn’t do it at all, it’s been a total pain in the neck. However, the metal powder composite worked extremely well in my speakers which are out of this world…
Marek
Thanks for the candid response. I'll be interested in hearing from you if/when you try tweaking it in anyway.
Thanks again,
Chris
Thanks again,
Chris
Project terminated!
Due to lack of funds for machine shop services and uncertain outcome I ditched the composite platter and returned to acrylic with conventional bearing.
One of the reasons I made a heavy composite platter was speed instability. I solved that problem by eliminating crooked belt that was supplied with the motor. I tried DIY belts made from holographic mylar, than a VCR tape but contrary to some positive reports I found both tapes unsuitable for the application. At the end I used high quality ½” leader tape spliced at an angle to reduce thumping. It works well, but it looks awful - ugly pink. Teres motor has a tendency to move around. To stabilize it, I made a wood enclosure filled with lead, which I mounted on spiked aluminum platform for easy leveling and motor distance adjustment.
Besides eliminating powerful ring magnets, I shielded the reference cartridge from 4 small magnets of the second tonearm and thus solved the problem of undesirable magnetic field.
To fill up the hole in the plinth after experimenting with composite platter I used lead/aluminum ring coupled to wood with DIY acoustic paste.
I don’t use copper foil on top of the acrylic platter any more, just on the side.
http://gallery.audioasylum.com/cgi/view.mpl?UserImages=21150&invite=
The new setup works well and thank God for that. My analog journey totally depleted my funds and my DIY energy, not to mention my low tolerance for high-end audio rip-offs.
Now I’m going to just listen to music, grow organic veggies and to relax for a while. I am stuck with two sets of ring magnets – I’ll see if they can help with growing cucumbers… - maybe some kind of enlargement machine will come out of it. LOL
Marek
Due to lack of funds for machine shop services and uncertain outcome I ditched the composite platter and returned to acrylic with conventional bearing.
One of the reasons I made a heavy composite platter was speed instability. I solved that problem by eliminating crooked belt that was supplied with the motor. I tried DIY belts made from holographic mylar, than a VCR tape but contrary to some positive reports I found both tapes unsuitable for the application. At the end I used high quality ½” leader tape spliced at an angle to reduce thumping. It works well, but it looks awful - ugly pink. Teres motor has a tendency to move around. To stabilize it, I made a wood enclosure filled with lead, which I mounted on spiked aluminum platform for easy leveling and motor distance adjustment.
Besides eliminating powerful ring magnets, I shielded the reference cartridge from 4 small magnets of the second tonearm and thus solved the problem of undesirable magnetic field.
To fill up the hole in the plinth after experimenting with composite platter I used lead/aluminum ring coupled to wood with DIY acoustic paste.
I don’t use copper foil on top of the acrylic platter any more, just on the side.
http://gallery.audioasylum.com/cgi/view.mpl?UserImages=21150&invite=
The new setup works well and thank God for that. My analog journey totally depleted my funds and my DIY energy, not to mention my low tolerance for high-end audio rip-offs.
Now I’m going to just listen to music, grow organic veggies and to relax for a while. I am stuck with two sets of ring magnets – I’ll see if they can help with growing cucumbers… - maybe some kind of enlargement machine will come out of it. LOL
Marek
Sorry to bother you again but I want to clarify something about motor leveling.
When both the motor and the platter are leveled, the belt travels down my Teres pulley very slowly (about 1mm per 10 LPs). Increasing belt tension doesn’t help; the sound gets worse and the wear of the bearings increases.
Instead of leveling the motor, I adjust it in such a way, that the axis of the motor leans very slightly towards the leveled platter. This way strait belt works fine without much tension.
Marek
When both the motor and the platter are leveled, the belt travels down my Teres pulley very slowly (about 1mm per 10 LPs). Increasing belt tension doesn’t help; the sound gets worse and the wear of the bearings increases.
Instead of leveling the motor, I adjust it in such a way, that the axis of the motor leans very slightly towards the leveled platter. This way strait belt works fine without much tension.
Marek
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