The Kronos turntable is a bit of an odd beast. I've never heard one, or even seen one in the flesh, but have heard very good things about the sound quality. The whole point of having two counter-rotating is to cancel out sub-chassis "shimmy" . The Kronos is a suspended sub-chassis belt drive turntable. On a normal single platter deck as the platter rotates you have a tension in the belt that is counteracted by the bearings friction. This belt tension pulls the sub-chassis causing it to twist on the suspension, a torque reaction. The sub-chassis doesn't just twist so far then stop. The belt tension sets up an oscillation in the sub-chassis, similar to a flag flapping in a constant breeze. The normal way of countering this is to heavily damp the suspension. Unfortunately this diminishes the effectiveness of the suspension at isolation from the outside world, the one thing it's designed to do. By having two tensions acting in opposition the idea is that they cancel out. This seems to work.
There are a couple of other ways that this shimmy can be reduced or eliminated without resorting to damping the decks suspension. By reducing the amount of friction in the main bearing the torque reaction is also reduced. The most effective way of eliminating the torque reaction is to mount the motor on the sub-chassis. As the platter and drive system now form a closed system they are independent of the suspension and have no effect on it. Both of these approaches are a lot simpler than the Kronos approach.
I would expect that a turntable of the calibre, and price, of the Kronos to have absolutely no visible runout.
Niffy
There are a couple of other ways that this shimmy can be reduced or eliminated without resorting to damping the decks suspension. By reducing the amount of friction in the main bearing the torque reaction is also reduced. The most effective way of eliminating the torque reaction is to mount the motor on the sub-chassis. As the platter and drive system now form a closed system they are independent of the suspension and have no effect on it. Both of these approaches are a lot simpler than the Kronos approach.
I would expect that a turntable of the calibre, and price, of the Kronos to have absolutely no visible runout.
Niffy
I would expect that a turntable of the calibre, and price, of the Kronos to have absolutely no visible runout.
Maybe available as optional, with a small surcharge: but consider that you'll get at least a double bearing noise for free.
carlo
Despite the age I still seem to remember funnier ways of throwing one's money
Maybe available as optional, with a small surcharge: but consider that you'll get at least a double bearing noise for free.
carlo
Despite the age I still seem to remember funnier ways of throwing one's money
Wobble parade
most beloved by DJs and Scratchers (that's why)
YouTube
YouTube
YouTube
YouTube
YouTube
cheap, and not so cheap
https://www.youtube.com/watch?v=JsijtccUkFg
https://www.youtube.com/watch?v=xJw5b0z6hAA
https://www.youtube.com/watch?v=m7ttCMhuTqg
https://www.youtube.com/watch?v=kdQ2NnLqjoo
https://www.youtube.com/watch?v=OL9jR9_-MXg
https://www.youtube.com/watch?v=x1qJNXDJm9c
https://www.youtube.com/watch?v=Iv46rdg5-E4
https://www.youtube.com/watch?v=B7NHxwk8HxA
https://www.youtube.com/watch?v=hzrW0Y-cpM0
https://www.youtube.com/watch?v=jIy2JvMNyd4
https://www.youtube.com/watch?v=cYyZCeXlfVg
https://www.youtube.com/watch?v=F57ig7rKjYQ
https://www.youtube.com/watch?v=WrsMNjZKi_A
https://www.youtube.com/watch?v=hY_ghzeiTNI
https://www.youtube.com/watch?v=CHPQ7iyByG
There seems to be plenty of space for us diyers...
carlo
mumbling - the platter wobble behaves exactly like the disk warp (while runout and off-balance = eccentricity). It is only more sneaky to be heard (with low mass TA) than a warp because the variation is usually slower.
1mm disk warp is quite unlistenable (but unavoidable, sometimes). 1mm of wobble is simply unacceptable (since avoidable with appropriate manufacturing and assembly).
Warps&wobble love each other, multiplying
most beloved by DJs and Scratchers (that's why)
YouTube
YouTube
YouTube
YouTube
YouTube
cheap, and not so cheap
https://www.youtube.com/watch?v=JsijtccUkFg
https://www.youtube.com/watch?v=xJw5b0z6hAA
https://www.youtube.com/watch?v=m7ttCMhuTqg
https://www.youtube.com/watch?v=kdQ2NnLqjoo
https://www.youtube.com/watch?v=OL9jR9_-MXg
https://www.youtube.com/watch?v=x1qJNXDJm9c
https://www.youtube.com/watch?v=Iv46rdg5-E4
https://www.youtube.com/watch?v=B7NHxwk8HxA
https://www.youtube.com/watch?v=hzrW0Y-cpM0
https://www.youtube.com/watch?v=jIy2JvMNyd4
https://www.youtube.com/watch?v=cYyZCeXlfVg
https://www.youtube.com/watch?v=F57ig7rKjYQ
https://www.youtube.com/watch?v=WrsMNjZKi_A
https://www.youtube.com/watch?v=hY_ghzeiTNI
https://www.youtube.com/watch?v=CHPQ7iyByG
There seems to be plenty of space for us diyers...
carlo
mumbling - the platter wobble behaves exactly like the disk warp (while runout and off-balance = eccentricity). It is only more sneaky to be heard (with low mass TA) than a warp because the variation is usually slower.
1mm disk warp is quite unlistenable (but unavoidable, sometimes). 1mm of wobble is simply unacceptable (since avoidable with appropriate manufacturing and assembly).
Warps&wobble love each other, multiplying
@Niffy
Hi, I am really curious how you have managed to do all the precise machining for your table with no lathe or milling machine. Ive built all the rest of my stuff with a table saw, router, and assorted hand tools, but a platter seems really difficult.
Even with your no-sleeve hack, how did you machine an acceptably flat surface for the top, perpendicular sides, and a perfectly centered dimple on the underside...router, sleds, jigs ??
Also, when you are lowering a platter with no bearing sleeve, how do you meet the tiny ball with your tiny dimple ?
Anyways, thank you for all the ideas and designs you have shared, its given me a couple really cool projects to work towards
Hi, I am really curious how you have managed to do all the precise machining for your table with no lathe or milling machine. Ive built all the rest of my stuff with a table saw, router, and assorted hand tools, but a platter seems really difficult.
Even with your no-sleeve hack, how did you machine an acceptably flat surface for the top, perpendicular sides, and a perfectly centered dimple on the underside...router, sleds, jigs ??
Also, when you are lowering a platter with no bearing sleeve, how do you meet the tiny ball with your tiny dimple ?
Anyways, thank you for all the ideas and designs you have shared, its given me a couple really cool projects to work towards
Hi ppap64,
Almost every component of my turntable had a jig, template or both used in its production. I probably spend as much time making jigs and tools as I do the components themselves. As I tend to only make one or two of each component the materials used for the template or jig are recycled into my scraps bin for making the next jig or component.
As you ask about the production of the platter I'll describe its production in detail. Unfortunately I don't have any photos of the jigs used and the materials used have mainly be reused. The platter consists of a solid 300mm diameter, 40mm thick main platter with a 111mm diameter, 25mm thick sub-platter. The bearing/lower part of Reflex clamp sits in a 60mm diameter, 3mm deep recess in the top of the main platter.
The platter was cut from a 350mm square block of acrylic using a router. First I had to drill a 12mm diameter hole in the centre of the block. I couldn't use my pillar drill as its reach was too small. I built a jig that had two aluminium plates separated by 50mm. Each had a hole with a 12mm bush in it. I adjusted the alignment of the bushes so that a rod passed through both would be exactly at 90° to the base plate. I used this as a drill guide using a 12mm drill bit in a hand held drill to make the hole in the centre of the block.
The router jig consisted of two components. The upper part was the actually the vertical drilling rig repurposed. The base plate of this jig had an attachment for my router set so that it would cut a disk just over 300mm in diameter. The two bushes fitted over a 12mm steel shafts that extended up from the lower part of the rig. Again this shafts was made adjustable so that it could be made absolutely vertical. The base of the jig was made from 18mm marine plywood. An M5 hole was tapped in each corner of the acrylic block, in the offcut portion, to allow the workpiece to be firmly bolted to the jig. Having the two bushes vertically separated by 50mm as well as the wide base of the router jig insured that the router remained perfectly aligned. The rebate for the bearing used a shorter shafts and just a 12mm hole in the base of the router jig. I now had a 300mm+ disk with a 12mm hole and rebate for the bearing. A similar but simpler vertical drilling jig was used to drill the holes for the bolts that would hold the bearing and sub-platter. If I recall correctly I actually drilled these before I cut the platter with the router.
I attached the bearing plate into its rebate at this point and then placed this assembled onto the main bearing shafts, which had an early prototype bearing fitted at the time. By adding and moving a blob of blutak around I could balance the platter on the bearing so the top surface ran flat and true, measured with another jig. I could then check the vertical edge of the platter for trueness relative to the bearing. I marked the high points then over the period of several days using progressively finer wet and dry paper hand sanded the edge of the platter until it also ran true.
The sub-platter was produced in a similar manner. The bolt holes that hold the two parts of the platter together are slightly oversized to allow for fine alignment. I initially sanded the edge of the sub-platter smooth then fitted it to the main platter. I then balanced the whole, with blutak, so the upper surface of the platter ran true. I then measured the direction and magnitude by which the sub-platter was misaligned. By clamping blocks of wood against the edges of the sub-platter and the use of shims I could loosen the bolts then shift the sub-platter by small amounts in exactly the direction I wanted. I was actually using cigarette papers as my shims for final alignment. I didn't stop there. I could still detect slight variations in the trueness of the edge of the sub-platter. These were due to it being not perfectly circular. So again I measured for high spots and hand sanded until the edge ran perfectly true.
Even though the surface of the acrylic used to make the platter was very flat it did vary very slightly in thickness across its width. Even though everything ran true this caused the platter to be slightly out of balance. I had anticipated this and had made the sub-platter with six M10 holes positioned at equidistant. By inserting different length flat-ended grub screws into these holes I balanced the platter perfectly. The ball and thrust pad used to this point were discarded as they would have been contaminated by all the sanding. Before I attached the separate parts of the platter together I broke the surfaces with 400grit paper tangentially to give a frosted appearance. This was purely asthetic as I personally don't like the look of totally transparent platters.
The main bearing shafts is 10mm in diameter and the hole through the platter is 12mm so there is only a 1mm clearance. When dropping the platter onto the bearing it pretty much automatically aligns and has never really been a problem.
As I said earlier most of the components of the deck were built using jigs and templates. Due to the precision required the platter was a bit more involved than most. The construction of the plinth was probably the most labour intensive.
Niffy
Almost every component of my turntable had a jig, template or both used in its production. I probably spend as much time making jigs and tools as I do the components themselves. As I tend to only make one or two of each component the materials used for the template or jig are recycled into my scraps bin for making the next jig or component.
As you ask about the production of the platter I'll describe its production in detail. Unfortunately I don't have any photos of the jigs used and the materials used have mainly be reused. The platter consists of a solid 300mm diameter, 40mm thick main platter with a 111mm diameter, 25mm thick sub-platter. The bearing/lower part of Reflex clamp sits in a 60mm diameter, 3mm deep recess in the top of the main platter.
The platter was cut from a 350mm square block of acrylic using a router. First I had to drill a 12mm diameter hole in the centre of the block. I couldn't use my pillar drill as its reach was too small. I built a jig that had two aluminium plates separated by 50mm. Each had a hole with a 12mm bush in it. I adjusted the alignment of the bushes so that a rod passed through both would be exactly at 90° to the base plate. I used this as a drill guide using a 12mm drill bit in a hand held drill to make the hole in the centre of the block.
The router jig consisted of two components. The upper part was the actually the vertical drilling rig repurposed. The base plate of this jig had an attachment for my router set so that it would cut a disk just over 300mm in diameter. The two bushes fitted over a 12mm steel shafts that extended up from the lower part of the rig. Again this shafts was made adjustable so that it could be made absolutely vertical. The base of the jig was made from 18mm marine plywood. An M5 hole was tapped in each corner of the acrylic block, in the offcut portion, to allow the workpiece to be firmly bolted to the jig. Having the two bushes vertically separated by 50mm as well as the wide base of the router jig insured that the router remained perfectly aligned. The rebate for the bearing used a shorter shafts and just a 12mm hole in the base of the router jig. I now had a 300mm+ disk with a 12mm hole and rebate for the bearing. A similar but simpler vertical drilling jig was used to drill the holes for the bolts that would hold the bearing and sub-platter. If I recall correctly I actually drilled these before I cut the platter with the router.
I attached the bearing plate into its rebate at this point and then placed this assembled onto the main bearing shafts, which had an early prototype bearing fitted at the time. By adding and moving a blob of blutak around I could balance the platter on the bearing so the top surface ran flat and true, measured with another jig. I could then check the vertical edge of the platter for trueness relative to the bearing. I marked the high points then over the period of several days using progressively finer wet and dry paper hand sanded the edge of the platter until it also ran true.
The sub-platter was produced in a similar manner. The bolt holes that hold the two parts of the platter together are slightly oversized to allow for fine alignment. I initially sanded the edge of the sub-platter smooth then fitted it to the main platter. I then balanced the whole, with blutak, so the upper surface of the platter ran true. I then measured the direction and magnitude by which the sub-platter was misaligned. By clamping blocks of wood against the edges of the sub-platter and the use of shims I could loosen the bolts then shift the sub-platter by small amounts in exactly the direction I wanted. I was actually using cigarette papers as my shims for final alignment. I didn't stop there. I could still detect slight variations in the trueness of the edge of the sub-platter. These were due to it being not perfectly circular. So again I measured for high spots and hand sanded until the edge ran perfectly true.
Even though the surface of the acrylic used to make the platter was very flat it did vary very slightly in thickness across its width. Even though everything ran true this caused the platter to be slightly out of balance. I had anticipated this and had made the sub-platter with six M10 holes positioned at equidistant. By inserting different length flat-ended grub screws into these holes I balanced the platter perfectly. The ball and thrust pad used to this point were discarded as they would have been contaminated by all the sanding. Before I attached the separate parts of the platter together I broke the surfaces with 400grit paper tangentially to give a frosted appearance. This was purely asthetic as I personally don't like the look of totally transparent platters.
The main bearing shafts is 10mm in diameter and the hole through the platter is 12mm so there is only a 1mm clearance. When dropping the platter onto the bearing it pretty much automatically aligns and has never really been a problem.
As I said earlier most of the components of the deck were built using jigs and templates. Due to the precision required the platter was a bit more involved than most. The construction of the plinth was probably the most labour intensive.
Niffy
My experiments with belts and idlers has continued. I tried using 2mm round section belts but the clearance between the idler mounting bracket and sub-platter was not great enough and caused the belts to foul. Also the belt did not seem flexible enough and didn't bend neatly around the motor. This would suggest that hysteresis losses would be rather high. Looks like I'll be sticking with the 1.5mm belts for now.
I was running the idlers with the pin bearings as these seemed to give a slightly more dynamic immediate sound. Having lived with them for a while I'm finding that the greater dynamics is actually more a case of greater hardness to the sound. This is probably down to these bearings being noisier than the Teflon version. I've reworked the Teflon/delrin bushes and refitted them. They are noteably quieter than the pin bearings and the hardness has been alleviated. The sound is smoother now. It still has a better sense of pace and timing than with the single belt. I also think that low level detail is better portrayed. All of these differences are very subtle, nothing transformative. I does show how relatively quick comparisons can be misleading. I was seduced by what appeared to be greater dynamics.
I was running the idlers with the pin bearings as these seemed to give a slightly more dynamic immediate sound. Having lived with them for a while I'm finding that the greater dynamics is actually more a case of greater hardness to the sound. This is probably down to these bearings being noisier than the Teflon version. I've reworked the Teflon/delrin bushes and refitted them. They are noteably quieter than the pin bearings and the hardness has been alleviated. The sound is smoother now. It still has a better sense of pace and timing than with the single belt. I also think that low level detail is better portrayed. All of these differences are very subtle, nothing transformative. I does show how relatively quick comparisons can be misleading. I was seduced by what appeared to be greater dynamics.
ppap64,
Judicious use precision jigs, tool skill, and thinking outside the box goes a long way to making a precision product. If you think making precision turntable parts is difficult, try to explain how in the 1700's, a mechanical doll was made that can sign a piece of paper !!!
mechanical doll with cams that can draw a signature - Google Search
Judicious use precision jigs, tool skill, and thinking outside the box goes a long way to making a precision product. If you think making precision turntable parts is difficult, try to explain how in the 1700's, a mechanical doll was made that can sign a piece of paper !!!
mechanical doll with cams that can draw a signature - Google Search
nocdplz,
I have also noted the wobble in many turntable platters over the years. It was not my intention to just criticize the Kronos turntable, as you rightfully pointed out that many turntable mfg's have the same problem. I know that a lot of turntable platters are made of cast metal alloys and not solid billets. When you are machining a platter casting, there is a need to let the material relax a certain amount of time before and after rough machining and then another amount of time before final machining. If you rush the process, there is a good possibility of the platter having some measure of warp. For the crazy high prices that some of these turntables demand, any visible warp in the platter is totally unacceptable !!!
I have also noted the wobble in many turntable platters over the years. It was not my intention to just criticize the Kronos turntable, as you rightfully pointed out that many turntable mfg's have the same problem. I know that a lot of turntable platters are made of cast metal alloys and not solid billets. When you are machining a platter casting, there is a need to let the material relax a certain amount of time before and after rough machining and then another amount of time before final machining. If you rush the process, there is a good possibility of the platter having some measure of warp. For the crazy high prices that some of these turntables demand, any visible warp in the platter is totally unacceptable !!!
Great Niffy,
years of experience and fatigue into one page. Now a question: which tools on the router to cut 40 mm of acrylic?
Won by laziness I'm thinking to buy a 310X40 mm disk and work on it to run true. I also do not like the plexy boorish look (previously tried with a beautiful grey water jet cut sandstone - impossible to machine, was like a grinder wheel) but it is very comfortable to work on and opaque to the sound. I am also tempted by black PVC (vinyl for vinyl), what do you think?
Hottattoo:
with that cash you may buy a wonderful vintage 45' wooden sailboat, with no runout. Seems far better, to me. As for the monster Hulk TTs .... no comment
What's a lathe if not a very versatile jìg? and think that Greeks were using lathes with great skill 2200 years ago, and even more
Antikythera mechanism - Wikipedia
carlo
working on the carbon Lil Casey, fighting gram after gram, Weight more than halved, but who knows..
years of experience and fatigue into one page. Now a question: which tools on the router to cut 40 mm of acrylic?
Won by laziness I'm thinking to buy a 310X40 mm disk and work on it to run true. I also do not like the plexy boorish look (previously tried with a beautiful grey water jet cut sandstone - impossible to machine, was like a grinder wheel) but it is very comfortable to work on and opaque to the sound. I am also tempted by black PVC (vinyl for vinyl), what do you think?
Hottattoo:
with that cash you may buy a wonderful vintage 45' wooden sailboat, with no runout. Seems far better, to me. As for the monster Hulk TTs .... no comment
What's a lathe if not a very versatile jìg? and think that Greeks were using lathes with great skill 2200 years ago, and even more
Antikythera mechanism - Wikipedia
carlo
working on the carbon Lil Casey, fighting gram after gram, Weight more than halved, but who knows..
Hi Carlo,
The router bit I used was a 12mm diameter 63mm long kitchen counter cutter. This type of bit is only available with a 1/2" shank. As I didn't own a 1/2" router I had buy one specifically for this one cut. Apparently spiral fluted cutters work better than straight fluted cutters with acrylic. I used a straight cutter as they are readily available and considerably cheaper. As I was going to be doing a lot of hand finishing the finish of the initial cut was not of great importance.
The choice of material for the platter is another one of those that is going to be controversial. Each material will have its proponents.
For me the most important aspect is the speed of sound through the material. Ideally the speed of sound through the platter material should be the same as through the vinyl of the record. If the speed of sound is the same any compression waves will not reflect at the interface between the two. PVC comes in many formulations with vastly differing mechanical properties. Most of the bulk PVC that I have played with is much softer than that used for the production of records and will have a lower speed of sound. If you can find bulk PVC with the same formulation as record vinyl then this will work very well. Of course record vinyl does vary but will be within a narrow range.
Acrylic tends to be a lot more consistent in its mechanical properties. The speed of sound through acrylic and record vinyl is normally within 1% of each other. This means that there will be very little reflection at the record platter interface and energy from the stylus /record interaction with dissipate into the bulk of the platter.
The other property of importance is the damping of the material used. Once the compression wave energy has made it into the platter you want it to be converted to heat and not returned to the record. You want a material that doesn't transmit sound efficiently. Acrylic is quite good in this aspect.
Aluminium is a popular choice but it does have a much higher speed of sound than record vinyl and is quite good at transmitting sound waves.
I have heard a turntable with a polycarbonate platter and I didn't like the sound. It was hard and shouty. This might have been down to the design of the rest of the deck so I can't place all the blame at the feet of the platter material.
POM/acital/Delrin has quite an up and coming reputation. I have not heard a Delrin platter and haven't investigated it in this application.
You then have the entire field of platter mats. My preference is for a direct coupling of the record to the platter. The use of a clamp that forces the record into a more intimate contact with the platter, allowing a better transmission of energy, will reduce reflection at the interface and improve sound quality.
Niffy
The router bit I used was a 12mm diameter 63mm long kitchen counter cutter. This type of bit is only available with a 1/2" shank. As I didn't own a 1/2" router I had buy one specifically for this one cut. Apparently spiral fluted cutters work better than straight fluted cutters with acrylic. I used a straight cutter as they are readily available and considerably cheaper. As I was going to be doing a lot of hand finishing the finish of the initial cut was not of great importance.
The choice of material for the platter is another one of those that is going to be controversial. Each material will have its proponents.
For me the most important aspect is the speed of sound through the material. Ideally the speed of sound through the platter material should be the same as through the vinyl of the record. If the speed of sound is the same any compression waves will not reflect at the interface between the two. PVC comes in many formulations with vastly differing mechanical properties. Most of the bulk PVC that I have played with is much softer than that used for the production of records and will have a lower speed of sound. If you can find bulk PVC with the same formulation as record vinyl then this will work very well. Of course record vinyl does vary but will be within a narrow range.
Acrylic tends to be a lot more consistent in its mechanical properties. The speed of sound through acrylic and record vinyl is normally within 1% of each other. This means that there will be very little reflection at the record platter interface and energy from the stylus /record interaction with dissipate into the bulk of the platter.
The other property of importance is the damping of the material used. Once the compression wave energy has made it into the platter you want it to be converted to heat and not returned to the record. You want a material that doesn't transmit sound efficiently. Acrylic is quite good in this aspect.
Aluminium is a popular choice but it does have a much higher speed of sound than record vinyl and is quite good at transmitting sound waves.
I have heard a turntable with a polycarbonate platter and I didn't like the sound. It was hard and shouty. This might have been down to the design of the rest of the deck so I can't place all the blame at the feet of the platter material.
POM/acital/Delrin has quite an up and coming reputation. I have not heard a Delrin platter and haven't investigated it in this application.
You then have the entire field of platter mats. My preference is for a direct coupling of the record to the platter. The use of a clamp that forces the record into a more intimate contact with the platter, allowing a better transmission of energy, will reduce reflection at the interface and improve sound quality.
Niffy
Hi Niffy
Interesting read on your take on platter materials
Is there any table/resource that lists these properties?- lazy-yes I know
Is there a consensus on these properties relevance to sound quality -probably not- hahahaha
Following your comment on PVC for platter, maybe to use a stack of record blanks, fix them together drill the hole and lathe to outer edge for run out - this puts you quickly near the net shape of the platter.
Drill at 60 degree intervals at 2/3 diameter holes for bolts and nuts with recessed heads- can be used to correct built up warp- if crazy, put the pack in an oven for a while and let it simmer
In this way the difference in properties is eliminated and best match is achieved
The surface of the record is not flat off course, use inlayer for the 0,38 mm each side recess compensation
Think this an interesting approach, there is a record presser nearby me, will give them a call and see what gives- you can use a stack of oldies too off course- if you do that, you’ll have the worlds first playable platter- hahahah- I’m too funny
Best
Coolerooney
Interesting read on your take on platter materials
Is there any table/resource that lists these properties?- lazy-yes I know
Is there a consensus on these properties relevance to sound quality -probably not- hahahaha
Following your comment on PVC for platter, maybe to use a stack of record blanks, fix them together drill the hole and lathe to outer edge for run out - this puts you quickly near the net shape of the platter.
Drill at 60 degree intervals at 2/3 diameter holes for bolts and nuts with recessed heads- can be used to correct built up warp- if crazy, put the pack in an oven for a while and let it simmer
In this way the difference in properties is eliminated and best match is achieved
The surface of the record is not flat off course, use inlayer for the 0,38 mm each side recess compensation
Think this an interesting approach, there is a record presser nearby me, will give them a call and see what gives- you can use a stack of oldies too off course- if you do that, you’ll have the worlds first playable platter- hahahah- I’m too funny
Best
Coolerooney
Last edited:
Sorry Coolerooney,
No easy list that I know of. The formula for determining the speed of sound through a material is based on its bulk modulus and density. It's a pretty standard equation and is readily available on the Internet via Wikipedia. I can't remember the formula of the top of my head. The difficult part is finding the exact properties of the materials you're purchasing. Many suppliers offer data sheets. Often the suppliers that sell in small quantities don't have this information, especially those on eBay. If I recall correctly the speed of sound through record vinyl is 1565m/s. (don't quote me on that).
Record vinyl would seem like the obvious choice for platter material. It may be possible to recycle junk records though this is likely to be very difficult. To form old records into a solid billet from which to make a new platter would involve either melting or dissolving the old records. Both of these approaches is likely to alter the properties of the vinyl. I think melting old records in a controlled atmosphere at precisely controlled temperatures is most likely to succeed. Just putting a load of chopped up records in a pan and heating them wouldn't work. Outgassing would likely cause the vinyl to form a brittle foam.
The easiest way to make a platter from record vinyl is to find what the formulation of record vinyl is and buy a billet of this material. (This is not guaranteed to give you the best platter. It will certainly allow for the most efficient transfer of energy from the record to the platter but might not then dissipate that energy as well as an alternative material might.) Vinyl is likely to be the best single material for a platter though not by a large margin. Possibly the best platter would have a gradient of material starting at the record interface with vinyl then having the speed of sound decrease and the damping increase through the thickness of the platter.
If you do talk to your local record presser ask about the designation of the vinyl used.
Niffy
No easy list that I know of. The formula for determining the speed of sound through a material is based on its bulk modulus and density. It's a pretty standard equation and is readily available on the Internet via Wikipedia. I can't remember the formula of the top of my head. The difficult part is finding the exact properties of the materials you're purchasing. Many suppliers offer data sheets. Often the suppliers that sell in small quantities don't have this information, especially those on eBay. If I recall correctly the speed of sound through record vinyl is 1565m/s. (don't quote me on that).
Record vinyl would seem like the obvious choice for platter material. It may be possible to recycle junk records though this is likely to be very difficult. To form old records into a solid billet from which to make a new platter would involve either melting or dissolving the old records. Both of these approaches is likely to alter the properties of the vinyl. I think melting old records in a controlled atmosphere at precisely controlled temperatures is most likely to succeed. Just putting a load of chopped up records in a pan and heating them wouldn't work. Outgassing would likely cause the vinyl to form a brittle foam.
The easiest way to make a platter from record vinyl is to find what the formulation of record vinyl is and buy a billet of this material. (This is not guaranteed to give you the best platter. It will certainly allow for the most efficient transfer of energy from the record to the platter but might not then dissipate that energy as well as an alternative material might.) Vinyl is likely to be the best single material for a platter though not by a large margin. Possibly the best platter would have a gradient of material starting at the record interface with vinyl then having the speed of sound decrease and the damping increase through the thickness of the platter.
If you do talk to your local record presser ask about the designation of the vinyl used.
Niffy
Like this
https://www.nakan.com/wp-content/uploads/2016/09/VINYL-RECORD_product-sheets.pdf
They supply granulates, no bars/plates/slabs
https://www.nakan.com/wp-content/uploads/2016/09/VINYL-RECORD_product-sheets.pdf
They supply granulates, no bars/plates/slabs
I've just been doing a bit of browsing on the Internet looking for a bit more information on the vinyl used for making records. As it is formulated specifically for the pressing of records it is unlikely to be available as a billet suitable for making a platter. It may be possible to source the raw material in virgin pellet form and mould a platter or billet from these.
Record vinyl is apparently not pure polyvinyl chloride but a mixture of PVC and polyvinyl acetate in about a 80%-20% ratio. I wish I could remember where I got the information on the mechanical properties of record vinyl.
Pure PVC is unlikely to be a close match to record vinyl as the added PVA will inevitably change its properties.
Acrylic is likely to be a better match, other materials may be closer still.
I have always liked the sound of turntables with acrylic platters over other materials so personally I am happy to stick with acrylic.
Niffy
Record vinyl is apparently not pure polyvinyl chloride but a mixture of PVC and polyvinyl acetate in about a 80%-20% ratio. I wish I could remember where I got the information on the mechanical properties of record vinyl.
Pure PVC is unlikely to be a close match to record vinyl as the added PVA will inevitably change its properties.
Acrylic is likely to be a better match, other materials may be closer still.
I have always liked the sound of turntables with acrylic platters over other materials so personally I am happy to stick with acrylic.
Niffy
Corian and other similar solid surface materials could make a very good platter material. It come in 1/2" thickness with many colors available along with same colored glue. Many custom counter fabricators have cut offs suitable for diy platters. You can stack / glue as many layers as you like, machines well with a router / sander etc. Add a router mounted circle jig and you are in business.
These are instead the simple impressions of a sunday machinist, having turned some rods of many plastic materials.
bakelite - phenolic resin (kraft) - delrin+graphite - plexiglas - hard PVC - lexan - delrin - nylon - soft PVC - teflon
better ------------------------------------- -------------------------------------------------------------------------- worst
In order from the easiest (regular chip, excellent surface finish) to the worst (bristled chips or tool blocking - bad finishing - measures difficult to comply)
Obviously the hardest materials are the easiest, but it is not always true: the softening point counts even more. Each material would ask for a different rake angle, but making just a piece or two i had angled at most the tool holder. Many materials like cooling and lubrication; some with diluted cutting oil or petroleum, many with simple water and dish detergent.
sound
A continuous chain (press fitted or epoxied) of materials, from the hardest and most sounding to the softest and opaque (brass -aluminum - carbon - lead - delrin - forex) is where i came (in my arms, but also in my attempt to TT) trough 10 years of diying. Sandstone or lime stone (not marble or granite) would be great, but a nightmare to machine.
The idea is to remove resonances and disperse far from the source, preventing them from going back: difficult to achieve, but when possible works great
disk to platter - quote for direct coupling absolutely. Now on my Lux I use a simple porous cardboard mat, soaked in diluted epoxy (now harder than vinyl); below on the outside, there is a ring of the same 1mm cardboard - all contact glued to the platter). Together with a clamp creates a small tapering that flattens small warps. Hoping to turn this way directly the plexi or pvc disk to be made.
As to the aluminum platters (but I have seen even in bronze for bells!) I fought 2 years against that of my Lux (2,5 at start, not so bad but ringing - now 3,8 but more dead silent); so I have already paid a trip that I do not intend to repeat.
carlo
bakelite - phenolic resin (kraft) - delrin+graphite - plexiglas - hard PVC - lexan - delrin - nylon - soft PVC - teflon
better ------------------------------------- -------------------------------------------------------------------------- worst
In order from the easiest (regular chip, excellent surface finish) to the worst (bristled chips or tool blocking - bad finishing - measures difficult to comply)
Obviously the hardest materials are the easiest, but it is not always true: the softening point counts even more. Each material would ask for a different rake angle, but making just a piece or two i had angled at most the tool holder. Many materials like cooling and lubrication; some with diluted cutting oil or petroleum, many with simple water and dish detergent.
sound
A continuous chain (press fitted or epoxied) of materials, from the hardest and most sounding to the softest and opaque (brass -aluminum - carbon - lead - delrin - forex) is where i came (in my arms, but also in my attempt to TT) trough 10 years of diying. Sandstone or lime stone (not marble or granite) would be great, but a nightmare to machine.
The idea is to remove resonances and disperse far from the source, preventing them from going back: difficult to achieve, but when possible works great
disk to platter - quote for direct coupling absolutely. Now on my Lux I use a simple porous cardboard mat, soaked in diluted epoxy (now harder than vinyl); below on the outside, there is a ring of the same 1mm cardboard - all contact glued to the platter). Together with a clamp creates a small tapering that flattens small warps. Hoping to turn this way directly the plexi or pvc disk to be made.
As to the aluminum platters (but I have seen even in bronze for bells!) I fought 2 years against that of my Lux (2,5 at start, not so bad but ringing - now 3,8 but more dead silent); so I have already paid a trip that I do not intend to repeat.
carlo
Impedance not speed of sound.
Hi everyone,
I made a big mistake in the properties that make a good platter material. It must be over 10 years ago that I did the research into platter materials and was trying to recall of the top of my head. I said the most important factor was the speed of sound through the platter material. It is in fact another factor that is closely related to the speed of sound. The most important factor is the mechanical impedance of the material. The mechanical impedance is the product of the speed of sound and the density. Ideally you want the impedance of the platter and record to be as similar as possible. I also remembered the speed of sound through record vinyl completely inaccurately. It is 2400m/s and not 1565m/s (I did say don't quote me on that) . With a density of 1360kg/m^3 record vinyl will have an impedance of 3.27x10^6 kg/m^2. For ease of typing I'll say it has an Z of 3.27. Acrylic has an Z of 3.26 so is very closely matched. The amount of reflection at a boundary is calculated as (Z1-Z2)/(Z1+Z2). Between record vinyl and acrylic the amount of reflection is 0.15%. This assumes a perfect contact between the two so in reality the reflection will be stronger.
Aluminium has a much higher Z of 17.6. This will result in a much stronger reflection of 70%. This will give aluminium a much brighter sound and could explain why many people who prefer aluminium platters think acrylic sounds dull.
Pure PVC is a much better option with a Z of 2.96. This will have a reflection of only 5%.
Delrin has a Z of 3.45 and a reflection of 2.7%
The second most important platter material property is damping or how much the acoustic wave is attenuated as it passes through the platter. Acrylic is quite good in this respect. Pure vinyl attenuates by about twice as much and Delrin by four times. The attenuation in aluminium is considerably lower.
When I was researching platter materials I didn't consider Delrin. Although the reflection at the record interface is greater than for acrylic its damping is much greater. This may actually be a better choice for a single material platter. Maybe the best option would be a two layer platter with the upper layer made of acrylic and the lower made of Delrin. The acrylic takes the vibration away from the record and the Delrin damps it. As the Z of acrylic is similar to the Z of Delrin there will only be a 2.8% reflection at this second interface. As the joint between the two layers can be made very intimate the reflection will be very close to this figure.
Joe mentions corian. Corian is an acrylic resin with a stone filler and is much denser than regular acrylic and apparently has good damping properties. It's impedance will be determined by what filler is used. It would probably work very well as a platter material if topped with a piece of regular acrylic.
Sorry for the erroneous information in my previous post. I nearly got it right, just forgot the density bit.
Niffy
Hi everyone,
I made a big mistake in the properties that make a good platter material. It must be over 10 years ago that I did the research into platter materials and was trying to recall of the top of my head. I said the most important factor was the speed of sound through the platter material. It is in fact another factor that is closely related to the speed of sound. The most important factor is the mechanical impedance of the material. The mechanical impedance is the product of the speed of sound and the density. Ideally you want the impedance of the platter and record to be as similar as possible. I also remembered the speed of sound through record vinyl completely inaccurately. It is 2400m/s and not 1565m/s (I did say don't quote me on that) . With a density of 1360kg/m^3 record vinyl will have an impedance of 3.27x10^6 kg/m^2. For ease of typing I'll say it has an Z of 3.27. Acrylic has an Z of 3.26 so is very closely matched. The amount of reflection at a boundary is calculated as (Z1-Z2)/(Z1+Z2). Between record vinyl and acrylic the amount of reflection is 0.15%. This assumes a perfect contact between the two so in reality the reflection will be stronger.
Aluminium has a much higher Z of 17.6. This will result in a much stronger reflection of 70%. This will give aluminium a much brighter sound and could explain why many people who prefer aluminium platters think acrylic sounds dull.
Pure PVC is a much better option with a Z of 2.96. This will have a reflection of only 5%.
Delrin has a Z of 3.45 and a reflection of 2.7%
The second most important platter material property is damping or how much the acoustic wave is attenuated as it passes through the platter. Acrylic is quite good in this respect. Pure vinyl attenuates by about twice as much and Delrin by four times. The attenuation in aluminium is considerably lower.
When I was researching platter materials I didn't consider Delrin. Although the reflection at the record interface is greater than for acrylic its damping is much greater. This may actually be a better choice for a single material platter. Maybe the best option would be a two layer platter with the upper layer made of acrylic and the lower made of Delrin. The acrylic takes the vibration away from the record and the Delrin damps it. As the Z of acrylic is similar to the Z of Delrin there will only be a 2.8% reflection at this second interface. As the joint between the two layers can be made very intimate the reflection will be very close to this figure.
Joe mentions corian. Corian is an acrylic resin with a stone filler and is much denser than regular acrylic and apparently has good damping properties. It's impedance will be determined by what filler is used. It would probably work very well as a platter material if topped with a piece of regular acrylic.
Sorry for the erroneous information in my previous post. I nearly got it right, just forgot the density bit.
Niffy
hi Niffy: if you think to use delrin or nylon look for the black one, loaded with graphite (it's used to make self-lubricant pulleys, I used it to rebuild a rudder bushing) - the first tends to lock the tool (the chip thickens up to blocking) the second one is a pleasure to machine = night vs day
Problem for both: difficult, if not counterproductive to sand finish. the surface worsens a lot
carlo
thanks for the scientific clarifications: however, the role of the various materials was very clear. Maybe one of the most important factor is the crystal structure of the material: e.g. lead = high density but great impedance
Problem for both: difficult, if not counterproductive to sand finish. the surface worsens a lot
carlo
thanks for the scientific clarifications: however, the role of the various materials was very clear. Maybe one of the most important factor is the crystal structure of the material: e.g. lead = high density but great impedance
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As to platter or mat material, any experience with shellac? I'm thinking of gluing several shellac LPs together and further machining proper platter mat of it... By the way, shellac records do not have warp problems of the vinyl ones, and also are much heavier. Seems to be a very sound friendly material, used in musical instrument industry.
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