Thanks. A few of these can be answered right away. Yes, it looks ling a jungle to me, that is why I am trying to get things clarified.
Belt drive - single drive, single motor, DC motor, speed controlled. The motors and controllers exist, these are expensive, however, the 'stepper motor' controllers and DC motors are available for much less. I think my 0.22% USB turntable uses one of these, does not sound too bad, but then again, it is a small plastic platter that weighs very little.
Maybe I can transfer the EZcap USB turntable mechanical to a proper plinth and add a tone arm.
Tonearm - is the tonearm a completely independent system from the platter and drive motor? It seems to be so, electrically, and some replace and build tone arms so that gives a hint. The tonearm wires can be connected directly to a phono pre-amplifier, is that correct?
So far it has been difficult to get a clear answer, though I have been searching.
Bearings and platter will have to be from an existing turntable, I cannot see how to get both built with the required quality, however one DIYer did build a plywood platter.
Non-floating plinth.
Matching the drive system - yes, this will be a problem, because a heavy platter will have to be started up quickly with a high-powered motor that is also noiseless and vibration free. It has been suggested elsewhere that a heavy platter is a good way of ensuring short term speed stability. The speed control system will have to be matched to the moment of inertia of the platter.
There is also the braking system to stop the thing when the record stops, or is it needed?
This is a design exercise, maybe a prototype will be built, but it may not be worth it.
The minimalist designs of recent years have really impressed me. I would want the platter to be removable and a removable cover under that so the turntable does not have to be turned upside down to access the mechanical parts.
There is a Sony SONY PS 333 turntable that stopped working, can the parts be used to convert it to belt drive, I wonder. The motor and controllers seem to be available on Ebay.
https://audiokarma.org/forums/index.php?threads/sony-ps-333-runaway-speed.898476/
https://audiokarma.org/forums/index.php?threads/sony-ps-333-runaway-speed.898476/
With the smartphone based app which measures the wow and flutter of a turntable, it occurred to me that it would be possible to test the variation in speed of any rotating turntable, even a simple one. I decided to set up a turntable with a simple motor and measure it with the smart phone app, to get an idea of what sort of speed variations take place.
This was a cardboard turntable with the common type of DC motor and a 1.5 V battery. It was difficult to get the turntable turning with the weight of the phone on top of the turntable, so it had to be turned by hand, once it started moving, it kept moving.
Here is a screenshot:
2.71 % is ten times the minimum value it should be, but this is without a speed controller of any sort. The experiment highlights the need for a powerful motor to start up the turntable, which in any case will be heavy, even given the multiplier effect of the belt, though in this case a direct drive was used.
I might try again with a more powerful motor and a speed controller. If the speed of the turntable can be somehow controlled to within 0.20% then it looks like it
could be the basis for a drive system, otherwise I will have to look for alternatives.
Even if it does not work out, I can test the effect of turntable weight on speed stability.
This was a cardboard turntable with the common type of DC motor and a 1.5 V battery. It was difficult to get the turntable turning with the weight of the phone on top of the turntable, so it had to be turned by hand, once it started moving, it kept moving.
Here is a screenshot:
2.71 % is ten times the minimum value it should be, but this is without a speed controller of any sort. The experiment highlights the need for a powerful motor to start up the turntable, which in any case will be heavy, even given the multiplier effect of the belt, though in this case a direct drive was used.
I might try again with a more powerful motor and a speed controller. If the speed of the turntable can be somehow controlled to within 0.20% then it looks like it
could be the basis for a drive system, otherwise I will have to look for alternatives.
Even if it does not work out, I can test the effect of turntable weight on speed stability.
I thought I'd add my experience modifying a Technics direct drive motor. Hopefully this will give you some insight to making a bearing and platter for your TT.
The original motor used a 9/32 spindle in the usual way with the point of rotation under the motor. I modified the motor to use an inverted bearing.
The journal is 12mm Silver Steel and the sleeves are made from Vesconite. The sleeves are a very close slip fit this is not a hydrodynamic bearing. A custom platter was made from aluminium and POMC. The large journal sleeve carrier only mates with the Al base of the platter the POMC does not touch the bearing and the LP spindle is decoupled so it also doesn't touch the bearing. Bearing noise in the platter is below the noise floor (-110dB) of my test equipment.
I guess the takeaway is POM is a great material for platters. Placing a stethoscope on a stock platter mat you can clearly airborne sound in the platter, the POM platter there is zero audible sound emanating from the platter. Vesconite is a good polymer to use for bearings, once run in (about 1hr) it's almost totally silent when measured directly on the motor housing. I add a couple of drops of ISO68 oil to ball on the top of the spindle and that's it.
Pictures
1 stock Technics motor
2 inside the modified inverted bearing motor
3 new rotor and inverted bearing sleeve carrier
4 finished turntable
The original motor used a 9/32 spindle in the usual way with the point of rotation under the motor. I modified the motor to use an inverted bearing.
The journal is 12mm Silver Steel and the sleeves are made from Vesconite. The sleeves are a very close slip fit this is not a hydrodynamic bearing. A custom platter was made from aluminium and POMC. The large journal sleeve carrier only mates with the Al base of the platter the POMC does not touch the bearing and the LP spindle is decoupled so it also doesn't touch the bearing. Bearing noise in the platter is below the noise floor (-110dB) of my test equipment.
I guess the takeaway is POM is a great material for platters. Placing a stethoscope on a stock platter mat you can clearly airborne sound in the platter, the POM platter there is zero audible sound emanating from the platter. Vesconite is a good polymer to use for bearings, once run in (about 1hr) it's almost totally silent when measured directly on the motor housing. I add a couple of drops of ISO68 oil to ball on the top of the spindle and that's it.
Pictures
1 stock Technics motor
2 inside the modified inverted bearing motor
3 new rotor and inverted bearing sleeve carrier
4 finished turntable
Not formally, but informally, yes. It has been incredibly productive experimenting with what I have, and with low cost components. I have learned much.
Only a few weeks ago I did not know the difference between a tone arm, MM cartridge, MC cartridge and tone arm head.
I have become disillusioned with entry and mid level commercial products, and have had a very rewarding time experimenting with low powered speakers and amplifiers. I has helped me learn things that will help me when choosing a good system, someday. Now, on to turntables.
I would rather build 100 $10 amplifiers than one $1000 amplifier. Experiments in how low you can go in cost.
I would like to maybe write a book about my experiences, if I am successful.
Only a few weeks ago I did not know the difference between a tone arm, MM cartridge, MC cartridge and tone arm head.
I have become disillusioned with entry and mid level commercial products, and have had a very rewarding time experimenting with low powered speakers and amplifiers. I has helped me learn things that will help me when choosing a good system, someday. Now, on to turntables.
I would rather build 100 $10 amplifiers than one $1000 amplifier. Experiments in how low you can go in cost.
I would like to maybe write a book about my experiences, if I am successful.
That's a really nice turntable, thanks for sharing. Many questions: Vesconite? POMC? Is that a linear tonearm?
Some say a turntable is a precision machine, this certainly looks like it.
Vesconite is a polymer specifically designed for bearings in hostile environments it's used in train carriages. IMO it's better than PEEK and Torlon as it's far quieter due to its lower coefficient of friction. BTW I use Hilube.....
https://www.vesconite.com/vesconite-hilube/
POM is Polyoxymethylene there are 2 variants Copolymer and Homopolymer, also known as Acetal which can be C or H. Dupont has a proprietory version called Delrin which is a specific Homopolymer.
Yes that is a linear tonearm which I made.
I'm in the "Turntable is a precision measuring instrument" camp. Most audiophiles have no understanding just how sensitive of a seismograph a TT is. It is so sensitive it can pick up a conversation 10 meters away in another room. If you can design the TT to isolate the stylus/LP interface from all of the external vibrations happening then you are well on the way to an exceptional TT.
As you have indicated you're fairly new to this I'll go into more detail.
There is a considerable amount of energy generated by the stylus in the groove, this energy needs to go somewhere if the platter is well designed then the energy can be transferred into the platter where it travels through to the bottom and some reflects back to the stylus. The idea is to make this journey as slow as possible. POMC has similar acoustic impedance to the LP so there is good energy transfer into the POMC. POMC also has greater density than acrylic so the energy attenuation in POMC is greater. The aluminium base does 2 things it prevents the POMC warping (I use 30mm flat sheet) as well as providing stiffness and an interface where there will transmission and reflection of energy spreading and attenuating the returning energy wave back to the stylus.
I use a stethoscope to listen to various parts of the TT and it's interesting just how much of the music you can hear the stethoscope from the LP.
There is a reason a lot of highend TT manufacturers are using POM for their platters now.
https://www.vesconite.com/vesconite-hilube/
POM is Polyoxymethylene there are 2 variants Copolymer and Homopolymer, also known as Acetal which can be C or H. Dupont has a proprietory version called Delrin which is a specific Homopolymer.
Yes that is a linear tonearm which I made.
I'm in the "Turntable is a precision measuring instrument" camp. Most audiophiles have no understanding just how sensitive of a seismograph a TT is. It is so sensitive it can pick up a conversation 10 meters away in another room. If you can design the TT to isolate the stylus/LP interface from all of the external vibrations happening then you are well on the way to an exceptional TT.
As you have indicated you're fairly new to this I'll go into more detail.
There is a considerable amount of energy generated by the stylus in the groove, this energy needs to go somewhere if the platter is well designed then the energy can be transferred into the platter where it travels through to the bottom and some reflects back to the stylus. The idea is to make this journey as slow as possible. POMC has similar acoustic impedance to the LP so there is good energy transfer into the POMC. POMC also has greater density than acrylic so the energy attenuation in POMC is greater. The aluminium base does 2 things it prevents the POMC warping (I use 30mm flat sheet) as well as providing stiffness and an interface where there will transmission and reflection of energy spreading and attenuating the returning energy wave back to the stylus.
I use a stethoscope to listen to various parts of the TT and it's interesting just how much of the music you can hear the stethoscope from the LP.
There is a reason a lot of highend TT manufacturers are using POM for their platters now.
Besides a stethoscope, another sometimes interesting test that can be done is to drop the needle on a record when the TT isn't spinning. Turn up the volume some, and go tapping on various parts of whatever the TT is sitting on, etc. Very interesting how much of that gets picked up by the stylus. Also interesting the various resonance modes that can be excited. Be very gentle, of course. The stylus, cartridge, and or arm can be damaged if sufficient care is not taken.
I am, of course, attempting to put this together at the least possible cost, maybe about $50. Of course the second prototype will cost more and so will the third.
This is a very sensitive mechanical sensor for a rotating surface.
I will try some tests with my smart phone accelerometer and phone microphone. Should be interesting.
This is a very sensitive mechanical sensor for a rotating surface.
I will try some tests with my smart phone accelerometer and phone microphone. Should be interesting.
I think a microscope for viewing the stylus and an automatic roller brush to clean stylus after each side might be a good idea.
I have not been able to find such a feature on any turntable. The black screen in front will show a magnified image of the stylus.
Something like it: https://patents.google.com/patent/US3405946A/en
I have not been able to find such a feature on any turntable. The black screen in front will show a magnified image of the stylus.
Something like it: https://patents.google.com/patent/US3405946A/en
I disassembled an USB turntable, the EZCap 613 as seen in the image below, and it has a motor that looks like the motor sold on Ebay.
The wow figures dropped considerably with the record and the 185g smart phone on the platter, so a heavy platter and suitable bearing should ensure that the speed variation is within acceptable levels. Assuming this is the case, and that this is a servo motor, not needing any extra speed controlling hardware, the following preliminary design is suggested. The black rectangle is the mounting plate that is shown suppressed for clarity. The motor will be mounted in a cut out in the MDF layered plinth.
The rated power is 1 Watt, is this sufficient, given the Project turntable is rated at 5W maximum.
The wow figures dropped considerably with the record and the 185g smart phone on the platter, so a heavy platter and suitable bearing should ensure that the speed variation is within acceptable levels. Assuming this is the case, and that this is a servo motor, not needing any extra speed controlling hardware, the following preliminary design is suggested. The black rectangle is the mounting plate that is shown suppressed for clarity. The motor will be mounted in a cut out in the MDF layered plinth.
Last edited:
Nice drawing work.
A mechanics one i likely best, very useful for sorting speaker box resonance.
If anyone watching wants to short circuit the development i have a Linn LP12 bearing and inner platter, as well as a 50Hz motor for cost of shipping.
I saw a DD motor in the thread. I am not a fan at all of DD.
dave
A mechanics one i likely best, very useful for sorting speaker box resonance.
If anyone watching wants to short circuit the development i have a Linn LP12 bearing and inner platter, as well as a 50Hz motor for cost of shipping.
I saw a DD motor in the thread. I am not a fan at all of DD.
dave
I do not feel comfortable experimenting with expensive, high quality components. That Linn bearing and platter on eBay looks a real professional work of engineering. How do they do it.
Thanks.
One option is to use a large platter that has a greater moment of inertia. I have a strobe printout that seems to indicate a speed variation with the bars on the disk moving in pulses instead of being steady, on the small mini platter EzCap 613. Adding weight, that is, about a total of 115g in terms of the record, to an already heavy weight of the smart phone of 246g reduced speed variation, as well as the overall speed. The question is, can this turntable sustain a total of over 350g on the bearing? What about motor torque?
Thanks.
One option is to use a large platter that has a greater moment of inertia. I have a strobe printout that seems to indicate a speed variation with the bars on the disk moving in pulses instead of being steady, on the small mini platter EzCap 613. Adding weight, that is, about a total of 115g in terms of the record, to an already heavy weight of the smart phone of 246g reduced speed variation, as well as the overall speed. The question is, can this turntable sustain a total of over 350g on the bearing? What about motor torque?
With the motor secured (virtually, in 3D, and the belt in place, time to source the platter and bearing. The platter weight does not seem to have a bearing(!) on speed variation, I have found from testing the EZCap. Wow is at 0.23% or so, but depends on the time of day, it may be the power line. Will test with batteries.
Here we are: platter, bearing, motor and everything else. Free shipping as well. A cork mat should improve things, hopefully wow and flutter is at a minimum. I purchased this in 2020 or 2021 and cancelled the order because I was not sure if it was a complete turntable or just parts. I know better now.
