This project illustrates how a mediocre mass –produced turntable can be given an upgrade with some adventure and patience. Generally I have accepted that a mass-produced turntable is a fait accompli and nothing much can be done beyond tinkering for improvements. That changed when I relocated and decided I needed a turntable and ended up with a Denon DP-30L. My turntables at that point were a Sansui SR 222 MK V and a Sony PS-212. Verdicts on these tables:
Sansui SR222 MK V- Good arm, mediocre everything else (belt drive)
Sony PS-212 - Good motor (BSL). Crap plinth, mediocre everything else (direct drive).
The following project is in 3 parts: bearing treatment, plinth treatment and arm rebuild.
Before and after pictures of Denon DP-30L
Sansui SR222 MK V- Good arm, mediocre everything else (belt drive)
Sony PS-212 - Good motor (BSL). Crap plinth, mediocre everything else (direct drive).
The following project is in 3 parts: bearing treatment, plinth treatment and arm rebuild.
Before and after pictures of Denon DP-30L
Attachments
Part 1 - Bearing treatment
A direct drive Denon DP-30L came up at a low price (before the current vinyl resurgence). It had decent specs and was fuss free. It was dour cosmetically and looked like an electric oven ring with the piano controls in front of the lid. I christened it ' the gas stove'. The arm was heavy and the weak aspect of the deck. The plinth and motor are surprisingly good. Denon's platter uses a magnetic pulse strip and tape head sensor for speed control, the same as Sony's Magnedisc on the PS-212. The plinth is a kind of resin/plastic that Denon claimed to be anti-resonant. It was better than the cheapest plastic affairs, although I have seen examples of better implementation. The overall result is a very good rumble spec which models further up the portfolio in nice wooden plinths, can't match. The best part of the deck is the auto-lift at the end of play which is optically controlled without mechanical linkages.
The first task was to see if the motor bearing needed service. I disassembled the motor and found the main bearing is a ball at the end of the spindle, sitting on a brass pellet with a central hole. Not dissimilar to some high quality designs. It was at this point inclination to experiment took hold.
A direct drive Denon DP-30L came up at a low price (before the current vinyl resurgence). It had decent specs and was fuss free. It was dour cosmetically and looked like an electric oven ring with the piano controls in front of the lid. I christened it ' the gas stove'. The arm was heavy and the weak aspect of the deck. The plinth and motor are surprisingly good. Denon's platter uses a magnetic pulse strip and tape head sensor for speed control, the same as Sony's Magnedisc on the PS-212. The plinth is a kind of resin/plastic that Denon claimed to be anti-resonant. It was better than the cheapest plastic affairs, although I have seen examples of better implementation. The overall result is a very good rumble spec which models further up the portfolio in nice wooden plinths, can't match. The best part of the deck is the auto-lift at the end of play which is optically controlled without mechanical linkages.
The first task was to see if the motor bearing needed service. I disassembled the motor and found the main bearing is a ball at the end of the spindle, sitting on a brass pellet with a central hole. Not dissimilar to some high quality designs. It was at this point inclination to experiment took hold.
Part 1 - Bearing treatment
Some time earlier, I had attempted drilling a neodymium magnet and failed, due to the drill being unable to bite into the greasy metal. I began to think about replacing the brass pellet bearing thrust pad, with a neodymium magnet. I reasoned the greasy material and its strength would work perfectly well as a thrust pad. What drove this approach was my wish for a service-free solution. Pure synthetic oil does not become waxy as lighter fractions evaporate. I had a supply of various viscosity ferrofluids and thought that the neodymium magnet would act to keep lubricant where it is needed most.
Ferrofluid is intersting stuff. It is structural. In the 2nd pic a dome of ferrofluid sitting on the neodymium magnet is supporting the weight of the brass pellet. This structural property would act to support the spindle.
Some time earlier, I had attempted drilling a neodymium magnet and failed, due to the drill being unable to bite into the greasy metal. I began to think about replacing the brass pellet bearing thrust pad, with a neodymium magnet. I reasoned the greasy material and its strength would work perfectly well as a thrust pad. What drove this approach was my wish for a service-free solution. Pure synthetic oil does not become waxy as lighter fractions evaporate. I had a supply of various viscosity ferrofluids and thought that the neodymium magnet would act to keep lubricant where it is needed most.
Ferrofluid is intersting stuff. It is structural. In the 2nd pic a dome of ferrofluid sitting on the neodymium magnet is supporting the weight of the brass pellet. This structural property would act to support the spindle.
Attachments
Part 1 - Bearing treatment
Magnets surround the spindle shaft. This would act to hold ferrofuid in the shaft and create an anti-rock bearing. I have read many reports of turntable manufacturers striving to achieve ever tighter tolerances, using engineering effort to justify pricing.
Magnets surround the spindle shaft. This would act to hold ferrofuid in the shaft and create an anti-rock bearing. I have read many reports of turntable manufacturers striving to achieve ever tighter tolerances, using engineering effort to justify pricing.
Attachments
Part 1 - Bearing treatment
It took several attempts. Issues encountered were getting the magnet to stay flat at the bottom of the shaft while the steel ball was introduced. Dropping it down the shaft didn't work. Magnets were placed around the spindle and ferrofluid applied to the spindle under the bell. This held the steel ball in place in the spindle cup as it was introduced into the shaft.
The structural nature of the ferrofluid caused a perfect air pocket in the shaft and the spindle refused to go down. I tested the air pocket support by applying as much weight as possible with thumbs and upper body. No movement. Removing the magnets from the spindle top allowed the ferrofluid to flow into the shaft. It took several minutes for the bell to settle and allow the air to escape. This creates another conjecture that a zero friction air-ferrofluid bearing is a possibility.
It took several attempts. Issues encountered were getting the magnet to stay flat at the bottom of the shaft while the steel ball was introduced. Dropping it down the shaft didn't work. Magnets were placed around the spindle and ferrofluid applied to the spindle under the bell. This held the steel ball in place in the spindle cup as it was introduced into the shaft.
The structural nature of the ferrofluid caused a perfect air pocket in the shaft and the spindle refused to go down. I tested the air pocket support by applying as much weight as possible with thumbs and upper body. No movement. Removing the magnets from the spindle top allowed the ferrofluid to flow into the shaft. It took several minutes for the bell to settle and allow the air to escape. This creates another conjecture that a zero friction air-ferrofluid bearing is a possibility.
Attachments
Part 1 - Bearing treatment
There were some issues getting the height of the magnet to match the brass pellet so that the spindle sits correctly relative to the platter. When all was done and reassembled I tried the first spin, and found the next mistake.
I had chosen a higher viscosity ferrofluid in the belief that would achieve the anti rock property. Unfortunately, the tight tolerances of the shaft and spindle resulted in drag and the motor was working noticeably harder. It was disassembled for a lower viscosity ferrofluid. After four assembly cycles I managed to achieve a successful implementation, a service-free anti rock bearing. At least I think it is.
There is one caveat. The neodymium magnet turns the spindle into a bar magnet. Lines of magnetic force sprout from the spindle tip. I wonder how this interferes with the Earth's magnetic field. I wasn't too concerned that the cartridge would be influenced. There is always recourse to a brass puck as shield. A ceramic spindle would have solved that problem.
In course of this exercise I realized that the major source of vibration is the motor stator coils. This is an AC motor, therefore a 50Hz/60Hz component is transferred to the platter and plinth. The later model DP-31L motor is a good solution for direct drive as it is DC, and motor stator coils are excited at platter speed. It seems similar to the Sony BSL motor. For the DP-30L, vibration would be dealt with by treatment. My favorite tool is Dynamat, a mastic compound that comes in LP-sized sheets. The motor housing was wrapped in Dynamat. Vibration control splits into two camps. One group favors a light mass construction that can be damped. The other group favors mass to reduce the magnitude of vibration. On balance I go with the light mass approach since materials like Dynamat can quell vibration over a broad range of frequencies. The other benefit is a lighter, user-friendly end result for relocation of equipment.
There were some issues getting the height of the magnet to match the brass pellet so that the spindle sits correctly relative to the platter. When all was done and reassembled I tried the first spin, and found the next mistake.
I had chosen a higher viscosity ferrofluid in the belief that would achieve the anti rock property. Unfortunately, the tight tolerances of the shaft and spindle resulted in drag and the motor was working noticeably harder. It was disassembled for a lower viscosity ferrofluid. After four assembly cycles I managed to achieve a successful implementation, a service-free anti rock bearing. At least I think it is.
There is one caveat. The neodymium magnet turns the spindle into a bar magnet. Lines of magnetic force sprout from the spindle tip. I wonder how this interferes with the Earth's magnetic field. I wasn't too concerned that the cartridge would be influenced. There is always recourse to a brass puck as shield. A ceramic spindle would have solved that problem.
In course of this exercise I realized that the major source of vibration is the motor stator coils. This is an AC motor, therefore a 50Hz/60Hz component is transferred to the platter and plinth. The later model DP-31L motor is a good solution for direct drive as it is DC, and motor stator coils are excited at platter speed. It seems similar to the Sony BSL motor. For the DP-30L, vibration would be dealt with by treatment. My favorite tool is Dynamat, a mastic compound that comes in LP-sized sheets. The motor housing was wrapped in Dynamat. Vibration control splits into two camps. One group favors a light mass construction that can be damped. The other group favors mass to reduce the magnitude of vibration. On balance I go with the light mass approach since materials like Dynamat can quell vibration over a broad range of frequencies. The other benefit is a lighter, user-friendly end result for relocation of equipment.
