This is second (and last) blast from the past project that I will publish. Its from early 2000's when I was very much into doing different audio things.
Other of my old projects have no much difference from usually seen executions, so I will skip those.
As elementary school kid (in 1977), my older sister left me her BSR turntable system (in Yugoslavia than called Tosca) and some 50LP's, good stuff of the time, Leonard Cohen, Dylan, Cat Stevens, Janis Joplin, Roberta Flack, Jimmy Smith, some classic and so on... Anyway, I felt in love with LP's and HIFI forever, this still goes on.
Anyway, few friends (actually their parents) had Thorenses, Sondeks and Duals, , I always wanted proper turntable. By the time I made my own money, CD came into play and I bought one of the first Philips CD player.
Few years after I still wanted TT, bought one crappy example, throw it away and decided to make my own. Intention was not to make hi end piece, but to make vintage looking TT similar to those that I was wishing for:
This is the result:
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Idea was just decent vintage looking TT, so i did not do many scientific exercises , like I see here on forum a lot, but went straight ahead with what I thought is good and available. I'm mechanical engineer so in this segment I do feel more comfortable .
First choice made was plinth and disc material. Here in Croatia we have particular limestone mined on island Brač, it is construction material used around the world, very homogeneous but not too dense (knock on it with hammer makes much less noise than similar done with slate) . It is pure white, and most importantly locally abundant with many workshops machining it for cheap.
Second choice was the bearing, here I wanted something that is absolutely precise and doesn't move anywhere except around. The shaft is D20mm x 90mm length from ASI304 SS, turned and polished. The bushing is bronze, turned and honed and the trust bearing is just one ball from ball bearing.
The tolerances of the bearing are so tight that it takes about 30 minutes for heavy stone platter to sit in its place after it was reinstalled:
The third choice was the motor, I used Papst asynchronous outer-runner (aussenlaufer) used as rewinding motor for reel to reel tape recorder driven by Siemens Micro Master Junior frequency inverter.
The drag from the bearing is obvious but quite constant. The speed consistency is very good (as measured with stroboscope) but the speed tends to drop depending on time used and room temperature. It took me a while to find right bearing oil, ended up with motocross drive chain lubricant that has longest constant speed. Anyway, it needs oil replenish every month or so to keep speed at target, no surprise as motor is asynchronous without feedback. But I will come back to this in details later, hope for help about new motor choice.
First choice made was plinth and disc material. Here in Croatia we have particular limestone mined on island Brač, it is construction material used around the world, very homogeneous but not too dense (knock on it with hammer makes much less noise than similar done with slate) . It is pure white, and most importantly locally abundant with many workshops machining it for cheap.
Second choice was the bearing, here I wanted something that is absolutely precise and doesn't move anywhere except around. The shaft is D20mm x 90mm length from ASI304 SS, turned and polished. The bushing is bronze, turned and honed and the trust bearing is just one ball from ball bearing.
The tolerances of the bearing are so tight that it takes about 30 minutes for heavy stone platter to sit in its place after it was reinstalled:
The third choice was the motor, I used Papst asynchronous outer-runner (aussenlaufer) used as rewinding motor for reel to reel tape recorder driven by Siemens Micro Master Junior frequency inverter.
The drag from the bearing is obvious but quite constant. The speed consistency is very good (as measured with stroboscope) but the speed tends to drop depending on time used and room temperature. It took me a while to find right bearing oil, ended up with motocross drive chain lubricant that has longest constant speed. Anyway, it needs oil replenish every month or so to keep speed at target, no surprise as motor is asynchronous without feedback. But I will come back to this in details later, hope for help about new motor choice.
Bearing, platter and plinth assembly:
Bering was produced by professional machinist.
Plinth was made by stone mason, cut in shape, 2 holes drilled (bearing and arm) and polished.
Platter was roughly turned on masons lathe, with hole in the middle.
Then I epoxy glued shaft into the platter, when glue settled took it to precision machinist, he turned it again on precision lathe holding by the shaft, he was swearing as his nice metal lathe was full with stone dust, but he did it. We tried to balance it , but there was no need really, this stone is rather homogeneous.
Last and trickiest part, how to glue bushing into the plinth to be 100% 90°angle, precisely. The plinth is machined flat from the top so that is not the problem, the platter too.
So what I did is to place platter horizontally upside down, with shaft up. Than I put bushing on the shaft, than placed 3 precise feeler gauges on platter corners, 120°apart, and than I put the plinth on top, so it rest on feeler gauges.
Like this I could turn the plinth around and ensure that the platter and plinth are perfectly aligned. Drop few spots of epoxy inside to fix bushing to the plinth.
When epoxy cured, turned whole thing in normal position, removed feeler gauges and turned the platter around, it was good so I pored epoxy to completely seal bushing to the plinth.
This worked only from second time, at first it was not good so I hammered bushing out with some small damage to stone plinth.
Bering was produced by professional machinist.
Plinth was made by stone mason, cut in shape, 2 holes drilled (bearing and arm) and polished.
Platter was roughly turned on masons lathe, with hole in the middle.
Then I epoxy glued shaft into the platter, when glue settled took it to precision machinist, he turned it again on precision lathe holding by the shaft, he was swearing as his nice metal lathe was full with stone dust, but he did it. We tried to balance it , but there was no need really, this stone is rather homogeneous.
Last and trickiest part, how to glue bushing into the plinth to be 100% 90°angle, precisely. The plinth is machined flat from the top so that is not the problem, the platter too.
So what I did is to place platter horizontally upside down, with shaft up. Than I put bushing on the shaft, than placed 3 precise feeler gauges on platter corners, 120°apart, and than I put the plinth on top, so it rest on feeler gauges.
Like this I could turn the plinth around and ensure that the platter and plinth are perfectly aligned. Drop few spots of epoxy inside to fix bushing to the plinth.
When epoxy cured, turned whole thing in normal position, removed feeler gauges and turned the platter around, it was good so I pored epoxy to completely seal bushing to the plinth.
This worked only from second time, at first it was not good so I hammered bushing out with some small damage to stone plinth.
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I did not want the motor attached to the plinth, so i installed in new part, housing, and plinth resting on 4 heavy springs (heavy because the weight of this is significant) heavily dumped by common flexible sanitary silicone. Here are few pictures before housing was made, I used it like this for several months:
Finishing the plinth:
Bottom of the plinth is layered in heavy copper film, same as used for housing. The reason is 3 fold:
Bottom of the plinth is layered in heavy copper film, same as used for housing. The reason is 3 fold:
- It shields preamp that I built inside from outside world and from 3 phase 116V motor. Also shields cartridge and cables from the same motor.
- It grounds possible static potential that is quite likely with vinyl records
- It adds additional mechanical dumping to the plinth, even the copper + glue is much thinner than stone plinth, it still adds to the dumping, there is theory about that.
For the arm I have chosen at first cheap-ish Project 9.1 arm, It was available at the time. This is first iteration with ALU tube, not as today with carbon parts.
The cartridge was high output MC Sumiko Blue Point.
Well, this sounded much better than I expected, even with crappy records, me on the hook again!
Very soon I invested in real cartridge, Benz Micro Ruby 2 Naked, spent a fortune on that but don't regret any penny. Comparing the average Sumiko with this Swiss jewel is actually no comparison, 2 different worlds.
Long time I was tinkering to change the arm too, at some stages actually had enough cash at account to go for Kuzma Air tangential, fortunately stopped myself in time. This basic Project is very sturdy, doesn't move anywhere unless allowed, its mass complements Ruby cartridge. Only "problem" with it as I can see is lack of precision VTA adjustment, and very rudimentary side tracking force compensation (thread and weight) . But both are manageable with some fiddle.
Also my philosophy is that the cartridge along with speakers (both being electro mechanical devices) are by far most influential in audio chain, that's where the money should go for the best parts you can afford.
The cartridge was high output MC Sumiko Blue Point.
Well, this sounded much better than I expected, even with crappy records, me on the hook again!
Very soon I invested in real cartridge, Benz Micro Ruby 2 Naked, spent a fortune on that but don't regret any penny. Comparing the average Sumiko with this Swiss jewel is actually no comparison, 2 different worlds.
Long time I was tinkering to change the arm too, at some stages actually had enough cash at account to go for Kuzma Air tangential, fortunately stopped myself in time. This basic Project is very sturdy, doesn't move anywhere unless allowed, its mass complements Ruby cartridge. Only "problem" with it as I can see is lack of precision VTA adjustment, and very rudimentary side tracking force compensation (thread and weight) . But both are manageable with some fiddle.
Also my philosophy is that the cartridge along with speakers (both being electro mechanical devices) are by far most influential in audio chain, that's where the money should go for the best parts you can afford.
Szia, nice you first reply, this TT was actually built in Budapest, Szilagy Erzebeth Fasor, that's where I lived then.
Cant say why your TT did not meet expectations, you wrote just basic things, besides marble and marble are different things, so many varieties, and I don't thing neither marble neither slate are really best.
The preamp,
First , I wanted preamp installed inside , as close as possible to the cartridge.
Second, I'm fully balanced freak, cant stand that cartridge which is transformer like floating source to have one leg grounded.
On next picture is block diagram of first stage with RIAA thats built inside the TT and the second stage is outside in preamp. Originally the second stage was Nelson Pass balanced Zen preamp with few mods (added current sources) but with time it turned problematic with many years of use; rotary switch balanced attenuator is loosing contacts, and IRF610 are playing strange things after long time baking, this needs repair and that needs my time.
In the meantime I put KISS (Keep It Stupid Simple) OPA2134 balanced amp in place, works ok but for whatever reason I'm not happy with it.
I am still looking for better second stage; or I will rebuild Nelson's preamp, or might be new OPA828, advice needed. In any case I want it fully balanced.
The first stage with paralleled but opposite SSm2017 is good for me. The gain of each SSM is x1000 , this could raise some eyebrows because of overload margin, but Ruby 2 has 0.34mV output at 1000Hz, that's 340mV after gain, no problem.
Problem could be +20db high frequency output of the cartridge, that would be 3.4mV output, amplified by 1000 equals 3.4 Volt RMS. Both my amp with +-18V supplies and RIAA network (of big RIFA PS 1% capacitors) can handle this.
Then there is concern of over the limit headroom (some people were talking of another 20db needed which would bring this to 34 V RMS capable preamp) . But who has ever seen even full signal on 20kHz, not mentioning reserve headroom. I had no problems with any of many records played.
First , I wanted preamp installed inside , as close as possible to the cartridge.
Second, I'm fully balanced freak, cant stand that cartridge which is transformer like floating source to have one leg grounded.
On next picture is block diagram of first stage with RIAA thats built inside the TT and the second stage is outside in preamp. Originally the second stage was Nelson Pass balanced Zen preamp with few mods (added current sources) but with time it turned problematic with many years of use; rotary switch balanced attenuator is loosing contacts, and IRF610 are playing strange things after long time baking, this needs repair and that needs my time.
In the meantime I put KISS (Keep It Stupid Simple) OPA2134 balanced amp in place, works ok but for whatever reason I'm not happy with it.
I am still looking for better second stage; or I will rebuild Nelson's preamp, or might be new OPA828, advice needed. In any case I want it fully balanced.
The first stage with paralleled but opposite SSm2017 is good for me. The gain of each SSM is x1000 , this could raise some eyebrows because of overload margin, but Ruby 2 has 0.34mV output at 1000Hz, that's 340mV after gain, no problem.
Problem could be +20db high frequency output of the cartridge, that would be 3.4mV output, amplified by 1000 equals 3.4 Volt RMS. Both my amp with +-18V supplies and RIAA network (of big RIFA PS 1% capacitors) can handle this.
Then there is concern of over the limit headroom (some people were talking of another 20db needed which would bring this to 34 V RMS capable preamp) . But who has ever seen even full signal on 20kHz, not mentioning reserve headroom. I had no problems with any of many records played.
And at last, here I need help, a lot of it!
Recently Micro Master Junior, Siemens frequency inverter, went to smoke, and I am without turntable :-(
Siemens made it impossible to service this unit, I had to destroy it to find what went wrong, apparently it was 5V PS chip for logic supply. Googled it and datasheet says made for consumer & low cost electronics parts. Thank you Siemens, Micro Master is industrial equipment costing 500€ and more!
Even before this smoking event I wanted synchronous motor to avoid regular sped adjustments, but it is difficult choice. Old good motors are not made any more.
What I found most interesting is now unobtainable synchronism hysteresis motor as found in ancient reel to reel studio capstan drives, Akai, Revox Sony and alike... But I cant find any, if somebody could offer one I will buy it! (if price in gold equivalent weight is not asked for
)
I found the way how to turn my platter in to the frequency encoder, continuously measuring short term speed wobble and long term speed stability, all with possibility to carefully apply servo feedback to the motor drive. However that will be a lot of work even it would allow also to reuse my original asynchronous motor, or pure DC motors.
In my opinion best solution is good synchronous motor with new drive. I was planning to built one drive around TA7259 chip, that's 3 phase motor driver made for turntables and such purposes, I have one. The chip would be followed by 4th order LP filter, analog power amps and (depending on motor voltage rating) transformers (or not). I have seen 2 very nice treads here using Audrino as supply for 3 phase signal, but me being old don't want any microcontroler in such supposedly simple task.
Here are motor candidates that I hoarded:
From Left to Right:
1. Linn Sondek LP 12 with Valhalla original PS. Problem is that this motor has feel of poles when turning by hand, don't like that! Next is there is no possibility for 45rpm, best EP's are at 45rpm. Third is that my secondary pulley is 300mm platter, not smaller sub platter as in Sondek, so must redo the pulley to much larger.
2. Second is BLDC capstan motor salvaged from cheap VCR, This is mini cheap **** but with many pole pairs and outer rotor. The best is very long shaft extending 5 cm outside the motor, with bushings! I personally think this is the best option, but I need to remove BLDC electronics which is pain job, and add my own 3 phase supply.
3, 3rd is new generation Papst outer runner. This thing I paid darling, for 2 of them. Originally they are for precision peristaltic pumps used in medical applications. BLDC with 3 pole pairs (so nominal RPM at 50Hz is 1000, ok with me) , integrated drive that I have no schematics for !! Balanced outer rotor which is great, but not really needed for TT speeds, and ball bearings that I need to replace with bushings if I want to get what I want, super silent and continuous high torque turning
Anyone with suggestion how to go ahead with this?
Recently Micro Master Junior, Siemens frequency inverter, went to smoke, and I am without turntable :-(
Siemens made it impossible to service this unit, I had to destroy it to find what went wrong, apparently it was 5V PS chip for logic supply. Googled it and datasheet says made for consumer & low cost electronics parts. Thank you Siemens, Micro Master is industrial equipment costing 500€ and more!
Even before this smoking event I wanted synchronous motor to avoid regular sped adjustments, but it is difficult choice. Old good motors are not made any more.
What I found most interesting is now unobtainable synchronism hysteresis motor as found in ancient reel to reel studio capstan drives, Akai, Revox Sony and alike... But I cant find any, if somebody could offer one I will buy it! (if price in gold equivalent weight is not asked for
)I found the way how to turn my platter in to the frequency encoder, continuously measuring short term speed wobble and long term speed stability, all with possibility to carefully apply servo feedback to the motor drive. However that will be a lot of work even it would allow also to reuse my original asynchronous motor, or pure DC motors.
In my opinion best solution is good synchronous motor with new drive. I was planning to built one drive around TA7259 chip, that's 3 phase motor driver made for turntables and such purposes, I have one. The chip would be followed by 4th order LP filter, analog power amps and (depending on motor voltage rating) transformers (or not). I have seen 2 very nice treads here using Audrino as supply for 3 phase signal, but me being old don't want any microcontroler in such supposedly simple task.
Here are motor candidates that I hoarded:
From Left to Right:
1. Linn Sondek LP 12 with Valhalla original PS. Problem is that this motor has feel of poles when turning by hand, don't like that! Next is there is no possibility for 45rpm, best EP's are at 45rpm. Third is that my secondary pulley is 300mm platter, not smaller sub platter as in Sondek, so must redo the pulley to much larger.
2. Second is BLDC capstan motor salvaged from cheap VCR, This is mini cheap **** but with many pole pairs and outer rotor. The best is very long shaft extending 5 cm outside the motor, with bushings! I personally think this is the best option, but I need to remove BLDC electronics which is pain job, and add my own 3 phase supply.
3, 3rd is new generation Papst outer runner. This thing I paid darling, for 2 of them. Originally they are for precision peristaltic pumps used in medical applications. BLDC with 3 pole pairs (so nominal RPM at 50Hz is 1000, ok with me) , integrated drive that I have no schematics for !! Balanced outer rotor which is great, but not really needed for TT speeds, and ball bearings that I need to replace with bushings if I want to get what I want, super silent and continuous high torque turning
Anyone with suggestion how to go ahead with this?
This looks to be what you need for the three-phase VCR motor: https://www.audio-talk.co.uk/phpBB3/viewtopic.php?t=8861
Hi, Thanks for suggestion, I also think VCR motor will be most adequate solution, since I cant find tape reel capstan motor.
Looked at the link quickly, smart way to make 3 phase sine, I like it. But it seems it cant change frequency, fixed by RC, or I see it wrong? So far I think one 3-phase chip followed by low pass filters to get better sine will be better for me, I can set 33,3 and 45 rpm with switch then.