Sourcing DIY turntable parts.

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brad1138

brad1138

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Joined 2017
#1
I am considering trying to build my own Turntable. The arm is easy with, but where is good place to find motor, spindle bearing, sub platter and platter?

I could just by an upgrade spindle bearing/sub platter kit like this ( https://www.acoustand.co.uk/collect...ter-upgrade-for-pro-ject-xpression-turntables ), but annoyingly, these have nearly tripled in price in the last year or 2... I could also buy a matching Acrylic plater.

I see this on Amazon https://www.amazon.com/Vbestlife-Turntable-Recorder-mounting-Turntables/dp/B084G2W85H But I am hoping there are better options... the wiring diagram is also above my head (without studying it more)

My plan for a plinth is this https://www.amazon.com/gp/product/B01L5NQ6MQ I already have one I use as a TT base. It is about perfect size wise for me.

The only other question is the belt and speed control. Either I assume you either have variable speed, or Fixed speed with the right size size pulley.

Thanks
 
#4
I fear you are looking for very specialized stuff in a niche within a niche situation.

How many people are DIYing turntables?

What is the market size for somebody to invest in manufacturing and offering those parts?

* Manufacturing and offering the finished product? .... check

* Offering some aftermarket pat for improvement? .... check

* Halfway? .... sort of complicated.
 
#5
A turntable only has two parts... a lathe and a mill. IMO, you can probably find those cheaper than what boutique parts go for. After much study of motors, I'd go with a 3-phase BLDC. The well known names are expensive but there is at least one Asian one that's decent and not crazy priced. Unfortunately, I can't remember the name.
 
#6
Looks to me like the motor out of Trabant with the bearings off a Renault and the woodgrain interior out of a luxury car. I don't rate any of the turntables that are listed as using that Pro-Ject bearing. If you are going to put so much effort into the plinth, then an Isokinetik Peek Ceramic Bearing Sleeve, a Tango Spinner metal subplatter with silicone decoupling, and an Origin Live DC Motor Kit and any aftermarket Rega type platter that takes your fancy would be more in keeping with the effort, and create a vastly superior turntable.
 
#7
johnmath said:
Looks to me like the motor out of Trabant with the bearings off a Renault and the woodgrain interior out of a luxury car. I don't rate any of the turntables that are listed as using that Pro-Ject bearing. If you are going to put so much effort into the plinth, then an Isokinetik Peek Ceramic Bearing Sleeve, a Tango Spinner metal subplatter with silicone decoupling, and an Origin Live DC Motor Kit and any aftermarket Rega type platter that takes your fancy would be more in keeping with the effort, and create a vastly superior turntable.
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Thank you, that is exactly the type of answer I was looking for. All the prices are quite reasonable, aside from the motor kit.

Would the OL Kit be variable enough to run the belt around the sub platter or platter? I haven't decided which way I want to go yet.
 
#8
It is technically feasible for the range of speed control of the motor to be broad enough, but I can't say for certain that Origin has provided that range of adjustment but they do work with Linn, Thorens and similar sub-platter drives. With a bit of hunting another source of DC motor and controller may be found.

In any case a flat belt driving the rim of the platter will give superior wow & flutter performance compared to driving the sub-platter, especially compared to an o-ring driving a sub-platter. The quality of the belt is critical, because variations in thickness along the belt contribute to wow, the surface roughness of the belt contributes to flutter and the elasticity of the belt is implicated in how much motor noise and vibration is transmitted to the platter.

A belt is 'pinched' as it goes around the pulley (and to a lessor extent around the platter or sub-platter) because the inside surface of the belt has to compress and the outside stretch. The compression of the inside of the belt means that the belt contact surface has to slip or pinch across the pulley surface and this is a source of stiction noise that contributes to flutter.

The thicker the belt, or o-ring relative to the contact surface radius, the greater that amount of linear compression when the belt is forced to bend, hence the greater the amount of slippage between the pulley surface and the belt, and the greater the amount of noise generated. A large pulley relative to belt thickness is better. Also a lubricant on the belt, such as talcum powder, helps ease the stiction noise as the belt pinches. Driving the rim of the platter reduces the impact of belt irregularities of all types.

Another issue is runout in the main bearing / platter. Horizontal or vertical runout manifests as cyclic speed variation that occurs once each revolution. If you listen to a pure tone, it sounds like the doppler effect of a noise source traveling toward the listener and then receding again, a sort of coming and going effect. It is critical the the shaft is straight so there is no horizontal runout or eccentricity, and that the platter is perfectly perpendicular to the shaft so there is no vertical runout or wobble.

The flatness of the platter also affects vertical runout. I use a dial gauge to measure the runout, and often it is possible to find a relative position of the platter / sub-platter where the runout is minimised, or even nulled out. I mark this position so that the platter can be removed and replaced in the same relationship.
 
#9
Found the motor supplier- https://assunmotor.com/products/brushless-coreless-motor Seems like an excellent selection for a reasonable price.
I'll play devil's advocate on where to drive a platter. When you drive the rim you're in tight control and not getting the full advantage of the platter inertia unless you have a very compliant belt. It's too easy for any drive system irregularity to almost instantly affect the platter speed. When you drive a smaller diameter, say a sub-platter, you can get some isolation without resorting to a very compliant belt. It's a mechanical filter system that can be analyzed for any given case. IMO, it comes down to execution (like everything) and the perfection of the parts, but driving a sub-platter will be better if you're not investing a small fortune in perfection of everything. (FWIW, the light/heavy platter and tight/loose control argument has never been won!)
 
#10
Conrad Hoffman said:
I'll play devil's advocate on where to drive a platter. When you drive the rim you're in tight control and not getting the full advantage of the platter inertia unless you have a very compliant belt.
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Not true. To have any benefit the platter and sub-platter would have to have seriously compliant coupling. And any battle is won by physics. As I said previously, it seems to me that few designers of turntables have much grasp of mechanical engineering. Personally I don't want fairy floss on top if what I am listening to, no matter how sweet it is.
 
#11
Hi, You are asking a question that has been asked at least a couple of hundred x's over the last few years. Use GOOGLE to search for the answers. There is a lot on other sites as well as this one.
The 1st thing people need to know is what is your budget. You can do a V/G T/T / arm & re-tipped cart for $1000, any less than that then you need to be a seriously good lathe & mill operator as well as having access to one.
One tip, do not use a part i.e. motor, that has not been used successfully by other people. If you want to use a DC, T/T motor, (easiest way) then you need one that operates between 6 - 24 VDC running at about 3500 RMP.

It could be just easier to re-furbish a older T/T, but to do that properly will most likely cost well over $1000.

Cheers
 
#12
johnmath said:
I don't rate any of the turntables that are listed as using that Pro-Ject bearing.
Click to expand...
Not the bearing, but the motor and the belt...( my attempt to a 10 " tonearm, platter&bearing from Pioneer PL12)
here_we_go.jpg
 
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#15
picowallspeaker said:
I must add to your knowledge that often another important piece is not considered: a flywheel...
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If the project motor includes a flywheel, then all other things being equal that would be a really good thing. It does not change my apprehension about Pro-Ject yet, which is based on >20 years of first hand experience of often intractable design deficiencies over many models of turntables they have produced. I sincerely hope that Pro-Ject has turned a corner. 🙂
 
#16
johnmath said:
Not true. To have any benefit the platter and sub-platter would have to have seriously compliant coupling. And any battle is won by physics. As I said previously, it seems to me that few designers of turntables have much grasp of mechanical engineering. Personally I don't want fairy floss on top if what I am listening to, no matter how sweet it is.
Click to expand...

Wouldn't having a smaller subplatter multiply the flywheel effect of the platter? The torque would be multiplied by the product of the difference in diameters, wouldn't it?

I'd think with the lossy belt in there it would be a benefit.
 
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#17
cgallery said:
Wouldn't having a smaller subplatter multiply the flywheel effect of the platter? The torque would be multiplied by the product of the difference in diameters, wouldn't it?

I'd think with the lossy belt in there it would be a benefit.
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As a thought experiment, imagine one of those playground merry go 'rounds the kids play on, one with a stationary bar suspended over, for the user to hold onto. Imagine you're the motor and holding onto this bar and trying to maintain as constant a speed as possible. Is that going to be best accomplished by running towards the center, or running towards the outside edge of the go 'round?

The center, because at the outside edge your torque is multiplied and each footfall jolts the platform to a greater degree.

You're an imperfect motor and you vary your speed. The further you keep away from the outside edge, the less apparent this will be.

No?
 
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#19
cgallery said:
You're an imperfect motor and you vary your speed. The further you keep away from the outside edge, the less apparent this will be.

No?
Click to expand...
No.

The platter and sub-platter act as one mass, so the important difference here is the drive diameter as you have recognised. All things being equal (which of course they never are) there are some limiting factors at play. Drive belts are ground to a flat surface and there is a limit (or cost) to how flat the belt surface can be made. The roughness of the belt surface causes variations on torque coupled to the platter. If the drive diameter is 50% of the overall diameter then the is a magnification factor of 2, or 6dB, in the belt noise transmitted to the platter. It is amplified by the mechanical leverage of the drive to overall diameter ratio.

In terms of the ability of the belt to isolate motor vibration from the platter, there is no fundamental difference in the physics of different diameters. Without changing the belt material or thickness, but merely physical doubled everything in size means half the noise generated by surface roughness of the belt at both the large (platter) and small (motor) pulleys, and double the resilience of belt between the two, though the latter effect is canceled by the double diameter of the large pulley. (In any case the belt resilience is a property that can be selected for the design, so it's effect can be taken out of the comparison of pulley size.)

It might be surprising that surface roughness of the belt is a source of flutter, but it is actually the main source of flutter IME. As an experiment I invested in about 30 different brand name and generic belts for my turntable and measured them all. The variation in flutter ranged from ~0.02% for the best to ~0.3% for the worst. Even the turntable manufacturer's own expensive premium belt performed poorly. For reference, the best direct drive turntables perfume better than <0.02%.

The best belt was nearly twice as good as the second best, which mean only one of the twenty or so different manufacturers (some had multiple belts) actually dod a good job of grinding the belt flat. You can even feel the difference in belt surface roughness by pulling belts through your fingers if you have enough dexterity ( a stone mason may struggle here!)

Another factor with belts is thickness consistency along the length of the belt. Inconsistence in thickness cause a per-revolution speed variation or 'wow'. Again the smaller the diameter of the two pulleys, the greater the sensitivity of the drive system to belt induced wow. That is because the the effect of thickness variation is a function of belt thickness divided by pulley thickness, and this worsens as pulley diameters get smaller. Like flutter above, the belt is the main source of wow in a belt drive turntable. I don't recall specific figures, but the range is similar to the figures for flutter above.

Other frustrating factors with smaller drive diameters is the increased wear rates of the belts and increased sensitivity to temperature and humidity, dust etc. Even the change in belt temperature from cold to finish of the first side of record is significant with a small drive diameter in my experience. Of course temperature changes applly to rim drives, but the effects are much reduced by the ratio for belt to pulley sized and a reduction in temperature build up in the belt due to longer belt, lower torque forces on the belt, less contortion of the belt going around larger diameter pulleys, etc.
 
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