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DIY turntable considerations and questions

N

Nightshade_

New Member
I have recently started creating a turntable from the ground up I will be creating a blog with an extensive writeup of exactly what I did and more Importantly - why.

Things purchased:
Tonearm/Cartridge
Cables
Protractor
Platter Mat
Motor / motor driver / motor belt
Isolation feet

Things I will be creating from scratch:
Bearing for platter
Platter
Plinth

Platter: The platter I have decided to go with is a 13" diameter 4" thick disc of solid Aluminum (54lbs). I chose aluminum over other metals due to cost. I decided to not go with acrylic due to the bearing setup I am using.

Platter bearing: completely custom ferrofluid double pocket bearings for the axial load and a Clearaudio CMB surrounded by sorbothane for radial loads. This means the platter will effectively have no physical contact to transmit vibrations through as ferrofluid pocket bearings actually use a rigid cylinder of air held in place by ferrofluid rings held in place by the magnetic flux of an axially magnetized ring magnet. this will reduce wobble of the platter to sub 0.01mm tolerances while still having the vibration mitigation of a magnetic bearing.

Motor: Am in talks with 3 motor manufacturers, Will likely be going with a Kollmorgen 3430-A10 stepper motor (part of its PMX line). This motor will deliver around 800 oz-in or a little over 4.16 ft-lb.
Motor driver: likely a Kollmorgen P6000
Motor belt: probably REGA - EBLT Advanced Drive Belt

Tonearm: Linn Akito Tonearm

Cartridge: Whatever I have laying around, probably a AT231LP for now.

Isolation Feet: Probably sorbothane feet.

Plinth: Will be isolated from the platter to reduce harmonic coupling and various issues. Will likely be made of rose quartz for wow factor.

Questions for the forum:
What have I overlooked?
How can I reduce motor noise?
What do you want to know about the bearing? I spent nearly a month designing it.
 
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Sincere question: Why? There are many good TT for a nice price. Many more that can be modded. Why DIY a TT?

Missing:
switches for what ever control you are planning
Platter speed control circuitry.
 
I say build it, have thought of building a diy tt myself but life keeps getting in the way, maybe someday I will get it done. Will the motor be mounted on the plinth or remote, mounting it off the plinth might reduce some mechanical noise. Looking forward to pics of the build and interested in your bearing, so will be watching for pics.
 
Excellent project, looking forward to pics and details of the process.

Thought of building a custom tonearm as well? I'm considering that for my next project.
 
Any idea what the wave form of the motor driver looks like? Depending on how clean it is, that may introduce a bunch of weird harmonics and vibration as a result. Not sure if you've ever seen videos of the Floppotron on youtube, but basically he's using computer hardware with stepper motors to produce various tones to play music on. If you've never seen it, have a look, its totally dorky but you'll hear what I mean.


I'm thinking the same thing could happen unintentionally if the motor driver signal is overly dirty. Stepper motors are something I know extremely little about so fixing it is something I don't know how to do.

I do know a guy who came up with his own driver setup. @SteveJewels used low distortion function generators linked together to provide a specific phase offset and a Crown amplifier to bump the voltage to drive the motor on his DIY table. Some more info can be found in his thread on it, maybe worth a read for ideas.

Steve's portable turntable... | Audiokarma Home Audio Stereo Discussion Forums

looks like thats an early version using a VPI speed control device. Later iterations involved the sig gens and Crown amp.
 
Yep, please keep us posted. I'm kinda with gadget73 on the stepper motor. They can be pretty uneven in their torque delivery (aka "cogging"), so watch you drive ferquency/speed, and belt drive ratio.
 
Keep us posted please. It look like a very interesting thread.
If you are going that far, make your tonearm too!!
AG.
 
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