Let's make a DIYAUDIO TT

Hi guys!

After a few talks on other threads I thought to make one exclusively dedicated (yeah, right!) to build a turntable.

Send all your ideas, and pics of allready made stuff, or projects.

If anyone needs help in drawing I can help with CAD (I hope so!)

My DIY turtuble will be based on my two turntables:

- Audio Note TT1
- El cheapo Thorens TD190

I guess I'll use the motor, arm and plint from AN and make a "open chassis" like JA michell Gyro SE. What U think?
 

Brett

Member
2002-01-07 6:02 pm
Hi Pedro,

I'd be interested in being involved in a DIY TT project if it were on the level of the Teres / Redpoint TTs or better. I already have a much modified Gyro and would like to build something if possible to substantially improve on it.

Cheers
Brett
 
TT: Technical specification

All,

let's start with a technical specification to gather some understanding what a turntable is expected to do in detail as well as in entirety.

Let's form an opinion on what we want and let us derive later how we want to achieve it. Let's not hamper our imagination by having a particular design in mind form the start. OK?

BTW, Teres is awesome, agreed. But if we arrive at a design very similar to the Teres one later by accident, we know why it is built that way.

So, what is your opinion, what is a TT meant to do and what is it meant to avoid?
Suggestions?
 

gilid

Member
2002-01-25 9:28 pm
France
tt spec

Good idea to start with specification.

1) platter bearing should minimize (ideally eliminate) mechanical noise/vibration

2) platter material should minimize interaction with vinyl record

3) constant speed rotation (no cogging effect)

4) isolation from external vibrations

5) tonearm should accept wide range of cartrigdes

6) tomearm should minimize (or eliminate) tracking errors

7) most importantly, complexity should be mimized,to make project feasible.


these are what I consider 'generic' requirements, each one of which can be expanded, and added to.

Myself, I have been toying with this idea for several years. I am quite interested in participating in this project!
 

Lenin

Member
2002-02-15 1:42 am
London
Some initial thoughts

Yeah, yeah - lets go for it comrades.

I agree that we should't get too hung up on particular models of turntables we are trying to emulate, but references to particular types will be inevitable from time to time.

A couple of points, based on my own experinces and understanding of turntable design.

1. Inverted bearing, in line with the interface point of bottom of plying groove. The arguments in favovour of this approach are pretty straightforward - essentially that deviation from this ideal introduces progessively more deflection and error at the platter/cartridge interface as the bearing point is moved further away from the 'ideal' point. (I know of just one UK turntable manufacturer who have slavishly followed this approach)

2. DC motor. Quiter, better speed stability, better recovery from speed disturbances with no overshoot (with a properly designed supply)

3. Open design.
Mmmmmmm... I've owned a VPI, Gyrodeck and Pink Triangle Anniversary. This last turntable I had a reluctant listen too at a friends insistance. My jaw hit the floor. I took the thing home , where it preceded to wipe the floor with my Gyrodeck. To my amazement, not only was it an apparently 'closed' plinth, but was, in fact, filled internally with a wierd material - wood? MDF? some weird composite? I don't know. Anyhow, the point I'm trying to illustrate is that an open design is generally better at ensuring that resonances arn't reflected around a plinth, this isn't always the case. The trick would appear to be to design a quiet system in the first place.

4. Arm design
Let's maximise our chances of actually finishing this project by agreeing to shelve the arm element of this project and standardising on a Rega armboard. An arm design could form a dedicated project, in fact I seem to remember a thread on just this subject some time ago.
 
Gilid,

some comments.
1) agreed.

2) not sure about that. platter could act as vibration sink, isn't it? it could "suck" the 3dimensional vibrations happening in the record at the very proximity of the momentary stylus position away from that position. Atleast to a high percentage. Platter can do this job best if it is impedance-matched mechanically: same or similar material for the record and the platter.

3) agreed.

4) agreed

5) and 6)
tonearm, be is gymbal or unipivot or linear tracker, is a supercomplex topic itself and should be a separate project
Can we settle on a universal tonearm basis?

7) totally agreed. KISS rules !! :)

Lenin,
the Pink Triangle is a fun machine. Certainly a question of taste. Not necessarily achieving an honest reproduction of music. And i would loathe to have the subchassis to be re-adjusted for any record with a slightly differning weight.

You ask for a DC motor, gilid asks for no cogging. no Q, agreed, but that narrows choice on (ironless) voice coil motors with 11 or 13 separate overlapping windings. Maxon and Faulhaber manufacture such motors.

Could you please elaborate on what you mean by "Inverted bearing, in line with the interface point of bottom of plying groove." and why is this so advantageous? I can see why one should want his bearing point above the platter's center of inertia, but why in the record plane? (i hope i understood it right)

Inverted bearing: is not a bad idea at all, but it is not as vital as most people believe, it is possible to use an ordinary bearing and still get 1st class results. My own DIY TT built 17 years ago has a non-inverted bearing, it sounds terrific. Recently it got high praise from a buddy knowing them all and stating he would esteem my TT better than a Platine Verdier. Also the Teres has a non-inverted bearing albeit the whole bearing unit is located inside the platter completely.
Something to be mused about ....
 

BrianL

Member
Paid Member
2002-03-29 5:19 am
USA
You know, you guys are about to reinvent the Teres.
So what's the point? It exists, it's beautifully machined,
it's proven. It is now a bit more costly than the first
batch, but significantly cheaper than the brand names.

Maybe a better project would be a killer tonearm kit
to go on the Teres.
 
I guess a thing like the teres is the path, but if a closed plinth is the most wanted, we should go for it.

I also think that we should be democrats on this. If the majority want's to do something, the oppositions should accept .

I think we can do better than teres, at least try :D

We could also make a full specification of the finished project with drawings and 3d models for future diyers have a base for further development.

What do you think?
 
BrianL,

AFAIC, i do not need a TT. I have one (and it just is getting a new motor and a new plinth i just need the space). I just have fun to help others with what i started 17 ys ago, to offer insights and ideas how it could be done, maybe a different successful way.

While i have the Xsectional drawings of the Teres platter in my files, i have the Verdier drawings. I have th SCheu drawings. I have my own platter and bearing drawings. I am not going to volunteer any of them at the moment. I want the others participating in this thread to develop their own concepts from own thinking. I plea for original thinking! And i am dead sure i am not the only one here able to come up with original ideas.

I do not think the Teres is the TT to end all TTs. I do not think it is cheap. From European point of view, it is expensive, Europeans better order a Scheu Kit. Which is not cheap either but, design, manufacturing quality and tolerances considered, certainly worth the money. As is the Teres.
There are ideas out there with patents on them and forbidden to any other commercial venture but available to the DIY community. I just have the platter bearing of the WellTemperedTurntable in mind.

Why inhibit creativity, let the folks try their own thing! No naysaying, please!! :(
I for instance have some ideas how a DIY TT could be made on low money but WITHOUT compromising quality or sonics.
See, a DIY TT can look weird and be completely unsellable, it can be made from surplus parts if you know which to choose. Needless to say that any sane audio manufacturer stays far apart from surplus components.
A DIY TT can be cheaper and better than existing high gloss retail devices. It can follow design necessities to a commercially insane extent. And it can be smarter designed than preceding, exitisting devices. And again, i am dead sure i am not the only one here able to come up with original ideas.
No naysaying, please!! :(

Tonearm:
Let's gather feeling and understanding by designing a TT together. Let's leave a tonearm project for later and with the considerations and insights gathered here in mind.

Do you know the story behind redpoint audio design? The founders, Thom and Peter, wanted to toy around with the design a bit more, to try different platter materials, to try different plinth etc. but Chris Brady, who had taken control over Teres, wanted to make business and inhibited further gain of knowledge, no PVC platters were made. Chris had thought to stop nuisant disturbers, but he did not. Thom and Peter decided to take a swing on it and founded redpoint. And i have heard fairly reliable rumours the redpoint sounds comfortably better than a Teres.
 
Guys & Girls (there must be some lurking at least),

More TT ideas are a good thing. I am happy with my TT, but know it could be better, so i am always interested in ways to make it better.

We should stick to just the TT, and design for almost any arm -- i'd actually like to have a TT with more than one arm again -- last one i had was an ERA with an SME3009 and a Grace 707, can't remember the one before except for the 3012.

Teres is a DIY project frozen in time... it has grown up into a nice little commercial product. I wish it good luck, but it is a product of other's thinking and just a kit now.

The RedPoint is an expression of lets make the Teres better. It is also more of a pre-done kit.

I would like to see an Open (as in open-source) TT project that lends itself to people making weird, whacky, and wonderful TTs. From the units where the machinist makes a bundle (there is a certain benefit to numbers in such a beast) and the TT goes head-to-head with the best, to the DIYer with no budget, some existing kit, and the desire to make the best TT he can from what he has.

A teres beater would be grand, but something you can cobble togther in a weekend out of the parts from a couple generic CEC (large Japanese TT OEM) TTs picked up at the flea market for $10 or less, some plywood, MDF, that piece of plexi or aluminum you weren't sure what to do with, and other found bits is something with a low enuff entry that it could do a lot to just increase the mass of people enjoying vinyl.

And then there is a huge middle ground in between. Downstairs i have an ERA, a Unity Rotary Platform, a Linn inner platter & bearing, a pile of CECs, not to mention all the vintage puck drives just waiting to become something new, unique, and able to help someone enjoy the vast riches of vinyl.

Tricks that can be done to tune your TT to play different kinds of stuff -- ie to be able to get the most enjoyment out of used vinyl played on less than stellar gear, optimization for 78s (listened to some Oscar Peterson on 78 compared to a CD on a CD12 -- the mono 78s were in many ways more musical), you get the idea?

And perhaps a way of turning that stack of really dead vinyl into a platter. bake at 35 min at 200 degrees C for 3 days with a 40 pound weight on top or until done?

Bernhard -- how applicable are old reel-to-reel motors to this kind of ap -- i know i have a couple Maxons.

dave
 

Havoc

Member
2002-02-06 9:16 pm
My idea is to somehow make the platter the motor. An extreme heavy platter being the rotor of the motor used. Stator is on the rim. Kind of direct drive to the extreme. I do not like DC motors with a transmission system, each transmission adds a mass-spring and to really get a dc motor stable you need a servo with all its complications.
With a magnetic bearing?
Plinth: solid cast concrete/plaster

Objections?
 
Dave,
how applicable are old reel-to-reel motors to this kind of ap
i would be not happy with the huge rotational intertia such motors have. They are usully eddy-current motors with a highly asynchonous behaviour and they usually need a speed control which incudes a negative feedback loop. In reel2reel they are usually torque controlled and not speed controlled.

I once had an interesting talk with an expert for precision speed control. He stated, if the speed is known and to be kept within a few % of a nominal value, then let the motor store about as much rotational energy as the driven load, the platter in our case. About as much can vary from a factor of 0.5 to a factor of 2.

But if the speed has to cover a wide range (which is the case with MY TT designs) then design the drive with as few rotational energy stored as possible.
In this respect the motors from maxon and Faulhaber are unbeatable. It must be reason why Manfred Huber used a maxon for his Teres motor unit. Which slowly gathers the reputation of beig the best TT motor unit in the world -- i agree with that rep. I hope Manfred joins us here.

Havoc,
i always second super heavy platters! Always did, always will do! :)
Nevertheless mym own TT is the proof a midweight platter can perform terrific.

Ok,
transmission system: a belt drive using a magnetic tape as belt behaves very well sonically. Moreover it is not finicky at all.
And spring constant of this belt is close to be negligible. Dynamic stability can be achieved with a DC motor. Long-term speed drift however must be either manually adjusted or by a speed control with an I or PI regulator . The DC motor itself however adds no spring constant, but a AC synchronous motor would do so.

Platter being the motor rotor: Onkyo did this once. Very smooth. but the stray fields generated by this sort of motor could the thing be unusable with LO MC cartridges.
Generally there is no reasonable objection against direct drives. But the motor usually uses up space needed for the bearing and inverse. IMO the platter bearing is the most important component of a TT. No compromises here!
So if the bearing is massive, the DD motor becomes physically big and so become its stray fields.

Magnetic platter bearing: used by the Platine Verdier. If the Verdier platter is slowly turned by hand, height variations of the platter surface become observable.
Goodbye stable VTA. Goodbye constant force situation for the platter bearing.
And the platter has to be very high inorder to minimizze bearing influence on MC cartridges. I am not happy with that.
Rather i would have a stainless steel platter swim in mercury (Hg). Not kidding here, this has been done by French TT maniacs. Hg evaporation was inhibited by a layer of silicone oil on top of the Hg.

Then: some others suggested isolation from ground vibrations, i agree. The magnetic bearing acts as a spring (later versions of the Verdier use a bearing ball to inhibit vertical movements of the platter, and they are reputed to osnd comfortably better than earier versions, particularly on the low end). So we have two masses (platter and plinth) and two srpings tucked in beteen masses and ground. A chaotic system, hard to predict when and at which frequencies these masses swing in phase or out of phase. A magnetic bearing alone (w/o the inhibiting bearing ball & trustplate) would be a nono together with a plinth suspension.

Plinth: resin-based concrete would be a world class solution. But ordinary concrete would be too resonant for my taste. Plaster: good idea! why not fill a wooden case with plaster inside, the case having having all needed mounting inlets and surfaces outside. Just watch shrinking during hardening.
 

gilid

Member
2002-01-25 9:28 pm
France
Re: tt spec

Just to elaborate on my earlier posting

1) platter bearing should minimize (ideally eliminate) mechanical noise/vibration

I am leaning towards an aerostatic bearing. I believe that this offers several advantages - a) complete elimination of mechanically sourced vibration
b) eliminates thrust point load problem, which is not trivial when using large mass platters
c) eliminates need for high precision machining of spindle/bearing

Granted, an air bearing presents its own challenges, but I believe that they are not insurmountable. Some time ago, I built a 15 cm dia air bearing, using relatively crude machining techiques, and I achieved excellent results, with a 25 psi air source. This 'proof of concept' gives me confidence that an air bearing is diy-achievable.

2) platter material should minimize interaction with vinyl record

Here, I would use an alumininum platter, approx 25 mm thick, with the lower surface functioning as the upper bearing surface. On top of the platter, a 50 mm vinyl layer would be bonded. This will provide an acoustically matched interface for the record, and would damp any resonances the al bearing would have. I also want to experiment with silicone oil pockets within the vinyl, which could function as vibration dampers.

3) constant speed rotation (no cogging effect)

Platter mass would be the dominant factor here, but I would also keep motor intertia as low as possible, and minimize motor cogging. The Maxxon motors are my choice. They need a carefully designed, stable DC power supply, but there are enough 'cookbook' type circuits out there.

4) isolation from external vibrations

Damped spring isolation is a possibility. I would first build a no-suspension variant (my sound system is on a concrete floor), with the option to add a suspension if it becomes necessary.

5) tonearm should accept wide range of cartrigdes

6) tomearm should minimize (or eliminate) tracking errors

Tonearem can be kept open, with a standard Rega or SME type provision

7) most importantly, complexity should be mimized,to make project feasible.

The biggest challenge I see is finding a willing machinist, who has the interest and patience to work with the group. As with anything, this will be an iterative process, and it is highly unlikely that the first item built will the the 'final' version. It is important to keep this in mind during the design process, so that subassemblies can be modified individually. I see a modular type concept.

I also favour an open chassis design - favours the modular approach, and is also aesthetically superior (my personal opinion).

For some interesting concepts, check out the 'turntable lust' web site - I do not have the URL, but a google search should find it.
 

BrianL

Member
Paid Member
2002-03-29 5:19 am
USA
Gentlemen (I don't think Morsel is reading this, but maybe
I'm wrong)

I don't intend to be naysaying. Yes, I have a Teres,(unassembled); got in too late for any design input but before it went commercial.
The thing you'll have difficulty replicating at an affordable price
is the machining. It's beautiful. Also excellent is the controller,
though nothing one couldn't do oneself.

Good luck, but consider whether there are other areas of
your system that would better benefit from improvement.
I know that there are many in my system. Heck, just getting
the Teres built and working would be a major improvement!

But this hobby is all about extreme effort. Ars gratia artis
and all that.

Have fun!
 
here goes a drawing of the platter based on my audio note TT1, (void design)

this has a cnc machined brass bearing with a stainless steel spindle with rounded end (see picture) with a drop of oil.

I ran some numbers and the projected weight in perspex is 4.98kg with a volume of 3519 cm3 and a moment of inertia of 11214cm4.

It has a top "hole" with 5cm radius and 2mm depht. I guess is for the label?
I made it with a hole in the bottom to "use" it with the axis of my current TT. what do u think of this kind on bearing?

maybe too simple :(
 

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technical specification -> Wiki

All,

comments later, just one idea now: why not write our technical specification into the diyAudio Wiki ?
This is an online document which can be edited by anyone of us and things wirtten there do not get lost in the thread?
We could make the spec a living document and adapt it when needed.

Oh, and morsel, why not invite her? :)

Ok folks, gotta sleep, (yawn) worked all night on my tonearm.
 

Havoc

Member
2002-02-06 9:16 pm
Dice, I mentioned the plaster because at the diy shop in the building section I found plaster blocks (7x40x40 cm) but they have a tongue-groove for building walls etc. But it looked ideal for a TT! I don't know about poly concrete, but this can be checked. We could also use something like epoxy resin filled with ground stone.

As for the magnetic bearing, I do not think the height variations are a problem. True when you turn by hand, but when the motor drives it is at a constant torque in a totally different direction, so during playback this should be no problem. Damping of incoming vibration is a different problem and a serious one.

Direct platter drive: The field at the cartridge can be small if the platter itself can be the shield and thus thick and heavy enough. Only problem is how to do this! It would mean building a large stator with lots of field coils and control electronics. And dynamic balancing of the platter is not evident.

Most important would be a kind of self-aligning bearing that is almost unsensitive to machining variations. If this complicates the design, and adds components, who cares. This is for those who want to make it anyway.
 
Havoc said:
We could also use something like epoxy resin filled with ground stone.

Back in the late 70s, when the LP12 was the undisputed king, we made a Linn outer platter out of powdered copper & epoxy. It seemed to be a clearly better performer than the stock platter. The Linn distributor walked away shaking his head after a demo -- his whole belief system had been shaken.

dave
 
Dave,

unsurprised about your Linn platter.
The original platter was ringy. And i could hear that, e.g. violins would start to scream at exactly the pitch the platter was ringing with. They would scream, no matter how high/low the volume.

Havoc,
epoxy filled with ground stone is what i meant with poly concrete. I fell in love with this material years ago when i wrote my diploma thesis on TT design. But i had to learn that the gound stone is not easily brought into the resin, due to the resin's high viscosity. And it is necessary to have the right particle size distribution curve in oder to have the volumetric efficiency maximized, to have as much ground stone and as few resin as possible.
Methinks, this would be hard to achieve DIY att home.
Moreover, the epoxy concrete is hard to machine afterwards and even the surface is hard to be smoothened. So the mould has to provide form AND surface with desried precision/rougnness. And the mould has to withstand the hydrostatic pressure of the not-yet-hardened poly concrete. Which is considerable, due to density of about 4g/cm^2 .

But what i see as possible: to have a beautiful outer shell, thin-walled and with all needed tap inlets and then filled with plaster, self-mixed poly concrete, epoxy/leadshot or what ever. This shell can be from wood, corian, copper, whatever. And to have an outer mould made from rough material but exactly fitting to the shell and stiffeneing the shell against hydrostatic pressure.

Plaster: very good idea.

Magnetic bearing: go and watch a Platine Verdier (without axial ball bearing of course), or better, have a linear dial gauge measuring the height variations while the motor drives the platter. A frined of mine did so and then he reported he wnated to find out whether heigh variations could be caused by the varying magnetic field fo the ring magnets.
He told me, he had the impression of a mild form of cogging. From that day, i stopped to take magnetic bearing into consideration.

Havoc, i adored the Platine Verdier back then. But to day methinks a better TT can be built with less effort.

Direct drive: you are right, it could be done. But it would need shielding. And so platter design is limited by that.
Generally spoken: if we introduce a new feature or component, we have to watch the consequences on the whole design as could be: interactions between components, inhibiting the maximum performances of another component, violating safety rules, manufacturablility and so on. Methinks, a magnetic shielding could be a severe deterioation of a platter with mechanical impedance matching done by the platter material. Mumetal is not PVC or delrin or acrylic. And a mumetal inlet could be excentric and also hard to get centered. Okok, not a big objection (the platter i was going to suggest also needs balancing/getting rid of mass excentricities...)
Again, i would prefer better performance with less effort. No mumetal shielding needed because the motor is distant.

Self-aligning bearing: i also want that! i do favor Gilids suggestion: aerostatic bearing. Such bearings have the tendency to diminsh bearing surface imperfections by a factor of 100 maybe 200. The air film smoothes the imperfections out.
Ultra precision air bearing usually have cylindricity deviations of 0.05µ with bearing surfaces machined to 10µm or 5µm precision.