Motor for turntable.

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Hello, I think about building my own turntable. The first met obstacle is to find good motor. New ones are beyond my financial reach. Used ones, like from entry level turntables, are not powerfull enough for heavy platter. Is it possible to adopt electric motor not ment to be used for this purpose,, but with proper control circuit converted into precise turntable driver? Or.......any suggestion?
Thanks!!!
 
Hi,

i tried several motors on my diy tt and can tell you a few things:

a dc-controlled maxon needs a quite difficult control circuit (shown somewhere at www.teresaudio.com), i buil one just using a LM317 voltage regulator and this did not work well. When the needle tip dives into the groove of the record, speed decreases dramatically. Which means, the speed not only depends on the voltage, it also depends on the mechanical load. This varies across the radius of a record an from music to music.

Then I tried a PLL-regulated DC motor like the one Thomas scheu sells (www.scheu-analogue.com). It was only 10$ and works fine so far, you can adjust speed without having to lathe an new pulley. The only thing is that you should use a string belt (no rubber) an the motor is not the quitest I've heart yet.

Please read my experience at www.krishu.de > hifi stuff > turntable stuff > tt motor.

There are some people who sucessfully use stronger maxon motors than the one i had without the difficult control sold by teres. This uses a Linear Technology Chip (i forgot the number), but unfortunately i did not get a circuit until now.

Maxon motors are not too cheap, but the quality is really good.

Cheers
Christian.
 
krishu said:
i buil one just using a LM317 voltage regulator and this did not work well.

But you did not use the 101189 Maxon that the Teres people use, right?

Speaking from experience with the Michell motors, something of the torque and power of that Maxon runs constant enough for turntable use.

Of course, if you use a (much) smaller motor ...
 
I'm actually building a controller using the same motor krishu originally used with this rather simple circuit. It seems that you either need a ridiculously heavy platter or some kind of feedback to get an accurate speed. I could be wrong, but this is just my observation so far.

i haven't been able to test it properly as i haven't yet machined up my bearing, but i have done some rather rough and shoddy tests hooking it up to my Technics DD platter (don't ask......), and it seems to be better than just a voltage reg. It will however need some tuning to fit your application. As the pdf says, not the be-all-and-end-all, but better than a poke in the eye (so to speak).
 

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krishu said:
a dc-controlled maxon needs a quite difficult control circuit (shown somewhere at www.teresaudio.com), i buil one just using a LM317 voltage regulator and this did not work well. When the needle tip dives into the groove of the record, speed decreases dramatically. Which means, the speed not only depends on the voltage, it also depends on the mechanical load. This varies across the radius of a record an from music to music.

Before I upgraded from my Thorens to Linn LP12 about 15 years ago I read a lot of the material relating to motor control -- and just as you mention, the electronic means of control with an unsatisfactory feedback system -- i.e. an LM317 -- weren't sufficient for the Golden Ears of Linn-Land. If I can find some of the stuff I will post it.

Perhaps the most satisfactory means of control is just "mass" and the moment of the wheel.
 
speaking of mass and moment (and i hope this isn't far off topic), does anyone know where/how to find/make a nice balanced flywheel for turntable use? to my mind it seems more mass-efficient -- if also more labor-intensive -- to use a heavy 'ring' with most of the mass at the perimeter of the circle. (mass at the center doesn't do much for you, inertially.) any ideas?


/andrew
 
Before I upgraded from my Thorens to Linn LP12 about 15 years ago I read a lot of the material relating to motor control -- and just as you mention, the electronic means of control with an unsatisfactory feedback system -- i.e. an LM317 -- weren't sufficient for the Golden Ears of Linn-Land. If I can find some of the stuff I will post it.

This doesn't seem to make a whole lot of sense - Linn use an AC motor which requires no controller at all - just a cleanish 50Hz which a 317 obvioulsly cannot do.
 
analog_sa said:


This doesn't seem to make a whole lot of sense - Linn use an AC motor which requires no controller at all - just a cleanish 50Hz which a 317 obvioulsly cannot do.

No, Linn has (had) a whole range of power supplies for the LP-12 -- here's an article on the Linn Lingo: http://www.stereotimes.com/acc030903.shtm

oh, an LM317 can be used to regulate an A.C. waveform, or at least clip it at regular levels -- just look at the National Semi ap-notes. I wouldn't say that it's very good at it, not its intended purpose...people have been known to modulate the control pin!
 
diyAudio Senior Member
Joined 2002
Hi,

Just don't get me started on anything LINN, please?

Unless you insist on discussing the biggest ripp-off company in history?

Facts apply mainly to the later mid-eighties designs:

-Close tolerance turned into casserole fits for platter, bearing whatever.

-Add-ons like Lingo only made things worse.

- Felt mat used to cover design deficiencies akin to using too much feedback.

-How many people can set one up to make it sing? Regardless of coluorations?


All in all a flawed design that occasionally played a tune ( Linn-speak).

Not to mention these guys attitude towards the clientele and pundits...even Coca Coala could take a lesson here.

Absolutely outrageous...

Brett,

I don't know of any Nottigham Analogue design that needs a hand start and I all know them inside out.
I'm very familiar with Tom who's as helpful as I can possibly imagine.
Could it be the belt needs replacing?

Cheers,;)
 
fdegrove said:
Brett,

I don't know of any Nottigham Analogue design that needs a hand start and I all know them inside out.
I'm very familiar with Tom who's as helpful as I can possibly imagine.
Could it be the belt needs replacing?

Cheers,;)

Hi Frank,

I'd read so many comments about hand starting from people that I presumed it was built into the design. With no off switch and a low powered motor designed to stall wih a manually stopped platter, it made sense to me.

Nonetheless it still makes sense for a DIY design, rather than trying to find a high powered, low noise/vibration motor, affordably.
 
a few days ago i was at work on my car, in the middle of an engine overhaul and being a fanatic i also took the time to re-paint a few brackets and accessories including the cooling fan and motor.

i am also about to start building a TT and ran in to the same dilemma. so i took a look at the little motor for the fan and thought that this is almost a perfect size. i've yet to find out how quiet they are on their own or how much current they draw as per volt, but it might be worthwhile to stop in at a junkyard and pull out an old cooling fan or two to try out.
 
faustian bargin said:
where have i heard about someone using a disk drive motor...either a floppy disk, or a hard drive, i can't remember which.
Usually floppies, but they're steppers so need some control cctry. A 400 step/rev motor running> 300rpm should be smooth enough, and have a fair bit of torque. Can often be found surplus too. Not hard to drive if you're imaginitive with how to do it.
 
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