DIY TURNTABLE : ideas and comments.

[Hiten]

Thanks everyone.
@ navin : Noting is fixed yet. Only tentative plans.
@ bhaskarcan : thanks for encouragement. I needed that. But Please dont expect super high end turntable. Have to keep budget in mind. So bearing, spindle and shaft will be from old TT.
@ arj : Yes salvaging parts from high end TT is good option.
@ Sachin : That dude has spent huge amount of money. Platter is from scheu.
@omi : Bro kindly tell me...
- can a brushless DC motor be regulated to have stable speed ?
- can it have a three speed ? 78, 45 & 33 ? or atleast 45 and 33. I will see if replacing pulley can get me 78 rpm. as I will not be listening to them often.
- Monitoring the speed will not be a problem I have paper strobe disk. for a start it will be good enough.
my requirement is speed should be stable and should have 3 speeds. Nothing high end exotic stuff just good vfm circuit and motor.
Regards

 

[omishra]

@omi : Bro kindly tell me...
- can a brushless DC motor be regulated to have stable speed ?
- can it have a three speed ? 78, 45 & 33 ? or atleast 45 and 33. I will see if replacing pulley can get me 78 rpm. as I will not be listening to them often.
- Monitoring the speed will not be a problem I have paper strobe disk. for a start it will be good enough.
my requirement is speed should be stable and should have 3 speeds. Nothing high end exotic stuff just good vfm circuit and motor.
Regards

Sure! IMO any DC motor can be controlled for steady speed. You want those 3 speeds as selectable them we can add 3 preset values at once and then have some technics 1200 like slider or rotating knob for fine tuning the same keeping selected preset speed at middle of fine tuning position.

 

[Hiten]

A little update. Can get Technics sl-q303 which is semi working cheaply. So can salvage DD motor and spindle, shaft, bearing, But there would be no fun of DIY. just assembling things. Mods one can do is better plinth, isolating feets, discard semi auto mechanism. etc.

 

[navin advani]

A little update. Can get Technics sl-q303 which is semi working cheaply. ...

why not? it would be a nice basic table to cut your teeth on.

 

[Hiten]

Thanks navin,
have been reading up on DC and AC motors. The best no nonsense motor would be AC motor (like garrard) as it will not require any speed regulation but will need some kind of speed adjustment to finely adjust the speed. DC have their problems too. as stabilizing constant speed will require a modestly very good circuit design (Omi help).
Have downloaded Technics sl-q303 service manual. DD Motor is pretty good. As it is quartz phase locked (?) speed stabilization. But the turntable is fully automatic with mechanical levers and all directly coupled to platter motor and chasis and plastic cover. So I am pretty sure vibrations will have a field day travelling all over the turntable. So Salvaging this motor and proper isolated platter/motor/tonearm will take this up to one level. lets see. will update soon.
Regards

 

[Hiten]

Have been browsing the net. Some revelations are...
-Idler drive have good torque and affects SQ immensely. In better way ofcourse but vibrations/resonance can seep in to platter unless motor, idler is of very good quality.
-belt drive has advantage of motor isolation, but torque is the issue (Thats why High end TTs have belts on max. dia. of platter i.e. outer circumference).
-since Direct drive motor is bang right in the centre with good quality DD motor vibrations are very very less (but needs heavy platter).
- Tone arm base should be connected on the same base as spindle shaft so as vibrations dont compliments each other or increases.

... so gurus my question is how can one make sure the spindle and tonearm both are exactly on same horizontal plane ?

Bubble levels ?
Using straight plane surface for both ??
???
Regards

 

[Hiten]

Due to personal problems am finding it difficult to keep up with this DIY and logging in to forum. But here is a little update...

I have acquired Garrard Laboratory series synchronous AC motor. (A very well made stuff) Also have technics turntable feet with little threaded bolt to adjust height and level the TT. Also will be getting Quartz controlled Direct drive motor. have two New Cartridge+stylus too. So hopefully will decide which way to go about this DIY after studying all aspects.
Regards

 

[omishra]

... so gurus my question is how can one make sure the spindle and tonearm both are exactly on same horizontal plane ?

Bubble levels ?
Using straight plane surface for both ??
???
Regards

I feel that could be done with cheapo transparent rubber pipe (like doctor use for putting Glucose) or thicker 5-6mm diameter (rs 10/-). Fill it some water and level the water at the both ends. Water remains in same horizontal plane.

 

[Hiten]

Good thinking Omi. Also as an after thought I think I can use bubble level. First I can level a plane with bubble level, put spindle and tonearm base on them level them and fix them. Lets see.

I opened the garrard motor to calculate the speed. It has 18 poles so RPM comes to about 333.33 Exactly 10 times the vinyl speed. So I think speed ratio would be 1:10 For belt drive TT 1cm dia. pulley will require 10 cm. dia. platter base to turn. Which I think is too small as torque will suffer. I can put center weight but that will put load on the motor.
Making simple things work efficiently is not easy.

 

[sachu888]

Good thinking Omi. Also as an after thought I think I can use bubble level. First I can level a plane with bubble level, put spindle and tonearm base on them level them and fix them. Lets see.

I opened the garrard motor to calculate the speed. It has 18 poles so RPM comes to about 333.33 Exactly 10 times the vinyl speed. So I think speed ratio would be 1:10 For belt drive TT 1cm dia. pulley will require 10 cm. dia. platter base to turn. Which I think is too small as torque will suffer. I can put center weight but that will put load on the motor.
Making simple things work efficiently is not easy.

Good going Hiten bhai.See here for replinth.
Technics SL-1500MK2 Replinth Project - The Art of Sound Forum

Regards,
Sachin

 

[Hiten]

Just browsed through the link you have give Sachin. Very Pro job. Thanks for sharing.
regards

 

[entsurgeon]

Good thinking Omi. Also as an after thought I think I can use bubble level. First I can level a plane with bubble level, put spindle and tonearm base on them level them and fix them. Lets see.

I opened the garrard motor to calculate the speed. It has 18 poles so RPM comes to about 333.33 Exactly 10 times the vinyl speed. So I think speed ratio would be 1:10 For belt drive TT 1cm dia. pulley will require 10 cm. dia. platter base to turn. Which I think is too small as torque will suffer. I can put center weight but that will put load on the motor.
Making simple things work efficiently is not easy.

i dont understand. if you are reducing the speed by a factor of 10, that will not be a burden on torque capabilities of motor as it has to make 10 rotations to move the platter 360 degrees.
also please check this cross posted from the link mentioned on page 1 of this thread:
[/QUOTE]Geordie,
I have experimented with various materials for mats, starting with felt, rubber varius foam packing materials . . . . I eventually found an article somewhere on the web (where else!) about a mat made of some super duper high density foam arranged in little balls connected together. Now I was sure that I'd seen a similar material in my travels to one of our local shops here in Australia, called Clark Rubber. They basically supply all sorts of rubber and matting products and similar shops would be found around the world. I bought a meter x 1.5m for about AU$10 and cut a bit into a circle. The sound was fantastic, and with some experimenting I found that it sounded best with the felt mat underneath it. The really good thing about this stuff is that the record does not move at all it sort of gets gripped by the mat. It leaves no residue either.
So there you have it!
efgee
junior member

Posts: 17
Images: 16
Joined: 31 May 2008 11:54
Location: Melbourne, Australia[/QUOTE]
such a mat is readily available cheap with automobile accessory shops where its sold as a dashboard mat to keep your mobile phone stady.

 

[sachu888]

Just browsed through the link you have give Sachin. Very Pro job. Thanks for sharing.
regards

Hi Hiten,
It is not complicated any CNC shop will do that if you provide CLD drawing to them.

Regards,
Sachin

 

[Hiten]

@Sachin : Luckily we do have Laser cutter here in our small town. I just have to give them diagram. So lets see first have to sort out which path to choose.

i dont understand. if you are reducing the speed by a factor of 10, that will not be a burden on torque capabilities of motor as it has to make 10 rotations to move the platter 360 degrees.

A small dia. pulley rotating large dia. platter will have more torque. Bigger the dia. of the platter more torque it has. Thats why most high end turntables use maximum dia. available i.e. the platter.

unfortunately with garrard motor with 333.33 RPM it turned out to be just 10 cm. But I am not giving up hope will experiment and see.
Regards

 

[Hiten]

Bros,
Where can I get cheap variable AC sinewave generator with fine adjustment ? Looking for cheap readymade solution to supply 50hz or 67.5 hz to AC motor. Will this work ?

something like this - XR2206 based functional generator DIY kit - Sine and Triangle Wave 1Hz - 1MHz | eBay ???
Thanks & regards

 

[Hiten]

Ah! Oh! Wait. Ignore previous post. I was planning to feed 220v 50hz in to synchronous AC motor. but...

ClariSonus - Clear and enjoyable sound ? Mark Kelly on Empire Motor Project, part 2

audio sine wave generator

... it looks like will need generated signal and amplifier to run it.
a complicated job for me.
Sorry.

Regards

 

[omishra]

... it looks like will need generated signal and amplifier to run it.
a complicated job for me.
Sorry.

Regards

You are spot on. Now tell me -
1. Do you want to change frequency of supply to motor w/ constant supply voltage?
2. Do you want to change only voltage//current to motor w/ constant frequency?

 

[Hiten]

You are spot on. Now tell me -
1. Do you want to change frequency of supply to motor w/ constant supply voltage?
2. Do you want to change only voltage//current to motor w/ constant frequency?

Thanks a lot Omi.
1-Yes frequency should change with constant supply voltage. As more voltage would make the coil more magenetic and will attract induced magnetic rotor more so speed will not be stable.
2- Voltage current should be as stable as possible but need only frequency to change.
-- I read people use MP3 player and class A amplifier to put out sine wave to ac motor. But I have a feeling a brushless DC motor with voltage regulator will be more easy. I dont know.
-- Other crude way is to have mechanical speed adjustment like Lenco 75 which has tapered pulley. So I can directly run AC motor from powerline with stable frequency.
-- Also was wondering is our power line frequency stable 50hz. Has anyone tested it at different time of the day?
Sorry lots of questions
Regards

 

[omishra]

Thanks a lot Omi.
1-Yes frequency should change with constant supply voltage. As more voltage would make the coil more magenetic and will attract induced magnetic rotor more so speed will not be stable.
2- Voltage current should be as stable as possible but need only frequency to change.
-- I read people use MP3 player and class A amplifier to put out sine wave to ac motor. But I have a feeling a brushless DC motor with voltage regulator will be more easy. I dont know.
-- Other crude way is to have mechanical speed adjustment like Lenco 75 which has tapered pulley. So I can directly run AC motor from powerline with stable frequency.
-- Also was wondering is our power line frequency stable 50hz. Has anyone tested it at different time of the day?
Sorry lots of questions
Regards

No problem! I have a clock circuit which uses some crystal and has frequency divider network. Its output is approx 50-60Hz stable. But its not sine wave. If you want sine wave then we need to built good sine wave oscillator. I have seen readymake kit at Vega/kitsnspares. Also leverage any cheap amp based on 4440 in bridged mode. It will give good stable output if installed on heatsink. Otherwise we can built MOSFET based class AB amp. or buy this kit and use its single channel.

One more link for function generator

And chip

 

[Hiten]

So we need sinewave oscillator and amplifier. so will require more electronics which I am trying to avoid. How about UPS inverter (the small ones with 20/25 min. backup) I presume they must be having voltage regulation and oscillator (not by capacitors) for steady frequency. If possible we can supply regulated 12 V DC supply (as they get from lead batteries). what say ??? once voltage and fq. is stabilised I can use AC motor without worrying about major speed drifts.

Sorry for repeating wouldn't brushless DC motors be easy to control and stabilize as it will only need feedback and voltage regulation. I checked with friend at lamington road. Only DC motors they have are for aeromodelling and robotics from Rs. 500 onwards.
Thanks again