Building a Turntable? (a little long) - diyAudio
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Old 28th May 2006, 11:21 AM   #1
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Default Building a Turntable? (a little long)

hey,

I'm looking into building a turntable and have some questions that I could not find answer to on the forum.

motors - I saw many people use the maxon motors but I did not see anything with more than 4 poles on their website. I saw some "high-end" turntables with motors that have 12 and even 24 poles. I'm pretty sure this is the right way to go for the smoothest turn possible and if I am going through the trouble of building a turntable while getting a perfectly good one for under $500 is possible, it should be top notch or I'll feel like I wasted my time.

in general I want to use a very heavy plate and was wondering if there is a way to calculate what kind of motor I'll need based on various parameters? it sound logical that the motor should be just powerful enough to keep the plate turning so the speed will be constant and determined mostly by the momentum of the plate (flywheel effect?)

I was also wondering where do people get the bearings and what types are better? what about shock mounts for the entire player? any sources for that? I'm in Israel and it is not easy to locate this kind of stuff.

last thing is the tone-arm. I'm pretty sure I do not want to build something like that myself because it is too complicated and I don't have access to machinery that is needed for it. any good manufacturers out there? and how do I mount it, I guess the location is very important.

last thing is the motor speed control. I was thinking about building a controller based on photocells that could adjust the motors speed in real time, anyone got access to a design like this?

thanks everyone!
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Old 29th May 2006, 10:38 AM   #2
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Default DIY TT in Israel

Quote:
I'm in Israel and it is not easy to locate this kind of stuff.
Look here:
One more DIY TT is born
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Old 29th May 2006, 12:46 PM   #3
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I have not built a DB using the fostex 127 driver however I have built this design using a 4 inch redback driver that is very similar to the FE 103, it may actually be from the same factory.

Bottom line is I built these as an experiment and have carried out all sorts of mods to tame the midrange etc, the end result is quite stunning sonically and has exceeded all my expectations, I imagine the proper fostex driver implementation would be better still.

Have a look at these posts on to get some insight in the processes I went through and the mods, I am sure many will apply to the 126/7 drivers as well.

Just two things, my implementation is run in conjunction with a bass extender module that is available as a kit from altronics in Australia and the boxes also have a top rear facing port in the top outside corner, with a reflector to send some bass into the corner. I know it sounds like it wouldn't work but it does, these speaker utterly cream my B and W 602 s3s and the 2 other pairs speakers I have that sound better than the 602s. Amazing from 4 inch drivers!

They actually produce useful output now down to about 40Hz, no I am not kidding, however I think a supplementary sub that cuts in a 55hz or so would complement things nicely, which is something I'm working on.

http://fullrangedriver.com/forum/viewtopic.php?id=615

http://fullrangedriver.com/forum/viewtopic.php?id=660

http://fullrangedriver.com/forum/viewtopic.php?id=593

http://fullrangedriver.com/forum/viewtopic.php?id=574

I hope this is helpful, the one thing I have found is that smaller drivers such as these are very tuneable and it is really worth putting in the time to tinker.

All the best
Brad.
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Old 29th May 2006, 12:48 PM   #4
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Sorry somehow this posted in the wrong spot
Brad.
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Old 29th May 2006, 04:39 PM   #5
ssmith is offline ssmith  France
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hi space-cake,

best of luck building your own turntable.... it's a huge undertaking.

I'm still in the process, and found it easier to divide the project up into sections. in these forums you'll find tonnes of info...

1) platter/plinth - I decided to go for some hardwood like the teres... but this remains on the drawing borad until I find a good woodworker with a lathe who can do it for me...

2) motor/controller: I tracked down a cheap Russian 36V DC motor and a cheap variable VDC lab supply to control it. This is far from ideal, and would mean I would need to calibrate speed regularly. But good for starter. Need to make a nice motor pod...
I'm totally ignorant when it comes to electronics, so haven't thought of DIYing anything too complicated here.

3) Bearing... one of your fellow countrymen provided his input on this site a sintered bronze sleeve + stainless rod ... basically I got the parts (cheap), have to find someone with machine tools to finish off.
Got the parts from sdp-si.com, smallparts.com and mcmaster.com

4) tonearm: worked up a rough design -- based on the Scheu-Analog Classic MKII or otherwise rolled up balsa wood (which you'll find on here). Need to get the parts though... from smallparts.com and mcmaster.com

So far I haven't put much money into it... but reading through these forums takes alot of time. This, I feel, will be a loooong term project..... involving lots of trial and error.... and finding a machiner and woodworker.

Great you are in Israel -- there are few of your fellow countrymen in here, so worth checking out the archives and I'm sure you'll get a tonne of help.

good luck!
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Old 29th May 2006, 09:27 PM   #6
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live music - nice work!!!

ssmith - thank you very much for the answer!
I was thinking about using a DC motor but controlling it only by voltage might not be good enough because the spin won't be the same throughout the turn. there is something called PWM (Pulse Width Modulation) which might be better for this application. in general you send many short pulses to the motor to keep a given speed. there are very simple PWM controllers available for next to nothing, using them is usually easy and you don't really program them only change some resistors and caps. I was thinking about building a real-time system with photo-cells and a controller that would calculate if the speed is right and will increase or decrease the motors speed. this would be a little complicated but can be done. another idea would be using an AC motor and set the speed using the freq. but I have no idea how to generate freq. like that and could not find any info on this subject.

I got an email from maxon and they said someone will contact me about a motor, maybe they have a DC motor with 10 or 20 poles. that would get me interested!

since I don't have too many tools I can't fabricate anything for myself so all should be machined by CNC so I'll use Perspex or delerin. they are both great materials and I personally think the platter material should not make any difference (I'm sure people will disagree).

about the arm, I will look up that name you stated. until now I didn't see anything too interesting, I am thinking about suspending it using magnets but we'll see how that works out.

I agree this is not a simple project but like any hard work it is very rewording. at any case more rewarding than buying a turntable for $1500
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Old 2nd June 2006, 12:59 PM   #7
EC8010 is offline EC8010  United Kingdom
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Quote:
Originally posted by Zero One
Sorry somehow this posted in the wrong spot
Brad.
Let me know where it should have been and I'll move it.
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