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DIY Tonearm/Turntable Project

69.146.180.90

Posted on September 1, 2010 at 17:31:00
Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007


I picked up a Marantz 6170 servo controlled DD turntable at a yard sale over the weekend for five bucks. Great motor/turntable unit with rock-steady speed, but the tonearm cueing has issues and I'm not impressed with the cheesy plastic and MDF plinth.

So I decided to cannibilize this unit and create what I expect will be a great sounding and unique DIY turntable.

The basic guts of the Marantz (motor & platter) will be placed in a massive wooden plinth. I've got tons of scrap wood laying around and lots of woodworking tools, so that'll be the easy part.

It would be simple enough to buy a nice tonearm, but that kind of defeats the DIY spirit of the project and the cheap-ass low dollar approach, so I'm making an oak unipivot tonearm. The whole theme of this turntable will be WOOD. I want it to be aesthetically pleasing as well as capable of sounding great. The cartridge used will be a wood body Grado Reference Platinum.

Some photos of the project:





Five bucks at a yard sale. SCORE! It doesn't get much better than this. Dead accurate speed with no wow/flutter or audible rumble.





The rough cut of the two tonearm pieces.





The tonearm is being designed to Baerwald alignment. Effective length 303 mm, with an 18% offset angle to the 'headshell.'





I used my router to create a groove in the two halves of the tonearm. Once laminated together, the tonearm will have a hollow center, providing a passage for the tonearm wires.





Glueing up and clamping the basic tonearm assembly. The sharp-eyed among us will notice that the oak I'm using is 'flawed' with wavy grain (due to a knot). That's intentional. I have "perfect" wood to use, but I prefer to use a piece with 'character.'

More pics to follow.

 

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RE: DIY Tonearm/Turntable Project, posted on September 1, 2010 at 18:00:46
shallow pockets
Audiophile

Posts: 765
Location: Michigan
Joined: June 27, 2009
That is a ambitious project. DIY tonearms are a road less traveled and for good reason. Please post some pictures of your future progress. Best of luck.

 

RE: DIY Tonearm/Turntable Project, posted on September 1, 2010 at 19:19:03
goblin141
Audiophile

Posts: 620
Location: So California
Joined: December 26, 2000
I have a Teac idler (very rare) that I want to put a wood arm on. Will follow. Your are right I was shocked, yes shocked at first with your selection of wood but go for it....

 

RE: DIY Tonearm/Turntable Project, posted on September 1, 2010 at 20:22:51
Fred J
Audiophile

Posts: 21808
Location: Southern Wisconsin
Joined: April 24, 2002
Sounds like a righteous project, I am curious however why you choose Oak ?

Regards Ferd

 

RE: DIY Tonearm/Turntable Project, posted on September 1, 2010 at 21:03:18
Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
I wanted to use hardwood, and I happened to have several pieces of Oak out in the shop. So that's how I settled on Oak. Now I realize it's fairly dense and heavy wood, but it's also very durable and rigid, two qualities I see as beneficial.

I have the rough tonearm stem/headshell assembly completed and it weighs 30 grams. Not too bad. Keep in mind it's hollow inside, which keeps the weight down. I'll probably run it through the planer a few times, further reducing the outside dimensions and weight. Then I'll work on it with the router, pocketknife, files, and sandpaper.

 

RE: DIY Tonearm/Turntable Project, posted on September 1, 2010 at 21:23:46
Fred J
Audiophile

Posts: 21808
Location: Southern Wisconsin
Joined: April 24, 2002


Very sound reasoning, every wood imaginable seems to have been used at one time or another.

Kind Regards Ferd

 

RE: DIY Tonearm/Turntable Project, posted on September 2, 2010 at 02:19:06
Kiwi Brian
Audiophile

Posts: 311
Location: Auckland
Joined: December 26, 2004
Go for it! I am pretty convinced that DIY tonearms and wooded tone arms are capable of surprisingly good results. Unipivots, magnetic stabilised suspended designs (a la Schroeder) and linear tracking air bearing arms are all eminently DIY-able.

This was my first effort...
Photobucket

...and my second..
Photobucket


Number 1 has now donated itself to my airbearing linear tracker, which has been an utter revelation.

My designs have been Kwila, chosen by the same meticulous process you employed - I thought a hard(ish) wood would be good, rummaged around till I found something vaguely suitable! The Kwila does have a nice tight regular grain which seems like it should be a good thing.

Next project is Mark 2 linear tracker with easily interchangable arm wands. Might then be able to look at relative merits of different woods, dimensions and wood treatments (there is a lot of talk about oiling the wood for instance).

Look forward to seeing your progress
Cheers
Brian

 

GEEZ MAN!!!! right when I am almost done my 'table DIY, you throw this at me????, posted on September 2, 2010 at 06:01:33
Dman
Audiophile

Posts: 7211
Location: Kansas
Joined: January 28, 2001
Well, I might just have to think on this one for a bit...

Dman
Analog Junkie

 

RE: DIY Tonearm/Turntable Project, posted on September 2, 2010 at 07:47:07
Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
Brian,

Thanks for posting those photos of your DIY tonearms. Very nice!

I'm curious about the string arrangement? Are your tonearms patterned after the Well Tempered design?

 

RE: DIY Tonearm/Turntable Project, posted on September 2, 2010 at 09:31:15
powermatic
Audiophile

Posts: 5843
Location: central oregon
Joined: November 24, 2005
Looks great so far-looking forward to how it works out vis'-a-vis' the bearing, counterweight, etc. As far as your choice of woods, I'm in the same camp as you in as far as the whatever-is-around-the-shop-at-any-given-time selection process. If you do want to try a more exotic species sometime, and I don't know what your local hardwood selection is like up there in WY, 'Rockler' carries turning blanks in a rotating variety of wood species that are often available in the perfect size for a tonearm (say, 1 1/2" x 1 1/2" x 18") that, depending on the kind of wood, are relatively reasonably priced. Just an FYI.

I'm trying something somewhat similar, though forgoing the bearing problem by using my "parts" SAEC WE308 bearing/base-the 9" arm is attached by two set screws, so it's fairly easy to replace with a longer, turned wooden arm. At least that's the idea...

Have fun.



"dammit"

 

RE: DIY Tonearm/Turntable Project, posted on September 2, 2010 at 12:20:37
Kiwi Brian
Audiophile

Posts: 311
Location: Auckland
Joined: December 26, 2004
No - they are Schroeder inspired - his earlier designs didn't involve drilling through the magnet (something I decided was in the "too hard" basket).

Photobucket

Photobucket

Another couple of pics to illustrate - magnet on tonearm and in the base attract and keep the suspending string tight, essentially setting up a close to frictionless bearing; the "tightness" of the bearing controlled by the magnet gap; antiskate provided by the string torqueing up as the arm rotates. Frank Schroeder is a bonafide genius I suspect with such an elegant design. He has been very co-operative in the past with DIY'ers - try searching DIYAudio forums etc if you are interested.

Cheers
B

 

The amazing thing is that, posted on September 2, 2010 at 14:03:27
jedrider
Audiophile

Posts: 15154
Location: No. California
Joined: December 26, 2003
we could be put back into the stone age, but with a little knowledge, can still listen to our record collection!

 

Update 9_3_10, posted on September 3, 2010 at 17:12:29
Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
I worked on the tonearm this afternoon, adding the slotted holes for attaching the cartridge and overhang adjustment. It was real tempting to use my router or Dremel tool and 'get it done quick', but I didn't want to #&%$ things up. So I clamped an old ADC headshell onto the oak (to use as a guide) and used the drill press to punch six small holes into the headshell. Then I used my trusty old pocketknife and a needle file to clean out the groove and shape it into a slot. Sometimes carefully working by hand is the best approach.





7/64" holes drilled into the oak headshell.




Rough work done with a pocketknife.




A needle file was used for finish work to the slots.



Nice fit and finish. The headshell is complete.



Here are the "big money" parts of the project.... ha ha ha! (Actually very inexpensive.) A high quality stainless steel pivot and sapphire jewel bearing. From what I've researched, the advantage of a unipivot tonearm is the bearing itself, which is in essence a zero-tolerance design. There's a lot of other design considerations at play here, but if carefully executed, it should provide excellent results. I've never owned an unipivot tonearm, so I'm excited to hear this in actual use.

The pulley will be used for the antiskate mechanism, which will be the tried & true 'fishing weight and string' assembly.

 

Update 9_13_10, posted on September 13, 2010 at 18:36:49
Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
Cannibilizing the Marantz turntable, pulling out the direct drive motor unit and platter:








What to use for a plinth?



I hiked down to the nearby Shoshone River with my chainsaw, and spotted this downed cottonwood tree.



Six nice slabs. Good size but unfortunately they developed bad checks as the wood dried out in the following days. Scratch that idea.



I opted to use scrap 2x4s I had laying around. I ran them through the table saw and planer prior to glueing them up.



Cut square with the radial arm saw and sanded down real quick with the belt sander. The platter and tonearm wand are propped in place to give a quick visual perspective. Just a rough finish, but it's looking good!



Plinth measures 14.75" x 21" x 3". Next step will be using the drill press and router to shape the plinth, fitting switches, the platter & motor, pcb, etc....into place. Then on to finishing the tonearm.

 

RE: Update 9_13_10, posted on September 13, 2010 at 22:20:53
shallow pockets
Audiophile

Posts: 765
Location: Michigan
Joined: June 27, 2009
Nice work ! I was reading your post and you mentioned cottonwood, not the most revered tree in Michigan here. My intial thoughts were that you could have done a little bit better in Wyoming, just guessing. Regardless, the 2X4 looks very good and has a lot of character. Keep up the good work and looking foward to the next post.

 

Update 9_20_10, posted on September 20, 2010 at 21:24:22
Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
The plinth is done, after five coats of tung oil and fitting the platter, and controls in place. Everything looks good. The platter spins precisely at 33 1/3 and 45 rpm. Next step is to finish construction of the unipivot tonearm.





Tung oil finish drying.





Motor unit in place.





The housing for the strobe light is a common copper plumbing fitting, press fit into the plinth.





Power on/off switch to left. 33/45 rpm selector and speed adjust pots to the right.






 

Tonearm is done, I am SPINNING VINYL!!!, posted on September 25, 2010 at 23:34:49
Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
WHOO HOO! I finished the tonearm tonight and as soon as the needle hit the groove I knew I had a winner. Excellent sound reproduction. Sharply focused with superb detail. PRaT, it's all there.

I compared some WAV transfers (a couple of Cult 45 rpm 12" singles and a Classical solo piano LP) that I'd done with my modified Technics SL-1200 w/Grado to the same transfers done with the DIY turntable/tonearm with the Grado. Doing this, I can easily make A:B comparisons. Both sounded great and the differences are subtle. I think the DIY tonearm/turntable produces a slightly sharper sound with a bit more dynamic range. That it sounds as good as my Technics has me thrilled. I've got all of fifty bucks into this DIY machine and it's definitely producing 'big league' performance.





Not the best sounding recording, but it sure makes for a cool picture.




MFSL DSOTM spinning and sounding great. Effective length of tonearm is 303mm or just shy of 12".





Here's the business end of things. The pivot is stainless steel with jewel quality finish. Nothing loose or sloppy here. The fit into the tonearm is very tight. The pivot point and stylus tip are at the same distance from the tonearm tube centerline (and bottom of the headshell).



The matching sapphire jewel bearing is epoxied into the head of an 8-32 socket-head bolt. I drilled a pilot hole into that monster lag screw and tapped it with 8-32 threads. The jam nut ensures a rigid connection between bolt and lag screw.

Just to give you an idea of the quality of the bearing.... I had the tonearm assembled and balanced out in my shop, with the lag screw held upright in a vise. No tonearm wires, so it could move freely. I blew lightly on the headshell/cartridge. The tonearm spun slowly and kept spinning for five minutes before it stopped.




Designing and building the tonearm required a great deal of thought. I do not have any formal training in Physics, but I quickly realized that many factors such as quality of materials, distribution of mass, center of gravity, pendulum effect, moment of inertia, etc.... had to be carefully considered.

The lag screw makes a firm connection to the plinth. Note that the socket head screw (which hold the vee jewel bearing) can be adjusted up or down, allowing changes in VTA. Note the two 'outrigger' bolts on either side of, and in line with the pivot. The brass thumbscrews allow for easy adjustment of azimuth. As you might imagine, the unipivot design lends itself to rocking or 'wiggle' action, side to side which is undesirable. The low-slung weights help provide stability and balance.

The counterweight was taken off the Marantz tonearm. Note that the bolts which secure it allow for fine adjustment of the weight up and down, thus altering center of gravity. Center of gravity in relation to the pivot is highly critical. Too high (COG above pivot) is unworkable of course, as the tonearm would fall over to the side. So the trick is to have the COG slightly below the pivot. Just enough to provide stability, but not so much that tracking of warped records is compromised.

Yes, that is a wire brad between the pivot and the counterweight. I don't yet have antiskating, but the wire brad will provide an anchor point for a string-and-weight antiskate device.



Pull the two acorn nuts and this small panel is easily removable, a nice feature since the Cardas tonearm wires are soldered directly to the RCA jacks.



This was my first DIY tonearm project. I'm very happy with the outcome. However, there are two design flaws that became evident well into the process. They both can be seen here.

First, note the offset of the headshell and position of stylus. That's fine if this were a conventional gimballed bearing tonearm. However, as a unipivot, I realized that the stylus tip should ideally be inline with the center of the tonearm, pivot, and COG. In theory, with the stylus offset from the COG (as I built it) a warp would create a twisting motion, altering azimuth. However in actual practice, it tracks warped records quite well. It seems the mass of the tonearm is sufficient to resist the twisting motion.

Secondly, the tonearm lift also has that same COG problem. Lift it and the tonearm wants to twist. Not good! I should've anchored the tonearm lift in the center of the tonearm. This is something I will fix. I don't plan to install a cueing mechanism, as I prefer to cue by hand. BTW, that tonearm lift is nothing more than a wire brad with its head flattened out.

I hope you've enjoyed seeing my DIY project. I just wish you could hear it.

 

RE: Tonearm is done, I am SPINNING VINYL!!!, posted on September 26, 2010 at 00:46:14
Marc Almirall
Audiophile

Posts: 292
Location: San Diego, Ca.
Joined: August 3, 2009
I definitely enjoyed seeing it come together. That's something to proud of for sure. Nice work!

 

RE: DIY Tonearm/Turntable Project, posted on April 25, 2011 at 08:52:25
nmourik@hol.gr
Audiophile

Posts: 1
Joined: April 22, 2011
please if you disire send me your project for tonearm .
I am architect and i try to trasforme in good desing the principal theory of tonearm .
Thanks
nikos Mourikis

 

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