My DIY tonearm project continues

Discussion in 'Audio Hardware' started by Phil Thien, Aug 7, 2019.

  1. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    [​IMG]

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    My DIY tonearm project continues.

    I got my parts from McMaster. Right now I'm using the aluminum spacers (instead of the stainless I also ordered) because they're light. The overall height of the arm is 1-3/8" but you need some clearance at the bottom for pivoting action. I'm trying to keep the height down because my platter/motor won't be too terribly high (they are pulls from an old Technics SL-6, if you recall).

    I'll likely replace the screws with flat-heads to reduce the overall height and compensate for the tonearm wiring having to clear that front screw on top. My tonearm material is just 3/16" thick, so I might end up needing to order undercut screws (should have thought of that). I'll try countersinking carefully.

    The wire I'm using is from a travel mouse, it is very fine, probably nearly 32 AWG. You can't tell from the pic but the section of wire with the insulation still in place has the shield wire running into the same hole as the rest of the wires, and then it wraps around the top part of my pivot component. So ground will be carried down through the pivot. I don't know at this point whether I'll even need a ground, but this is my pending/untested solution if I do.

    The counterweight idea worked out extremely well. I can adjust weight and azimuth (because the counterweight can be shifted left/right). Right now I'm using washers and a nut/wingnut as my actual counterweight. Once I get further along, I can come up with a properly-sized more elegant solution.

    The entire thing is very light, and extremely responsive without being wobbly. I think I could further lift the "headshell" area to do an even better job of aligning the stylus with the pivot, due to my low center of gravity counterweight method, without making for a wobbly unit.

    The steel nut you see where the cartridge should go is my attempt at approximating the weight of a cartridge. It is just 2-sided taped in position.

    I need to find a very inexpensive cartridge and screws to mount it to my tonearm for initial testing. Also the proper clips to go on the end of my wire (the ones there were from a shell for the mouse connection, and I can't make them work for a cartridge for reasons I won't bore you with).

    I'll keep watching eBay for a crap cartridge and screws and cartridge clips. The little things start to add-up, as the shipping starts to eat into the cost on this stuff.
     
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  2. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Nice! Was there a previous thread you can provide a link to?
     
  3. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
  4. timind

    timind phorum rezident

    Location:
    Westfield, IN USA
    How does it pivot vertically? Can you take a shot from below? Looks like a lot of work went in to that.:righton:
     
    Manimal likes this.
  5. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    It is a unipivot (so a point into an inverted cone). The picture is confusing because it looks like that threaded rod pokes through the arm.

    But that bit of metal between the two top screws is actually an inverted dowel center. You could also use a blind hold spotter (the machinist's version of a dowel center).

    The threaded rod is actually a long stainless set screw. It has a cup end, and the dowel center's point pivots on this.

    Next time I work on it I'll take more pictures.

    Figuring out a way to use off-the-shelf parts makes it a challenge. I have a bit of a history of coming up with ideas that other people want to DIY-duplicate, so I try to make it as easy as possible. But I'd also like people to be able to take the idea and run with it. Imagine the same arm with anodized aluminum and carbon fiber arm and bottom plate, it could start to look pretty cool.
     
    Last edited: Aug 7, 2019
    timind likes this.
  6. regore beltomes

    regore beltomes Forum Resident

    Location:
    Helenville, WI
    I like it. Reminds me of something I might try. I once repaired a Kyrocera turntable that had the arm snapped off in back of the pivot. I fabricated an extension out of aluminum. For the counterweight I used a flywheel from a RC boat engine. It worked very well. Customer was happy and I was proud. The AT-3600L is an excellent choice for a test cartridge. 10 to 12 dollars shipped from China. If you screw up It's no big loss. Best of luck with your endeavor. Keep us posted !
     
  7. stereoguy

    stereoguy Its Gotta Be True Stereo!

    Location:
    NYC
    Do you plan on staining the wood?
     
  8. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I probably won't use these two pieces beyond testing, I'll likely use something a little darker/nicer.

    I also have some extremely old-growth fir akin to what Stradivarius would have used for his sound boards. These boards I have are remains from making flat-sawn veneer. The most valuable wood is rarely sold as lumber but rather flat-sawn (not rotary cut) into veneer, so they can make bank on it.

    When they get down to about the last 1/4 to 5/16 and can't slice any more off, they have these pieces left, and I have several of them. A high-end supplier had a bunch at a show and I purchased all of them. They've been sitting, waiting for a project for maybe ten years.

    The rings are so tight in some spots that trying to count them causes my eyes to cross.

    Or I could end-up using carbon fiber. Enough carbon fiber to make seven or eight of these would only be $30.

    I did counter-sink the screw holes this evening, and that looks a lot nicer, too.

    Now I'm looking for cartridges + screws + clips that won't take 3 weeks to arrive from China.
     
  9. regore beltomes

    regore beltomes Forum Resident

    Location:
    Helenville, WI
    Try Amazon. 27.50 and 2 day shipping. I'm old, frugal and patient. I don't mind waiting but I see your point.
     
  10. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I found a cartridge on Amazon for $20 and I ordered a finger lift on eBay for $2 from China. The cartridge from Amazon includes screws which may not be long enough, but I can counter-bore those holes or I might even be able to get screws that size at my hardware store.

    Now just clips for the wires...

    I have to get the motor and platter mounted to something for testing anyhow.
     
  11. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Had some time to think about what to do for a plinth today. I decided to go with a minimalist "Tee."

    Test/prototype is walnut with cross-grain jointing issue, which will warp with humidity changes. Once I get further along, I'll likely use a single CNC-cut piece of Baltic birch I think.

    I'm going to use Vibrapods for feet, my table will use three feet. The Vibrapods are intended to be used as supplemental feet, but I'm going to use them as my only isolation feet by making 1-5/16" wood doughnut that go on the bottom of my plinth, and I'll "slap" the Vibrapods on those. I'll make the doughnuts for a snug fit.

    By using this method, I'll be able to allow that 1/4-20 set screw I use as half my unipivot, to extend down through the doughnut and the Vibrapod even.

    The wiring for the motor will snake around to the bottom of the plinth, where I'll place a 6-pos terminal block for wiring. I'll be able to connect my DC power (in), and two switches (on/off and 33/45) to this same terminal block. I'll place the switches to the right of the tonearm, facing up. I have to find switches that will mount through 3/4" material.

    Finally, the tonearm wiring. I've braided the wire and find it now poses little impedance to movement (twisting wires results in a spring effect). So I'm going to use a 3.5MM TRRS coupler that mounts THROUGH the plinth just to the left of the pivot. The tonearm leads will form a loop that looks like an upside-down "U" between this jack, and the arm. From the bottom of the coupler, I'll be able to attach a 3.5MM to RCA TRS cable. NOW, I've already had discussions at other sites about whether I can combine the commons of the L/R of the cartridge, and it appears so far that because they are combined at the preamp, it is worth a shot trying this. If combining doesn't work out, I can switch from TRS to TRRS connectors and separate them, but then that slightly complicates my 3.5MM to RCA adapter (I'd have to make my own, I don't think they're commercially available).

    Anyway, that's where things stand. I'm waiting for parts, refining my CAD for my eventual actual plinth (with radiused corners, etc), probably going to actually give this tonearm a try in the next few days and see how it performs without anti-skating (I have plans for anti-skating "schemes," but they will require some testing. Just accurately measuring anti-skating might require some sort of a jig).

    [​IMG]

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  12. Tom Littlefield

    Tom Littlefield Forum Resident

    Location:
    New Hampshire, USA
    Yes you did put a lot of work into this but for what?

    Just my opinion but it probably will not wound very good at all...
     
    Don Parkhurst likes this.
  13. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Discovery, knowledge, fun.

    Maybe you wouldn't understand...
     
  14. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    The challenge, and because what I'm after isn't commercially available.
     
  15. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    You hit the nail on the head.

    You cannot assemble a turntable and build an arm without learning a ton.
     
    JNTEX, dmckean, timind and 1 other person like this.
  16. Vinny123

    Vinny123 Forum Resident

    Location:
    Florida
    Very cool. Great looking project. Keep the photos coming.
     
    dmckean likes this.
  17. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Received my 3.5mm TRRS coupler today, I'm using it as a means to easily disconnect/remove my tonearm. So the coupler is mounted through the plinth, and below the plinth I then connect a 3.5mm to RCA adapter cable (you can see a black connector currently plugged in below).

    I also received the clips to attach to the cartridge, I have not wired that up yet. Still waiting for my P-Mount to 1/2 adapter.

    Also found a nice DPDT rocker switch yesterday that is on/off/on, so that will be my 33/off/45 switch.

    Also cut off one side of the motor wiring harness and wired a Euro style terminal block. The switch will connect to this block.

    I still need to figure out an arm rest, a cueing mechanism, and some isolation feet. Also anti-skating in some form.

    Just a reminder that this is a prototype. IF the turntable works and has promise, I will then remake the plinth with incorporating everything I've learned, adding radiused corners and rounded edges.

    [​IMG]
     
  18. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Also, the piece of particle board it is sitting on, that isn't part of the table, just a way to move the project around in my limited-room shop.
     
    bluesaddict likes this.
  19. dub_siq

    dub_siq Well-Known Member

    Location:
    Portland, Oregon
    I know its still in the development / prototype stage , but that is looking sharp. I like the minimalism and modernity of the repeated circle and line. Not sure if I want to place an order or get the plans.

    Keep us updated!
     
  20. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Figured out a way to make an arm rest (those white/natural-colored spacers). There is a socket-head cap screw through those spacers, the arm has a hole that fits over that screw's head.

    I don't need anything more secure than that, because if I need to move the unit, the arm has to come off (the thing you learn quickly when it comes to unipivot arms is that there is nothing holding them in place but gravity, so if you're going to transport the table, best to remove the arm).

    Still pondering ideas to make a DIY cueing lifter.

    At this point I really need to get a cartridge mounted and perform some testing, before going much further.

    Waiting on Amazon to deliver my T4P to 1/2" adapter. I have a sort of "beater" T4P cartridge that might work well for testing this thing, and the adapter was only $10.


    [​IMG]
     
    Last edited: Aug 11, 2019
  21. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Phil, with your skills you should be able to make a body for the T4P and skip the adapter, which is a structural compromise, IMO. Only issue then will be the sub-sized cartridge pins, but I'm sure there's an easy work around for that.
     
  22. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    That is very kind. I hadn't even thought of making some sort of adapter myself. You're right, those pins would be a challenge. If I had more room in my shop (and the money), I'd get a used one of those little mini metal lathes, I think that would be a game changer for me.

    At this point, though, I just want to see if I can track a record. For all I know, I'm going to find some major issue once I cue a record up on this thing. If I can actually make it work, I'll look for a deal on a real 1/2" cartridge.

    But standby people, this thing can still crash and burn. Cue (no pun intended) the dive bomber sound effects.
     
  23. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    I've used my Unimat lathe to make tonearm parts but wooden cartridge bodies can be made with woodworking tools...I used a router to make them. There's a fellow here who made one for his T4P; I also have a couple of bodies posted in the thread (for some reason I can't upload jpegs here..)



    Wood body for cartridge part II
     
  24. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I'll read up on that. As a joke, I told someone I'd make my own cartridge. Maybe not so funny after all?
     
  25. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    The T4P adapter arrived. After getting my cartridge mounted, I found I had to raise the arm about .25".

    That tiny digital scale I got on Amazon sure is nice for setting tracking force, very sensitive. Got that dialed in at 1.25-grams.

    When I set the stylus in a groove, it leaned over a tiny little bit. So I had to adjust the azimuth using my left/right counterweight method. It just took a tiny shift, maybe less than 2 degrees. I went too far the first time. Right now it is set by eye, I don't have a cartridge setup kit, just the scale.

    But it works! My test album is an old Ahmad Jamal Trio album, which is approx. 65-YO (I'm 55). I got it on eBay for $3.50 shipped because I wanted a test album and I like Ahmad Jamal. If you're going to HAVE to listen to something while testing, might as well like it.

    I've listened a while with headphones, it sounds "fine." It is tracking fine. I need to figure out the isolation feet, it needs some isolation.

    Also really need to figure out a cueing device. I don't even have a finger lift yet ($2, ordered from China). My hands aren't as steady as they once were. Yowsa.

    I think I'll drag it upstairs and connect it to the hifi to get a better sense of how it sounds.

    Here is a pic of it playing:

    [​IMG]

    And here is a movie proving it works:

    http://www.jpthien.com/temp/IMG_5158.MOV
     
    Last edited: Aug 11, 2019
    JNTEX, 33na3rd, Socalguy and 4 others like this.

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