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
    I’ve looked at those. My table is such a lightweight though, I’m not sure how they’d work.

    Today I redid how the feet work. Before, the pivot for the arm had to tighten into a threaded insert in the foot underneath. Now I added a threaded insert to the plinth itself. So the foot is more independent.

    Now if I flip those rubber expansion nuts upside down, and find springs with a 1/2” ID at at least one end, I can add springs.

    So I’m gonna check the hardware store for springs this weekend and see what they have.

    Otherwise I could also get some sorbethane donuts and make new feet.

    But I’m hoping I can make the springs work because I watched a video on the Mitchell table and the bouncing is kinda kewl.
     
  2. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Doubled-up thread from my wife’s sewing kit so far.

    It worked well because if the way I loop it.

    Button thread, a heavier thread for attaching buttons is also an option but might actually be too heavy.
     
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  3. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Last night I was watching a video where Schoeder was discussing one of his tonearm designs, and he went into the importance of vibration isolation of the table itself.

    I felt like this was an area where I still had a decent amount of room for improvement. I had made progress with the expansion nuts, but I could still introduce noise by moderate to hard rapping on the shelf or wall with my knuckles. I felt like, especially at higher SPL, this was a problem, and that wall-mounting the table wasn't as much of a magic bullet as I had hoped.

    It just so happens that I was on the other side of town today where there is a larger Ace hardware store featuring a decent selection of springs. I picked up some I thought would be suitable. This evening I made some more feet, flipped the expansion nuts upside down (flange up), and gave it a test.

    First, it is fun pushing on the table and watching it bounce around, then eventually settle.

    More importantly, rapping on the wall/shelf no longer introduces any sound into the playback, even with the needle sitting on a non-spinning record and high gain on the amp. Simply amazing.

    Next-up, finishing-off an improved azimuth adjustment. Offsetting the counterweight left/right is too fiddly, so I've added an azimuth weight to the counterweight "stack." This azimuth weight can be rotated 360-degrees after I set tracking force. Now adjusting the azimuth is quick/painless.

    In fact, the reason I originally wanted to visit that larger hardware store was to pickup some mylar washers for a limited-slip sort of clutch for my azimuth adjuster, the springs were really just a bonus.

    Initial limited (due to time of day) listening tests at higher SPL, with the new springy feet, seems very promising.


    [​IMG]
     
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  4. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Been a while since I posted anything on my arm.

    Most DIY unipivots are unconstrained. I guess most commercial ones are, too. Unconstrained arms can wobble, which can be a turn-off for some users. Mine wobbled less than most, but still friends that have never used a unipivot can be like "wth?"

    So I decided to add constraint.

    That red plastic bottom plate on the arm replaces the previous wooden piece, and has a rectangular hole just large enough for the white threaded nylon spacer to pass through with about a .002" gap.

    The left/right balance of the arm is adjusted so that the right hand side of the red plate is always in contact with the bushing, with the .002" gap on the spindle side.

    So now the arm feels exactly like a conventional gimballed arm, but still has much lower resistance than any gimballed arm could achieve.

    I just need to keep an eye on that .002" gap. If seasonal or temp changes cause parts sizes to change, it could bind. I don't expect problems but will watch.

    And yes I need to dress the wires better and clean stuff up, but I have a new plinth design I will get done first. The problem w/ DIY table and arm design is, you end up listening a lot, it is fun listening to music on something you made.

    [​IMG]
     
    Last edited: Jun 4, 2020
  5. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    I was thinking of trying something like this with the Sol arm, but abandoned the idea when I discovered a simpler form of constraint using the antiskate thread caused issues with sonic blurring.

    Can you comment on how this modification has affected the sound?
     
  6. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I don't think I've found any "tells" yet. It is pretty easy for me to go back and forth by unscrewing the white spacer to above the red plate. The few times I thought I heard something, I wasn't able to prove so to myself by undoing it.
     
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  7. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Thanks.! If there's no 'tell' then there probably isn't any difference. The problem with using the antiskate thread as a restraint is likely due to the springiness of the thread, offering up a delayed correction with stored energy that blurred the timing cues in the music. It was quite obvious too.

    I should give this approach further consideration, but I've since moved the antiskate to a pulley on the pivot itself, a change with enough positive attributes to keep it, but which would complicate the implementation of this form of restraint.

    Like all things in design, the easier it looks the harder it is to do in reality!
     
  8. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Well I don't know if you changed-out the anti-skate thread, but I do not like those monofilament type threads for skate weights, much much prefer the (I think cotton) thread I sound in my wife's sewing stuff. Much more consistent performance.

    I also found I preferred the sound of the anti-skating weight pulling directly behind the pivot, than offset to the left like the Sol does (and like I did). So you'd think that this latest change would have more audible consequences.

    All I can say is, results often don't meet expectations.
     
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  9. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    No, I don't like the monofilaments myself....the Sol now is kitted out with white polyester sewing thread lol. Much more flexible, necessary because of the way it attaches to the 2 pulleys. The pulleys not only eliminate the sawing back and forth of the thread over a hook, but they seem to attenuate the vibrations that could develop in the tread itself, thus isolating the side bias from the downforce so they can each function without influencing the other. Harder to change arms, though, so every gain has its price.

    Yah, you never know what's around the next corner. I love this stuff!
     
  10. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    So, you've made his vocalizations more audible? - Great o_O

    Can you also do the reverse?
     
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  11. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    The vocalizations don't bother me at all, I rather like them. I can hear his frustration and his joy in them.
     
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  12. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    Hi-density PU foam. Cut discs the size of cork disks you have under the table now, and glue them under.
     
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  13. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    As much as I love Jarret's piano playing (he's pure genius), his vocalization drives me mad! To the point I find myself listening to his records very seldomly, and I have a few...
     
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  14. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    You are not alone, but I guess they have grown on me.
     
  15. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I went with springs. Completely isolated now.
     
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  16. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    If springs fail with time - keep the foam in mind.
     
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  17. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Okay will-do, but what is "PU" foam?
     
  18. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    Poly-urethane. Or just Urethane. It needs to be high-density foam. It also comes die-cut, somethimes even in discs, if you're lucky. Just look to google suppliers, and you will find it.
     
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  19. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Duh, sorry, it has been a long day.
     
  20. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
  21. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I forgot to mention when I posted that last pic, but it occurred to me when I was considering the previous mod, that I'd be able to reconfigure the counterweight to perhaps achieve a neutral balance. Neutral balance means the VTF stays the same no matter the height of the stylus relative to the record.

    Most unipivots (including mine in its original configuration) are stable balanced, which means elevating the stylus (like climbing a warp) increases VTF. Lowering the stylus (line descending from the top of a warp) decreases VTF. This is due to the offset counterweight, which is offset to keep the arm "stable."

    On stable balance arms, the VTF increases slightly if playing thicker albums.

    So anyway, this evening I reconfigured the arm and adjusted some screw lengths (to fine-tune mass distribution) and now the arm is indeed neutrally balanced. Whether I check the VTF with the scale on the bare platter (w/o mat) or 1/2" above an album (resting on the mat resting on the platter), I get the same (1.5g in this case) VTF reading.

    I only had a little while to listen, but this one did change the sound. Likely not because of the neutral balance, but rather because I've switched-out the stainless pillars for nylon, and moved the counterweight higher. These two changes modified the "resonance profile" of the arm.

    I like the sound a lot but need to listen more.

    The arm is extremely tunable and I've adjusted it into a new range, so it will be fun to listen and tweak. But it is kinda neat to achieve one of the best aspects of a gimballed arm w/o any of the downsides.

    [​IMG]
     
    Last edited: Jun 6, 2020
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  22. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I would like to amend my previous response.

    With the constraint (which provides a constant 2nd point of contact between the wand and the pivot pillar), the overall response stays far more consistent throughout the cartridge's entire VTF range

    Without the constraint, there is a somewhat narrow sweet spot, where increases especially can substantially reduce bass.

    So a benefit of the constraint is that simultaneously optimizing for sound quality, tracking, and minimal surface noise is much more easily achieved.

    Without the constraint, optimizing for one could cause problems for the other two.

    I hadn't noticed this because after adding the constraint, I just set the VTF back to 1.5g, the previous sweet spot. Later I was playing some noisier vinyl and increased the VTF to 2g and then observed this behavioral change.
     
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  23. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Are you suggesting it can allow for a reduced VTF? I have noticed that in order to obtain proper tracking with the Sol unipivot I've had to raise VTF ~10% in order to achieve the same tracking as I would with gimballed arm. If I used VTF alone to evaluate an arm's performance I'd probably go back to using a gimballed arm, but the Sol's arm is so much more revealing of recorded nuances, especially phrasing. It would be nice to bring the VTF back down, so long as it is without compromise.
     
  24. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I need to do more testing but yeah I think that is the long and short of it.

    It would be fairly easily tested (and completely reversible) on the Sol with some double sided tape and small scraps of plastic or wood.

    You just need the arm to very lightly "lean" into the pivot stem at the bottom on the left side. If you don't like the sound, remove it. If you do, pursue a more polished mod and see them on ebay.
     
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  25. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Thanks, Phil. I'll start giving it some serious consideration....
     

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