My DIY tonearm project continues

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

  1. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Proof of concept:

    https://www.tinkercad.com/things/hJeaLoCVVAq-stablizer

    Clips into the bottom of the ring (it's shown upside down for printing purposes). Takes seconds to install. The opening for the pivot is exact, which led to my discovering that a level azimuth at the shell means the ring is tilted slightly. I reversed the stabilizer but got the same tilt which means it's the arm, not the print. I filed the opening till I could obtain proper azimuth, backed out the azimuth weight till the stabilizer was barely touching the pivot, and put a record on.

    Can't say yet that tracking has improved but I think the bass is a little more fleshed out. Need more time for listening, and ultimately a better, more adjustable design.
     
    Phil Thien likes this.
  2. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    (1) Getting an error on the link.

    (2) I'm assuming the wand, ring, and headshell are cemented together?
     
  3. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Sorry about that. It works for me even though I'm not logged in, so I have no idea what's wrong or how to fix it. It's just a thin platform like yours, with a slot for the pivot and tabs on the outer corners to keep it centered in the bottom of the ring.

    Yes, epoxy, I think.

    Anyway, I printed another that allowed for adjustability and gave it a listen. I'm afraid it's a no go, but I shouldn't be surprised. When I was testing the pivot AS pulley I noticed that the sound wasn't the best at the very beginning of a record. Close inspection revealed that the thread was touching the unused AS hook on the ring, but only at the very beginning. After a few minutes the thread cleared the hook and the sound improved. I pivoted the other pulley on the weight end to allow for more clearance and it's been fine ever since. Lesson learned is that nothing must touch the ring, so naturally this stabilizer, since it clips to the ring, doesn't sound great, either. Other than putting two and two together I have no idea why this is...

    Back to the drawing board. My original plan was to modify the pivot AS pulley to do both jobs. This is going to be more work because a retrofit to the existing pulley is not really feasible. Anyway, this isn't the first time an idea went bust, and so help me, it won't be the last lol.
     
  4. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Can you describe how the sound quality changed? Also what cartridge are you using?

    My arm is quite a bit different than the Sol (wood wand, neutral balance, anti skate aligned with center of arm, etc.).

    At least now you now know one more thing that doesn't work.
     
  5. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    The same thing I experienced with the Sol when i first got it. We were expected to tie the AS threads ourselves but I was more interested in hearing it, so left the AS hook-up for later. When I did hook it up, there was an obvious decrease in focus. At best, it blurred the instruments; at worst it resulted in mistracking, particularly on vocals. What I experienced with the stabilizer was similar, but it didn't have the channel bias that the AS had, in this case it was evident equally on both channels, whereas the AS tended to be more problematic on the left channel. The distortion is slight, but with an A /B it's pretty obvious, and knowing it's there is another problem....for me at least.

    Yes, your arm is very different, with different materials joined together differently,. We're talking about two different beasts. The Sol arm is springy, I think. It's the stored energy that's causing the problems. I don't think yours stores energy quite the same way.

    The cartridge I'm currently using is another DIY project, an AT95 in a printed PLA body and coin epoxied to the top. Nothing to look at, but great fun to listen to!
    [​IMG]
     
    Last edited: Jun 20, 2020
  6. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    The stored energy theory is interesting, one of these days I'd love to perform some resonance tests on my wood arm and compare to some more conventional arms.

    And that is a nifty cartridge project for sure.
     
  7. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    I've made the stabilizer public, so maybe the link works now? There's a new 'share' button on the page but it opens to a FB log-in page, so I'm still just copying the address from the title bar. I'm surprised Autodesk doesn't make this easier.

    3D design stablizer

    Energy management is the be all to end all responsible for an analogue component's sonic signature, IMO. The AT95 has a signature many consider thin and bright, but it's usually attributed to its electrical properties. I've deliberately over damped the generator capsule and fixed it to a high mass rigid platform in order to maximize vibration absorption and transfer from the capsule to the arm. It seems to be working. The sound is no longer thin (though it is still bright-ish) and there's a clarity and separation of instruments that is unusual even in cartridges at higher price points. It's also more dynamic while at the same time less aggressive, with seemingly double the channel separation and a much quieter noise floor. I think the real problem with the stock AT95 is the minimal body structure resulting in insufficient damping of internal resonances. The trick now is to reduce mass w/o losing the high damping....the holy grail of any good design.

    I apologize for the thread crap, I hope you don't mind. I should start my own thread on a site that allows image posting, but I'm notoriously bad at these things, as you can plainly see...
     
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  8. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Not a thread crap at all, DIY is all directly on-topic AFAIC.

    I'm using an AM10S cartridge. I had been using a T4P cartridge with a 1/2" adapter, but the AM10S/arm interface is much more solid, which results in greater clarity. Same stylus as I was using on the T4P+1/2" adapter, basically the same generator, the only difference is that the cartridge and arm wand are much better coupled.

    Do you happen to know the mass of your modified AT95?
     
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  9. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Thanks, we're almost on the same page. The modded AT95 is just over 10g. Not the heaviest body I've encountered, but getting up there. The nickel topper alone is 4g, so there's considerable saving to be made there. It's just that I have a 10lb a jar of these, so they're pretty handy...not to mention cheap lol.

    Just out of curiosity, did the new link work? The 3d view is the updated version.
     
  10. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Oh I forgot, yes the model is visible now, thanks! The shape surprises me, it looks more involved than I had assumed the opening of the Sol's pivot assembly would be.

    I'm fascinated by your AT95E modifications. Have you done any "needle drops" with it? I haven't done any needle drops at all, but have been thinking I should give it a shot.
     
  11. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    The 2d view is the first prototype. The shape is intended to straddle and grip the bottom inside of the ring. The 3d version is the adjustable one, with a flex tab and a pilot hole in the side for tapping an M2.5 screw. I probably could've come up with something simpler, but I wanted something that I could put in and take out very quickly without having to completely remove the arm.

    I haven't done any needle drops yet, but I'd like to! I'm hoping to score a Behringer UCA 202 but they're currently listed as out of stock just about everywhere. I might find a used one for pick up locally. The UCA is supposedly compatible with a smartphone recorder app (USB Audio Recorder Pro) using the USB OTG function, together forming a sort of budget field recorder. I have Mytek Stereo96 ADC but it's not USB capable, which makes doing the drops a lot more complicated as it and the Sol are in 2 different locations, and moving either one to the other is more work than I care for.

    I have a body for an AT3600 printed up and another for a Shure M44 still in the hatching stage. If I see a favourable trend I'm going to try it with an AT125LC, which is as high risk as I'm willing to go with these projects.
     
  12. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    My latest tweak has been to rewire the arm.

    The loop was a common concern. That loop was long to provide me an opportunity to make changes w/o having to rewire. If I needed to move the coupler or change connector types, for instance, I'd be able to do so w/o completely rewiring the arm.

    Also, I have an idea for VTA adjustment, and simplifying the grounding will make implementation easier. The original grounding was unnecessarily complicated.

    I found "Mogami Ultraflexible Miniature Cable." 32-AWG, two conductors plus a shield. The stuff is so flexible it is almost like holding a cooked noodle. So I made a new cable that is shielded all the way back to the jack. The grounds for the cartridge run over the shield (this isn't uncommon). I grafted two short cut-offs of 32-AWG to the shield at the cartridge end, to facilitate connecting the cartridge.

    Seeing as I was doing this, I also picked up a crimper capable of handling the 1mm cartridge tags, very handy.

    I fitted the loop by measuring from coupler to arm, using this as the D to calculate circumference, took half and added 1.25" to accommodate the connector. I arrived at exactly 4" (exactly half the old loop length).

    To make sure the new wiring wasn't pulling/pushing/twisting, I tested by re-checking the anti-skating test tracks on my test album. I had previously set the AT10 cartridge to be able to pass the first three tracks (it cannot get through the last one). I'm using an AT10 because it is a little more demanding of anti-skate settings than a line contact (I swear I can put a line contact on this arm and pass the first three tracks w/ any amount of anti-skating).

    Anyway, with the new wiring, I had to reset the VTF, but that is all I changed, and the arm sailed right through the first three bias test tracks again.

    The arm was quiet before, it is even quieter now.

    [​IMG]
     
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  13. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    That's nice & neat!
     
  14. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Holiday weekends means time to tweak the tonearm. Well I started this last weekend, technically.

    On the previous page, you'll see I constrained the pivot using that red plate at the bottom. It tamed some resonances, but there was still room for improvement.

    Enter "suspension by Scunci." You know Scunci, they make the hair bands found on pony tails. It is an elastic band covered in some sort of nylon.

    I replaced that red plate with hair bands. ("Oh no you didn't." "Oh yes I did!").

    The hair bands are wrapped around the two pillars on the arm wand, which means they go around the pillar on the pivot. The hair bands are very slick, adding no detectable resistance to movement (I'm sure there is some, I just have no way of measuring it, all of my acoustical/tracking/skating tests show no difference), and yet they're doing an amazing job controlling resonances. Of course, they maintain perfect azimuth for the arm wand, too, and maintain that gimballed arm feel.

    So if you look at the back of the arm, you'll see the two black lines at the bottom, those are indeed hair bands.

    I've also been experimenting with a magnetic unipivot. The purpose is to actually couple the two halves of the pivot better, using a magnet. The only thing holding a unipivot together is weight, and I've really decreased the weight on this latest arm. I have a prototype for a magnet at the pivot which couples the two halves together without adding much in the way of effective mass. That is, I get a good deal of apparent mass without much effective mass.

    [​IMG]
     
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  15. Agitater

    Agitater Forum Resident

    Location:
    Toronto
    Interesting solution. If hair elastics can last as long as they normally do under the onslaught of outdoor pollution, dirt and hair/scalp oils and rough handling, they should last a very long time in your application without changing tension on their own or deteriorating and losing tension.

    The whole assembly is starting to look quite slick.
     
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  16. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Yes, the elasticity and longevity are critical. You get it (again)!

    While the bands cost about a nickel U.S., a catastrophic failure could be, well, catastrophic.

    So I'm going to always use at least two and maybe three. I guess the final number will depend on measurements and listening.
     
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  17. Davey

    Davey like smoke from a lithium dream

    Location:
    SF Bay Area, USA
    If you do pursue the magnetic circuit, you may want to look at the Schroeder arms, if not already familiar. They are of the suspended unipivot type, with thread and magnets. They make a very nice line of tonearms, albeit very expensive as well ... Clearaudio has some that use the same principle, except upside down, not quite as stable in practice, I think Shroeder has the patent on his way. He has a pretty big presence in the DIY community and helps quite a few people with their copies of his designs (berlinta at diyAudio.. DIY Schroeder Tonearm??? - Page 10 - diyAudio ) ...

    [​IMG]
     
    Last edited: Sep 7, 2020
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  18. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I'll still be using a point into a cup, the change is that that stainless cup will be swapped for a non-stainless, and a magnet will be added above the point to pull the two halves together.

    When I first thought of doing so I didn't figure there would be that much pull between the point and cup, but a quick test proved me wrong. I'd say it is akin to adding about 25% more mass to the arm with really no consequence other than having a powerful magnet sitting at the pivot.

    Those Schroeder string-pivot arms are amazing. We need to do a throw-down between my Scunci arm and his string arm, loser gets a free arm of the winner's design.
     
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  19. Agitater

    Agitater Forum Resident

    Location:
    Toronto
    The finer the polish on the thrust point and the finer the polish of the bearing surface well in the cup, with lubricant always in place, the lower the amplitude of any trace resonance that might be generated by the design. Polish, polish, polish, polish - that's what my engineers tell me - checking frequently under the strongest magnification available to ensure evenness. It can be the difference between something good and functional and something excellent and functional.

    A lubricant 'bath' of a several drops of light machine oil protects the assembly bearing point - it eliminates micro stiction too - and also damps micro resonances at the point of contact.

    Phooey on magnets, even though I don't actually get a vote.
     
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  20. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Well I'll see how this latest change tests and then decide on the magnet. I have to listen for a week or three, then measure, then decide what to do next.

    I can try finer polishing before the magnet and see how that goes.
     
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  21. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Been working on plinth V3.

    Original (V1) was replaced after only a few days, it was crap. V2 evolved in quite a few ways, eventually using springs for the suspension.

    V3 (this one) uses a Sorbothane-like rubber for isolation, and the plinth was redesigned for a more even weight distribution among the three contact points.

    Ignoring the matter of external vibration rejection for a second, the difference in how a table sounds switching from springs to Sorbothane is quite remarkable. When it comes to vibration control on turntables, suspensions are two-way streets.

    The question is, will the Sorbothane adequately reject external vibrations? My table is on a wall-mounted shelf, but I live on a busy street and in cold weather, the cold/hard/out-of-round tires hammer the pavement expansion joints. The springs reject the resulting vibration famously. Time will tell if the Sorbothane is as effective.

    Why not just stick with springs? Well, I thought I'd like to give the Sorbothane a listen and see how I like it. That is the fun aspect of this never-ending project, making changes and seeing what I like.

    [​IMG]
     
  22. Agitater

    Agitater Forum Resident

    Location:
    Toronto
    Has the tonearm wood remained stable so far, i.e., without any slight axial twisting or lateral warping? A change of seasons and a drop in humidity is approaching.
     
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  23. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    Surprisingly stable, but I do see VTF fluctuations due to humidity.

    The current wand is hard maple and is unfinished. I have a variation I'll be making that will likely be at least hard maple (Janka: 1450) if not something harder like cocobolo (Janka: 2960), and that one I'll finish with shellac (which may slow moisture migration).
     
  24. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    I recall reading in Korf's blog a bit about how essential the surface treatment was in a wood wand. Of the various species tried, all seemed to benefit from some form of applied finish. I imagine anything hard like shellac or varnish will stiffen the surface fibres....maybe the entire wand.
     
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  25. Phil Thien

    Phil Thien Forum Resident Thread Starter

    Location:
    Milwaukee, WI
    I didn't have any spray shellac when I made this one, or I would have given it a coat. So I should probably make the next out of hard maple and spray it with shellac, so I can hear what difference the shellac makes.
     

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