+ Reply to Thread
Results 1 to 12 of 12

Thread: Syrinx PU2

  1. #1
    Join Date
    Oct 2007
    Location
    Lancashire.
    Posts
    4,134
    Blog Entries
    1
    Rep Power
    324039

    Default Syrinx PU2

    My Lenco has been sitting alone with no arm for a while. I was going to fit a Syrinx PU2 that's been languishing in a box for donkeys but when I removed the old arm I didn't realise what I was letting myself in for. Forget the problems with the turntable/plinth, the arm was in a bad way with shot bearings and rust all over it. It was like that when I bought it but it was cheap, twenty quid I think I gave for it
    I managed to get hold of some bearings and duly replaced them but the skinny pillar and the awful wiring needed attention. I only have a couple of pics as I lent my camera and it came back with less pics on it than when it went I turned a new 23mm diameter pillar and the arm's own 6mm pillar slides into this and is locked in place with two 3mm grub screws. The bottom half of the pillar is opened out to 16mm so the wiring can be connected up in there a la Rega etc.



    The arm mount has been machined with three contact points and the locking screw exits through one of these.

    Getting it to fit on the deck wasn't plain sailing either but I got there in the end

    Si.

  2. #2
    Join Date
    May 2007
    Location
    Next door to the Clangers
    Posts
    11,901
    Rep Power
    40369214

    Default

    Schweet, nice work Si

  3. #3
    Join Date
    Jun 2009
    Location
    glorious Devon
    Posts
    1,090
    Blog Entries
    1
    Rep Power
    3428817

    Default

    one of the few arms where the cartridge is not mounted at the extreme end of the wand, just where there is most vibration in the arm. In fact, a little way from the end (as per your pic) is a very good place to mount it, as it is at a minimum vibration point (node) for second order bending. Very clever! I may pinch that idea for my next tone arm design.
    cheers.....Bryan

    http://qualia.webs.com/

  4. #4
    Join Date
    Oct 2007
    Location
    Lancashire.
    Posts
    4,134
    Blog Entries
    1
    Rep Power
    324039

    Default

    Hello Bryan, how's it going?

    Well I've wondered the same thing myself but does moving the cart down the armtube move the nodes?
    Si.

  5. #5
    Join Date
    Jun 2009
    Location
    glorious Devon
    Posts
    1,090
    Blog Entries
    1
    Rep Power
    3428817

    Default

    not my understanding, Si, the nodes are fixed by the arm (wand) length, look here, down the page at mode shapes

    http://en.wikipedia.org/wiki/Bending

    look at the second mode, a blue region near the 'free end' is the least vibration region/s.
    Last edited by cat's squirrel; 31st March 2013 at 20:08.
    cheers.....Bryan

    http://qualia.webs.com/

  6. #6
    Join Date
    Oct 2007
    Location
    Lancashire.
    Posts
    4,134
    Blog Entries
    1
    Rep Power
    324039

    Default

    Are you looking at the I beam diagrams? Will the bending modes be the same/similar for tube?

    I would have thought that the point of excitation had some effect on the bending characteristics and as the cartridge is the source of excitation, well you know where I'm coming from.
    Si.

  7. #7
    Join Date
    Jun 2009
    Location
    glorious Devon
    Posts
    1,090
    Blog Entries
    1
    Rep Power
    3428817

    Default

    I think my answer is 'very similar', a beam is a beam, but the second moment of inertia will be different, so, for the same thickness, the bending stiffness will be different. To excite the beam, one would use the free end, not the fixed one (at the bearings, in this case). But excitation can be from the cartridge or up through the base of the arm, (about equally, I have measured on a Lenco deck, with a MM cartridge, YMMV). MC's are said to pump more energy into the arm than MM's.
    cheers.....Bryan

    http://qualia.webs.com/

  8. #8
    Join Date
    Oct 2007
    Location
    Lancashire.
    Posts
    4,134
    Blog Entries
    1
    Rep Power
    324039

    Default

    I don't know whether I'd say an I beam is similar to a tube but there you go. Lets put that aside for the moment as the basic design of a conventional tonearm is pretty much cut in stone now and I for one am not clever enough to take it further.

    Going back to your original thoughts about mounting the cartridge part way down the tube, is there a rule of thumb for this like say a quarter of the way down the tube or a third etc. I ask because one of my previous home built tonearms consisted of one tube sliding inside the other to set the length, the joint being around one third from the free end. It actually sounded quite good but the seat of the pants engineer in me couldn't come to terms with it lol.
    Si.

  9. #9
    Join Date
    Jun 2009
    Location
    glorious Devon
    Posts
    1,090
    Blog Entries
    1
    Rep Power
    3428817

    Default

    I'll try to give a definitive answer to just where is best, but we have only considered the second harmonic, and I've a feeling many tone arms don't suffer from them, more like the fundamental and the third. Its going to be one of those 'compromise' situations, unless you can damp the structure to provide an essentially vibration-free environment (sounds like an April fool's, but it isn't)

    Will look into this later, but I have band rehearsal now, and off to Beer (the place, not the pub!) after that.
    cheers.....Bryan

    http://qualia.webs.com/

  10. #10
    Join Date
    Oct 2007
    Location
    Lancashire.
    Posts
    4,134
    Blog Entries
    1
    Rep Power
    324039

    Default

    Did someone post here today at 12.44?
    Si.

  11. #11
    Join Date
    Jun 2009
    Location
    glorious Devon
    Posts
    1,090
    Blog Entries
    1
    Rep Power
    3428817

    Default

    I believe it was a spammer, now dealt with, chops.
    cheers.....Bryan

    http://qualia.webs.com/

  12. #12
    Join Date
    May 2007
    Location
    scotland, , United Kingdom
    Posts
    5,809
    Blog Entries
    1
    Rep Power
    351395

    Default

    yea was a spammer chops
    www.audioorigami.co.uk

    And visit my face book page--- check out Audio Origami

    http://www.facebook.com/AudioOrigamiTonearms

+ Reply to Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts