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DIY corner bracing an old LP12 plinth

Discussion in 'audio' started by Chris, Jul 30, 2020.

  1. Chris

    Chris pfm Member

    Will be helping a mate rebuild his LP12 with new subchassis next weekend. I was thinking of making and glueing some corner braces into his ancient afromosia plinth - it has no groove to wedge the braces into so any recs for size and material of the triangular parts to make ? What thickness ply ? Any no-nos ?
  2. JensenHealey

    JensenHealey pfm Member

    Can you buy triangular shape profile from hardware stores? Cut to length required and glue firmly into place?

    Not looked inside an LP12 for a long time now.
  3. trick cyclist

    trick cyclist pfm Member

    Cut four corners from a scaffolding plank?
  4. fegs

    fegs pfm Member

    has it got to be wood?
  5. fegs

    fegs pfm Member

  6. peterm

    peterm pfm Member

    There was a thread many years ago on here (or maybe somewhere else) about this and I tried it using 19mm ply for the corner braces, screwed and glued into the internal corners of the plinth.
    I can't honestly say it made any difference!

    As I understand it the corners braces came about because, in some humid climates that LP12s were sold in, the glue failed at the plinth corners and the plinths came apart!

    As usual with Linn it immediately became Linn mythology that the corner bracing made a significant upgrade to sound quality.
  7. Sean K

    Sean K pfm Member

    I understood received wisdom was that if the plinth is stable after all these years, it will probably remain so and there's not much to be gained from the mod. <ducks and runs for cover>
  8. suzywong

    suzywong Wot, no electrons?

    Although IIRC, Linn put an extra bolt from the top plate through the back left corner brace, "to cure a rattle", sorry, "stabilise the motor".

    My (1982) plinth is way too old to have the corner braces, but is still as solid as a rock. :)
  9. 9designs

    9designs pfm Member

    Plenty of plinths for sale, pick up a more recent one. Or leave as it is.
  10. peterm

    peterm pfm Member

    Yes, they stud welded an extra bolt to the top plate to go through a hole in the top left corner brace to cure a loose fit of the top plate to the plinth.

    If you look at the Cymbiosis set up guide it appears that is just a lazy way to avoid getting the correct curvature of the top plate to ensure a snug fit against the supporting wood strips in the motor corner once the screws fastening the top plate to the plinth are tightened up to avoid the motor corner of the top plate being free to vibrate.

    No wonder there's such a lot of mythology surrounding setting up an LP12 (do you think Hamish, or Thorens before him, thought about this or did they think it would be done right in the first place?)
  11. Chris

    Chris pfm Member

    After fitting the arm for him the other day and a cursory shifty to check the bounce I got the feeling that the plinth was flexing. No two sides seemed to be on the same level plane. I messed around twisting and de-stressing the springs til I got bored. Limited success. So I thought the braces might improve things.I’ll take a closer look at things
  12. ncp

    ncp Active Member

    I did put corner braces into mine but really only to support a Prefix phono stage. The deck was subsequently set up in Leicester with no howls of derision. I used ply cut in a mitre saw and then some ordinary wood glue and clamps to hold them in place while glue dried.
    good luck - it's not difficult though.
  13. Alan Chung

    Alan Chung Member

    If your plinth is already warped adding corner braces will not fix it. Years ago I also glued some ply braces to mine for the prefix but eventually the plinth gave way to the heat and humidity and was bent to the extent that I had to replace it.
  14. hp1

    hp1 pfm Member

    The braces are there for Linn so they didnt have so many plinths returned because they were not flat.

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