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conductive plastic pots/trimmers

Discussion in 'd.i.y.' started by Jonathan, Oct 18, 2019.

  1. Jonathan

    Jonathan pfm Member

  2. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Eh!? That's a Hall effect shaft position sensor! Conductive plastic tracks have been common for donkeys years and the Alps Blue Velvet is just such a thing... which I will be removing from my own system to replace it with a switched attenuator, because they sound much better... In fact I'm planning on making an attenuator which uses relays to switch the resistors and should have 256 positions.
     
  3. Barrymagrec

    Barrymagrec pfm Member

    New application for a Strowger uniselector?
     
    Arkless Electronics likes this.
  4. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Strangely enough I did "work experience" as a young 'un at the huge GEC factory in Hartlepool where they made them! Long ago shut down with loss of something like 4000 jobs....
     
  5. andrewsutton

    andrewsutton pfm Member

    Stepped attenuators every time, if you have the cash.
    Fit them and forget them.
    Accurate and cleaner sound.
    Cheers Andy.
     
    Arkless Electronics likes this.
  6. sq225917

    sq225917 situation engineer

    I went from a 64 step to tkd ko-on, theres no quality difference. Not all film pots are equally good.
     
  7. andrewsutton

    andrewsutton pfm Member

    I’m sure you are right that all pots are not equal but the TKD pot I tried didn’t sound any better than others and had a very similar channel mismatch when tested.
    Not sure which TKD pot it was but it cost about £70. Cheers Andy.
     
  8. sq225917

    sq225917 situation engineer

    Mine is better than 1% across the board, are you sure the pot was the mismatch?
     
  9. Jonathan

    Jonathan pfm Member


    sorry that's the first link to show up when i searched for 'conductive plastic trimmer' on that site! well i think you'd be hard pressed to find trim pots or faders in 'stepped attenuator' format - which is my interest (trim pots and faders - for an older soundcraft mixing board)
     
  10. Jonathan

    Jonathan pfm Member

    i'm pretty sure there's a place for conductive plastic wipers in the audio world if they are clearly superior to carbon ones (?) let's not be TOO snobby here!
     
  11. Barrymagrec

    Barrymagrec pfm Member

    I seem to remember that Neve used Penny and Giles conductive plastic faders on their mixing desks in the late sixties, so as Jez said, not very new.
     
    Jonathan likes this.
  12. Jonathan

    Jonathan pfm Member

    ok - certainly new to me ... but I was reading some rant about how great they were as a 'new' technology on a pro audio forum - so who knows. I guess the transistor was invented in 1958 or so (in practical terms) but didnt see common use until the 70s so ...
     
  13. cctaylor

    cctaylor pfm Member

    Transistor demonstrated 23rd December 1947. First commercial transistor radio on sale Christmas 1954. The portable radio was the product which made the impact, due to heavy power requirements of valves away from mains.

    Gradually the improved reliability performance of semiconductors in most applications drove the general adoption of them.
     
    Jonathan likes this.
  14. Julf

    Julf Evil brother of Mark V Shaney

    "The Sony TR-63, released in 1957, was the first mass-produced transistor radio, leading to the mass-market penetration of transistor radios. The TR-63 went on to sell seven million units worldwide by the mid-1960s."

    The TG12345 solid state mixing desk at Abbey Road Studios is from 1968. SSL (Solid State Logic, the famous mixing console company) was founded in 1969.
     
  15. Barrymagrec

    Barrymagrec pfm Member

    Leevers Rich were the last manufacturer of professional studio tape machines to switch from valves to transistors, which they started to do in 1969 and shipped the last valve machines in 1971. Most other manufacturers of professional equipment had gone solid state in the mid / late sixties.

    The iconic Bush TR82 transistor radio was released in 1959.
     
  16. andrewsutton

    andrewsutton pfm Member

    If you agree that 25% difference on testing with a meter is a mismatch then yes.I got tired of sending them back to suppliers. The differences were repeatable.
    Don’t know if you have been lucky or me unlucky.
    Cheers Andy.
     
  17. sq225917

    sq225917 situation engineer

    Maybe I hit lucky. I swapped plates from five noble pots before I could come up with a solid match previously. I would have kept the Khozmo if I could have eliminated the added him from the split power grounds, superb thing.
     
  18. Jonathan

    Jonathan pfm Member


    Yes ... notice I said ‘in practical terms’ ... nearly all the early germanium point contact and Mesa transistors failed from the fifties through the mid to late sixties ... it was only once the ‘modern’ type silicon transistors were in production (in practical numbers not really before as a coarse estimate) did they really see full integration in products. There’s a very interesting docu on the ‘transistor wars’ on YouTube I just finished watching for the umpteenth time ... I knew I’d get into trouble for stating it like that though :)
     
  19. 337alant

    337alant Negatively Biased

    Jonathan likes this.
  20. Jonathan

    Jonathan pfm Member

    so no one knows of any higher-quality-than-carbon trimmers out there? not having great luck finding ones that fit the right hole pattern (three hole staggered -you know the type - sitting upright like a windmill)
     

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