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Cassette tape delay

Discussion in 'General Electronics Chat' started by Rorut, Dec 19, 2017.

  1. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Watkins electronic music, a blast from the past, they made a load of stuff including the cry baby waa pedal, I fixed a few of those too, very popular.
    I've never heard of an echo room, interesting I wonder if thats where the term 'echo chamber' came from, those 'orrid Cb mikes that had one inside back in the 80's.
    I experimented a while back with an audio delay line memory, storing bits in switched audio tone bursts recycled over a mike & speaker.
     
  2. Rorut

    Rorut Member

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    This unit actually has a pitch on the front that is letting you adjust the speed but only during playback, not while recording. And I read it has a small range. But the pot mod should bypass this and giving wider control. This is only what I read from a blog post. Making a cassette loop sounds great! Good idea!

    The copycat sounds interesting

    Would it be an idea to clean the tape deck and demag?
    Any suggestions about that for keeping it spinning for the future?
     
  3. Rorut

    Rorut Member

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    Would either of these work?
    1.
    [​IMG]
    2.
    [​IMG]
    3.
    [​IMG]
     
    Last edited: Dec 30, 2017
  4. dave miyares

    Dave New Member

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  5. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    I've never messed with one but I'd think the lack of speed control while recording is probably a inhibit contact on the play/record switch, usually a schadow multi contact switch, with a little knowledge it might be possible to overide said function and have variable speed while recording.

    Regular cleaning and demagging is important for a tape deck, you can probably still get demag wands from china, isopropyl alcohol is usually ok for cleaning, the rubber pinch roll is the thing to be carefull of with cleaning solvents.
    If you want to spend a bit more and you can still gettem you can get cleaning/demaging tapes that run from batteries.

    The last of the filter circuits look the best, you'll need to wind down the output level control on the echo circuit to compensate for the gain, a 10k inbetween the pot and the op amp on the output level control will permanently drop the signal 6db.
    Also you might need to solder say a 22uf cap inline with the input and output of the filter boards just in case theres any Dc on them, as there doesnt look to be any decoupling caps on the boards.
     
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  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Cleaning yes, demagging no - I've demagged countless tape decks over the years, and it's never made the slightest bit of difference.

    But even more to the point, this is an echo unit, so it's recordings only have to last a fraction of a second - and perhaps a second or two if you move the play head further away, but it's difficult with a cassette.
     
  7. Rorut

    Rorut Member

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    Thanks for the good advices!
    Is this the way you suggested?
    [​IMG]
     
    Last edited: Dec 31, 2017
  8. dave miyares

    Dave New Member

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  9. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Yup thats the one.
    Give it a try see how it works.
    Some amps might have a low input impedance and that may require a op amp follower after the pot, but most should be Ok.
     
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  10. Rorut

    Rorut Member

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    Thank you so much for all help!
    Is there any software that can make a pcb layout automatically from a redrawn circuit layout?
     
  11. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Lots, but not really my scene, I work with vero and protoboard mainly.
    Design spark and eagle are free design packages that have schem capture, the latter is popular with students.
     
  12. Rorut

    Rorut Member

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    I can get 5 pcb for about $15 and free delivery.
    I gave diptrace a try, if this looks ok im ofcourse implementing the mods aswell.

    [​IMG]
     

    Attached Files:

    Last edited: Jan 1, 2018
  13. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Looks Ok.
    I've had many a board made, I used to run a business selling products, but for one off's I use either stripboard, padboard or metal clad dead bug.
     
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  14. Rorut

    Rorut Member

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    I added the components for the modification you helped me with. Did I got the components on the correct place on the PCB layout? :)
    [​IMG]
     
    Last edited: Jan 2, 2018
  15. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    R17 will give you a level control for 'dry' zero to full, and R11 will give you 'wet' from zero to full.
    If this is what your after then good.
    I havent really checked the pcb layout proper I'm at work, but quick glance it looks Ok.
    C14 and the 10k look Ok.
     
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  16. Rorut

    Rorut Member

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    Yes I hope it will work :) thank you
     
  17. Rorut

    Rorut Member

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    I added some connection places for making assembly easier, does this make any sense? Hope I didnt create any problems :facepalm:
    [​IMG]
     
  18. Rorut

    Rorut Member

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    If this look ok? Im sending it to the manufacturer this week. Really hope I have not made anything wrong :nailbiting:
     
  19. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    I dont see anything obvious, but dont take my word for it.
     
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  20. Rorut

    Rorut Member

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    Thanks that is making it more easy to move on :) will post the results here (video) when I get the pcb and put it together
     
  21. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Look forward to seeing it.
     
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  22. Rorut

    Rorut Member

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    Received the tape recorder a couple of days ago but ran into some problem. When opening the bottom for making the pitch modification (Slow down speed of motor) the PCB looks different from the one I linked here before. So now I dont have a clue how to connect a pot for changing that speed.
    My pcb looks like this:
    4E4A820F-CCE8-407C-9F34-58481A24E599.jpeg
    The one from before I found that is modded looks like this:
    65628EC8-6916-4D08-B19B-69CE511B1083.jpeg
     

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