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    Using ST-70 kit 16 ohm tap

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    Mike16W

    Posts : 39
    Join date : 2009-11-03

    Using ST-70 kit 16 ohm tap

    Post by Mike16W on Thu Mar 03, 2011 3:54 pm

    My speakers are 16 ohm and I wanted to try the ST-70 with the 16 0hm tap. It is used on the feedback loop. Can I just move the loop to the 8 ohm tap or will that change the sound of the amplifier?


    bigmm79

    Posts : 23
    Join date : 2010-09-15

    Re: Using ST-70 kit 16 ohm tap

    Post by bigmm79 on Thu Mar 03, 2011 4:48 pm

    I'm using 16 ohm on mine. Bob had me use the 16 ohm line for feedback as well, you just run a wire from the speaker posts to the spots on the board. There are previous posts here, I believe, on this. Maybe even a picture.

    Mike16W

    Posts : 39
    Join date : 2009-11-03

    Re: Using ST-70 kit 16 ohm tap

    Post by Mike16W on Thu Mar 03, 2011 5:01 pm

    Thanks, I searched prior post but couldn't find one. I will double check.

    Bob Latino
    Admin

    Posts : 2415
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Using ST-70 kit 16 ohm tap

    Post by Bob Latino on Thu Mar 03, 2011 5:55 pm

    Hi Mike,

    The slight wiring differences for 16 ohm speakers on either the VTA ST-70 or ST-120 are below ..

    Bob

    Special instructions for 16 ohm speakers

    Under step # 10 on page 5 > do C below instead of either A or B since you have 16 ohm speakers

    C. If you are using 16 ohm speakers in your system then connect the YELLOW wire from the right output transformer to the RIGHT RED speaker post. Also connect one end of a 12 inch wire to the RIGHT RED speaker post (S). Now coil up and cut off the bare end of the ORANGE (8 ohm) wire and the BROWN (4 ohm) wire. Place a small piece of tape over the end of both wires so they won’t short out to the chassis. The other end of 12 inch wire will be connected at a later stage in construction.

    Now > Repeat step C above for the LEFT RED speaker post.

    Under step 4 on page 9 under “Connections to the VTA driver board”
    Disregard what it says there and do this instead

    4. Connect the free end of the 12 inch wire from the LEFT RED SPEAKER POST to the eyelet marked “NFB” on the LEFT side of the driver board. (S) Connect the free end of the 12 inch wire from the RIGHT RED SPEAKER POST to the eyelet marked “NFB” on the RIGHT side of the driver board. (S)



    Last edited by Bob Latino on Sun Mar 06, 2011 2:59 pm; edited 1 time in total

    Mike16W

    Posts : 39
    Join date : 2009-11-03

    Re: Using ST-70 kit 16 ohm tap

    Post by Mike16W on Thu Mar 03, 2011 6:27 pm

    Bob,
    Thanks for the detailed instructions.

    Mike

    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: Using ST-70 kit 16 ohm tap

    Post by Luddite on Fri Mar 04, 2011 11:42 am

    Bob Latino wrote: Place a small piece of tape over the end of both wires so they won’t short out to the chassis. [/i]

    HINT: As an alternative to taping the wire ends, you can use a small (about 3/4") length of heat shrink tubing. Slip the tubing over the end of the wire about 1/2" leaving about 1/4". Heat the tubing until it shrinks tight and then quickly squeeze the end closed with long-nosed pliers before it cools. IMHO this will be a more permanent solution over the long term.

    Best Regards,
    Charlie

    Mike16W

    Posts : 39
    Join date : 2009-11-03

    Re: Using ST-70 kit 16 ohm tap

    Post by Mike16W on Fri Mar 04, 2011 2:33 pm

    Charlie,
    Thanks for the hint. I heat shrinked the wired but never thought about squeezing the heat shrink shut. I will try that next time.
    Once I switched to the 16 ohm tap, the sound seemed to have more on the lower end. Nice improvement.

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