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OTL tube headphone amp

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by ian mason, Jan 10, 2018.

  1. ian mason

    ian mason New Member

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    Thanks, I will do that tomorrow to the wires, perhaps I should have asked that first as they are a real pain, thanks for the schematic, as I see it all of the smoothing capacitors
    are running to chassis ground but I will double check everything tomorrow and report back.
     
  2. ian mason

    ian mason New Member

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    This is an early picture of all of the smoothing capacitors all of the - are connected to a terminal strip which is bolted to the chassis with a buss wire running the length of
    the terminal strip. Is this acceptable or will I have to change it.
    Thanks Ian
     
  3. ian mason

    ian mason New Member

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    The hum has been significantly reduced by tidying up the 6.3v wires and twisting them however it appears that I have wired the potentiometer wrongly as the volume is going neither up down and the sound in general is just poor, can anyone provide a small diagram please to show which pins that the audio cables from the valve pins 1 and 4 of the 6SN7 and from the rca inputs should be going please.
     
  4. dave miyares

    Dave New Member

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  5. Les Jones

    Les Jones Well-Known Member

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    This is a view looking at the back of the dual gang potentiometer. (I consider the front end the end with the spindle sticking out.)


    130118.jpg


    Both sections of the pot are wired the same way. one for the left channel and one for the right channel. If I remember correctly (As it is over 60 years ago.) the heater windings sometimes had a centre tap that could be connected to ground. You could achieve a similar effect by connecting a 100 ohm resistor between each end of the heater winding and ground. If the noise is more of a buzz than a hum connecting a small capacitor (Say 10 nF) across each diode of the bridge rectifiers might help.

    Les.
     
  6. ian mason

    ian mason New Member

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    Thanks so much Les, I haven't had a chance to do anything today but I will try these things tomorrow.
     

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