Audio output stage Query

Discussion in 'Analog & Mixed-Signal Design' started by Arcadus, Dec 10, 2017.

  1. Arcadus

    Thread Starter New Member

    Dec 10, 2017
    2
    1
    The sound board amplifier output stages shown, are from late 1970s monochrome arcade machines.
    They both use a push pull amplifier but differ slightly.
    The earlier one has the volume control in the feedback to the op amp, the other varies the I/P to the op amp.
    My question is the technical function of the diodes (D6, D7) between base/emitter of the later version.
    I assume they are some form of protection.
    I found the fault on the earlier version being an o/c pot in the feedback cct which caused the volume to be flat out.
    I was wondering if it would be an advantage to add the diodes and emitter resistors. Starhawk audio op.jpg
     
  2. Arcadus

    Thread Starter New Member

    Dec 10, 2017
    2
    1
    Ok, I researched it myself and found the diodes are ther
     
    GopherT likes this.
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