What is an audio buffer?

April 11, 2021
 by Paul McGowan

7 comments on “What is an audio buffer?”

  1. Paul describes an amplifier with unity voltage gain, high input impedance, low output impedance, and sufficient output current capability to drive a range of different loads. It creates an output voltage that is exactly the same as the input voltage. The output current is exactly whatever is needed to maintain that output voltage into the connected load. The output current might well be larger than the input current, but the buffer isn’t a current amplifier because it doesn’t generate an output current that is a precise larger version of the input current. By contrast, a current amplifier with a gain of (say) 10 would take an input current of 1 mA and generate an output current of 10 mA. A current amplifier should have a low input impedance and a high output impedance.

    1. Good morning Mark!
      What you said in your comment, happens to be correct.
      How you described it, is exactly how a buffer amplifier works.
      Granted that I don’t fully understand how this is done with transistors, but I can tell you how it’s done with tubes.
      You have two double triode tubes, that are almost the same, or you can use two of the same tubes.
      Lets just say, we’re gonna use two 6922 tubes to make a buffer amplifier.
      You have the plates of one tube feeding in to the screens of the other tube.
      The first tube, is gonna give you the high voltage, the second tube, is gonna give you the high currant.
      In most cases, you don’t need anymore then 250MV going in.
      When the first tube is combined with the second tube, you’ll get 500MV or grater then that, to drive long inter connects.

      1. Hello John! I was just being pedantic about Paul’s terminology. We don’t disagree about the function of a buffer as he describes it, but it isn’t what we understand as a “current amplifier” in normal electronics. However, I guess this is Paul’s forum, and his rules apply, so “current amplifier” means whatever he wants it to mean.

  2. One of the applications mentioned in the video is a buffer following a potentiometer-type volume control, where the buffer isolates the volume control from the cable capacitance. Consider a 10 kohm potentiometer and 6 feet of unbuffered cable at 20 pF/foot capacitance. The high frequency attenuation is approximately 0.004 dB at 100 kHz. It’s not clear that a buffer would provide a really noticeable improvement to frequency response. There must be something else happening.

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