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Vintage threads from the first ten years

previous: cbs Does anyone know or have a circuit ... -- 1/8/1998 2:14 PM

Re: Damping control

1/8/1998 3:03 PM
R.G.	Re: Damping control To reduce damping, just insert resistance in series with the speaker. To increase it... ah, that's harder. There was a series of magazine articles on loosely this topic that appeared in Audio Engineering in about 195x. The gist of the articles was that even if you had perfect damping at the amp output terminals, the speaker resistance would loosen up the damping at the speaker. The articles (by a couple of different people who had different opinions, early printed flaming...) talked about using a resistor to sample speaker current and feed that back into the amp. The phase was adjusted so that the current feedback was positive, and the normal voltage feedback was negative. The positive current feedback made the amp put MORE current into a load as the current went up, which could be seen as a kind of negative resistance. Many claims were made about the tonal aspects of perfect damping. Reducing plate voltage produces a loose bass response in some cases because this reduces the open loop gain of the amp and this reduces the gain available for feedback to increase the closed loop damping factor. It's less damped.

1/8/1998 3:03 PM

R.G.

Re: Damping control

To reduce damping, just insert resistance in series with the speaker. To increase it... ah, that's harder.

There was a series of magazine articles on loosely this topic that appeared in Audio Engineering in about 195x. The gist of the articles was that even if you had perfect damping at the amp output terminals, the speaker resistance would loosen up the damping at the speaker. The articles (by a couple of different people who had different opinions, early printed flaming...) talked about using a resistor to sample speaker current and feed that back into the amp. The phase was adjusted so that the current feedback was positive, and the normal voltage feedback was negative. The positive current feedback made the amp put MORE current into a load as the current went up, which could be seen as a kind of negative resistance. Many claims were made about the tonal aspects of perfect damping.

Reducing plate voltage produces a loose bass response in some cases because this reduces the open loop gain of the amp and this reduces the gain available for feedback to increase the closed loop damping factor. It's less damped.