the active damping control switch does not switch between high and low, it os more a switch between a max of damping factor in the low frequency range and a linearization of the damping factor over a wide frequency band.

better described here:

4. 2. 1 General information

The damping factor D of a power amplifier is determined from the load resistance RL (connected loudspeaker, but for the measurement assessment 8 Ω resistance) divided by the internal resistance of the amplifier Ri.

Physical equation: D = RL / Ri

D : damping factor (calculated number)

RL : load resistance (connected loudspeaker, for the measurement assessment 8 Ω resistance) * Ri : internal resistance of the amplifier (usually measured at 1 kHz) **

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Example: A power amplifier has (at 1 kHz) the internal resistance Ri =16 mΩ

The damping factor is then calculated to be 500. Physical equation: 8 Ω / 0.016 Ω = 500 *** This is a typical value for modern transistor power amplifiers.

(In comparison: at 1 kHz full tube power amplifiers usually have an internal resistance in the range of 0.4 Ω to 4 Ω and therefore a calculated damping factor in the range of 2 to 20)

Technical background:

* Loudspeakers do not have the same resistance at all frequencies. They are characterized by dynamic resistance, whereby the so-called complex load is formed by the spring mass system, deflection and movement speed of the membrane, induced counter-voltage in the voice coil, and crossover.

** The internal resistance of a power amplifier is also a dynamic variable. It is only valid for a certain working point, with a certain frequency and for a certain modulation. In addition, it can be determined in a number of ways.

*** These above-mentioned mathematical considerations do not take the loudspeaker cable resistance values or contact resistance (banana connector, cable lugs, etc.) into account. In reality these loudspeaker series resistance values and contact resistance values are naturally added to the internal resistance.

4. 2. 2 The technical part

As described above, due to the required high negative feedback reserve modern high power amplifiers with transistors have very low internal resistance (Ri) and therefore high damping factors. These high damping factors are desired because they have a very positive effect on important technical parameters, e.g. on distortion characteristics.

At 5 kHz the damping factor of a power amplifier is relatively linear and has a high value, but then for physical reasons (limitation of bandwidth) goes down with higher frequencies.

The degree and progress of the damping factor influence the in- and outswing behaviour and therefore the control of the connected loudspeaker by the power amplifier.

4. 2. 3 Claims and reality

Claims are often made that a higher damping factor is better for controlling the loudspeaker and therefore the system sounds better. This is not the case.

Correct is that a power amplifier with a very low damping factor is not able to sufficiently control the loudspeaker. It is, however, true that a loudspeaker does not have the best outswing behaviour with the maximum damping

factor.

The truth is that the value of the damping factor should in fact be within a certain range which is ideal for the loudspeaker and should also be linear for as long as possible over the frequency range.

4. 2. 4 Solution: damping factor linearization

In order to meet these two requirements (ideal range and linear curve), in the switch position "DAMPING FACTOR - ON" we lower the complete value of the damping factor slightly to the ideal value and then linearize it over a wide frequency range. In this process the advantageously high negative feedback reserves remain completely intact (see text above). If the push switch on the rear is not pressed, the function is not activated. The absolute damping factor is then maximized, but from 5 kHz decreases considerably. According to his preference, the customer can choose to activate the damping factor linearization or not.

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Fig. 5: This simplified diagram serves to illustrate damping factor linearization

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