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Old December 13, 2008, 02:06 PM
crash01 crash01 is offline
Join Date: Nov 2008
Location: Ontario
Posts: 25

I want to select a stepped attenuator with an appropriate impedance value. If the impedance value of the attenuator is too low relative to that of the output on the source it presents too heavy a load for the source, but if the value of the attenuator is too high relative to the poweramp input impedance it will not be able to drive it properly. Poor matching on either end can cause significant distortion. With an active preamp this is usually not a problem because the input values are high and output values are low, however with a passive volume control (ie. a stepped attenuator) the input and output values are exactly the same so you have to be careful to balance the impedance needs of the source output and amp input.
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