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In the Forum: Melquiades Amplifier
In the Thread: A proper implementation of low-pass filters
Post Subject: Use constant impedance attenuation.Posted by Romy the Cat on: 12/31/2010
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Mark, if you have volume-pot preceding the filter that all that you need to do is to put the volume after the filter, of to load the filter to your volume control. The volume control of cause in this case shall not be a regular pot but it shall be a constant impedance volume control. There are an army of L-pads and T-pads that maintain constant impedance for load (L-Pad) of for both source and loads (T-pad). The idea is that if you have voltage divider that give to you your necessary db attenuation then you need to have a contra-divider to balance impedance. Look for ladder-type attenuators. You can easy find 24-42 step attenuators for any impedance you wish. If you search at eBay “Step Attenuator Dale” then you will see a lot of Hong Kong resellers who sell them. There are a few circulators and you can get the value and make the attenuators yourself with better switches but I do not feel that it worst to but fingers if ready to do attenuators cost sub $40.
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