Tom, Audio that is too bassy has very often been de-emphasized twice, or at least, incorrectly.
If you can't switch to "flat" audio somewhere in the chain, then you can possibly rectify the problem by using a coupling capacitor that is sized to counteract the de-emphasis. That is, exchange the positions of the resistor and capacitor in the simple circuit that was previously posted. The de-emphasis circuit that was posted uses a series resistor and a shunt capacitor. As the frequency of the signal increases, the capacitive reactance decreases and causes more and more of the signal to be attenuated. When the components are properly selected, the rolling off of the frequency response exactly cancels the "rolling up" of the earlier pre-emphasis circuit. The catch is that every pre-emphasis circuit must eventually be followed by a complementary de-emphasis circuit. If one pre-emphasis circuit is followed by two de-emphasis circuits, the audio sounds bassy. A pre-emphasis, or, in this case, an "un-de-emphasis" circuit, uses a series capacitor and a shunt resistor. In contrast to the de-emphasis circuit, the pre-emphasis circuit allows higher frequencies to pass more easily, while the lower frequencies are attenuated. When the components are properly selected, the bass frequencies are reduced and the treble frequencies are enhanced. The above mini-tutorial is "Audio Equalization 101" and simply skims the basics. Ideally, the end-to-end audio processing in any repeater or link chain should result in an output that duplicates the frequency response and deviation of the input. There are good reasons for linking flat audio, but what goes in from a user should match what comes out. YMMV! 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Sent: Saturday, December 30, 2006 3:33 PM To: [email protected] Subject: [Repeater-Builder] Re: audio equalizers for repeater audio -Ok, just out of mere curiosity, what about for audio that is too bassy? Happy New Year NB2A Tom
