Re: [Repeater-Builder] Audio Reproduction

[scomind]

Hi Eric,   Anyone have a good design for a high quality Audio circuit to put in between  the discrimanator and the TX audio?  I not looking for the typical repeater controller design as I've been there and done that. I want the highest posible quality of audio reproduction I can get.   As we're finding out via experiments here, there are other interesting sources of distortion (especially in older technology repeaters) besides those created in the audio circuits.   For example, PMs built with a varicap and LC resonant circuit are based on the assumption that the phase shift of the circuit is linear as the varicap voltage is changed. This isn't true because the phase shift follows a tangent curve, thus you get more distortion at the ends of the curve than at the flattest part.   Similarly, quadrature detectors use an LC resonant circuit and thus add distortion of their own to the recovered audio. Since the distortion occurs at the high end of the frequency response, tapping into this kind of discriminator for your audio results in more distortion, not less, than tapping into the audio after the de-emphasis. That's because the de-emphasis rolls off the distortion products.   A surprising amount of distortion comes from multiplier stages that are mistuned.   And, we've previously talked about the distortion that comes from the audio 'blobs', especially from the soft action of some limiters.   For these reasons, I don't get too particularly worried about adding a couple of parts in the external audio chain - - especially since I'm in the controller business...  :-)   73, Bob     Bob Schmid, WA9FBO S-COM, LLC 970-416-6505 phone 970-419-3222 fax www.scomcontrollers.com Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/   To unsubscribe from this group, send an email to: [EMAIL PROTECTED]   Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.