From: Garey Barrell 
Subject: Re: [Drakelist] R4C  IC audio amp and T4XC Spot on SSB


Art -

Good point.

It is better to just leave the output transformer in place, with the 
primary AND secondary still connected.  Then the audio is "stepped up" in 
impedance and voltage for the Spot AND Anti-Vox functions.  The audio chip 
has no problem driving a speaker and the essentially open circuit
"primary" 
of the transformer.

73, Garey - K4OAH
Atlanta

At 02:24 AM 12/29/2002, mdg wrote:

>I was asked a question by one of the members of this List  regarding his
>newly installed audio IC amp and I thought this subject may be of
>interest to others... .
>When installing an IC audio amp in your R4C it may be tempting to just
>skip the original audio output transformer and connect the speaker
>directly to the IC (through the headphones jack contacts of course). The
>problem is that you will lose your T4XC Spot function when on SSB
>(Separate Mode). The Spot on SSB uses the feedback from R4C through the
>Anti Vox line which is connected to the output audio transformer.  When
>installing the IC audio amp you may want to connect the primary of the
>output transformer to the output of the IC to maintain that feedback.
>Impedance of the primary is relatively high and doesn't load  the IC to
>any considerable extent. Purists may argue that the audio phase changes
>adding to the distortions but, really, you won't nottice any difference.
>
>73 Art VE3PND


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