Additional Information about the audio options in a GE Phoenix:
New 3/11/02: A few words about the different audio outputs from a Phoenix.
There are 3 options:
Speaker audio. Great if you don't mind having the volume control active and need de-emphasized audio. Just use J910, Pin 3. W 902 has to be installed between holes HL10 and HL 11. That's right next to Pin 3. Down side: You're going through audio circuits you may not need to. You also have the cheap, prone to failure Phoenix volume control in your system. How the volume control is set will effect your application. Risky
"Filtered VOL/SQ Hi": It is before de-emphasis, but AFTER the sub-audible CG tone high- pass filter. This come comes out of the radio without modification on J910, Pin 4. This connection works well if you want the radio to handle any sub-audible tones, like for a simplex repeater, for a link radio, or for 1200 bps packet. If you need to get CG out of the radio, then this point is too late since low frequency audio is already filtered out.
"VOL/SQ HI" Pure de-emphasized audio, as close to the receiver as you can get. To get audio before this high-pass filter, you'll need to make a simple modification (jumper only). Applications for this mod include any controller that's looking for a sub-audible tone, or 9600 bps packet.
Audio Circuit description:
VOL/SQ leaves the receiver, goes to the Synthesizer/Interconnect board, gets switched off for PTT, then the sub-audible tones are filtered out, goes through an RX MUTE switch, then back the receiver board for amplification in U601. In case you need it, the de-emphasis is provided by R618 and C615 just before U061, on the receiver board, near the volume control. U601, the 5 pin audio output IC is near the front panel, between the volume control and the speaker. "Linear Audio Amplifier, sim to TDA 2003" You only need this IC if you're using the speaker output. Also check your volume control. One of the real weaknesses of this model. See Service Tips.