Walter W9KJO in writing to the list says,
” The yellow wire on the volume control does not have enough audio for my Signal Link to work with. I have to reconnect to the 3.5mm Audio Out jack and turn the volume up about half way. which is too loud for my headphones so I need to install a second 3.5mm for my Head Phones.
“I would be much better if I could find a way to get enough audio separate from the actual audio out to the 3.5mm jack.”
Modifications to the µBITx to add a second audio channel for computer use
- Remove R75
- Connect U1 pin 6 to VOL-H. This will give you an auxiliary sound output that is independent of the volume control.
- Connect the + terminal of a 470 µF, 16V electrolytic capacitor to U1 pin 3.
- Connect the – terminal of the above cap to your auxiliary out mini jack.
- Earth the auxillary out mini jack sleeve connection.
- The 470 µF could very likely be much smaller, depending on the input impedance of your Signal Link. Experiment, it won’t hurt.
- You may also want to add a resistor divider between the cap and jack to reduce the signal strength, depending on how much your Signal Link can tolerate.
- Considering the problem others are having with the TDA2822 you probably should add a resistor in series with the cap, unless you implement the resistor voltage divider, that will provide the same protection.
- Rather than use a voltage divider on the output of your second audio amp, you may want to incorporate a trimmer potentiometer between VOL -H and pin 6 of U1 similar to the primary volume control to set the auxillary audio output level.