Now we’re in business. 
After some fun with the signal generator, I found that both volume boards were working properly. I knew they were both working in my previous post, but did some more exhaustive testing.
I first tested volume board addressing by swapping it onto my first main board. When in balanced mode, both boards worked. When in single-ended mode, one volume board worked and the other didn’t, as expected. In balanced mode, a jumper on the volume board determines whether it is a left-channel board or a right-channel board when the microcontroller is talking to them.
When in single-ended mode, the jumper is expected to be in a specific position. The one that was out of position could not be addressed and no sound came out. Also as expected.
So next thing to do was remove the lower main board (the channel that wasn’t working) and attach some jumpers into which I could inject signal into the volume board. I sent a 2V 1000Hz sine wave into one channel and 2000Hz into the other, just so it was easy for me to identify. I turned it on, turned the volume up, and sound was passing through it. Huzzah! So now I know the problem was on the main board.
After a visual inspection and some probing with my DMM, I noticed a difference. The output relay from the main board is not supposed to have its center contacts shorted as the input relays do. I fixed that problem and now signal is flowing through the entire device properly. Outstanding!
Hooked up my laptop to Modius and pushed some music to it. Modius through Muses, and then back to Magnius and my headphones. All working! I’m a happy guy now.
The one remaining oddity that I didn’t experience with the single-ended version I built is it won’t come out of mute when switching channels until I push the input selector a second time. It’s something I can live with and can work around, but thought it was odd compared to the other one I built.
Otherwise, a successful day I’d say.
After some fun with the signal generator, I found that both volume boards were working properly. I knew they were both working in my previous post, but did some more exhaustive testing.
I first tested volume board addressing by swapping it onto my first main board. When in balanced mode, both boards worked. When in single-ended mode, one volume board worked and the other didn’t, as expected. In balanced mode, a jumper on the volume board determines whether it is a left-channel board or a right-channel board when the microcontroller is talking to them.
When in single-ended mode, the jumper is expected to be in a specific position. The one that was out of position could not be addressed and no sound came out. Also as expected.
So next thing to do was remove the lower main board (the channel that wasn’t working) and attach some jumpers into which I could inject signal into the volume board. I sent a 2V 1000Hz sine wave into one channel and 2000Hz into the other, just so it was easy for me to identify. I turned it on, turned the volume up, and sound was passing through it. Huzzah! So now I know the problem was on the main board.
After a visual inspection and some probing with my DMM, I noticed a difference. The output relay from the main board is not supposed to have its center contacts shorted as the input relays do. I fixed that problem and now signal is flowing through the entire device properly. Outstanding!
Hooked up my laptop to Modius and pushed some music to it. Modius through Muses, and then back to Magnius and my headphones. All working! I’m a happy guy now.
The one remaining oddity that I didn’t experience with the single-ended version I built is it won’t come out of mute when switching channels until I push the input selector a second time. It’s something I can live with and can work around, but thought it was odd compared to the other one I built.
Otherwise, a successful day I’d say.
