When I tested the MFOS mixer I found a problem. When trying out the stereo output and some stereo channels I found that I was missing some channels. I checked my wiring and I couldn't find any mistake there. Then I started measuring signals and found quickly that I had signal in the input of the stereo potmeters, but NOT on the output. I thought that was very strange. So I started measuring the potmeters themselves and it turned out that some of them didn't work at all :( So after that I decided to test the other set I have. They worked so I decided to replace them.
Replacing the potmeters was not very easy. As I said in the previous post it is sometimes hard to reach the solder lugs. But I first removed the old potmeters with the wires attached. Then inserted the new potmeters and then finally soldered the wires one by one so that I couldn't go wrong with that. You can see it in the top left picture. In the picture on the right you can also see that I didn't shorten the shafts of the potmeters yet. These ones are made of plastic so with a small saw you can easily shorten them even when they are already mounted.
After this I redid my testing procedure and found that everything was working OK. These plastic stereo potmeters just don't feel so solid as the metal ones. I might replace them in the future when I can source better ones. Then I encountered another challenge. These new potmeters didn't have round shafts but they have a flat side. This is normally to have the knob on at a fixed position. I found that when I put the knobs on it didn't align with the scale on the front panel. So I had to twist the potmeters a bit to get that right. You can see that in the picture on the left.
And here is the final module. It is not really that bad I think :) It works great. I played a bit around with the Mooger Froogers on the Send and Return channels even though they are not stereo. But this way I could add some sound effects to the input signal by turning the send potmeters. And of course there was one thing that I gambled. And that was the polarity of the headphones stereo jack. And of course I switched left and right. Well 50% change eh? :) I think this is quite a nice mixer and you can build is very cheap if you are interested take a look on the MFOS website at this URL:
http://www.musicfromouterspace.com/analogsynth/STEREOMIXER2006/STEREOMIXER2006.php
When I tested the MFOS mixer I found a problem. When trying out the stereo output and some stereo channels I found that I was missing some channels. I checked my wiring and I couldn't find any mistake there. Then I started measuring signals and found quickly that I had signal in the input of the stereo potmeters, but NOT on the output. I thought that was very strange. So I started measuring the potmeters themselves and it turned out that some of them didn't work at all :( So after that I decided to test the other set I have. They worked so I decided to replace them.
Replacing the potmeters was not very easy. As I said in the previous post it is sometimes hard to reach the solder lugs. But I first removed the old potmeters with the wires attached. Then inserted the new potmeters and then finally soldered the wires one by one so that I couldn't go wrong with that. You can see it in the top left picture. In the picture on the right you can also see that I didn't shorten the shafts of the potmeters yet. These ones are made of plastic so with a small saw you can easily shorten them even when they are already mounted.
After this I redid my testing procedure and found that everything was working OK. These plastic stereo potmeters just don't feel so solid as the metal ones. I might replace them in the future when I can source better ones. Then I encountered another challenge. These new potmeters didn't have round shafts but they have a flat side. This is normally to have the knob on at a fixed position. I found that when I put the knobs on it didn't align with the scale on the front panel. So I had to twist the potmeters a bit to get that right. You can see that in the picture on the left.
And here is the final module. It is not really that bad I think :) It works great. I played a bit around with the Mooger Froogers on the Send and Return channels even though they are not stereo. But this way I could add some sound effects to the input signal by turning the send potmeters. And of course there was one thing that I gambled. And that was the polarity of the headphones stereo jack. And of course I switched left and right. Well 50% change eh? :) I think this is quite a nice mixer and you can build is very cheap if you are interested take a look on the MFOS website at this URL: http://www.musicfromouterspace.com/analogsynth/STEREOMIXER2006/STEREOMIXER2006.php
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