In my last blog post I mentioned about an ambitious project I was thinking about starting on.
Well I did make something, but it didn't work. Looks neat though!
What I initially set out to do was to create an analog mixing board to funnel 8 channels into 4 different outputs with 4 different mixes. This is because one of my cover bands has 4 members with 4 instruments each. The motivation was that with such a board we could just plug in all of our instruments (yes including a set of electric drums) and our mics into this board, and have individualized mixes for both. (So you know if someone thought my bass playing was particularly trash you could just not listen to it.) Since we don't have external mic preamps, I also needed to add preamps to the proposed mic channels.
From the photo above you can see that each output channel has 8 associated knobs that were meant to control the output volume of each input channel. The switches above that are meant to switch between going through the preamp or not, depending if you wanted instead to use a line-level device.
These were the intention, but ultimately this project was an utter failure for a variety of reasons. I think I naively thought that sound in audio circuits ultimately get converted into different voltages, so I figured if the "headphone" outputs for each instrument were the right level you can just connect the circuits together. I think fundamentally this is probably true, but when you start mixing 8 channels together, things might start getting a little more crazy. For whatever reason I could not get the sounds coming out of my bass amp + my guitar amp to get to a reasonable level just by mixing them together. I think I ultimately should have added some sort of amplification to the "instrument" channel. I also kinda YOLOed on the mic preamps because I just picked an amplification factor and figured I could just attenuate the output later. Well it turns out when you amplify something by 200x, you amplify a lot of random noise too, especially if your power supply injects noise (I presume that's where the random noise was coming from). What ended up happening was that the output of the vocal preamps waaaay overshadowed the instrument channels. So I wasted a bunch of time, money, and resources on something that looks interesting but is ultimately useless. (As a final aside, I think adjusting the amplification to only 20x should be rather easy, requiring only desoldering 1 capacitor, which might make this somewhat salvageable, but I haven't really looked into turning this into something useful yet.)
In the end I ended up just buying a cheaper used mixing board and an powered headphone splitter for future use. The only downside is that everyone playing will have the same mix....
I took some photos of the assembly process of the failed mixing board pictured above.
Well I did make something, but it didn't work. Looks neat though!
What I initially set out to do was to create an analog mixing board to funnel 8 channels into 4 different outputs with 4 different mixes. This is because one of my cover bands has 4 members with 4 instruments each. The motivation was that with such a board we could just plug in all of our instruments (yes including a set of electric drums) and our mics into this board, and have individualized mixes for both. (So you know if someone thought my bass playing was particularly trash you could just not listen to it.) Since we don't have external mic preamps, I also needed to add preamps to the proposed mic channels.
From the photo above you can see that each output channel has 8 associated knobs that were meant to control the output volume of each input channel. The switches above that are meant to switch between going through the preamp or not, depending if you wanted instead to use a line-level device.
These were the intention, but ultimately this project was an utter failure for a variety of reasons. I think I naively thought that sound in audio circuits ultimately get converted into different voltages, so I figured if the "headphone" outputs for each instrument were the right level you can just connect the circuits together. I think fundamentally this is probably true, but when you start mixing 8 channels together, things might start getting a little more crazy. For whatever reason I could not get the sounds coming out of my bass amp + my guitar amp to get to a reasonable level just by mixing them together. I think I ultimately should have added some sort of amplification to the "instrument" channel. I also kinda YOLOed on the mic preamps because I just picked an amplification factor and figured I could just attenuate the output later. Well it turns out when you amplify something by 200x, you amplify a lot of random noise too, especially if your power supply injects noise (I presume that's where the random noise was coming from). What ended up happening was that the output of the vocal preamps waaaay overshadowed the instrument channels. So I wasted a bunch of time, money, and resources on something that looks interesting but is ultimately useless. (As a final aside, I think adjusting the amplification to only 20x should be rather easy, requiring only desoldering 1 capacitor, which might make this somewhat salvageable, but I haven't really looked into turning this into something useful yet.)
In the end I ended up just buying a cheaper used mixing board and an powered headphone splitter for future use. The only downside is that everyone playing will have the same mix....
I took some photos of the assembly process of the failed mixing board pictured above.
Wow you printed a PCB? How much did you test the circuits before getting it printed? I love the commitment/blind optimism.
ReplyDeleteEven if it doesn't work it looks super fun to mess with. Just gotta add flip switches and clicky buttons
HAHAHA, I didn't really test anything at all, I didn't breadboard anything, definitely failed because of hubris. Totally, went in with blind optimism. I've done a few digital logic PCBs without much testing ahead of time because those are more simple, I've generally had minimal problems with those.
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