It lives!
However I do have a question/concern. I based the core on sams buffered multi designs. Is it normal for there to be a faint signal coming through the extra channels when they are not in use? I might have inadvertently created a mixer.
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I’ve had similar issues, usually when I think diodes are switches or ignore shielding. That said. Test and see.
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Getting down to where I need to make some decisions that I have been putting off.
I am still attempting to figure out what R1 resistor I need in conjunction with the +/-15v meter. I can tell you that it has a 15K impedance value when I just check it with my voltmeter. Not sure if that helps any.
Do you think it is ok for both the audio ground and the GND hookups to both share a common ground?
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Also starting to wonder if I need the op amps at all. At least on the LED meters. I feel like I still need the one on the +/-15 volt meter.
I should probably take things one step at a time. Right now I disconnected all of the metering things to focus on getting the actual splitting done right.
What is the best way to quiet the signal noise on my channels? Right now its acting as a pretty low key mixer.
Are the inputs floating if they are not connected to a signal source, thus maybe picking up some stray signal or are they pulled to GND by some high value resistor? That could be the cause.
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That is very likely how it is intended to be.
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I feel like my lack of having a multi is really holding me back right now, so I’ll focus on this beast some more.
First off, my original hope that I could just plug the negative reference voltage for one of my ready made ten segment displays were quickly dashed when it promptly popped the 10r resistor on my supply rail. After fixing that (and making sure everything was functioning as it was before) I addressed the issue of my segments being inverted - the motion of the LED’s on the +12 were going from the top to the bottom instead of the bottom to the top. The solution:
A bit of wire salad, but it works.
So now it becomes an issue of getting the second ten segment display to read negative voltages. I did a small amount of research and I see there are several ways to do this. However as I would like to have things buffered we should be able to take advantage of this by inverting the signal. Assuming I am beginning to understand how this works.
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I think after two years of ruminating on this, I might have had an epiphany.
Most mults (including sams) have the LED driver on one of the TL074’s opamps with the rest being for the audio outputs. I put all four of my LED’s on a separate TL047. I bet this is why I am getting cross-talk on the channels.
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Resurrecting this project again in an attempt to tie up some loose ends and get a much needed mult working.
I pulled the tl04 controlling the LED’s and sure enough - no more cross talk. Now the question is, is there a way to eliminate the signal bleed issue without heavily altering the circuit? I imagine I’ll have to separate out things into individual tl071’s. Not exactly ideal but do-able.
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