Hello, again…
I have put together my first stripboard layout using this simple sub-oscillator schematic and am having a strange issue with the output. When I plug the output directly to my little micro cube amp it gives plenty of output, but when I plug it into my mixer module (lmnc super simple mixer) the output is extremely low UNLESS I JUST TOUCH THE CABLE TIP TO THE SLEEVE of the oscillator output jack. Why would my amp and this mixer module react so differently? Is it something to do with giving the TL072 only +12v and ground?
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Im pretty sure you need a dc blocking cap on the output, also there might be an issue with the input given the single rail supply to the opamp, I will get back to you on this.
EDIT:
I Think this should fix the problem:
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Thank you! Could you explain the theory behind why it gives plenty of signal through the guitar amp, yet low signal through the mixer?
When I have a cable plugged into the mixer and touch the tip to the sleeve of the jack it gives me a lot of output. WTH
Its hard to say for sure what the problem is without seeing a schematic of the mixer. As for the amplifier it probably has a capacitor at the input, I will say more on that later.
Concerning capacitive and direct coupling: direct coupling works whenever bipolar power rails are used. In the case of the suboctave circuit the opamp was operating from a single rail supply so the signal which is AC needs to be capacitively coupled and a dc bias added in order for the opamp to be able to deal with both the positive and negative halves of the signal, If the opamp is powered from bipolar power rails this biasing is unnecessary and the signal can be directly coupled to the input of the opamp.
As the output is from a logic circuit it wont be bipolar, but rather flipping between ground and the positive supply rail. Therefore to cuple it to a directly coupled mixer, there needs to be a dc blocking capacitor between the output of the logic chip and the input to the mixer, the absence of this capacitor might upset the mixer circuit, again its hard to say for sure without seeing the mixer circuit itself
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I built a 6 channel version of this LMNC Super Simple Mixer [Strip Board Layout + BOM].
What you are saying is exactly where my brain was headed. If I had an oscilloscope this would be much easier to figure out on my own, even with my limited hobbyist understanding of electronics. I will try this tomorrow and report back. Thank you so much for taking the time to help me, it means a lot.
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As i suspected, a DC coupled mixer circuit. I think the problem here is that the signal from the sub oscillator circuit has pushed the mixers opamps outside of their acceptable input range, given that the 4024 would be outputting more or less +12v during the on part of the signal. This would have pushed the tl072 outside of its acceptable input and output limits thus failing to function in the normal way. With capacitive coupling the max +ve level would be +6v and the minimum would be --6v and within the acceptable input range of the mixer.
Getting a scope is definitely a priority when you’re learning and doing electronics. I can remember when I got my first 'scope at 17 years old. It revolutionised my understanding of what circuits were doing. Prior to that it was like feeling my way around in the dark.
You can get them so cheaply now that every hobbyist should have one.
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@shawneesnaketail I saw you post this on Eddy’s FB page and asked you about a verified strip board layout. I should have looked here first.
Chris
use the one I posted on FB as it implements the changes that gasboss discussed on this thread! It works perfectly and is a great addition to an oscillator. I would rather use my clock divider for other things.
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