@@Jaws19show I'm learning...slowly... Excellent course on Udemy by a provider called Hardware Academy. I also watch a lot of Look Mum No Computer videos :D
As long as they're isolated from mains earth, you could use another one of those 9V supplies with its output wired backwards to get a -9V source. That way is far less headache than low voltage single supply design. Avoiding a negative rail means a LOT of scaling and offsetting of signals everywhere in every circuit, and it becomes a nightmare. I ended up using the standard ±12V for all my synth stuff.
Thanks for this. Funnily enough I've been thinking about the possibility of adding in a negative rail. I expect most of the circuits I'll build are single DC. This is sort of aa toy build to try stuff out before I do 'proper' modular. But I probably should have just built the +/- 12V.. When you say isolated from the mains earth I'm struggling to visualise how to do that, I can see wiring backwards the potential difference is correct for the negative rail but wouldn't the plus and minus need a common ground? I'd assumed with just 9v DC I'd have to stick ground in the middle
Single supply only seems easier. With AC signals it is far easier to work around a 0v reference than to have to shift it up to VCC/2 everywhere so the signal is centered on the middle of the power supply range. For small circuits you can get away with it, but as they grow it becomes tedious to maintain the VCC/2 offset everywhere. With split supplies the middle point is circuit ground, which is all around easier to deal with. By 'isolated from mains earth' I mean there must be a transformer in the power supply that provides galvanic isolation between the input and output. Using a Class II double insulated power supply (labelled with a square inside another square) guarantees that. Their outputs are floating and you can tie the "+9V" of one supply to the "0V" of another supply. Using that connection point as your ground reference, now you have +9V and -9V available from the other two power supply pins. Of course this is a big potential noise source. For long term experimenting the best solution is a dedicated split supply made with a center-tapped transformer. This page has lots more information for how to make a ±12V split supply from a wall wart power supply with 12VAC output: musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php . This might be useful as well: electronics.stackexchange.com/questions/396201/is-it-safe-to-make-a-dual-supply-out-of-two-wall-adapters A third option is to use an ICL7660 voltage converter to generate a negative rail, but it has very small current capacity and plenty of noise.
I actually have a kit from MIAW to make a 12V split supply's from an AC transformer I just decided I wouldn't need it for this project But I'd *really* like a resonant filter..
@@chrisbullock613 👍🏻 thanks for replying, TH-cam was gracious enough to not notify me 👎🏻. Was just watching the live quiz episode of Barshens and thought “I haven’t seen a Chris video pop up recently “ and was worried that TH-cam had un subbed me lol.
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I rarely have any idea what you're talking about but I love the noisy results.
Thanks for sharing this stuff with us, Chris
Heh maybe I'm really bad at explaining then 😆
@@chrisbullock613 Nope, I'm just dense where electronics is concerned
@@Jaws19show I'm learning...slowly... Excellent course on Udemy by a provider called Hardware Academy. I also watch a lot of Look Mum No Computer videos :D
As long as they're isolated from mains earth, you could use another one of those 9V supplies with its output wired backwards to get a -9V source. That way is far less headache than low voltage single supply design. Avoiding a negative rail means a LOT of scaling and offsetting of signals everywhere in every circuit, and it becomes a nightmare. I ended up using the standard ±12V for all my synth stuff.
Thanks for this. Funnily enough I've been thinking about the possibility of adding in a negative rail. I expect most of the circuits I'll build are single DC. This is sort of aa toy build to try stuff out before I do 'proper' modular. But I probably should have just built the +/- 12V..
When you say isolated from the mains earth I'm struggling to visualise how to do that, I can see wiring backwards the potential difference is correct for the negative rail but wouldn't the plus and minus need a common ground? I'd assumed with just 9v DC I'd have to stick ground in the middle
Single supply only seems easier. With AC signals it is far easier to work around a 0v reference than to have to shift it up to VCC/2 everywhere so the signal is centered on the middle of the power supply range. For small circuits you can get away with it, but as they grow it becomes tedious to maintain the VCC/2 offset everywhere. With split supplies the middle point is circuit ground, which is all around easier to deal with.
By 'isolated from mains earth' I mean there must be a transformer in the power supply that provides galvanic isolation between the input and output. Using a Class II double insulated power supply (labelled with a square inside another square) guarantees that. Their outputs are floating and you can tie the "+9V" of one supply to the "0V" of another supply. Using that connection point as your ground reference, now you have +9V and -9V available from the other two power supply pins. Of course this is a big potential noise source. For long term experimenting the best solution is a dedicated split supply made with a center-tapped transformer. This page has lots more information for how to make a ±12V split supply from a wall wart power supply with 12VAC output: musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php . This might be useful as well: electronics.stackexchange.com/questions/396201/is-it-safe-to-make-a-dual-supply-out-of-two-wall-adapters
A third option is to use an ICL7660 voltage converter to generate a negative rail, but it has very small current capacity and plenty of noise.
@@staevobr this is extremely helpful, thanks for taking the time to explain.
I actually have a kit from MIAW to make a 12V split supply's from an AC transformer I just decided I wouldn't need it for this project
But I'd *really* like a resonant filter..
This sounds amazing!
Keep up the good work! 👏
Thank you, I've started assembly but drilling the plastic is a real ballache!
Love your voice it’s so calming 😁 Ever thought of doing ASMR?
Thank you, I don't really know anything about it although a lot of my channel is just me.. Talking about stuff 😆
@@chrisbullock613 👍🏻 thanks for replying, TH-cam was gracious enough to not notify me 👎🏻. Was just watching the live quiz episode of Barshens and thought “I haven’t seen a Chris video pop up recently “ and was worried that TH-cam had un subbed me lol.
@@MudSluggerBP i really should do another video!
@@chrisbullock613 too right 👍🏻😁