Best way to get stable +-9 volts AND 5 volt from a 9V DC source

[JK Sleepling]

I'm quite new in electronics, but I'm not scared to try it (Look Mum No Computer). So please bear with me and tell me how to improve my asking.

Yes I am building a guitar pedal. It's a op-amp based parallel effect loop with boost controls for each channel. These are controlled digitally by an Arduino. And yes, it might sound like a wild beginners project, but I don't mind the project moving veeery slowly. And I'm currently a the point where all programming is done (and working), and I'm tinkering with the analogue parts.

My challenge now is to get the power I need.

For the op-amps I would like to use 18V (+-9) for a bigger amount of headroom. I use a TL074 to split, buffer and boost the audio signal. Later in the chain I will have a TL071 op-amp to boost the mix. Sometime later I'll maybe add in a TL072 for phase shifting possibilities.

Currently using an Arduino I can feed it 9V though the VIN input, but in the long term I would love to use a standalone circuit with the ATMega328 chip. Therefore I need to think the 5V into the power circuit.

Here's what I've tried:

Firstly tried dividing my 9V input with a resistor divider giving me +-4.5V. When measuring, the negative volts looked just right, but using it through an op-amp it went out of balance causing the sound to overdrive an make ugly clicks. My cheap oscilloscope showed me beautiful waves on the upper (+)side and ugly cut off waves on the lower (-)side.

Then I found the ICL7660/MAX1044 chip and made a circuit to double the voltage supply to +-9V, using this schematic:



The measuring looks fine, although not giving me +-9 but +-8.1 using a 9V battery. Putting it through the op-amp circuit it sounds a lot better! No clicking and overdrive not as present. This is probably due to the larger headroom. But using a sound generator and oscilloscope, it shows me that this supply is also moving out of balance. The negative waves are cut half. And the power supply is no longer +-8 but more like +12/-4. How can I get a stable dual voltage supply?

Regarding the extra 5V. I can get beautiful 5V by adding a LM7805 converter to the input 9V, but I am unsure if this is the best way to do it. It has no visible effect on the output of the ICL7660.

How would you do it? How to get a stable +-9V plus a 5V from a 9V DC source? It doesn't have to run on batteries, a DC adapter will also do.

I would love if there was a relatively simple solution that doesn't require a lot of space

Here is a current oscilloscope shot:

[Ben N]

Chiming in mainly to give you a warm welcome to the forum. You'll find some excellent people, smart people who know a lot and are happy to share, here. I'm not one of them (happy to share, yes, but not all that smart). And, BTW, people who you'd probably be happy to share a beer with in real life.

But I will throw this into the pot: Have you tried with a power supply? Having a bit more current on tap may make the difference.

Also, while I'm not familiar part by part, charge pumps in general are limited in how much current they can supply. You would want to calculate your load and check that against the 7660 datasheet.

A recent/current thread (sorry, you'll have to search for it) with a design for a CMOS alternative to rotary switches, I think, uses boost/buck boards to provide a more robust bipolar supply. Check that out.

Finally, yes, a five volt regulator should be fine to power your uC. That's how I've seen it done, at any rate.

As I said, I'm not all that smart or knowledgeable, so I look forward to some of those cats chiming in, too.

[Vivek]

There are many cheap and simple "Buck Convertors", "Boost Convertors" and "Buck Boost Convertors" to do this job

Each costs 3-5 USD on Alibaba/ eBay / Amazon


A dear friend informed me he could get +/- 9V using two of these:
https://www.amazon.com/MP1584EN-DC-DC-Converter-Adjustable-Module/dp/B01MQGMOKI/

and the 5V could be had with a regulator, or even buffered voltage divider.

[antonis]

Hi & Welcome..

Any data for your particular current demand..??

P.S.
You can implement "all time classic" NE555 for voltage doubler and any kind of rail splitter (BJTs, op-amp) for +/- 9V..

[JK Sleepling]

Thanks Ben!   
Just checked if a power supply would make a difference, but unfortunately no. Gives the same wave image.

I have currently separated the digital and analogue circuits to keep things clear.
My primary challenge now is to feed the op-amps (7 in total) with stable +-9V.
The TL07X op-amps draw a maximum of 2.5mA each (17.5mA). But in the current setup I'm only using three of them. The ICL7660 should be able to deliver up to 20mA.

Been looking at a TLE2426 Rail splitter. It might split the voltage in a stable way, but then I also need to double the voltage before it, to get to +-9V from a 9V DC source. Any thoughts on that?

[Vivek]

to get to +-9V from a 9V DC source. Any thoughts on that?

Boost Converter !

[JK Sleepling]

You can implement "all time classic" NE555 for voltage doubler and any kind of rail splitter (BJTs, op-amp) for +/- 9V..

Is NE555 better than ICL7660 or how are they different?

Boost Converter !

I prefer to put the components together myself, even though it might be more expensive and cumbersome. What is the secret of boost converters?

[r080]

Firstly tried dividing my 9V input with a resistor divider giving me +-4.5V. When measuring, the negative volts looked just right, but using it through an op-amp it went out of balance causing the sound to overdrive an make ugly clicks. My cheap oscilloscope showed me beautiful waves on the upper (+)side and ugly cut off waves on the lower (-)side.

You might consider getting it to work with a single supply amplifier first.

https://www.ti.com/lit/an/sloa030a/sloa030a.pdf