This is not necessarily for real life application, but more for the challenge: would it be possible to power an existing guitar pedal (let's say a Roland / Boss saturation, fuzz, reverb, delay, etc.) with just a single AA battery?

I've recently tried different cheap step up converters from ebay, and they work with as little as 2V input to 9V-12V-or even 27V output.

But I haven't found any which works with 1.3 V as input.

Question: are there some chips able to do this, in a micro-size like these step up converters?

Or is there an electronic reason for which there is a threshold near 1.5V / 2V (below: doesn't work, above: working)?

PS: such pedals usually work with a 500mAh 9V battery (4.5 Wh), so I think it would also work with a 2500mAh 1.5V AA battery (3.75 Wh).

  • \$\begingroup\$ If you design your guitar pedal around operating off a single AA battery, it probably could, but that would probably be a difficult design to make. I don't know what goes into a guitar pedal (or even what a guitar pedal is), so I couldn't really give any full answer to this. \$\endgroup\$ – Hearth Oct 1 '19 at 18:54
  • \$\begingroup\$ @Hearth: I'm speaking about an existing pedal (let's say a classical Boss pedal) that requires 9V DC (not a pedal I'm designing myself). \$\endgroup\$ – Basj Oct 1 '19 at 18:56
  • \$\begingroup\$ I don't know what a classical Boss pedal is, but it's likely that 9V is itself stepped down to a lower voltage at some point. Put an energy-harvesting boost converter up to whatever the main power voltage is inside the thing (probably 5V or 3.3V). Depending on how much power it needs a AA might not be able to supply enough current. \$\endgroup\$ – Hearth Oct 1 '19 at 18:58
  • \$\begingroup\$ @Hearth: Guitar pedals are small boxes used to distort or otherwise modify the sound of an electric guitar. They operate directly from a 9V battery, and draw relatively little current. \$\endgroup\$ – JRE Oct 1 '19 at 19:03
  • \$\begingroup\$ @Hearth: I added a link to an image in the edited question (the "PS"). \$\endgroup\$ – Basj Oct 1 '19 at 19:04

Such converters exist.

That link goes to the datasheet of the Texas Instruments LM2621. It takes in from 1.2 V to 14V, and puts out a regulated voltage at up to 14V. It can deliver up to 1A.

This is the datasheet of the LT1073. The datasheet includes an example of boosting 1.5V to 9V. It is only intended for low current, though. Like 16mA when boosting 1.5V to 9V. Might be enough if your guitar pedal doesn't need much current.

The things you are looking for exist. They aren't as common as boost converters that start with higher voltage, but they are out there.

Making it work together with an amplifier might be tricky, though. Switching regulators are notorious for "noisy" output. They operate by switching current through an inductor rapidly. The on/off cycles cause "bumps" in the output voltage. These "bumps" can cause audible intereference in audio circuits. The switching frequency of the examples I linked to should be high enough that you can't hear it, but it can still interact with other parts of your gadgets and cause noise.

You can try filtering the output, or you can boost a little higher and use a linear regulator to lower it a bit - that will remove some of the switching noise.

This site gives the power consumption of some common pedals. Some would work with the low current booster, many would not.

Something to keep in mind:

When you boost the voltage, you also multiply the current.

If you need 9V at 100mA and you use a boost converter starting at 1V, then the converter will have to draw 900mA at low voltage. The current goes up by the same factor as the voltage.

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  • \$\begingroup\$ You could also sidestep the switching noise issue by programming the part to switch at > 22 kHz. I found this out by having a comparator turn on EL wire inside a hollowbody guitar, so it would light up from the inside when I played hard. Seemed like a cool idea at first, until I discovered the EL wire switching circuitry switched in the audio range. Scrapped that project because I didn't have much know-how at the time. \$\endgroup\$ – schadjo Oct 1 '19 at 19:19
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    \$\begingroup\$ Of note is that, to get full use out of a typical AA alkaline cell, you want your boost converter to accept voltages down to at least 1.1V, all the way to 1V if you can. And if you want to get full use out of a NiMH rechargeable, you may want to try to go all the way down to 900mV. The LT1073 mentioned in this answer is capable of operating down to 1.0V at 25°C, though at other temperatures it only guarantees down to 1.15V. \$\endgroup\$ – Hearth Oct 1 '19 at 19:21
  • \$\begingroup\$ Thank you for your answer. Do you think they exist as a little ready-to-use PCB like this: ebay.com/itm/…? I haven't found any based on this chip, but maybe I searched with the wrong keywords. \$\endgroup\$ – Basj Oct 1 '19 at 19:22
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    \$\begingroup\$ It would may be more clear to say the current and voltage are inversely related. a la P = IV. Increase V and I must go down, and vice versa. P (power) effectively stays the same on both sides of the converter. \$\endgroup\$ – schadjo Oct 1 '19 at 19:22
  • \$\begingroup\$ I don't know if there are prebuilt modules. There probably are if you search long enough, but E-Bay is not where I'd go to look for or buy that kind of thing. \$\endgroup\$ – JRE Oct 1 '19 at 19:24

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