3 ms·
The theory on this is correct, but the ICL7660 is not designed to provide the kind of current you'd need to run a 12W audio amplifier. It maxes out around 50mA
by morcheeba 5y ago
The theory on this is correct, but the ICL7660 is not designed to provide the kind of current you'd need to run a 12W audio amplifier. It maxes out around 50mA - see figure 7 of the datasheet[1]. 50mA*17v = only 0.85W.
Because I can't see the datasheet of the audio amplifier, it may be wired in a way that it doesn't use significant current from this supply (for example, in the pre-amp part of the circuit). But then we wouldn't be getting the advantage of 17v supply to make it louder than other games.
When overloaded, simple switching power supplies like this lose their regulation. In this case, the switcher operates at 10kHZ, so it might introduce a high-pitched sound to the output.
You can probably get away with connecting the -5v input to GND to make the circuit run at 12v instead of 17v. Or, look for a more capable negative power supply.
[1] https://www.renesas.com/us/en/document/dst/icl7660-datasheet https://www.renesas.com/us/en/document/dst/icl7660-datasheet
- nicole_express 5y agoThat's true; I should've made this more clear. I'm using a "supergun" tool that is designed to lower the level back down to line-level, so I don't actually need the amplifier to run at anywhere near its full capability; in fact, that'd just be a waste. I just need to give it enough power to work at all. Even so, I wouldn't be surprised if the high-pitched sound you can faintly hear in the video at the end is due to the effect you mentioned.
- mmastrac 5y agoWhat's a "supergun"? Basic googling didn't help.
- RetroSpark 5y agohttps://en.wikipedia.org/wiki/SuperGun https://en.wikipedia.org/wiki/SuperGun
- morcheeba 5y agoAh, cool, that makes sense! If you need more power, I'd suggest a module like this one: https://www.ti.com/lit/ds/symlink/ptn78000a.pdf https://www.ti.com/lit/ds/symlink/ptn78000a.pdf Switched capacitors are great for low currents, but inductors work better for higher currents.
- TD-Linux 5y agoJAMMA arcade PCBs normally only use the -5V for audio opamps or DACs. The power amplifier is powered by the +12V rail (in a bridge configuration to provide +/-12V swings to the speaker).
- Kubuxu 5y agoAnother option would be using an isolated DC-DC converter, like [this] one for $1.22. [this]: https://www.digikey.com/en/products/detail/mornsun-america-llc/B0505S-1WR3/13168098 https://www.digikey.com/en/products/detail/mornsun-america-l...