I'm a gigging guitarist, and until recently I was using a 30w Mooer Baby Bomb as a power amp to drive an 8 ohm load for performances. However, the Baby Bomb developed a harsh ground loop noise reminiscent of chirping crickets- I'm not sure if it's the power supply or not, as a new one has not arrived yet, but I decided to try building a DIY power amp of my own, as it sounded like a fun project.
I stumbled upon this diagram of a stereo amp using two TPA3118 chips. I only needed it in mono, so I essentially cut the diagram in half. I also ended up going with a TDA8932 chip and a TDA7492 so I could try multiple options- the TDA8932 is listed as 35w at 8 ohms, and the TDA7492 is listed as being 2x50w at 8 ohms, which I bridged- if my understanding of impedance and power is correct, it's still 50w at 8 ohms (going down from 100w at 4 ohms), but it should be putting less strain on the amplifier.
I wired everything up according to the diagram above, using the specified capacitors and potentiometer for volume. I let the solder cool and plugged everything in to test, and while I was able to get sound, they're both pretty quiet. At half volume, the Baby Bomb would be peeling the paint off the walls (and would distort past there), but at full volume with a 24v power supply, both of these weren't even loud enough to keep up with a drummer. By absolutely cranking the output of my preamp, I was able to get the TDA8932 nearly there, but at that point some kind of overload protection seemed to kick on and the chip started to cut out.
What might be affecting the volume level of these chips? Everyone else I've seen online seems to get plenty of volume out of these, but I'm not sure what I'm doing wrong. Should I be using a different chip?
I stumbled upon this diagram of a stereo amp using two TPA3118 chips. I only needed it in mono, so I essentially cut the diagram in half. I also ended up going with a TDA8932 chip and a TDA7492 so I could try multiple options- the TDA8932 is listed as 35w at 8 ohms, and the TDA7492 is listed as being 2x50w at 8 ohms, which I bridged- if my understanding of impedance and power is correct, it's still 50w at 8 ohms (going down from 100w at 4 ohms), but it should be putting less strain on the amplifier.
I wired everything up according to the diagram above, using the specified capacitors and potentiometer for volume. I let the solder cool and plugged everything in to test, and while I was able to get sound, they're both pretty quiet. At half volume, the Baby Bomb would be peeling the paint off the walls (and would distort past there), but at full volume with a 24v power supply, both of these weren't even loud enough to keep up with a drummer. By absolutely cranking the output of my preamp, I was able to get the TDA8932 nearly there, but at that point some kind of overload protection seemed to kick on and the chip started to cut out.
What might be affecting the volume level of these chips? Everyone else I've seen online seems to get plenty of volume out of these, but I'm not sure what I'm doing wrong. Should I be using a different chip?
That amp has too low an input impedance for a guitar amp - without a high impedance preamp (500k or more) it will attenuate the guitar signal badly, and limit the frequency response too.
I'm using a Nux Amp Academy as a preamp. Mark, thank you for the reply- according to Nux, the output impedance of the amp academy is 1k ohms. Is there a more suitable chip? I need at least 30 watts, but less than 120, as that is the max wattage my speakers are designed to handle.
Well that's got output impedance of 1k so that solves the impedance issue - but I presume there's still a lack of gain even with that Nux unit set to max gain? The TPA3118 chip has its gain resistor-programmable to one of four options, +20, +26, +32 & +36dB - perhaps the modules you have are set to a low gain option?