Hey everyone, I've got a bit of a puzzler with my audio setup. I've been using a budget subwoofer plate amplifier with pairs of 1942 and 5200 transistors, and it's been pumping out around 120 watts of clean power. On the other hand, I have a PA amplifier that uses 1186 and 2837 transistors (three pairs), but it doesn't seem to perform nearly as well with the same 8" passive subwoofer. Despite being rated higher on paper, the PA amp just doesn't sound as good or provide the same power level. The plate amp runs off a 12v supply from an old ATX power supply, while the PA amp has a toroidal transformer outputting 72vdc. What could be causing this difference in performance? Any insights would be appreciated!
3 Answers
Your experiments with the oscilloscope sound spot on! If your plate amp is designed for 4 ohms and runs cleanly under those conditions, then it may just have better compatibility with your sub compared to the PA amp, which despite higher ratings, may handle things differently—especially under load. Factors like current draw and amp design play crucial roles here. It's worth looking into those details for both amps, and possibly doing the tests you mentioned earlier at various volumes too. It could clarify whether you're hitting some limit.
It sounds like you're running into a common issue where amplifiers handle power in different ways. While you would think the PA amp should have more oomph since it's rated for higher power, it often comes down to the current output capability. If the plate amp is designed to drive a 4-ohm load, it might just have a better current capacity for your setup compared to the PA amp, which is rated for 8 ohms. It’s also possible that the PA amp is hitting current clipping before you hit voltage clipping, making it sound weaker. Testing both with an oscilloscope using a sine wave could reveal how they react to loads at varying frequencies, helping to pinpoint the issue further.
Definitely check the specs of your amplifiers. It's interesting that the PA amp is rated for 2 ohms but still doesn't seem to handle your 8" sub well. Sometimes, changes in impedance and how the load behaves across frequencies can also influence perceived power. You mentioned the plate amp sounds better, which might be due to it reaching its optimal performance range with the kind of subwoofer you're using. You might want to consider making sure the gain settings on both are on par, as well. Sometimes too much gain can lead to unwanted distortion which might be what's happening with your PA amp.