I have a simple adjustable power supply (1.8V - 16V / <1A) that I put together with an LM350, works great for the various small bench-top things I use it for. Typically on a load being applied, I see the typical small voltage drop as current spikes, all expected.
Last night I hooked it up to a hacked together transistor-as-audio-amp circuit I threw together on a breadboard to test the DAC on a new MCU. Eveything went as expected, sound played fine, but I noticed that my voltage went from 8.4V to 9.75V, around a 16% increase! I'm not completely new to building low-ish power circuits, but I'm trying to get better at the theory, and I'm not seeing why this increase occurs. It is constant, not a spike, and a jump of 1.35V seems like a lot.
Of course using a BC547 as an audio is non-optimal, and the transistor only does an ok job handling the current, but I only turn the circuit on for a few seconds at a time. I was thinking that there is some transistor-related phenomenon that I am unaware of that would account for the voltage, but it does occur in circuit simulators, which leads me to believe that it's a real parts vs ideal parts phenomenon. Can anyone point me to a source for understanding why this happens?