In the germanium era, it was especially hard to make reliable power NPN transistors. Thermal runaway can easily cause problems with germanium, but I have worked with the AD149 and it is a pretty rugged to3 device. I have not built this particular circuit though, so I don't know how it sounds.
Not really an inductor, It works like this: as current through it increases, temperature of the filament rises, and its resistance goes up, limiting the current.
Somebody wasn’t thinking too well here. “Dim bulbs” only work well when the average current is small compared to the peaks. Not the case in class A, so no real advantage over just a resistor. In class A there is no “going cool” on transients, which would be needed to get increased current swing.
Nobody said you had to use a snake oil filled resistor. Circuits as inherently limited as this make absolutely no sense to spend ridiculous money on. I’d just be using four 10 watters in parallel, whatever brand Mouser had on hand. How much inductance can four 10 watt sand box resistors possibly have compared with 8 ish ohms? So they’ve got a bit of steel in them that might magnetize. Get over it, the mosfet has more distortion.
Circuits like this are more about the learning experiences, no the end all be all of hi-fi. Build and be happy.
Circuits like this are more about the learning experiences, no the end all be all of hi-fi. Build and be happy.
Even a 10W resistor should be fine, you could put it in a bowl of destilled water or glue it on a heatsink
its slightly off topic becuse it runs on 24V but here is an little headphone amplifier i build, it provides around 300mw and i need to do a few changes to it especially ones in component values and layout. it provides 300/500mw. and eats up 8W.
Yes, this one can give say 200mW to 8ohm reistor, but can be listened at low level. Nothing wrong about how it sounds and can be build very quickly also without PCB. Sure no hifi or high-end, but can be fun to build and listen. Long time ago was thinking to build De-Lite with 300W 120V light bulbs and have four of these somewhere and also mosfet's ... which means can't find them anymore and they are very rare now. But these 300Watter bulbs are really big ones🙂
Thats why its a headphone circuit, i want to build a single ended amplifier with a darlington and a bjt ccs, since mosfets need higher voltages to get decent thd.
