Perhaps possible, but very unlikely. What is the mechanism for this alleged distortion?jpc2001 said:
Put a 10A peak 100Hz sinewave through the inductor of post #11 and a small 20kHz signal and see the effect of 1uH dropping more than 10% at the current peaks
The inductor in post #11 was put forward as higher rated than was being discussed earlier. Personally I would use the normal aircore on resistor and avoid these issues with some careful layout.
Ferrite cores have additional downsides, relatively expensive and fragile - have heard speaker crossover inductors making cracking noises.
i have some ferrite beads (i/d 10mm o/d14mm L 19mm)
when a wire is passed through it, these add about 1.2uH
do you think placing one on the cable between the amplifier and the output terminals will serve fine as an output inductor?
No. It will saturate very easily, and add measurable distortion.
If you give me some time, I can estimate the level of distortion, based on the inductance and dimensional quantities.
If you give me some time, I can estimate the level of distortion, based on the inductance and dimensional quantities.
Since these beads are generally group 4 (NiZn), they will be completely saturated at ~0.3T. With this example, for 1 turn, it means 9.5A. If the amplifier is 250W/4 ohm, it will deliver 7.9Arms, 11.2Apk.
Thus, to simplify, between 9.5A and 11.2A, the inductor will become a piece of wire.
At 5kHz for example, 1.2µH is 37 milliohm, around 1/100th of 4 ohm, which will be switched on and off for 1.7/11.2 of the cycle, ~0.15. The end result will be a distortion a bit under 0.15% at 5kHz and 250W, purely odd order.
These are back of an envelope calculations, but they give a realistic order of magnitude: it could be 0.1% or 0.3%, it doesn't matter: it is not negligible for a modern amplifier.
Note that saturation is not a binary mechanism: first signs will appear well below 0.3T, and there will be a residual inductance above, but distortions will be generated, and they aren't negligible.
If your amp is 25W/8 ohm, and you don't need to achieve ppm levels of THD, it would be fine though
Thus, to simplify, between 9.5A and 11.2A, the inductor will become a piece of wire.
At 5kHz for example, 1.2µH is 37 milliohm, around 1/100th of 4 ohm, which will be switched on and off for 1.7/11.2 of the cycle, ~0.15. The end result will be a distortion a bit under 0.15% at 5kHz and 250W, purely odd order.
These are back of an envelope calculations, but they give a realistic order of magnitude: it could be 0.1% or 0.3%, it doesn't matter: it is not negligible for a modern amplifier.
Note that saturation is not a binary mechanism: first signs will appear well below 0.3T, and there will be a residual inductance above, but distortions will be generated, and they aren't negligible.
If your amp is 25W/8 ohm, and you don't need to achieve ppm levels of THD, it would be fine though