MindsMirror
1000+ Head-Fier
- Joined
- May 9, 2014
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There are still a few thing that may be worth trying, however. What happens if you use 16.5 ohms serial resistors (2x33 ohms in parallel), or if you add the 33 ohms resistors to the sound card input instead (as close to the amplifier as possible) ?
With the splitter plugged directly into the amp, headphones directly into the splitter, and the line input connected to the splitter through 33Ohms, the distortion starts at 1Vrms. This time, unplugging the line input+resistor does not remove the audible distortion, so it seems like adding the resistor the the line input as you suggested prevents the interaction that was happening before. The first harmonic in the electrical measurement is at -60dB, but I would say that the audible distortion I can hear coming from the headphone is much higher than that. That seems to suggest that there is high distortion coming from the driver, and some of it is fed back to the amp/measurement.
I don't know if I mentioned this, or if it's relevant and would affect anything, but when I was testing with the series resistance between the amp and headphones, I only connected and measured the left channel, the right channel was open. I'm using alligator wires to connect the resistors, and the ends are almost too fat to fit on the right channel ring, so I didn't try it in case it would short the amp.