How to compare amps more fairly - my experience

General DAC/Amp/DAP Discussion
62

Volume match SP200 and V200:

  1. Connect headphones to SP200 and set Windows Audio to 50%. Adjust the volume knob for pleasant listening level. I had my SP200 set to ~3 o’clock.
    I chose 50% volume for Windows Audio, because 50% is enough for Spotify tracks, but there are some flac files where I need to go up to 100%.
  2. Disconnected headphone from SP200 and set Windows Audio to 100%.
  3. Get this cable and use this 3.5 to 6.3mm adapter on it.
    Picture: First this and then this.
  4. Plug either side into either amplifier and then lay the other side of the cable like shown.
    Use something heavy to fixate the cable.
  5. Play 3khz tone from online tone generator.
  6. Set multimeter to AC voltage like shown.
    Press “SEL” button to change to frequency, like here.
  7. Put the red side at the tip area and the black side at the sleeve area.
    It will look like this. Here are the areas for reference.
  8. The multimeter should show 3000hz, because the online tone generator was set to 3000hz.
  9. Press SEL button again to change back to AC voltage.
    Measure again and write down the voltage value. Mine was exactly 1.045 Volts.
  10. Do the same thing with the other amplifier V200 now. Check frequency, it should be 3000hz. Then set volume knob to 1.045 Volts, like SP200.
  11. Check again, if both amplifiers have 1.045 Volts.
    Here is a picture after I have set the same output voltage for both amps.
  12. Stop the tone generator and set Windows Audio back to 50%.
    This way I don’t damage the headphone.
  13. Connect both amps and the headphone to AB switcher box.
    I can connect both amplifiers to ab switcher box with two of these cables.

That’s it. I basically matched the output voltage of the amplifiers. I did not have to worry about the output impedance here, because of the following reasons:
SP200: 1.3 Ohm.
V200: 0.06 Ohm.
Both values do not audibly impact the headphone, because those values are very low.
The ohm impedance values have to be a lot higher to have an audible impact.
Here you can see the Focal Clear (which is the headphone used in this test) driven by 120 Ohm source.
Another example with Focal Utopia.
HD599 and HD800 with different ohm impedances.
As you can see, something like 10ohm is needed to maybe have 1dB impact.
That’s why 1.3 ohm is humanly audibly indistinguishable to 0.06 ohm.

Both amps sounded exactly the same on this method, I dont know what to do anything else besides this point.