@Ben Mah yes good point! That also supports my thought that we may actually see the distortion of the Scarlet instead of the amp.
@stef1777 The effect is clear at lower levels (5V) but much smaller at 10V. Again, at lower levels we may see the distortion of the Scarlet while at higher levels the amp distortion might dominate.
Not proven but a reasonable suggestion.
Can you think of a way to find if that is the case?
Jan
@stef1777 The effect is clear at lower levels (5V) but much smaller at 10V. Again, at lower levels we may see the distortion of the Scarlet while at higher levels the amp distortion might dominate.
Not proven but a reasonable suggestion.
Can you think of a way to find if that is the case?
Jan
I tested with another amp with REW's internal oscillator and the two cables. I found the same phenomenon.
To make comparison measurements during development, this is not too much of a problem as long as we keep the same test protocol but you have to choose the right output level for the tests.
If we do the tests at 1W as is often the case, this ultimately does not seem very useful for obtaining real, relatively reliable information. You should choose a stronger level, but which one!
Stef.
To make comparison measurements during development, this is not too much of a problem as long as we keep the same test protocol but you have to choose the right output level for the tests.
If we do the tests at 1W as is often the case, this ultimately does not seem very useful for obtaining real, relatively reliable information. You should choose a stronger level, but which one!
Stef.
I think I must have this measurement somewhere. I'll look.
Rent an Audio Precision 2700 and do level-by-level comparisons to find when the Scarlett and Co test bench becomes reliable.
To choose the test level, I would tend to say: let's take the average consumption level for HIFI listening at "domestic" sound level. About ten or fifteen Watts but maybe.
In any case, I will now be able to analyze the influence of the input sensitivity value of an amp (internal gain) on the results. Which was the purpose of this upgrade.
Stef.
Rent an Audio Precision 2700 and do level-by-level comparisons to find when the Scarlett and Co test bench becomes reliable.
To choose the test level, I would tend to say: let's take the average consumption level for HIFI listening at "domestic" sound level. About ten or fifteen Watts but maybe.
In any case, I will now be able to analyze the influence of the input sensitivity value of an amp (internal gain) on the results. Which was the purpose of this upgrade.
Stef.
It also depends on the sensitivity of the speakers. I have Dynaudio, they need much more than 1 Watt to know if the amp is on or not. 
It might be better if I change the resistors of the attenuator to give me a -6dB or -10dB. It will be simpler to boost the Scarlett input and still work at 1W in this case.
Stef.
It might be better if I change the resistors of the attenuator to give me a -6dB or -10dB. It will be simpler to boost the Scarlett input and still work at 1W in this case.
Stef.
My understanding of the Focusrite Scarlett is that its best performance is when its input level knob is set at approximately 11 o'clock. That is where I have mine set, and I use an adjustable attenuator to adjust the level to the Focusrite.
https://www.akitika.com/documents/BuildingTheAttenuatorRev4.pdf
I usually aim for about -10 to -16dBFS on the FFT. I get consistent results that are repeatable, and they seem to agree within reason with expected results for the components that I have built.
Attached is the result of the test of my earlier generation Victor oscillator. The oscillator was powered by a linear power supply and the laptop computer was on AC.
https://www.akitika.com/documents/BuildingTheAttenuatorRev4.pdf
I usually aim for about -10 to -16dBFS on the FFT. I get consistent results that are repeatable, and they seem to agree within reason with expected results for the components that I have built.
Attached is the result of the test of my earlier generation Victor oscillator. The oscillator was powered by a linear power supply and the laptop computer was on AC.
Attachments
It's an older version, and perhaps the Gen 2 Focusrite was also at its limit.
However for a diyer like me, it is more than good enough as I do not build extremely low distortion audio components.
Here are the specifications for the Focusrite Scarlett 2i2 Gen 2. Newer generations have better specifications.
However for a diyer like me, it is more than good enough as I do not build extremely low distortion audio components.
Here are the specifications for the Focusrite Scarlett 2i2 Gen 2. Newer generations have better specifications.
Attachments
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