Originally Posted by Tyll Hertsens
The DF had an early issue as well, and a subsequent change about 3 months in. (This stuff happens all the time.)
Do you know if you have the early or current DF?
I have the one prior to the change.
We have Gordon Rankin on this forum and Computer Audiophile responding to my concerns about output impedance claiming it to be sub zero prior to this change. The only thing I recall changing was there was a certain amount of distortion above 60 steps, so the range was changed from 64 -> 60 steps - just a volume limiter, nothing that would impact sonics. Any references detailing other changes? I certainly heard nothing about changes to output impedance or if that was an issue, but I largely tuned out from discussions on the DF awhile back.
"With the first sample of the DragonFly, a full-scale 24-bit signal actually clipped the bottom halves of the waveform with the computer's volume control set to its maximum, giving a THD+noise level of 3.8%. Backing off the control by one click (–0.17dB) reduced the THD to 2.14%, by a second click (–0.34dB) to 0.627%, and by a third click (–0.51dB) to 0.054%, below which the THD+N percentage plateaued. The second sample didn't clip with a 0dBFS signal at maximum volume, and the THD+N was 0.041% rather than 3.8%. According to Gordon Rankin, the volume control offers 64 steps of less than 1dB to –60dB and then mute (–100dB), but he used only 60 of those steps in the DragonFly, as the top four steps suffered from significant clipping into high impedances. "In retrospect," he wrote of the first sample, "I could have changed the maximum volume down a few more steps and then this would not have been an issue."
Basically, it looked as if the running change in production was to implement this suggestion of Rankin's, as the spectrum of the second DragonFly sample's output with a full-scale 1kHz signal at maximum volume was identical to that of the first sample's output set to –0.51dB (fig.8)."
Edited by bobeau - 3/6/13 at 10:27am