Is Someone Playing Fast & Loose With Measurements?

[Steve Silberman]

Hello Junker –

 

As you point out – the original (first production run) DragonFly did in fact clip when a 0db 24/96 signal was presented. Upon discovering this we took immediate steps to resolve the issue. It was only in the first production run (1.0) that the problem existed. the following production runs had a version 1.0c, which we used to identify amended DragonFly's (also measured by John Atkinson in Stereophile's review). Then in late November of last year we released the improved 1.2 version.

 

Regards,

 

Steve Silberman

AudioQuest

[email protected]

[Steve Silberman]

AudioQuest DragonFly USB D/A converter Measurements | Stereophile.com

 

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."

 

It's clear to get better measurements from the DragonFly the volume control needs to be dialed back.

 

Hello Junker –

 

Only on the first production run (1.0) was dialing back the volume control by .5db required to eliminate the clipping; and this clipping was present only when a 0db 24/96 test signal was sent. 1.0c and 1.2 do not have this issue.

 

Steve Silberman

AudioQuest