Using with my 6xx. Im a bit dissapointed as my hifime dac is cleaner sounding. The LQ is a bit grainy in comparison to using the hifime dac alone. Although you do get more power and a richer sound signiture with the spark. However the trade off in transparency does not bode well for using the spark.
I have about 25 hrs on the spark so it may get better with more usage.
Btw there is no comparison to my CTH (using Genalex Gold Lion) which excels in every catagory over the Spark and the hifime DAC.
I think that its laughable to compare the Spark to the CTH.
I never learn my lesson. After breakin this amp is superior overall to my CTH!
My volume dial on my CTH is totally shot being very noisy. I would now say my spark is cleaner and more transparent than my CTH! It even sounds very good on my elex at low gain using better interconnects. The HD6xx sounds great on high gain. Volume switch is totally quiet and has an unbelievable high end feel to it. The spark also has more power than my CTH. The only possible negative is that at extremely high volume (2 o'clock)using my dac on high gain the sound can be a little bit distorted and saturated on high volume tracks. However, I never need to go above 1 oclock unless i want to compromise my hearing.