UPDATE
I received the new Go-Vibe V6 from Norm yesterday as promised. He sent me a
low-gain version with the revised op-amps (AD8620/8610). I'm here to report that the problems with my AKG K81dj's no longer exists with the new amp!
Sound quality has improved in a dramatic sense, to my hearing. The AD8397 sounds warm to the AD8620 - which is brighter, more analytical/detailed op-amp.
Fast!
new - top. With the blue LED.
Sound Quality
Mids: Slightly recessed. It's not as pronounced or forward as the AD8397. Still clear and well defined.
Treble: So that's how it's supposed to sound! Breathes new life in my flat sounding K81's (I didn't know that these could sound like Grado's with healthier bass) and UM1's. Crispyness that extends in the higher range. The new soundstage is phenomenal - 'much larger than life'. Lots of 'air'.
Bass: Not as prominent as the AD8397, but still tight, refined and textured.
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PROS: Synergizes especially well with my "dark" sounding HD650's. Compliments my other cans quite good, too (k701, k81, um1/um2). Longer battery life (3x) 28-30 hours. More powerful! Despite of this amp being the
low-gain version, it powers my high-impedance cans the same as the standard-gain AD8397, same volume position. Background noise/hiss is less using my sensitive iem's to check.
Now I can plug in/out my headphones without turning the amp off. You can't do that without risking damage to the op-amp using the AD8397 - from Norm.
CONS: Turn on thump is more audible, turning off thump is even louder, "turn on/off noise is normal and harmless" according to Norm.
I tried a pair of Grado sr60's with the new amp. To my ears, it was too shrilly and unpleasant. I guess I'm too much of a basshead and slightly unattuned to good sound, says a friend who loves the grado + ad8620 combo.