The 6H30 is not as warm as, say, a NOS member of the 6DJ8 family. Or put differently, the 6H30 tends toward neutrality. Those preferring extra helpings of second order harmonic distortion may tend to back away from the 6H30. CJ used it in their ACT2 preamp and then went back to 6922s in their GAT. ARC uses the 6H30 in the power supply of their very successful PH7 and two 6922s in each channel of its secondary gain stage (initial gain via FETs - sounds like similar architecture in the new model). Interesting that the two manufacturers are going in opposite directions, re the 6H30, but perhaps each in accord with their house sound and design philosophies.
I've heard some really sweet airy old 6DJ8s and 7308s in preamps. While some folks have a tidy stash, its harder and harder to find quiet NOS tubes among those, 12AT7s, etc - I mean phono stage quiet. Even so, if your thing is tube rolling, you're out of luck with 6H30 devices - I found only the smallest satisfaction from the now pricey DR versions.
In my experience the 6H30 tends to be a quiet tube and it has a higher transconductance than, for example, a 6922. This means fewer tubes needed for an equivalent or greater gain, and correspondingly less tube noise. In the end I suspect the circuit design and power supply, rather than tube choice, have the biggest sonic influence.
ARC has really been on a role in the new century - I look forward to their new phono stage.
Tim
