I agree that introducing vintage 6DJ8 family tubes in, say, an ARC PH7 phonostage, can yield a much broader range of results (almost all favorable) than rolling 6H30s.
I did a comparo of stock 6H30-EB, cryoed 6H30-EB, and 'NOS' 6H30-DR in a CJ ACT2 and in the phase inverters of a CJ Premier 140. The DRs came from Evgueny at ConusAudio. Did I hear a difference? Yes. Was it significant? I don't think so. Maybe ... maybe ... a little more top end extension. Changing the Premier 140's single 6922 driver tube made a larger audible difference than rolling the 6H30 in either it or the ACT2.
Tim
I did a comparo of stock 6H30-EB, cryoed 6H30-EB, and 'NOS' 6H30-DR in a CJ ACT2 and in the phase inverters of a CJ Premier 140. The DRs came from Evgueny at ConusAudio. Did I hear a difference? Yes. Was it significant? I don't think so. Maybe ... maybe ... a little more top end extension. Changing the Premier 140's single 6922 driver tube made a larger audible difference than rolling the 6H30 in either it or the ACT2.
Tim