I have the HP-100 also, Stickman... the very unit used by a 'Famous 6Moons Reviewer' and tube "collector"/reseller for about 8 years as the reference. Unfortunately it's packed away for now until remodeling/reconfiguring is completed here, and I can't easily get at it to pop the top. However, it went through rounds of tube rolling by the previous owner -- to his, I'd tend to vouch, very balanced, musical tastes -- and interestingly, he found the cheerfully inexpensive JJ 12AX7's to be optimum in the phono stage, combined with the selected NOS he chose to employ elsewhere inside (which I don't recall, except for a Mullard, I believe, at the phono stage's output). So you might want want to give the JJ option(s?) a try: I suspect the Mullard adds a touch of addtl. warmth to the mix.
All the usual H. Grails were available, BTW. Also, his circumstances meant that a variety of different amps got hitched to the Hovland, which I understand retained a consistent, neutral character throughout. This result significantly influenced my purchase decision, being (I like to think) a practical guy. Write me, if you'd like, but I'd put it at < 50/50 that he'll remember the total tube mix exactly. Caution: this unit has had all the factory upgrades performed (you didn't say in your case), so your Hovland may be a somewhat different beast.
