Pulled the chassis out of my HT-5 head the other day, found that they run EHX valves as stock.
1x12AX7WA + 1x12BH7.
Replaced the EHX 12AX7 with an old JJECC83S preamp valve.
Much better, more open and airier crunch. Nowhere near as compressed and clean channel rings nicer and it more chimey!
Much happiness!