HT3.5 and 5 use the 4CX3500 last time I looked at the 5. HT7 and 10 use the 4CX7500 HT20 uses the 4CX12000 HT25 used the 4CX20000D I own a 3.5, maintained a 5 and 7 previously, and recently looked at a 20 and 25. MM > which tube does this one use for a final ? > > HT-20 = 8990 = 4CX20000 > HT-10 = 8989 = 4CX12000 > > HT-5 = ????