Re: BLACKSTAR HT-5R, HT STUDIO 20, H&K TUBE.18
I tested out an HT5 head and an HT1rh head through a 2x12 last Friday. I ended up buying the HT1rh and bringing that home. (wanted a little head for the lounge room)
The HT5 is so much louder than the HT1. They're voiced similarly, so basically what you're getting is an HT1 with an EQ stage, and....louder. So you don't get any tube saturation at low volumes. But still, sounds very similar, but can be made to sound better.
I also found that the HT1 and HT5's either sound dark and muddy, or crisp and crunchy depending on the speakers you're using. My preference is Celestion Vintage 30's. Nice and crunchy. On the flipside, Celestion Heritage sound like flub and mud with the HT1. Can dial some of that out with the HT5 though.
If you like the HT1, you'll like the HT5.