I’ve owned the E530 preamp, E570 (preamp of the E670), E670, Powerball I, Synergy Powerball and Synergy Savage.
The E530 is the rawest of the bunch, least compressed (but still way more compressed than a JCM 800, most open of the bunch , but still really saturated. The gain is more splatty while the gain of the others feels more tightly glued together. I go back & forth on whether it’s better with a TS in front while the rest of them definitely sound best without a “clean” boost.
The Powerball 1 was a total turd but the Synergy Powerball into VHT 2/90/2 is awesome so I’ll forever wonder if something was wrong with that used Powerball 1 I had.
E670 was the best head I’ve owned but E570 > 2/90/2 is considerably better. E570/E670 is somewhat more open than the Powerball and while it’s a modern high gain beast, something about the feel & tone has this little bit of vintage vibe compared to the Powerball. The Powerball is the smoothest of the bunch and the most compressed. The Powerball has a big sounding low end you might wanna high pass. The only thing I don’t love about the E570/E670 is the pinch harmonics, they’re kinda thin & hollow while with the Pball they’re full & screaming. The E670 cleans are nice. The Powerball is prolly my fav for high gain rhythm but the E670 is a close second. I play death metal, plenty of fast tech stuff. If I was in a thrash band I’d pick the E530. Heavy metal, I’d prolly skip Engl and do something Marshall based.
I don’t know how to describe the Savage pre, it was cool and I would have kept it if money was no object. Prolly won’t make sense but the gain was “chalky”. I can’t relate to ppl likening it to a Marshall, it’s not any more similar to Marshall than the E670 IMO.
As far as the complaints I read online about Engl’s not cutting in a live mix, I can’t relate. That just makes me question what their entire signal chain and settings are. Although I always run an EQ in the loop so there’s that.