Aurora pre-amp?
I have a Mesa JP-2C rack I use in 4CM with my HX-Effects:
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I sold my Engl E530 tube preamp, but kept my Engl E850/100 duall-100W rack power amp; I've tried it with my ISP Theta Pro DSP Michael Sweet as a preamp/effects into a pair of Engl PRO E212VHB. I'd like to get an EL34 rack power amp, but the prices are higher than I'd like.
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If you have a rack tube power amp, a rack helix or fractal for preamps and effects should work great IMO. Something else I've considered.