The Hilgen “Victor” Model R2522. For the tube geeks among us, this starts with a 5AR4 rectifier before running into a couple of 12AX7s for preamp and reverb send duties. Then comes the only expensive and hard to find (although not impossible) tube—a 7199 for ‘verb recovery. From the factory, it came with a 12AU7 for phase inverter, which I switched out to a 12AY7 for a little more drive on the output tubes. I tried going up to a 12AX7, but that made for too much gain and resulted in a mushy, compromised output. The 12AY7 gives it more heat than stock, but still retains the crisp, tight, articulate character of the amp, as intended.