It’s a little jewel of an amp. The quality of the steel metalwork, the five-step automotive paint job with hand-rubbed lacquer finish, and the soft orange glow of the tubes leave no doubt— this is a high-end amplifier. Another plus, it’s a lot smaller than I expected, so it should be easy to live with.
PrimaLuna reps are especially proud of this amp’s Adaptive AutoBias circuitry, which continuously monitors and adjusts the tubes’ bias voltages. PrimaLuna claims the proprietary circuit ensures not only the best performance as tubes age, but also lowers distortion by as much as 50 percent.
Actually, the most intriguing aspect of Adaptive AutoBias is that it makes tube changing a no-brainer operation. You can use EL-34, 6550, KT88, KT90, 6L6GC, KT66, 7581, or even 6V6GT power tubes and an equally broad selection of 12AX7 and 12AU7 input tubes with the ProLogue One. Kudos to PrimaLuna. They’ve bent over backwards to make an amp that even novices can use without getting jumpy about messing around with tubes. Tube swapping is as easy as changing a light bulb.
More positives: rather than go with printed circuit boards PrimaLuma amps use costly and laborintensive point-to-point wiring— something you rarely see in this price range. The ProLogue One is hand-built, and a peek to the underside of the amp with the bottom cover removed revealed build quality standards you’d expect from far more expensive components.
Tip: Tubes get hot, so make sure you give the ProLogue One room to breathe.
This amp lets you feel like you’re not just playing recordings; instead, you feel more like the musicians are performing for you. So it sounds less canned, closer to the real thing.
I’m thinking about that ‘live’ quality while listening to ‘All Blues’ from Mike Garson’s Jazz Hat CD [Reference Recordings]. There was something about the way I could hear the musicians listening to each other, the music was happening NOW. It’s that much more vital than what I get from most solid-state amps. The ProLogue One connects all the digital dots and breathes life into the sound. Eric Marienthal’s stunning alto sax solo on “A Song For You” was just amazing. I was sitting on the edge of my seat, hanging on every note.
So is the ProLogue One perfect? Not quite. The Talking Heads Remain in Light DualDisc [Sire/Warner Bros.] lost a bit of the “unk” in its funk. The band’s slippery bass lines felt soggy, and Chris Frantz’s drums were pushed back in the stage. Dynamic oomph was good, but not great.
Ah, but one of the great things about tube amplifiers is that you can change their sound by swapping out their tubes. Remember PrimaLuna supplies the ProLogue One with sweet sounding EL34 power tubes, so just for the fun of it I popped in a set of Svetlana 6550C power tubes (and thanks to the Adaptive AutoBias circuit, tube swapping was a plug ‘n’ play operation). Yikes, with the new tubes the bass firmed up, dynamics came to life, while maintaining the ProLogue One’s other sonic virtues. Further fine-tuning experiments with other types of power and input tube types and brands can pay big dividends. Your tastes and system synergies can and will lead to different conclusions about what tube combinations work best (your dealer might be a big help on that front). One last thing, with 35 watts per channel on tap, the ProLogue One won’t be the best choice for head bangers or anybody using powerhungry, low-sensitivity (88dB or less) or otherwise-hard-to-drive speakers, such as my Dynaudio C1s. That’s why the ProLogue One performed best with the Zu speakers in my tests.