PrimaLuna Prologue One

My first reaction to the Prima Luna Prologue One was based solely on looks: For this price, I might not have been disappointed had it sounded no better than a Bose Wave Radio. Its casework straddles the breach between vintage and modern in a way that little else does, at any price. The dark gray-blue finish, hand-rubbed to a tactile gloss, wouldn't look out of place on an Alfa GTV (the new one, which resembles a drop of oil). And for the first time in my experience, a high-end audio manufacturer has figured out a way to make a protective tube cage easy to remove and replace: with banana plugs and sockets. Why couldn't one of the high-price American brands have figured that out?
The theme continues inside, with point-to-point wiring that's carefully dressed and neatly soldered. All the hardware is bolted in place, not just stuck to the inside of the chassis with glue and hope, and well-finished metal shielding is installed wherever hum or RF interference might otherwise intrude. All the tube sockets are good ceramic ones, and the terminal strips are ceramic, too. Threaded parts are locked in place with a dab of red enamel. All the edges have been smoothed over. Inspectors' initials abound.
Here's where your music goes: Each channel's preamp tube is a 12AX7A dual triode, the two halves of which are tied together in parallel in the interest of current gain. From there it goes to the two halves of a 12AU7 driver, configured as a long-tailed pair. Then it's on to a push-pull pair of EL34s operating in "enhanced" class-A/B, with screen grids tied to the output transformer's primary so the tubes can deliver more power than if they were used in triode mode—yet also sound sweeter and exhibit a lower output impedance than if they were used in pure pentode mode. Tube-amp enthusiasts will recognize that as an Ultralinear output circuit, which the great David Hafler first described more than half a century ago.
Sounds pretty simple, doesn't it? It is—for the most part. Then again, because the Prologue One is aimed at the first-time owner of a tube amp, Prima Luna wanted to ensure reliable performance in almost any setting, with no need for adjustments. So chief designer Marcel Croese devised a new way to bias the output tubes.
 

Specifications:

Power 35 Watts per channel
Frequency Response 20Hz - 30 kHz +/- .5 dB
THD with AABB 0,25% @ 1W; less than 1% up to full power
S/N Ratio 89 dB
Input Impedance 65 kOhm
Input Sensitivity 225 mV (for rated power at maximum volume setting)
Maximum Gain 37,5 dB
Power Consumption 300 Watts
Net Weight 37.5 lbs / 17 kg
Shipping Weight 41.9 lbs / 19 kg
Dimensions 15.5" x 11" x 7.5" / 395 mm x 280 mm x 190 mm (L x W x H)
Shipping Dimensions 18.3" x 15" x 12" / 465 mm x 380 mm x 305 mm (L x W x H)
Inputs 4 pairs RCA
Outputs 4 & 8 Ohm Speaker Taps
Tube Complement 4 x EL-34
2 x 12AX7
2 x 12AU7