Buildign a Better Monoblock
In creating its monoblock amps, the design team at PrimaLuna faced a formidable challenge: How to match (or exceed) the sonic signature of its integrated and stereo amps in a set of monoblock amplifiers with twice the power. As many designers will attest, it’s quite easy to take a step backwards when creating a more powerful amplifier.
While many designers opt for larger transformers to double the output power, PrimaLuna team decided against that approach knowing that big output transformers sometimes don’t behave as well or sound as good as their smaller brethren. Instead, the company elected to use two discrete audio channels in one chassis and paralleled them at the loudspeaker terminals. Building an amp with two output transformers per monoblock amp is almost unheard of due to one simple reason. cost.
Yet the sonic benefits are significant. This design adds a 16-ohm tap to each transformer which, when paralleled in this circuit design, resulted in an eight-ohm output. So, you now have three sets of speaker taps: two, four, and eight ohm to get a perfect "handshake" from the amps to your speakers. The ability to drive planer and ribbon speakers is unmatched.
Of course, with this approach, you risk a percentage of power from one free-running transformer pushing into the other due to output-voltage differences caused by circuit tolerances and tube aging. To counter this problem, designers developed a specific cross-coupled positive/negative feedback scheme to balance out both channels — and lower distortion in the slipstream. In addition, newly designed pre-stages improved the drive capacity to the power tubes, resulting in lower distortion levels without the need for extra negative feedback. The circuit is now inherently more stable and virtually immune to drive imbalance and the distortions that accompany tube aging.
In sum: This innovative twin-channel-summing approach with cross-coupled positive/negative feedback results in surprisingly low harmonic distortion, further pushing the performance of all PrimaLuna mono amps.
Power: Stereo (8Ω, 1% THD), 40 watts x 2 (EL34)
Power: Mono (8Ω, 1% THD), 82 watts (EL34)
Inputs: Stereo RCA
Outputs: 4, 8, & 16 Ω (stereo); 2, 4, & 8 Ω (mono)
THD: < 0.1% @ 1W, < 2% @ Full Power
Freq. Response: 12Hz-85kHz +/- 1dB, 10Hz-95kHz +/- 3dB
S/N Ratio: 92 dB (stereo), 93 dB (mono)
Input Sensitivity: 880mV
Input Impedance: 100kΩ
Power Consumption: 270 watts (stereo), 280 watts (mono)
Standard Tube Complement: 2 - 12AX7, 2 - 12AU7, 4 - EL34
Dimensions (WxHxD): 11" x 7.5" x 15.9"
Weight: 37.4 lbs