Ultra Stiff Power Supply
The 350 incorporates a massive custom designed, toroidal power transformer, employing unusually heavy gauge wire that reduces copper losses to a minimum. An electrostatic shield prevents AC line borne interference from entering the signal path. The power supply filter capacitors, totaling 60,000uF (30,000uF per channel), have exceptionally low inductance and internal resistance. They charge and discharge in response to load demand far more rapidly than conventional storage capacitors and are capable of delivering the instantaneous current required by the output stages, providing optimum dynamic range and transient response. The wiring from the power supplies to the output boards is designed for unimpeded transmission of the required current and voltage and utilizes heavy gauge, tinned copper wire cables. Since power supply leads radiate at signal frequencies, all wiring is carefully loomed to minimise this effect.
Hybrid Class-A/AB
The bi-polar transistors used in the 350 are operating in Class-A. This avoids the crossover notch distortion and the resulting odd-order harmonics present, to some degree, in all other classes of operation. The devices used in the 350 output stage are MOSFETs, which with high quiescent current circuitry, are run in the equivalent of Class-A to 10 watts. Beyond this point the output class is technically Class AB (hence the hybrid nomenclature), but with a major difference. The combination of MOSFET characteristics and their application in this circuitry, result in crossover distortion so minimal that it is virtually non-existent.
MOSFET Output Stage
The 350 output stage takes full advantage of the unique qualities of MOSFET devices and in many ways they are superior to bi-polar transistors. A major advantage is their tendency to draw less current over a large section of the power bandwidth as their temperature rises (Negative Temperature Coefficient), hence self stabilising thermally, whereas bi-polar transistors draw more current as their temperature rises (Positive Temperature Coefficient) and protection circuits become mandatory to prevent thermal runaway and eventual self destruction. MOSFETs have the ability to swing fully across the amplifier’s internal DC voltage and are therefore true “rail-to-rail” devices. Using MOSFETs encourages the highest performance from the balance of the internal amplifier circuitry.
otal Harmonic Distortion (THD+N): Typically 0.004% @ 1kHz into 8Ω 20Hz to 20kHz <0.02% into 8Ω Frequency Response: 20Hz-25kHz, ±0.25dB Hum & Noise (unweighted): -100dB, ref. rated output Dynamic Headroom (rated with music): >1.1dB
Maximum Current Output: 80A per channel
Damping Factor: >700 @ 1kHz into 8Ω
Gain 30.7dB
Input Impedance:
Unbalanced 22kΩ
Balanced 3.3kΩ
Input Sensitivity:
Unbalanced 1.5Vrms
Balanced ±0.78Vrms
Dimensions:
Width 430mm (16.9″)
Height 186mm (7.3″)
Depth 497mm (19.6″)
Weight: 30.0kg (66.1lb)