DESIGN

APPLICATION

Technology

OVERVIEW

The importance of the power amplifier in the 2-channel system chain cannot be overstated, yet it’s often overlooked. It’s the rare few music lovers that truly appreciate the power amp’s critical role in preserving music’s nuanced details, because most amplifiers fail to preserve them. Overtones from plucked instruments, subtle cues defining placement, depth, soundstage width, and transient decays are often lost in the power amplifier. Suddenly revealed are the tiniest of details that now ring clear through the BHK, perfectly preserved through its low feedback, vacuum tube and MOSFET design. When it comes to musically controlling and powering loudspeakers, the BHK Signature 600 has no peer. The Signature 600 monoblock amplifier is a no holds barred upgrade from its series-mate, the BHK300. Its 1.6KVA power transformer is twice the size of the 300 and we didn’t stop there. The 600’s 300,000uF bank of low-ESR high-grade audio power supplies caps is double that of the 300 as are doubled the output MOSFETs producing some of the lowest output impedance and highest damping factors we have ever measured. The control this amplifier has over the music and the system is unrivaled.

INPUT STAGE

A power amplifier’s input stage is a critical interface in the quest to preserve music’s essential details and vacuum tubes for the input amplifier do it best. Especially when they are also used in the power supply rectification stage. Vacuum tube rectifiers have inherently lower noise contributions to the DC voltage of a power supply than solid-state diodes. The physics that govern a semiconductor-based diode makes for significant switching noise every time the diode blocks the negative voltage swing and turns on and off. Parasitics within the device can also cause ringing. This can get coupled into the DC supply causing unwanted noise in the musical signal. The BHK600 solves this problem by using a vacuum tube rectifier to power the matched pair of Gold Lion input tubes instead. The results are not only simply cleaner and quieter, but the music feels more open and spacious in ways few have had the opportunity to experience.

OUTPUT STAGE

A power amplifier connects its reservoir of energy to the loudspeaker through a type of valve (solid state or vacuum tube) controlled by the input stage. If the input stage has done a good job of preserving music’s subtle details, textures, timing and phase information, transferring it without loss to the power stage and eventually the loudspeakers is best handled by a tube-like solid state device known as a MOSFET. Not all MOSFETs are the same, their differences characterized by their relationship with the input signal and the power supply driving them: N-types for the positive going signals, P-types for negative. N-types have lower distortion and perform better than P-types but N-channel-only amplifiers are rare. Using only N Channel MOSFETS in its output stage, the BHK Signature 600 monoblock amplifier produces a near-perfect balanced waveform without the degradation inherent in a complementary design. A pure design like that in the 600 output stage also requires unrestricted access to the power from the unit’s massive 1.6KVA power transformer and its 300,000uF of energy reserves. Delivering this power from the supply to the output stage without restriction is not a trivial task. Wire and bus bar gauges must be massive. In the BHK Signature 600, gold plated solid copper bus bars tie to 2 gauge braided copper pathways connecting the high joule power supply with the demanding banks of MOSFET output devices. Music has rarely been reproduced with such effortlessness as in the BHK600.