PS Audio BHK 250 hybrid power amplifier

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Tubed power amplifiers
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PS Audio BHK 250
PS Audio BHK 250 hybrid power amplifier

I am always curious how a great piece of gear comes to be. Was it a singular vision of a talented engineer? Perhaps a group effort guided by an experienced team leader. In this case, it was indeed a visionary designer: Bascom H. King (hence the ‘BHK’ acronym). However, he had help in the form of a couple of long time industry veterans. Paul McGowan of PS Audio was looking to upgrade PS Audio’s amp and pre-amp offerings and was assisted in the effort by Arnie Nudell, of Infinity loudspeaker fame. Provided with an opportunity to create a signature set of electronics as a capstone to his illustrious career, Bascom King laboured alongside his long-time friends McGowan and Nudell and has succeeded brilliantly.

The BHK 250 stereo amplifier’s circuit design first appeared in 1979, when Bascom King created the HCA hybrid amp for Infinity. Harkening back to that original concept the BHK 250 has a tube input stage utilising a matched pair of Genalex Golden Lion 6922’s (a personal favorite of mine), allowing for no loss of musical information. The output uses only N-Channel MOSFETs to create a “near perfect balanced waveform without the degradation inherent in a complementary design” according to psaudio.com. Coming in at a hefty 38kg’s, the BHK 250 uses separate input and output power supplies keeping each part independent inside the single monolithic amplifier box design. PS Audio also offers the amp in monoblock form as the BHK 300. That version doubles the output current using only half of the impedance found in the BHK 250. Damping factor is also doubled in the mono amp, albeit at twice the price.

My first introduction to the BHK 250 was last year at Rocky Mountain Audio Fest in Denver. PS Audio’s room is always a must-hear treat, and the new amp was driving an imposing pair of YG Acoustics Sonja 1.3’s to great effect. The terrific musical presentation was made even more impressive when I found out the price of the amp was £8,000. This was very interesting as Bascom’s last collaboration was the creation of the extraordinary Constellation Audio Hercules amp, which costs more than ten times as much in its current version II guise! This more price aware approach was one of the design goals for the new PS Audio BHK lineup: to offer true world-class performance at a significant discount to the prodigious prices found in ultra high-end audio today. It took a few months but I was able to procure a BHK 250 for review along with the BHK Pre-amp. They would join my PS Audio DirectStream DSD DAC to join up with my Vandersteen Treo CT’s. Moving the BHK 250 onto its stand between the Treo CT’s I hooked up the AudioQuest CastleRock speaker cables and AudioQuest MacKenzie XLR interconnects. Burn-in time is recommended at 200 hours before critical listening should commence.

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