When I became aware that the legendary designer Bob Carver had started a new company
and was going to release a reference-level tube mono block amplifier, I was excited. Mr. Carver, starting way back in 1972 with Phase Linear, has always been a very creative designer. I was therefore quite interested in reviewing his new tube amps. The Black Beauty 305 Vacuum Tube Amplifier, which is valued at $12,900 per pair, has unique features and uses the relatively new type of power vacuum tubes called the KT-120. The dimensions of each 305 Black Beauty Mono Block are a little over seven inches tall by 12 inches wide and 14 inches deep. Each mono block amp weighs 43 pounds. This amp is offered in a standard black, with silver fleck finish accented with silver trim, but it can also be ordered in a gloss red. The front of the Black Beauty features only a bias meter, while the rear panel has the power switch, ICE connector and fuse, along with a power tube bias adjuster screw. In addition, it has speaker connections with two-, four- and eight-ohm taps with a single ended RCA input - remember, they're monaural amplifiers. Adjusting the power tubes' bias was one of the easiest procedures I have encountered on a tube power amp in years. You turn the volume switch, located on the top of the amp, all the way down, insert a screwdriver into the bias adjustment screw on the rear panel and set the bias to 100mA on the bias meter located on the front panel. Additional Resources
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During my auditioning process, the bias never wavered from this setting. Each Black Beauty used the following tubes: for input; one 12AX7 and one 12AT7, a 6AL5 for bias voltage regulation, and six KT-120 power tubes used in a push-pull configuration. This power tube is a variant of the KT-88 and almost offered double the power of the KT-88. Sonically, it is supposed to offer the midrange delicacy and body of the EL-34 tube with the extension, slam and control of the KT-88. My assumption is that, by using this power tube, the Black Beauty's chassis could be kept quite small and allowed the amp to deliver over 290 watts into four-ohm loads, and 305 watts into 8. You would have to use at least twelve or more KT-88s to get this type of power rating, requiring a much bigger chassis. Because the power tubes were biased in their lower range, the tube's life span is very long. The Black Beauty amps only use point-to-point hand-wiring, with no circuit board traces or detachable connectors. They also featured ultra-wide bandwidth output transformers with interleaved windings that offered huge peak output capacity. Each Black Beauty amp has a volume control to adjust to the gain of your preamp
. Finally, there is a toggle switch on the top of the amp that controls the amount of negative feedback that the amp uses. Pushed to the left, the feedback is approximately 20dB, which is what Carver calls the "classic" sound of vintage tube amps. Pushed to the right, the feedback is approximately 11dB, which Carver calls the "contemporary" sound that most modern amps use today.
When the Black Beauty was auditioned with the Magnepan MG-20 and the Lawrence Audio Cello with a variety of music selections, the "classic 20dB" left position was superior in timbres, overall tonality and liquidity. I found that when the toggle was put into the right "contemporary" position, the sound dried out and had the sonic qualities of an average solid state amp.
When I listened to the great tenor saxophonist Buck Hill on his album "Relax" on (Severn CD), it was very apparent that, when it came to timbres and the colors of the tenor sax, Hammond 3 organ, guitar and drums, the Black Beauty performed at a reference level. It also produced a large and lifelike soundstage, with very good layering of the different players in the acoustic space. The midrange, which is often the glory of great tube amps, was void of any grain. Additionally, the body and weight of each individual player was rendered in a realistic way. The lower frequencies were quite accurate in tone and speed. The Black Beauty has the power and control to produce macro-dynamics as well as any solid state amp.
The next musical selection revealed the specific area where the Black Beauty's performance did not match the reference level of my Pass Labs XA-60.5s. Because of this, I consider it to be something of a shortcoming in the Black Beauty's overall performance. Bill Cunliffe's "Imaginacion" (Toril Records) is a first-rate sonic recording of big-band Latin jazz. The amount of air, openness and natural sparkle that you naturally hear on cymbals, bells and triangles were somewhat missing with the Black Beauty's presentation of the high frequencies. I don't want to exaggerate this shortcoming. However, regardless of what music selection I used in my auditioning process, the fine details compared to the Pass Labs XA-60.5s were something that I found lacking. The MG-20s use a ribbon tweeter and the Cellos use an air-motion tweeter, which both are highly regarded high-frequency transducers. If your speakers are not as extended on the top end, you might not hear this to the degree that I did.Read about the high points and the low points of the Black Beauty on Page 2.