Sidebar 3: Measurements
The little Sonics by Joachim Gerhard Anima is of slightly below-average voltage sensitivity, at an estimated 85dB(B)/2.83V/m. Its impedance varies around an average of 8 ohms in the midrange and bass, but falls to a minimum of 3.6 ohms in the mid-treble (fig.1). As a result, it might sound a little more laid-back with tube amplifiers having a high source impedance than it will with typical solid-state amps. The electrical phase angle is generally modest, so the Anima should be fairly easy to drive.
Fig.1 Sonics Anima, electrical impedance (solid)…
There's something a bit oddball about the notion of a $16,500 integrated amplifier—until you stop to consider that the market is fairly drenched with preamps and power amps that, together, cost that much and more. And putting both pre- and power amp in a single chassis cuts down on storage (one less shelf), accessories (one less pair of cable), and electrical outlets (one socket freed up).
Still, it must be a tough sell; it seems a novelty, along the lines of the $100 Kobe beef burger or the $1000 caviar omelet offered at certain Manhattan restaurants. The kind of people who…
Finally, I switched to the CAST outputs, using Krell's proprietary CAST cable. That's when everything locked into focus.
Sound
As noted, I spent a few months last year listening to Krell's FPB-400cx, the beefier version of the 300cx that serves as the FBI's foundation. Certain things about the FBI sounded familiar: the tight deep bass, thunderous dynamics, and snappy transients. But, even at the outset, when I was using the single-ended inputs, there was something new: greater detail, even delicacy, in the timbres and textures of instruments.
Long gone are the days when…
Sidebar 1: Specifications
Description: Two-channel, solid-state integrated amplifier with 1 pair CAST inputs via 4-pin bayonet connectors, 1 pair balanced via XLR connectors, 3 pairs single-ended via RCA connectors, 1 pair tape via RCA connectors. Speaker outputs: 4 on binding posts. Preamp output: 1 pair single-ended via RCA connectors. Preamplifier section: Frequency response: 20Hz–20kHz, +0.0/–0.05dB. Power amplifier section: Maximum output power: 300Wpc into 8 ohms (24.8dBW), 600Wpc into 4 ohms (24.8dBW), 1200Wpc into 2 ohms (24.8dBW). Maximum output voltage: 138V peak–peak. Voltage…
Sidebar 2: Associated Equipment
Analog Source: VPI HW-19 Mk.14 turntable with JMW Memorial tonearm, Clearaudio Victory H cartridge.
Digital Sources: Krell Evolution 505 SACD/CD player, Simaudio Moon CD5.3 CD player.
Preamplification: Audible Illusions Modulus 3a (used only as phono-stage).
Loudspeakers: Verity Audio Parsifal Ovation.
Cables: Nirvana interconnects and speaker cables; Krell CAST interconnects.
Accessories: Bybee Technologies Signature Power Purifier, Monster Cable AVS-2000 voltage regulator; Black Diamond Mk.4 Racing Cones, Mapleshade pucks; VPI HW-19 record…
Sidebar 3: Measurements
Before performing any test on an amplifier, I precondition it by running both channels for 60 minutes at one-third the specified power into 8 ohms, which is thermally the worst case for an amplifier with a class-B or-AB output stage. At the end of that hour, the Krell FBI's entire chassis—not just the large vertical heatsinks on its sides—was too hot to touch. This is an amplifier that needs plenty of ventilation. The THD+noise percentage with the amplifier stone cold was 0.0142%; by the end of the hour's warmup, this had dropped to 0.0067%.
Without a…
Conrad-Johnson launched the all-tube Premier 7 in 1988 as an all-out sonic assault on the state of the preamplifier art. A great deal has happened since then. For starters, C-J has gotten a great deal of feedback from customers, dealers, and reviewers. None other than J. Gordon Holt (Stereophile, November 1988, Vol.11 No.11) concluded that: "It appears that nothing which could possibly have improved its sound had been omitted....It is, in fact, about as close as any tubed preamp has come to being perfectly neutral in sound—in nearly all respects." In the now-defunct Sounds Like... (issue 3…
• Replacing Tubes: While no other reviewer has mentioned this, I feel I must. Replacing tubes in the 7A is a big pain in the butt. The biggest problem is replacing any of the tubes in the right channel. Of the 7A's three chassis, both power supplies are in one box, the left- and right-channel circuitry in the remaining two. However, the left-channel box is fastened to and above the right-channel box. While getting at the innards of the power supply or left-channel circuitry is no big deal, access to the right-channel sockets is difficult enough that I advise having your dealer replace the…
Many tubed preamps can be described as being somewhere on the warm, musical, rich side of neutral. The 7A certainly isn't one of them. If anything, it sounds slightly analytical, favoring accuracy over euphonic colorations. Once again, what I heard through the 7A was very much what JA heard through the original 7. The midrange was phenomenally clean and detailed for a tubed product. With relatively simple music without a great deal going on, every little nuance is laid bare. A good example is Marianne Faithfull's Greatest Hits (London PS 547), which the 7A dissected surgically. Unfortunately…
Sidebar 1: Specifications
Description: Vacuum-tube dual-mono preamplifier. Inputs: phono (MC or MM), tuner, CD. Tape: 2 sets of inputs and 2 sets of outputs. Outputs: 2 sets, both phase-inverting, recommended for amplifiers with input impedance of 10k ohms or higher. Level control: 23-position stepped attenuators with front-panel LED level indicators. Tube complement: two 6CW4s and four 6GK5s per channel. Phono section: 40dB gain; overload in excess of 150mV at 1KHz; RIAA equalization ±0.25db (20Hz–20KHz); hum & noise 80dB below 10mV input. Line-level section: 29dB gain; 20V maximum…
