Solid State Power Amp Reviews

Aside from the choice of cables (not easy, in view of the performance potential), two further areas remain of interest: physical support and mains power supply. Like the FPB 300, the '600 benefits from something more than carpet under it. In any case, if the carpet is too deep, air flow will be restricted. I tried spiked marble slabs to good effect, and a pair of Mana platforms back to back—unwieldy and probably suboptimal, but nonetheless revealing. The floorspikes gave an impression of a deeper, clearer bass and a more solid mid. The platforms gave faster, more tuneful bass with a clearer mid. More work here would prove rewarding.

Conventional wisdom tells us that a fully regulated amplifier such as the FPB 600 will have superior isolation from line imperfections and noise emanating from the supply side of its transformer. Thus it should be relatively uncritical of supply quality. Though this may well be true on the usual basis of judgment, it remains a fact that both the '300 and the '600 were sensitive to supply quality. I experimented using conventional socket strips, standard wall sockets, and dedicated 45A, 240V supplies (equivalent to 90A on US 120V).

Easily reading these differences, the FPB 600 thrived on the dedicated facility, the sound improving still further when the end of the mains cable was hard-wired into the terminal strip of the supply outlet (consult a qualified technician on these matters). I wonder whether the detachable high-power cable connector Krell has adopted for this amplifier really gets the very best out of it. I also found that it sounded best with the supply ground installed as instructed. (With some amplifiers, floating the ground may improve performance.)

Comparisons
Working with my personal ranking order for power amplifiers, until now I've placed (with minor caveats) the Conrad-Johnson Premier Eight A monoblock (non-triode) at the top of the tree, especially for its vibrant tonality and lush transparency in the mid-treble, in addition to its great dynamic range, average-to-good load tolerance, and fine, tuneful bass. Once the Premier Eight A has been experienced in an appropriate setting, one is forced to question the fuss over little SE amplifiers.

Perceptibly close are both the Krell KAS-2 and Audio Research VT150SE. At the time of review, the KAS-2 was considered the best solid-state design yet, substantially improving on Krell's discontinued KSA-S series, but at a far higher price. Albeit with somewhat less power and bass slam, the VT150SE was and is head and shoulders above the rest of the Audio Research range, and often sounds very close to the KAS-2 in sonic merit while providing a still faster and better-resolved sound. Account has also been taken of other contenders: the Audio Research Reference 600, VT130SE, and VT100, and the Mark Levinson No.333.

Then Krell introduced the FPB 300. I finally rated this model above the C-J Premier Eight A for overall attainment, but still conceded that the "Eight A provides superior purity, delicacy, and 'air' in the mid and treble" (HFN/RR, December 1996). But now I have no hesitation whatsoever in rating the FPB 600 a full 20% better than the '300, and this in territory where improvements of just 5 or 10% are hard won, greatly valued, and willingly paid for. Yes, the '600 is quite expensive, but in real terms its price is actually lower than the competition's. (For readers who follow my personal numeric ratings for sound quality, as published in HFN/RR, the FPB 600 scored an industry record of 42 points.)

It would be too easy to mark the FPB 600's success with a torrent of superlatives. Indeed, I think I've strayed some distance down that path already—but what else can I do?

Take the comparison with Conrad-Johnson's Premier Eight A: Though the C-J still sounded a trace more liquid, the '600 reached right into this amplifier's previously undisputed territory. Precision, control, subtlety, superb detail, and state-of-the-art depth and transparency were all fully described by the new Krell. Detail was extraordinarily focused, right into the high treble. Once again in a review I must report that complex treble now sounded even more natural and even better differentiated than before, and was achieved with a greater sense of life, producing a sparklingly clear sound.

The broad midrange breathed tubelike tonality, the FPB 600 now distancing itself from many established solid-state contenders, cruelly exposing their old-fashioned hardness and glare—that "strained" coloration which can be mistaken for superior dynamics and precise transient edges, but which ultimately fatigues the ear. Such a compromised sound is also found to compress image scale and depth, and marginalize true dynamics.