Conrad-Johnson PF-1 preamplifier
The one-box PF-1 has disc and line inputs, the latter rather sensitive for CD use, and while the disc input is rated as universal, there may be questions about its compatibility with some cartridges on grounds of input noise and input overload margin. On the face of it, the PF-1 does have sufficient gain for the direct connection of a moving-coil cartridge.
The PF-1 is of 19" rack width but is quite compact at 3.5" high. Finished in a pale-gold brushed alloy, the front panel is well-laid-out, with clear, unambiguous legends. From the left we have the input selector with a choice from phono, tuner, CD, and tapes 1 and 2. The source/tape monitor follows, then the mode switch, stereo/mono, etc. Add the stepped balance control, and the lineup is completed by the standard volume control. On the back, the mains cable is captive while the sockets are unbalanced phonos.
The PF-1 is based on FET circuits, the low-feedback design intended to capture some of the character of tube technology. One striking aspect of the PF-1 is the complete absence of electrolytic capacitors, either in the signal circuits or in the power supplies. This is in accordance with C-J's wholehearted belief in the superiority of plastic film capacitors in all applications.
The power supply begins with a primary regulator feeding three secondary regulators, one for each gain-stage block. Described as a zero-feedback design, this gain-stage block employs distortion-canceling techniques to help achieve satisfactory linearity. Operating as a low-impedance buffer with a voltage gain of 20dB, it is used in both the line amplifier and the output stage of the disc amplifier. Between the first disc stage and the latter comes the passive phono-equalization network. The phono input uses a J-FET in a single-ended configuration, and is non-inverting overall. All capacitors are polystyrene or polypropylene film; with the single-rail circuits used, capacitors are necessary to couple the stages.
First trials suggested something special from the PF-1; accordingly, I gave it a generous level of care and attention during auditioning, including the use of worthy ancillary equipment.
I began listening through the PF-1's phono input after suitable conditioning and adequate warmup. Within a context of some absolute references, I was not disappointed. Certainly the PF-1 was not as neutral and as uncolored as the finest, nor did it display the same level of focus, precision, and stability. However, it did offer a sound quality in one way that was right up with the very best, and which was promised by the zero voltage feedback circuitry. That quality is a sense of liveliness, presence, transient believability, and dynamic excitementsomething that great audio is all about. As a rock fan would put it, the PF-1 sounds upbeat, with a great presentation of pace and rhythm. In fact, the more I became aware of this aspect of its reproduction, the more I saw it as a fundamental and necessary requirement. Returning to most other preamps gave the impression that they are slow and drowsy, diluting dynamic contrasts and returning a downbeat impression of rhythm. Make no mistake, the PF-1's phono stage is something of a reference in this area, and could well be bought for this alone.
Readers may recall several reviewers' similar reactions in the mid '80s to the Counterpoint SA7, a low-budget, zero-feedback tube design. I also recall remarking, when hearing the excellent bass performance of the Krell KSP-7B, that once you've lived with that kind of bass it's hard to give it up. This remark is equally true for the high level of pace and dynamics delivered by the PF-1. Such high performance is unexpected at this modest price level, and the overall performance is, in any case, difficult to fault; it does not let the side down.
Another strong quality of the PF-1's phono input was its ability to maintain high levels of detail regardless of the music's complexity. It consistently proved adept at revealing inner levels of orchestration with the full weight required for good counterpoint, and giving the feeling of many players working in concert on large orchestral pieces. Conversely, the sound was not excessively analytical in the sense that the performance was being unduly dissected. Throughout, I was aware of a unifying coherence to the presentation of all kinds of program.
The PF-1's phono stage was "boppy" and lively in the bass, tuneful and agile, if lacking the full weight, slam, and authority of the finest references. What also mattered was the evident ability of the PF-1's bass lines to keep excellent pace with the mid and treble. For want of a better comparison, the bass was more like that of a Roksan turntable than a SOTA.
The midrange was fascinating, as within its fairly close approach to neutrality there was also a hint of leanness and crispness, sufficient to align analog disc sound a little closer to the accepted sound of CD.
Dynamics were first-rate, the human voice sounding naturally expressive and allied to a strongly communicative import. "Hardness" in the accepted sense was absentinstead, singing voices sounded surprisingly real.
The treble sounded pure, with only the mildest loss of detail and transparency. Nonetheless, a good feeling of recorded atmosphere and air was presented in the treble, which also showed excellently controlled vocal sibilance and negligible grain or "edge."
Stereo images were presented with very good focus, good width, and fine depth. Recorded ambience was recovered well, and the general level of transparency approached audiophile levels. Well-worn LPs showed new levels of energy and detail, making the assessment of the PF-1 a continued pleasure.
If you think this all sounds too good to be true, you're right. Perversely, this C-J preamp did not maintain this exceptional standard when fed a CD diet (polarity-inverted, of course!). The presence of some moderate coloration gave a "harder," "darkened" sound; CD sources were not felt to be as well-balanced as the analog disc performance might lead you to suspect. It was as if a similar tonal flaw was present in both the PF-1 and CD, and was additive, whereas the analog source and RIAA equalizer lacked that flow, avoiding their sum rising above an audible threshold.
On CD, the PF-1 was a touch lightweight; comparison with a passive-controller connection showed this well. Nevertheless, much of the fundamental quality described earlier remained; if not, this assessment would be nonsense, as the analog disc signal did successfully pass through this very high line stage.
In absolute terms there was a loss of stereo focus and width, though what remained was still impressive, well beyond its price class. The sense of scale and of natural expressive dynamics was retained, and low-frequency sounds were lively and rhythmic, involving and interesting. Transparency was very good, sufficient for a strong impression of stereo depth and for the recovery of ample ambience and recorded acoustic.
Only the finest CD sources would begin to tax this line stage.
When the PF-1 was teamed with the MF-200, there was a clearly audible affinitya level of compatibility where much of the PF-1's virtue was communicated to the speaker load. While the MF-200 was not so obviously an exceptional performer, the two products partnered each other well, making it hard to argue with the overall result, notwithstanding the PF-1's ability to reach even higher.
The fun really starts with the PF-1, which I'm sure has surprised C-J as much as it did me. Sure, it isn't perfect. Care needs to be taken with the phono input matching, and it's advisable to use a sweeter, more musical CD source, like a Meridian Bitstream player (or even C-J's own). When all was said and done, however, it was the dynamic, rhythmic quality of analog disc performance that I especially remembered, and which took the PF-1 right into top audiophile territory.
Its performance on other subjective grounds was sufficiently good so as not to prejudice this result; thus the PF-1 must be rated as an amazing hit. Its musicality reached far beyond its modest $1295 price-tag, though your dealer will have to earn his sales commission in terms of advice to attain the optimum result. The lab results helped define the operating limits while also showing that the unit was fundamentally accurate, particularly in terms of its RIAA equalization. Low-powered, it may be left permanently warmed up, always ready for immediate use. This convenience is complemented by the compact, well-screened, one-box constructionneed I say more?