Solid State Preamp Reviews

One never knows, do one? Within the past year, I've had six preamplifiers in my system for critical evaluation, reviewing four of them and using another two as references. I was getting pretty tired of listening for sonic differences among preamps, and I told JA that I'd prefer my next reviewing assignment to be something different, like a speaker or a power amp. He agreed, but said he'd first like me to review just one more preamp, the Perfectionist Audio CPR/TIPS, which had been waiting patiently in the review queue in Santa Fe. Well, one more wouldn't hurt. Sounded kind of interesting, anyway: a preamp with a battery-operated power supply!

The CPR/TIPS arrived while I was still working on the review of the Mark Levinson No.28 for the July 1992 issue, and I put it aside until I could devote my full attention to it. A couple of weeks later, before I'd finished the No.28 review, there was a message on the answering machine from Perfectionist Audio's Larry Smith: Was the CPR/TIPS working OK? Did I have any problems or questions? Well, I thought, before I call him back to reassure him that his pride and joy has not exploded, I'd better hook up the preamp just to make sure that it does work. Plug in the power supply for a couple of days to charge the batteries; connect the preamp into the system; turn on the power amps; put on a CD, and flip the switch that disconnects the AC, making the preamp fully battery-operated.

Well, at least it works. Yes, works quite nicely. It sounds...very good. Hey, this may be a great preamp!

Better get on with the review.

Design & description
In the beginning, according to Larry Smith, there was a tube preamp called the Perfectionist Audio Components (PAC) Pro-Reference. Produced in very low volume, it's still available as the Pro-Reference IIb ($4295), and has been joined by the Compact Pro-Reference (CPR), a solid-state unit intended to produce the same kind of sound as the Pro-Reference, but at a more modest price ($1550–$2395, depending on phono options). Most recently, Larry Smith—whose design credits include the Distech LS2 amplifier (a former "Recommended Components" denizen), recording electronics for Chesky, and the well-known IDOS and DIF digital/analog isolation devices—came up with a battery-operated power supply for the CPR, calling it Total Isolation Power Supply (TIPS). Since the basic CPR preamp is available as a line-stage–only version (Ib), or as one that includes a phono stage (IIb, moving-magnet; IIIb, moving-coil), the full name of the product is PAC CPR IIIb/TIPS. It all makes sense, even if the name doesn't roll off the tongue like, say, "Consummate."

Other than in the area of the power supply, the design of the CPR appears to be fairly straightforward, based on high-quality op-amp ICs. Like the people at Madrigal (who use integrated-circuit op-amps in their Mark Levinson No.28 preamp), Larry Smith feels that IC op-amps have been unjustly maligned in high-end audio circles, and that, used properly, the best op-amps can offer performance superior to circuits based on discrete components. The active devices meet military or aerospace specifications, and are apparently "radiation-hardened," so that the CPR/TIPS with the power supply in the "Total Isolation" mode is said to be the only preamp that will function during a nuclear attack. (However, if it doesn't, you may have trouble making a warranty claim.)

The preamp's line stage has no capacitors in the signal path and is flat to DC, so it should not be combined with a direct-coupled amplifier. Operation is stable without any servo circuits. Considerable attention has been paid to passive components like internal wiring (silver/Teflon multi-conductor) and RCA jacks (Cardas gold/rhodium), as well as to the circuit's physical layout. Construction is modular, with four separate circuit boards, allowing for quick replacement. The moving-coil section has switchable gain; load impedance is variable over a wide range. There are two line inputs plus one phono (wired as another line input in the version without phono), and inputs/outputs for one tape recorder. The tape outputs are not buffered, so, for optimal performance, a tape deck should be connected to the tape-out jacks only when making a recording. The CPR has a balance control (Yeah!), and the input/output jacks are clearly labeled on top of the chassis (footnote 1).

The battery-operated power supply, TIPS, is identical in size to the CPR, and is meant to be stacked with it, connected to the preamp via a short plug-in wire link. The TIPS—which is specifically designed for the CPR and cannot be used to power any other equipment—contains Lead Calcium Rechargeable (LCR) batteries, which supply current for a large (80,000µF) capacitive storage bank. Unlike NiCads, LCRs do not suffer from the "memory" effect that would require that they be completely discharged before recharging.

Larry Smith prefers not to refer to the preamp as "battery-operated," pointing out that the preamp's circuits get their current from the capacitive storage bank, and that this design eliminates the frequency- and discharge-dependent impedance variations that characterize pure battery supplies. (The capacitive storage bank will actually allow the preamp to operate for several minutes after the batteries are removed.) A small toggle switch allows selection of the AC-coupled "Recharge" (suitable for "noncritical" listening) or the "Total Isolation" (ie, battery-operated) mode. There are two LEDs, which, if lit when the switch is in the "Total Isolation" position, indicate that the batteries are sufficiently charged to allow the preamp to function in this mode. When the switch is in the "Recharge" position, the LEDs glow brighter, indicating that the charging circuit is working. The CPR and the TIPS are identically sized flat black boxes with classy-looking 3/8"-thick anodized front plates, but with knobs and switches of somewhat utilitarian appearance.

Setup
It took only a brief listen for me to conclude that the CPR showed considerable promise. Because the review sample lacked a phono stage, and because Larry Smith had told me that there was now a slightly upgraded version of the preamp, I requested a sample of the latest version, with phono stage. For various reasons (including, apparently, PAC's tweaking of the phono stage), I didn't get the latest, all-singing, all-dancing version of the preamp for another six weeks. Meanwhile, I was listening to the original CPR sample (CPR-Ib/TIPS, to be precise).

By the time I got the new sample of the CPR, Except as noted, my comments about the CPR/TIPS's sound refer to the latest IIIb version. The moving-coil stage gain was set to the maximum, with load impedance at 100 ohms, a value I have found to work well for the AQ 7000.

Sound
First, let's deal with the obvious question: What difference does battery operation make? As the preamp is always getting its power from the batteries—the mode switch just selects between "Recharge" and "Total Isolation"—it's impossible to say what the CPR sounds like with the conventional transformer-based power supply, but a significant amount of electronic garbage is removed when the TIPS is in the "Total Isolation" mode. In particular, much of the harshness of CDs is revealed to be a function of connection to the AC supply. This is the case even though my system has dedicated AC lines, AC is conditioned by a Tice Power Block, and the digital transport and D/A processor are isolated from the rest of the system through the IDOS power strip. I don't know if the effect is due to a reduction of RFI or EMI, the elimination of ground loops, or some combination of these factors. I do know that it's not a matter of reduced noise as such. With the input switch set to one of the line-level sources, and the volume control at maximum—which, if a CD were playing, would cause my Quads to expire in about 42 milliseconds—there's a noticeable reduction in noise when the TIPS is in the "Total Isolation" mode. This effect is inaudible when the volume control is set at a normal listening level.

How good does the CPR/TIPS sound in the "Total Isolation" mode? The greatest compliment I can pay it is that I was seldom aware of the preamp's contribution to the sound; my attention was occupied by the music. I also found it difficult to switch myself into the analytical/evaluative mode (Where is that switch?) and to take notes on what I was hearing. In this "inviting" quality, the CPR/TIPS reminded me of a good tube preamp. With almost every recording, there was an ease and openness to the sound, with excellent timbral accuracy, a well-resolved sense of depth, and good focus on voices and instruments. Interpretive nuances and dynamic shadings, such as in Kun Woo Paik's performance of the Liszt Mephisto Waltz No.1 (Virgo VJ 7 91458-2), came through with great clarity (footnote 2).

One recording that had always sounded to me like an overly reverberant mess is the Cambridge Singers' Olde English Madrigals And Folk Songs (American Gramaphone AGCD-500). Through the CPR/TIPS it's still overly reverberant, but no longer quite as much of a mess: individual voices are more differentiated, and more clearly placed in the hall ambience. The highs were particularly impressive, with very little of the hardness and grain that often characterize CDs. (The PS UltraLink worked synergistically here.) The Rowland Consonance, which I certainly would not describe as hard-sounding, had, in comparison, a little more of an electronic edge.

The CPR/TIPS's soundstage was as wide as I've heard in my system, the "off-stage" exclamation ("Well done!") at the end of Anna Maria Stanczyk's Chopin piece on the first Stereophile Test CD sounding 'way off-stage. Bass extension and clarity were outstanding, limited, I suspect, mostly by the room and the associated equipment.

Detail? You got it! And without the overly etched quality that's typically part of the package. In its lack of electronic edge, the CPR/TIPS was similar to the Conrad-Johnson PV11, but with superior detail.

How about rhythm and pace, those attributes so valued by Linnies and by Martin Colloms? No problems here as far as I could tell; my toe tapped whenever my ears heard toe-tapping music.

In some listening sessions, I did notice the music not being as involving as I expected; I then checked the TIPS, and found that it was in the "Recharge" rather than the "Total Isolation" mode! Flipping the switch brought the sound into sharper focus, with a return of the sense of ease that I had come to think of as the CPR's signal characteristic. I spent a bit of time comparing the two samples of the CPR—just long enough to conclude that, indeed, the latest version (which differs from the first only in having Pro-Reference rather than Distech wire for internal wiring) sounds slightly more transparent.

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Footnote 1: I do wish manufacturers would agree on whether the right channel inputs/outputs are to be on the right as viewed from the front or as viewed from the back. Similarly, if the jacks are mounted top-to-bottom, perhaps manufacturers could agree on a standard convention for designating the bottom (or the top) as the right channel. I know, it's mostly audio reviewers who are inconvenienced by the lack of standardization in this area, but, hey, audio reviewers are people, too.

Footnote 2: Kun Woo Paik not only plays with prodigious technical facility, but his feeling for this music makes me think he must have grown up somewhere around Eszterhàza. Sound is a bit on the dry side, but very clean. I found out about this recording by listening to "Records in Review," a radio program originating from Toronto's CJRT-FM, also broadcast in Dallas (WRR) and Phoenix (KONC). On this show, Bruce Surtees (record-store owner/audiophile) and Paul Robinson (conductor) discuss new and old recordings in a lively, bantering style that recalls Siskel and Ebert in the days before they went commercial. The music they play is pretty good, too.