Tube Preamp Reviews

The $1485 PV-5 is a "budget" version of C-J's $2850 Premier Three preamplifier, but according to the manufacturer it embodies much the same kind of circuitry.

Tubed preamplifiers have a well-earned reputation as system busters. Many of them during warmup produce horrendous bangs or plops so severe that every speaker fuse in the system blows. If fuses are absent, or rated too high to protect things, the amplifier, speakers, or both are likely to blow up (not literally; they just twitch once and lie down dead). The PV-5 contains one of the most effective pop suppressors I've encountered, and produces no noise whatsoever during warmups and turnoffs. My Berning TF-10, on the other hand, produces a small plop when its delay relay turns it on, and a monstrous, fuse-popping thud when turned off. I have never given it a crack at an unfused system with a 500-watt/channel amplifier, and don't plan to.

The C-J is very quiet in other ways as well. At high listening level (100dB peaks) with a 5mV cartridge, hum and hiss were virtually nonexistent. And the PV-5 has scads of reserve gain; the volume control at the aforementioned listening level (with Conrad-Johnson's Premier One amp and Acoustat 2+2 speakers) was at 11 o'clock, and measurement showed that there was an additional 9dB of gain left. At 12 o'clock, in the absence of any signal (including surface noise), there was only a very faint rushing hhh. At full gain there was plenty of hhh but still no hum! All switched functions were completely free from clicks. (Note that slight DC leakage in the coupling capacitors of a high-level signal source can cause clicks which are not the fault of the preamp design.)

The reserve gain means that with most MM cartridges the volume control will be set rather low much of the time, a condition which can cause bad channel imbalance due to poor volume-control tracking in the 8, 9, and 10 o'clock range. Such is not the case with the PV-5. Tracking accuracy between the two halves of the ganged control was better than 0.5dB from 7:30 to 4 o'clock, which is unusually good. The advantage, of course, is that the preamp has enough gain to run many moving coil cartridges straight in, without a step-up device; more on this later.

Sound Quality
Our first sample of the PV-5 (obtained around October 1983) proved sonically to be a real puzzler. On bypass tests, with my inverse-RIAA input network (and using good CD and 15ips tape sources), there was so little difference with the PV-5 in-circuit and bypassed that it was almost impossible to tell which was which. On this basis the PV-5 was virtually indistinguishable from my "reference" Berning TF-10 preamp.

But with analog discs the PV-5's sound was not nearly so neutral. It reminded me, in fact, of the sound of C-J's own Premier One power amplifier: slightly bright and forward, very much alive, with remarkably good rendition of depth and perspective and a warm and full but slightly loose low end. Despite the unit's extraordinary (for tubes) high-end response, highs were somewhat sweetened rather than airy and open, with a hint of some fine-grained texturing. It was perhaps not surprising, then, that I found the combination of the Premier One and the PV-5 to be a bit much with many speaker systems. Their colorations compounded one another, and the result was quite noticeable. But the disparity between what I heard on bypass and with a phono source still had me baffled. Response measurements using the same inverse-RIAA box revealed nothing amiss. The PV-5's RIAA and high-level sections were as close to being right-on as anything I've measured.

Right around the time I'd finished my report on the first unit, and concluded the PV-5 couldn't really stand up to my Berning TF-10, C-J asked that we return our sample PV-5 for "updating." According to C-J, all they did was "trim the RIAA equalization and change a few tubes," but the resulting change in the preamplifier's sound was not subtle. The latest version still has some of the sonic earmarks of tubes, but every coloration has been reduced to the point where it is merely a slight "tint" rather than an aberration.

For example, the original warmth remains, but there is less of it-quite little, in fact-and instead of the slight looseness previously observed, the mid-bass is now surprisingly taut and "gutsy." Bowed basses sound awesome: realistically rotund with all the bloom of the real-instrument sound. The string vibrations are so clearly defined that I had the feeling I should have been able to "count the cycles." Not only that, the low end has a gorgeously full, deep weight to it. In short, the low end is now superb, bettering the Berning by a small but significant margin.

It now surpasses the Berning in two other respects as well: depth and transparency. The PV-5 has such liquid clarity, and reproduces perspectives so well, that the sound is sometimes spookily real. The preamp is an utter joy to listen to, and should be heard by anyone who maintains an aversion to tubes-not to mention those of you who already love tubes and may be looking for a new preamp! If the PV-5 doesn't convince you, nothing will.

Extreme highs, markedly improved over the first sample, are quick and detailed, yet exquisitely delicate. The slight graininess in the first unit is virtually gone, save for a very subtle crispness. The Berning is just a hair sweeter at the top, but the difference is now so slight that in actual use it would be swamped by far greater differences between loud speakers, cartridges and discs.

The PV-5 is still not quite as literally accurate as the Berning; it still has a slight forwardness and some brightness. The brightness may push some speakers and many recordings over the hill into shrillness, but I have yet to find a loudspeaker system that didn't respond to that forwardness by merely sounding more alive and realistic. This is one case where I have to say I'm more impressed by sheer seductive listenability than by accuracy. I keep telling myself that accurate is better, but accuracy by itself isn't why I derive so much pleasure from listening to the PV-5.

Interestingly, when driving C-J's Premier One power amplifier, this latest PV-5 almost seemed to disappear. I had the feeling that all I was hearing was the power amp (which, while superb-sounding on many top speaker systems, is more colored than the preamp).

Summng Up
In short, this has to be one of the world's great preamplifiers. It floors me that Conrad-Johnson has a still better preamplifier in their line, the Premier Three (see AHC's report elsewhere in this issue). It has not prompted me to turn in my Berning (for which my attachment is more than emotional; I paid good money for it), but it has made it clear that my 4-year-old TF-10 is overdue for an overhaul and upgrade (footnote 1).

A honey of a preamp!

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Footnote 1: Those who have witnessed JGH's loyalty to the Berning over the last four years will appreciate what a large step it has been to find a preamp that outperforms it in a number of ways. Interestingly, Berning has just announced their first official updating of the TF-10 (although it's been modified in minor ways all along), and it's described as making "significant" sonic improvements.—Larry Archibald