|The Vinyl Word
Back Issue Article
By now, the name Blue Circle should be a familiar one to most SoundStage! readers. The small Canadian concern has reaped its share of praise in this publication for achieving outstanding performance in its line of tube amps and line-stage preamps. The BC-23 phono stage is one of two products in the new BC-20 series of components -- the BC-21 tube linestage is the other. Blue Circles design goals for this series was to build the least compromised products possible, but at a lower price point than its previous offerings.
In the case of the BC-23 phono stage, the decision to implement solid-state circuitry, rather than a more costly tube or hybrid design, was the key element in holding the price to a mere $1250. Call me silly, but in a phono stage where you are looking for very low levels of noise combined with high gain and linearity, a well-designed solid-state circuit would appear to be the logical choice. After having auditioned a late version of the Lehmann Audio Black Cube phono stage in my reference system for the two months preceding this review, I can attest to the very high performance-to-cost ratio that such units are capable of delivering.
In the BC-23, printed circuit boards (PCBs) are employed due to the extremely low-level signals that a phono stage must deal with. Despite the use of PCBs, the BC-23 is totally hand-crafted. It utilizes ultra-fast diodes in its power supply and gold (rather than the gold-rhodium) Cardas connectors that are standard issue on their higher-priced brethren. Additionally, Cardas wire is used in the signal path. Polypropylene caps are used throughout, with the exception that electrolytic types are employed for the purpose of stiffening the power supply. A heavy-duty toroidal transformer is located at the far right-hand side of the chassis and is as far from the main PCB as space permits.
The BC-23 uses the traditional Blue Circle stainless-steel faceplate, but uses mild steel for the case. One curious aspect of the anterior fascia is the fact that the sole function of the lone on/off toggle switch is to illuminate the Blue Circle logo/circle. It has no effect on the actual circuitry because the unit is powered and operational whenever the preamp is plugged into the AC outlet.
Still, I have to admire a component that sits on wooden feet, wenge wood to be exact, and only three of them, which is odd but effective (the virtues of a tri-pod stance have been extolled at length in audio circles). What piqued my curiosity even more was the isolation system used for the PCB. Gilbert Yeung, the chief designer, intimated to me that the thick rubber-like bumpers that are used to anchor, isolate, and support each corner of the circuit board, are made from a compound comprised of rubber and neoprene. Neato! These custom bumpers help to shield the PCB from vibrations emanating from the power transformer as well as from airborne acoustic feedback.
My initial setup of the test sample was more problematic than it should have been -- for a couple of reasons. You must first remove the eight tiny cover screws to access the internal gain and load settings for your particular phono cartridge. After I located an appropriate size Allen wrench, a minor problem occurred when I tried to remove the two screws that are overhung by the curved edge of the faceplate. The screws were just long enough that they contacted the edge of the faceplate before they could be removed. Additionally, upon reinstalling the cover I found that the holes in the cover didnt align perfectly with the threaded screw holes in the chassis. This made for a tight and awkward fit. Gilbert Yeung of Blue Circle has assured me that the BC-23 I reviewed was an early production sample and that they have since taken steps to fix both of these minor annoyances.
Once inside the BC-23, I had no problem in setting the internal DIP switches for each channel to the proper input impedance for my Transfiguration MC cartridge. I used the 100-ohm positions to be fair because that is the same load I employ with my other phono stages for this cartridge. There are seven different load settings in this phono stage, one at 47k ohms and six more between 60 ohms and 475 ohms inclusive. This is very commendable and virtually ensures an optimal match for almost all phono cartridges currently available.
Additionally, there are two toggle switches that choose between 40dB and 61dB of gain. The 40dB position will work well for most MM and higher-output cartridges, while the 61dB setting will better befit low-output MC cartridges. One additional switch is provided that adds another 10pF of capacitance loading. When this capacitor is employed, a slight reduction to the high frequencies kicks in; this is intended for systems that are still a little too bright when loaded correctly. The trade-off here is that a mild reduction in transparency is likely. You do not need to use this feature, but its nice to have it, just in case.
My analog source was a Townshend Audio Rock Mk III turntable with a modified Rega RB-300 tonearm. The cartridge was a Transfiguration low-output moving-coil design, which fed the Blue Circle BC-23 phono stage. Wireworld Equinox III interconnects linked the phono preamp to an AHT tube linestage, which in turn delivered the signal to the InnerSound active crossover/bass amp unit via Wireworld Equinox III interconnects. From there, Monarchys SM-70 power amps (used as bridged monoblocks) sparked life into the electrostatic panels of the InnerSound Eros speakers, while the InnerSound bass amp drove the woofers. Additionally, a Paradigm Servo-15 powered subwoofer was used for infrasonic bass reinforcement. It was incorporated through Paradigms X-30 active crossover. The low-pass section was dialed to about the 40Hz mark, while the high-pass section was bypassed, allowing the Eros woofers to roll off naturally.
When I first installed the BC-23 in my system, it produced a noticeable low-frequency hum through the speakers. This is symptomatic of a ground loop and not at all uncommon. I used a cheater plug to float the ground pin, and the hum vanished. Taking a couple of test spins on the vinyl track revealed that the BC-23 sounded considerably better when the polarity of the AC plug was reversed. It was definitely sweeter and more transparent as a slight edginess disappeared. The edginess was evidenced only when the AC plug was inserted in its intended orientation. My advice is to try the plug both ways and stay with the orientation that yields the superior sonics. Be advised to turn off your preamp and amplifier for at least 30 seconds when plugging in or unplugging the BC-23s power cord because this can send a potentially damaging transient surge through your audio system. This could be a costly error!
The Circles game
After I had the BC-23 correctly set up in my system, I settled into my listening seat to hear if the Blue Circle phono stage would deliver a level of performance that I could respect. Further, how would it stack up against a solid over-achiever like the Lehmann Audio Black Cube? Let me preface my remarks by saying that I consider the performance of the Black Cube to be the benchmark for phono stages costing less than $2000. Even at its somewhat higher price, I didnt necessarily expect the BC-23 to outdo the Cube or for that matter even to equal it.
But when the music starts all expectations are moot as the truth is revealed. What I found was that the Cube and the Circle shared many common strengths. Indeed, there were far more similarities than points of divergence. Both exhibited taut, controlled, and reasonably extended lower frequencies. In the midbass and upper bass, the BC-23 may have been just a touch tighter than the Cube, but it seemed to be a very close contest. Their respective treble reproduction was likewise close with both units exhibiting clean, extended, and fast-sounding treble. Here I give the nod to the Cube because I thought that the lower treble was just a touch more transparent. The BC-23 seemed to have a mild lower-treble emphasis that limited soundstage depth to a small degree. Certain instruments were pulled slightly forward toward the plane of the speakers. In terms dynamic contrasts Id say that both units performed admirably, each exhibiting a very wide spectrum of dynamic gradations. This was a virtual dead heat.
The one area that I can point to where the BC-23 and the Cube parted company was in their midrange performance. This is the area where the Blue Circle glowed to its best advantage. It is blessed with a sweet, harmonically pleasing midrange portrait that makes it a joy to behold. In fact, I can recall a remark I made to a friend, stating that Id be hard-pressed to identify the BC-23 in a blind test against my reference phono stage, a modified American Hybrid Technology AHT/P. This is indeed high praise, especially considering that AHT/Ps price is more than double that of the Blue Circle.
Dont misunderstand, the Black Cube is very smooth and competent in the midrange as well. But in direct comparison with the BC-23 (as well as some more expensive tube units), it comes off as being just a touch dry-sounding.
True to the music
Early in my evaluation with certain types of music (notably rock and pop), I had the impression that although the bass was very well defined and dexterous, it might have lacked a modicum of weight and extension. Later on, when I had a chance to delve into some bass-heavy symphonic works, that impression began to change. Listening to Tchaikovskys Marche Slave, from Festival [RCA LSC-2423], I was happily sated with thunderous blasts from the powerful bass drum. Whats more, the broad dynamic range that this recording displayed through the Blue Circle was most impressive. I think that if Id had a signal compressor in the system during some of the crescendos I would have been inclined to introduce some compression, to save my delicate audiophile ears from excessive volume levels on the peaks. Unfortunately since the sound was so open and clear, without any harshness or stridency, I was able to absorb maximum dBs with nary a flinch. Oh well!
Speaking of open and clear, I found my ability to decipher lyrics with the BC-23 to be among the best in my experience. This may have been due to the isolation of the printed circuit board, but it could have also been due, in part, to a very mild emphasis in the upper midrange/lower treble area. Every now and then with instruments like the flute, especially in its upper registers, it seemed that some of the higher notes were a little more pronounced than they were with other phono stages. When I say "a little more pronounced," I mean precisely that, as in "perceptible," but by no means "glaring." For example, in playing Suzanne Vegas "Solitude Standing," from the album of the same title [A&M SP-5136], I thought that the natural sibilance in her voice was just a little overdone. Not that it was harsh or spitty, merely that it was slightly more prominent than with other units.
The Blue Circle BC-23 phono stage is a solid component. It is solid in its construction and build quality and in its sonic attributes. Having both the Lehmann Audio Black Cube and the AHT/P phono stages in-house to compare it against served only to solidify my respect for what Gilbert Yeung has accomplished. That he has done so at a bargain price makes the value all the more impressive.
Additionally, the flexibility afforded in the myriad loading options (without having to buy extra custom-value resistors) must be viewed as a real benefit to its user. Blue Circle must also be congratulated for making an attempt to control the resonances in the chassis and in the circuit board itself. Neither of the other units that I mentioned make much of an effort toward that end.
In designing the BC-23, the folks at Blue Circle aimed for a very high level of performance at a very reasonable cost. Surely their goal has been accomplished. If youve grown weary of searching for that perfect (but elusive) tube phono stage, the Blue Circle BC-23 is a honey of a sweet-sounding alternative.
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