Listening to the BC3000mk2 versus BC21.1

For the past eight or nine years, I have owned a Blue Circle BC21.1 tubed preamp. This used to be BC's entry level preamp, but is now discontinued and has been for some time. Every once in a while one of these puppies pops up on Audiogon, but not that frequently. Perhaps that attests to the love its owners have for it, that they keep it around for a long time, like I have. Perhaps five years ago, I sent it back to Gilbert at Blue Circle for a few upgrades - namely, a Level 1 outboard power supply, a new selector switch (same as that used in higher models), and to bypass the balance control which I never used anyways. Last year, I had another 10,000uF of cap added inside the chassis. While it is not as tricked out as a BC21.1 can be, it is fairly far along in that department. Certainly, a significant change from its first baby steps in my system.

Not only has the BC21.1 been trusty and true, but I have loved its beautiful music. The presentation is fairly dynamic in the bass department and full of PRAT (Pacing, Rhythm, and Timing). Put another way, it is full of life and passion. Not without its flaws, it can also tend to get a little bogged down when a musical passage becomes too complex, and it was not the last word in high frequency extension, with cymbals being the most obvious victim. But these errors are forgivable given its modest price point. In my system over time, it had never felt like the weak link. That is, until recent system upgrades such as the discerning and fast Bryston BDA-1 DAC, the TACT RCS 2.0 room correction "computer", the brilliant Salk HT1-TL ribbon speakers, and BC22mk2 POT+LOC monoblock amplifiers, have forced me re-evaluate and consider a more expensive alternative - the BC3000mk2.

I choose to stay with Blue Circle because I like their house sound, and I like knowing that Gilbert is up early and up late (I assume) working on all manner of pedestrian (read: stock) and exotic (read: as custom as you want to go) gear. I follow the BC blog regularly, and Gilbert is always innovating. And it's all handmade - by Gilbert. Fun.

So one day, a BC3000mk2 became available on Audiogon, for sale by one of the BC forum members. I leapt and bought it. But before I spend any time describing the differences between my old and new preamplifiers, let me first give a little more history. Since I have been contemplating a preamplifier upgrade, I contacted Gilbert with my likes/dislikes and he suggested a BC109. This is Blue Circle's only solid state preamp, and judging from the BC forum, it's a doozy. The BC109 has so much capacitance that, after a complete charge-up, it can run without connection to the wall for many hours, depending on how much capacitance it has. This supposedly yields an incredibly smooth, grain free, distortion-free sound that is pure heaven to hear. I am paraphrasing what I have read, of course. I haven't heard it yet, but I plan to do so in the not-so-distant future. Before I do, I first wanted to hear what the BC3000 was all about.

What does a more than doubling of price get you? Well, it offers tremendous technical improvement in almost every area of listening performance. In the bass region, notes are taught, starting and stopping quickly with little or no overhang, and reveal good texture (as the recording allows). In my system and even with the TACT, some low frequencies can suffer at the merciless hands of my room. With the BC21.1, certain bass notes are either lower or higher in volume, or are fast or bloated and slow. Switching to the BC3000mk2, these issues are nearly completely resolved. I am sure there are several reasons why this is the case, including the circuit design itself, but I suspect that the fairly large outboard power supply (roughly twice the size of the BC21.1 power supply) also plays a big role here. This also means that large swells in the music are indeed subjectively louder and more powerful thru the BC3000 than the BC21.1.

The midrange vocals are also well served, more polished and refined, less grain. High frequencies are clearly and without doubt more extended. Any song with cymbals in it easily demonstrates this fact. Interestingly, the sound from the BC3000mk2 appears to be more dynamic with regards to drums and acoustic guitars. It is as if these instruments hit you in the face, thru the higher level preamp. As they should. I am not saying that the presentation of the BC3000 is necessarily more forward compared with the BC21.1. Instead, it's more like the music is pushing up against the soundstage boundary more forcefully, as if it's filling the acoustic "room" of the recording more fully.

In my system, the front of the sound stage was a couple feet in front of the speakers, and extends by another couple of feet behind the speakers to the back wall boundary. If music is recorded with good left-right or vertical staging, then the BC3000 easily reproduces that, often extending outside the speaker boundaries. Vocals are well layered, separating the main singer from backup vocals. The sound space is somehow more densely populated in the BC3000 compared with the BC21.1, yet there exists more space between performers and instruments. The background of the BC3000 is extremely quiet - you could hear a pin drop in the recording venue.

The one drawback I have found is the way BC3000 presents its bass. I contrast this against the very positive bass qualities I commented on above. It's most expedient to say that, with the BC21.1, my feet were bouncing along with the song; with the BC3000 my body was swaying but the feet tended to be more still. Perhaps this is because the BC21.1 is more bass heavy while the BC3000 is more balanced over the frequency range. Probably the BC3000 is more correct in its presentation. But the BC21.1 wins me over in this area.

The BC3000 is staying in my system for the time being because it offers (nearly) everything. Can the BC109 solid state preamp offer me everything I want.... the best of both the BC3000 and BC21.1 worlds, plus an even more refined presentation? Or, would an even larger outboard power supply (like the Gzpz, or KQ) mated with the BC3000 completely win me over? I don't know yet. Until then, I will continue to enjoy the amazing Blue Circle preamps!

Measuring the TacT RCS 2.0 Performance - Part Two (Time Domain)

It's been a while since my last post. I chalk it up to an eclectic combination of factors. First and funnest, I received the BC3000mk2 preamp about 6 weeks ago, and have been immersed in listening to my system as if for the first time. More details of the BC3000's capabilities to follow in another post (no, really - I'll get to it!). Second, the work I do that pays the bills has been kicking me in the gnads and my weekends have recently been relegated to Rest & Recovery. While the siren call of adding more blog entries has never ceased - I hear her voice calling insistently - what really pushed me over the edge to continue writing is that a good audio friend recently commented over email "Your blog is getting stale". Wow! He is right!! So, as the dying light of a clear but chilly early summer Sunday evening in San Francisco illuminates my keyboard, I sit in the sweet spot with randomly selected songs streaming in thru Jody's MacBook and will attempt to illuminate you, my reader, with a second installment of TacT measurements. All of these measurements are with the BC21.1 in the system. Since then, of course, I have replaced the BC21.1 with the BC3000, and also subtly altered the TacT target response curve.... that, someday, could constitute another set of comparisons, another blog post. Will it never end!?! Apparently not.

The first TacT measurement installment concerned the improvements in frequency response that the TacT rendered. But that doesn't tell the whole story. According to the TacT website, their approach is to correct in the time domain, which naturally correlates to frequency domain improvement (I'll let you read more details there if you are so inclined). So let's see how the TacT performs. First set of three graphs are the Impulse Response Envelope (ETC) Traces with a 10mS smoothing applied. The goal of the first two plots is to show what the impulse responses looked like before (Bypass) and after TacT correction. Finally, the third graph demonstrates the left channel before and after correction. I am not showing you the right channel because the before and after responses are fairly similar as expected, but the left speaker, which is shoved (for lack of a better word) into the corner of my room, reveals by far the more dramatic changes.

Figure 1. Uncorrected (Bypass) left and right channel responses.

In Fig. 1, notice that there is a good amount of pre-ringing particularly in the left channel. After the impulse is applied, the channel responses do not decay together as the left channel reveals a longer delay.

Figure 2. Corrected (after TacT) left and right channel responses.

In Fig. 2, pre-ringing is GONE! The main impulse response is uniform and decays very consistently between channels. There is a some "roughness" evident in the right channel decay, which could be due to the fact that the 2nd order reflection point of the right speaker for the wall to my left was untreated when these measurements were taken. Today, an EchoBusters panel absorbs the reflections at that point, so future measurements may reveal a smoother decay for the right channel.

Figure 3. Uncorrected (Bypass) vs. corrected (after TacT) left channel response.

Finally, Fig. 3 is demonstrating the left channel uncorrected versus corrected responses, to highlight the dramatic improvement by the TacT unit.

The last two figures are the spectrogram frequency vs. time decay plots for the bass region from 20Hz to 200Hz. These graphs are with both channels driven simultaneously. Figure 5 with TacT correction demonstrates reduced pre-ringing, a more evenly distributed frequency response across the range, and superior damping at all frequencies. One more point of interest is that, before TacT (bypass mode), the frequency response extends strongly down to 20Hz. However, after TacT, the bass response begins to drop significantly below about 25Hz. This is by design, and reflects the TacT correction curve that was applied (see the first installment of this series). My system correspondingly has a much faster and cleaner bass response.

Figure 4. Spectrogram plot of the uncorrected (Bypass) response.

Figure 5. Spectrogram plot of the corrected (after TacT) response.