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!
Tuesday, May 31, 2011
Sunday, May 8, 2011
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.
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.
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.
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.
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.
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| Figure 1. Uncorrected (Bypass) left and right channel responses. |
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| Figure 2. Corrected (after TacT) left and right channel responses. |
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| Figure 3. Uncorrected (Bypass) vs. corrected (after TacT) left channel response. |
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.
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| Figure 4. Spectrogram plot of the uncorrected (Bypass) response. |
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| Figure 5. Spectrogram plot of the corrected (after TacT) response. |
Sunday, March 13, 2011
Blue Circle BC3000 Mkii To Replace My BC21.1
So I took the plunge and bought a used BC3000 mkii tubed preamplifier to replace my trusty heavily modded BC21.1. It should arrive in about a week or two. I am psyched!!
I am writing this painfully slowly on my iPhone so I will keep it short for now. More detailed info on why I made this decision, and where I hope to take my system, in a soon to follow installment.
I am writing this painfully slowly on my iPhone so I will keep it short for now. More detailed info on why I made this decision, and where I hope to take my system, in a soon to follow installment.
Thursday, March 3, 2011
Measuring the TacT RCS 2.0 Performance - Part One (Frequency)
I am posting exciting measurement results comparing the SPL room response before and after TacT correction, compared to the target curve I asked TacT to meet. I haven't personally seen this type of comparison done online (though it may well exist somewhere), perhaps because it requires two separate steps: first, measurement and correction with TacT; second, a way to measure the post-correction response. For those not familiar with the TacT unit, this machine does not allow you to measure the system response after correction has been applied. I have already showed in a previous blog entry the original room response (i.e., pre-correction) using TacT's measurement method compared to the target curve which is my goal.
For this exercise, I used REW software along with M-Audio hardware and microphone to measure the response both before (Original Response) and after (TacT Correction) of my system. The microphone has a calibration curve applied, specific to the microphone model. I directed REW to send the test sweep signal through both speakers simultaneously. This is contrary to advice, or maybe you would say common wisdom, that the averaged R+L response is "closer" to what we, as listeners, perceive to be the tonal balance of our system. However, what I have found is that when I compare the REW results of both speakers against the R+L averaged response, that the results of both speakers being driven are closer to the target curve. This is not conclusive proof of anything, but has led me to use this REW result in the graphs below. For the reason why my Target TacT curve looks the way it does, please check out my previous blog entry on TacT Curves - but, in summary, here is my rationale: 1) below 300 Hz, I want to tailor the bass response to slowly rise as frequency decreases, and then drop off quickly below about 25 Hz. This imparts a powerful character to the bass notes and balances the overall frequency response, while also respecting the physical limitations of my modestly sized speakers; 2) above 300 Hz, I like the overall balance in my system and choose to basically preserve the original response. Note: I believe the dip in response above about 8kHz is an anomaly in this graph, since it is not seen in some of my other measurements when the original response has been measured.
Figure 2 shows the result after Tact correction has been applied, shown with the target response. Overall, the target has been met, which is amazing to my eyes and to my ears! However, there are a few points worth mentioning. First, the response below about 150 Hz is almost exactly what I have specified. The goal here is to optimize (reduce) the demand on the amplifier and speaker in this region, which simultaneously frees up more power for the higher frequencies. Listening comparisons reveal that these goals have been achieved and result in a cleaner presentation of the music overall. Yeah for me, and yeah for the music.
Second, in the region between 150Hz and 300Hz, the TacT did a valiant job to help tame the suck out, but ultimately there is a still a sizable dip in frequency response. Generally this is to be expected since it isn't recommended to use an equalization tool (ultimately, that's what TacT is) to help fill in the dips too aggressively; however, the depth of the dip has been reduced. Whether this is due to TacT "filling in the hole" or whether the amplifiers are simply better able to compensate due to less demand in the lower bass region, I don't know. Either way, it's a win for my ears.
Finally, in the frequencies above 300Hz, the characteristics of my system have been well maintained. Score.
Of course, the graphs so far are the system response with both speakers driven simultaneously. If we think just a little deeper, we might wonder what the individual Left and Right responses look like, both before and after TacT correction. In other words, is TacT also helping to equalize the channels individually, a particularly relevant question for my off-center setup. Glad you asked! Let's take a look...
Fig. 3 shows the Left and Right individual speaker responses, before TacT correction is applied. Below 300 Hz and even up to 700Hz, there are fairly large discrepancies in the response of the two channels. Perhaps not surprisingly, above 700Hz, the responses are fairly well correlated.
Fig. 4 shows the Left and Right individual speaker responses, after TacT correction is applied. In the lower frequency domain, the responses are now very well correlated, though there are still some discrepancies between 30Hz and 70Hz. But, certainly, the magnitude of the differences is much less than before TacT was applied (Fig 3), and of course the overall bass response is as expected. Above 300 Hz, the channels are definitely even better correlated than before TacT, though there is now a difference in the region around 1kHz that doesn't exist in Fig. 3.
As you can see, the TacT has made a world of difference over the entire frequency response of my system, and is certainly doing an excellent job of correction when we review the measurement data. If you don't have one already, and you have bass problems that you can't tame - who doesn't? - then I recommend that you get one of these units as soon as possible. You will not regret it!
Next time - what do the time domain measurements look like??? Stay tuned for more measurement updates in an upcoming installment....
For this exercise, I used REW software along with M-Audio hardware and microphone to measure the response both before (Original Response) and after (TacT Correction) of my system. The microphone has a calibration curve applied, specific to the microphone model. I directed REW to send the test sweep signal through both speakers simultaneously. This is contrary to advice, or maybe you would say common wisdom, that the averaged R+L response is "closer" to what we, as listeners, perceive to be the tonal balance of our system. However, what I have found is that when I compare the REW results of both speakers against the R+L averaged response, that the results of both speakers being driven are closer to the target curve. This is not conclusive proof of anything, but has led me to use this REW result in the graphs below. For the reason why my Target TacT curve looks the way it does, please check out my previous blog entry on TacT Curves - but, in summary, here is my rationale: 1) below 300 Hz, I want to tailor the bass response to slowly rise as frequency decreases, and then drop off quickly below about 25 Hz. This imparts a powerful character to the bass notes and balances the overall frequency response, while also respecting the physical limitations of my modestly sized speakers; 2) above 300 Hz, I like the overall balance in my system and choose to basically preserve the original response. Note: I believe the dip in response above about 8kHz is an anomaly in this graph, since it is not seen in some of my other measurements when the original response has been measured.
 |
| Fig. 1. Original response of my system before TacT correction, shown against the target response that TacT is asked to achieve. |
Figure 2 shows the result after Tact correction has been applied, shown with the target response. Overall, the target has been met, which is amazing to my eyes and to my ears! However, there are a few points worth mentioning. First, the response below about 150 Hz is almost exactly what I have specified. The goal here is to optimize (reduce) the demand on the amplifier and speaker in this region, which simultaneously frees up more power for the higher frequencies. Listening comparisons reveal that these goals have been achieved and result in a cleaner presentation of the music overall. Yeah for me, and yeah for the music.
Second, in the region between 150Hz and 300Hz, the TacT did a valiant job to help tame the suck out, but ultimately there is a still a sizable dip in frequency response. Generally this is to be expected since it isn't recommended to use an equalization tool (ultimately, that's what TacT is) to help fill in the dips too aggressively; however, the depth of the dip has been reduced. Whether this is due to TacT "filling in the hole" or whether the amplifiers are simply better able to compensate due to less demand in the lower bass region, I don't know. Either way, it's a win for my ears.
Finally, in the frequencies above 300Hz, the characteristics of my system have been well maintained. Score.
 |
| Fig. 2. Corrected response of my system using TacT, shown against the target response that TacT is asked to achieve. |
 |
| Figure 3. Individual Left and Right speaker responses, before TacT correction (Original response) |
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| Figure 4. Individual Left and Right speaker responses, after TacT correction (Corrected response) |
As you can see, the TacT has made a world of difference over the entire frequency response of my system, and is certainly doing an excellent job of correction when we review the measurement data. If you don't have one already, and you have bass problems that you can't tame - who doesn't? - then I recommend that you get one of these units as soon as possible. You will not regret it!
Next time - what do the time domain measurements look like??? Stay tuned for more measurement updates in an upcoming installment....
Wednesday, February 16, 2011
New Music - Adele
Check out Adele's new album, 21. We've only listened to a few tracks, but her voice is AMAZING! I guess the album releases on Feb 22. I'm going to pre order it tonight.
Has anyone heard of her already?
ps - we found her from the song on the "I Am Number Four" movie trailer...
Has anyone heard of her already?
ps - we found her from the song on the "I Am Number Four" movie trailer...
Sunday, February 6, 2011
Digital Cable Shoot-Out: Cardas Neutral Reference. Finally, the Results Are In
Finally, I am ready to post the results of my first digital cable shoot-out. As a refresher, here are the contenders:
Before I begin, a summary of today's listening conditions is in order. The BC21.1 preamp is out of order probably until next weekend, when I plan to perform the needed repairs. This means that the analog outputs from the Bryston DAC are routed directly to the inputs of the BC22 monoblocks, and the TacT performs the (digital) volume control duty. I now have an all solid state system for the first time since entering high-end audio proper. This has been an eye-opening experience - some good, some bad - but I will leave a detailed write-up until after the BC21.1 is back in the loop. The music is Ceu's self-titled album Ceu (2006), a punchy but chill Brazilian sound with clear, expressive vocals played through the Arcam. My trusty dog Brodie is lying at the other end of the couch, and I have just started a glass of the fairly good Chalone Vineyard 2007 Pinot Noir.
The Neutral Reference (NR) cable lives up to its name, and its main strength lies in the bass region. Bass notes are more clearly delineated and textured, with a quicker start and stop. Voices are presented slightly forward of the speaker plane, and background vocals are more distinct, or separated in depth, from the main vocal. Background silence between notes is decidedly blacker, though only by a shade. Overall, the NR cable conveys quickness and precision. The HSD cable is also very good, with a nearly equal dynamic performance to the Neutral Reference. Its presentation is more inline with the speaker plane, not forward of it. A main differentiator is that the HSD cable imparts a breathy, glow-y quality to vocals. I would even go far as to say the HSD yields more vocal emotion in that tube way, while the NR is more akin to a solid state sound. Somehow, the HSD seems also to give a more funky, almost laid back, rhythm to Ceu's tracks, like this is a cable that is more in sync with the musical sense she's trying to convey.
As you can see - strengths and weaknesses, plus's and minus's. In my current all solid state setup, I prefer the High Speed Data cable for its more tube like presentation. My choice will probably swing back the other way to the Neutral Reference cable when the tubed BC21.1 is back in service. In fact, when I had a detailed listen a couple weekends ago when the Blue Circle preamp was in the driver's seat, the Neutral Reference cable was my choice.
- Cardas High Speed Data digital cable (S/PDIF, 1.0m) - retail $77 for 0.5m
- Cardas Neutral Reference Digital cable (AES/EBU, 0.5m) - retail $236 for 0.5m
Before I begin, a summary of today's listening conditions is in order. The BC21.1 preamp is out of order probably until next weekend, when I plan to perform the needed repairs. This means that the analog outputs from the Bryston DAC are routed directly to the inputs of the BC22 monoblocks, and the TacT performs the (digital) volume control duty. I now have an all solid state system for the first time since entering high-end audio proper. This has been an eye-opening experience - some good, some bad - but I will leave a detailed write-up until after the BC21.1 is back in the loop. The music is Ceu's self-titled album Ceu (2006), a punchy but chill Brazilian sound with clear, expressive vocals played through the Arcam. My trusty dog Brodie is lying at the other end of the couch, and I have just started a glass of the fairly good Chalone Vineyard 2007 Pinot Noir.
The Neutral Reference (NR) cable lives up to its name, and its main strength lies in the bass region. Bass notes are more clearly delineated and textured, with a quicker start and stop. Voices are presented slightly forward of the speaker plane, and background vocals are more distinct, or separated in depth, from the main vocal. Background silence between notes is decidedly blacker, though only by a shade. Overall, the NR cable conveys quickness and precision. The HSD cable is also very good, with a nearly equal dynamic performance to the Neutral Reference. Its presentation is more inline with the speaker plane, not forward of it. A main differentiator is that the HSD cable imparts a breathy, glow-y quality to vocals. I would even go far as to say the HSD yields more vocal emotion in that tube way, while the NR is more akin to a solid state sound. Somehow, the HSD seems also to give a more funky, almost laid back, rhythm to Ceu's tracks, like this is a cable that is more in sync with the musical sense she's trying to convey.
As you can see - strengths and weaknesses, plus's and minus's. In my current all solid state setup, I prefer the High Speed Data cable for its more tube like presentation. My choice will probably swing back the other way to the Neutral Reference cable when the tubed BC21.1 is back in service. In fact, when I had a detailed listen a couple weekends ago when the Blue Circle preamp was in the driver's seat, the Neutral Reference cable was my choice.
Wednesday, February 2, 2011
Major Ignition!
Last night when I turned on my preamp, I smelled smoke! Holy cow. Bending down to take a close look, I actually saw some wisps leaking gently from the top of the preamp cover. I have owned this preamp for 7 or 8 years, and it has performed flawlessly in every way, so - to put it mildly - this was unexpected and elicited quite a bit of alarm. I unplugged the beast, removed the cover, and found the culprit. I confirmed with Blue Circle that it is a blown filament regulator (a what??). After nearly a decade of faithful service, it just plain wore-out. Anyways, the plan is to buy a new regulator, which costs a few dollars from an electronics supply house, and install it myself with the blessing of the designer. The only operations are a couple of snips, unscrew, re-screw in the new part, then solder two leads. Simple - right? Right.
Here is a picture of the exploded device.
Lastly, I now have the Bryston DAC analog output connected directly into my amps. Digital volume control is provided by TacT. Hmm... Interesting. I don't want to write anymore on that right now, but I just know there will be plenty to report on the way this new configuration sounds when I get my preamp up and running again.
Here is a picture of the exploded device.
Lastly, I now have the Bryston DAC analog output connected directly into my amps. Digital volume control is provided by TacT. Hmm... Interesting. I don't want to write anymore on that right now, but I just know there will be plenty to report on the way this new configuration sounds when I get my preamp up and running again.
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