Blue Circle Audio NSL Stereo Amplifier
- Created on Saturday, 15 September 2012 00:00
- Written by Michael Wright
Last fall, I was talking to Gilbert Yeung, Blue Circle Audio’s founder and chief designer, about an amplifier he was working on. He felt it was something special. He told me he’d soon be in my area, and asked if I’d like to hear it.
Yeung came by with an unnamed prototype. When he told me that it generated only 18-20Wpc, I told him I didn’t believe it, and that even if it were true, I didn’t want to damage the amp by overdriving it. He invited me to give it my best shot. I smirked and thought, So be it.
For over an hour, I tried to shut that amp down by throwing at it every kind of deep-bass reference recording I could think of -- soundtracks such as Casper, Edward Scissorhands, Gladiator, Batman Returns, Seven Years in Tibet, and older references like “The Gates of Däfos,” from Mickey Hart’s Däfos. The prototype was unfazed. It didn’t flinch. I was throwing at it no more of a load than what’s provided by 6-ohm Meadowlark Heron i’s and Dynaudio Sapphires, but I’ve still been able to hear amplifiers clip with those speakers, given the right circumstances. I told Yeung I was impressed that an amplifier that outputs so little power could take such a pounding and still sound good.
Fast-forward seven months. Yeung told me he’d finished designing the amp and offered it for review. After I’d cleared things with my editor, Yeung came by with a production sample and set it up in my system.
Under the hood
The new Blue Circle amp is now named the NSL ($19,500 USD), which, rumor has it, stands for “not so little.” The transformation from prototype (of which there are photos on Blue Circle’s website) to finished product has been remarkable. Compare the robot C3PO in his unfinished state in Star Wars: Episode I -- The Phantom Menace to how he looked at the end of Episode IV -- A New Hope and you’ll get an idea of what I’m talking about.
The finished NSL measures 20.5"W x 9"H x 21.5"D and looks similar to a Blue Circle BC204, but weighs 65 instead of 85 pounds. Yeung was proud of the fact that he’d increased the prototype’s power output from 18-20 to 28Wpc into 8 ohms (or 42Wpc into 4 ohms). But when he told me that the NSL’s output stage uses 288 operational amplifiers wired in parallel, I said, “No way!” As most of you know, op-amps are usually used to amplify small signals, as in preamplifiers. To hear of them being the main component in a power amp’s output stage caught me by surprise. I wondered aloud if maybe that was why Yeung could get only 28Wpc out of the NSL.
The NSL’s faceplate is of Blue Circle’s traditional purpleheart wood, with a wide purple streak across the middle. (If you’d prefer a different color or finish, you can have it for a nominal cost.) The top and sides are encased in a cage of 14-gauge steel, with perforations that permit quick and easy cooling. The rear panel is straightforward, with your choice of single-ended RCA or balanced XLR input connectors, and two pairs per channel of some really nice, long speaker connectors that you can easily get your fingers or a ratchet wrench around. An IEC connector on the rear lets you use your choice of power cord.
The NSL is a “very low bias” class-AB design that uses a minimal amount of local feedback for an amplifier so dependent on op-amps. It’s DC coupled and truly balanced from input to output; both positive and negative binding posts are “hot” with signal. Yeung told me that the NSL’s filtering capacitors are placed close to the output devices for better transient response. The NSL has a 600W power transformer for the output stage only, and more than two farads of power-supply filtering. It sits on a base of 1"-thick MDF that’s tightly coupled to the bottom of the steel chassis, for ultrarigid damping. The NSL can also run on two 115Ah, 12V, deep-cycle batteries for up to 24 hours per charge.
I have finally seen the advantages of having a computer play music files. My digital front end now consists of an Asus laptop running JRiver Media Center and sending music via USB to an Abbingdon Music Research DP-777 D/A converter, whose excellent analog preamp section drives my McAlister OTL-195 monoblocks. I also use Purity Audio’s Silver Statement preamplifier. My loudspeakers were Dynaudio Sapphires and Meadowlark Heron i’s, connected with Grover Huffman and Sound Design Labs speaker cables. Stealth interconnects run between the DP-777 or Silver Statement and the McAlisters, and to my ASR Mini Basis phono preamp. All components are plugged into a Sound Design Labs power conditioner with Loyalty Nickel power cords.
The NSL did some things I’ve heard no other amplifier do. Then again, I’d never heard a power amp based on op-amps. No amplifier I’ve heard, whether tube or solid-state, has sounded as lifelike or as real as the NSL did. The palette of tonal colors with which it painted sonic portraits was breathtaking.
The NSL sounded tonally neutral -- not warm or cold, not tubey or etched or detailed. Rather, its “sound” was determined by the music I played. You want to talk about fast transient response? The NSL was honest and true, and made other amps, especially those I thought were leaders in this area -- from the Linn Klimax to the Spectral DMA series -- sound artificial. Nor was the NSL only about finesse -- it was easily one of the most powerful-sounding amplifiers I’ve had in my system, or have heard in most of my audiophile friends’ systems. I’ve been trying to reconcile this observation ever since Gilbert Yeung hooked up the NSL. It has produced some of the deepest bass I have yet to hear from an amplifier. Again and again I’ve asked myself, “Did I hear what I just heard, and with only 28Wpc?” Each time I had to conclude that that was exactly what I’d heard.
Another memorable thing about the NSL was how it handled high-frequency information. Cymbals sounded so real. It didn’t matter if the source was LP, CD, or download -- drumsticks hitting cymbals or drum rims struck a chord with my ears, so real and natural was their sound. Same for the reverberation and decay of struck triangles, and hall sounds in live recordings.
Before her popularity took off following last year’s Grammy Awards, in which she was named Best New Artist, double bassist and singer Esperanza Spalding had caught music lovers’ attention with her first album, Junjo (CD, Ayva Musica 36). Junjo is remarkable in that the music is clearly smooth, but not in an elevator-music way. Spalding’s quiet, laid-back style is at the same time full of an energy that goes along with her smoothness. Though her voice is soft, she even scats a little on several tracks. She makes such classic tunes as Chick Corea’s “Humpty Dumpty” and Jimmy Rowles’s “The Peacocks” her own. Through the NSL, the sounds of Spalding snapping her bass’s strings, the transients of her fingers sliding up and down those strings, and the inner details of drummer Francisco Mela’s playing, were all outstanding in their fidelity.
A visiting friend left behind a copy of Gretchen Parlato’s The Lost and Found (CD, ObliqSound 113). I’ve found it to be a revelation. Parlato’s way with a song is so intimate that she seems to be singing only for me. She runs the gamut on this disc, from the R&B-tinged “All That I Can Say” to the Brazilian-styled “Alô, Alô.” The NSL did a good job of pulling out a large amount of detail and musical information -- I was able to follow Parlato’s distinct vocal tone and phrasing. In the same vein is Amel Larrieux -- she wields her strong voice mellifluously and melodically, and her Infinite Possibilities (CD, 550 Music/Epic 69741) shows off her vocal range. I’m more partial to her slower, more ballad-like songs, such as “Sweet Misery,” than to up-tempo numbers like “Get Up.” Larrieux does a lot with her voice, such as some overdubbing and soft moaning. The resolving ability of the NSL made these subtleties very easy to hear and follow.
Another interesting album is Hot Club of Detroit (CD, Mack Avenue 1030). The group has two (sometimes three) guitarists, a bass, a clarinet and an accordion. Their sound is strongly and unsurprisingly reminiscent of that of Django Reinhardt’s Hot Club of France, and they cover several Reinhardt tunes here. The Detroit band’s niche is European music of the early 1930s and ’40s -- when I hear it, I feel magically transported to that time and place. The NSL made it easy to follow each player, revealing each in his own air and space and unique tonal structure, especially the guitarists. Paul Brady, and particularly Evan Perri, play so much like Reinhardt that I’m almost convinced that the great Gypsy guitarist has been reincarnated.
Further thoughts and comparison
It’s one thing to be able to make an amplifier with the wonderful sound of the Blue Circle NSL. It’s another thing altogether to ask $19,500 for an amp that generates only 28Wpc into 8 ohms.
If you look at all the $15,000-and-up amplifiers on the market, most look pretty much formulaic on the inside: they’re all laid out pretty much the same. You see transformers, power-supply capacitors, rails on either side, transistors running from front to back, and wires leading to the outputs. But the NSL’s rear third is filled, top to bottom, with two towers of circuit boards holding nothing but those 288 op-amps. That represents a lot of detailed and fastidious work, and such work comes at a cost. The NSL operates in very low bias class-AB, and never came close to running warm while in my system. In some of my listening sessions I played house music, Euro-techno, and Middle Eastern electronic music for two to three hours, and the NSL got only lukewarm. I caution listeners not to mate it to other electronics that aren’t up to the NSL’s sound quality. I hooked it up to preamps such as Blue Circle’s own BC109 ($7000) and the Herron VTPH-2 ($3650). The sound was good, but nowhere near where it could have been. When I swapped out those preamps for my Purity Audio Silver Statement ($20,000), the sound reached much higher levels of musicality, fidelity, and bass dynamics -- levels I otherwise would not have known were possible. The NSL deserves to be used with the best gear available -- it won’t be embarrassed.
I compared the Blue Circle NSL with my McAlister OTL-195 monoblocks ($8500/pair). The McAlisters are very dynamic and musical, very powerful at 195W, and have never made me wish I owned something else. When I restored the McAlisters in my system, after listening to the NSL for a month, I thought they were broken. I wondered what happened to the sound. I was on my hands and knees a good hour, checking out everything, trying to find what I’d done wrong to lose out on the music reproduction I’d been enjoying. Then I reinstalled the NSL.
Everything was right again. The NSL’s highs were more extended, its bass went deeper and with more authority, instruments and singers sounded eerily real. Overall, music was just more enjoyable with the NSL than with my McAlisters, and that was hard for me to admit -- the OTL-195s have always made other amps I’ve listened to sound not as musically involving as themselves. But the NSL was much better overall.
Is the Blue Circle Audio NSL a world beater? I don’t know how well it would work with 4-ohm speakers. Neither the Meadowlark Heron i nor the Dynaudio Sapphire, both 6-ohm models, presented a difficult enough load for me to be able to say that the NSL won’t be all things for everyone. However, I can say with confidence that if you have speakers that it can drive, the NSL will be a revelation of just how wonderful music can sound, rewarding you with making your music sound special in ways you probably haven’t heard from your system. The NSL was one of the best-sounding power amplifiers I have ever heard. I give it my highest recommendation.
. . . Michael Wright
- Speakers -- Meadowlark Heron i, Dynaudio Sapphire
- Sources -- Abbingdon Music Research DP-777 DAC
- Preamplifier -- Purity Audio Design Silver Statement
- Amplifiers -- McAlister Audio OTL-195 monoblocks
- Interconnects -- Stealth Audio Cables
- Speaker cables -- Sound Design Labs
- Power cables -- Loyalty Nickel
- Power conditioner -- Sound Design Labs
- Accessories -- Epiphany Stand Systems Celeste Reference equipment stand
Blue Circle Audio NSL Stereo Amplifier
Price: $19,500 USD.
Warranty: Three years parts and labor.
Blue Circle Audio
Innerkip, Ontario N0J 1M0
Phone: (519) 469-3215
Fax: (519) 469-3782