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[h=1]Conrad-Johnson ARTsa stereo power amplifier[/h] Equipment+
by Alan Sircom | Aug 23, 2013
Categories: Tubed power amplifiers | Products: Conrad Johnson ART sa
Back in the mid 1990s, the high-end valve power amplifiers to own were the conrad-johnson Premier 8a monoblocks. Commonly considered to be the most musical amplifiers of their generation, the Premier 8a still commands respect and high prices to this day. At the time, the idea of a stereo Premier power amplifier was simply never put forward, and those lacking either the physical space or the financial commitment for the mono amplifiers never got to experience just what c-j at its best was capable of.
The company learned its lesson. The big ART monoblock amplifiers have a ‘little’ brother, the ARTsa. In many respects, the 140 watt per channel (rated into four ohms) stereo amplifier is in the sweet spot, especially for European listeners, because it isn’t two large chassis, we seldom require more than 250 watts in our smaller rooms and because it isn’t north of £36,000 a pair. We felt this is the more comfy place for Hi-Fi Plus’ audience.
The two models look virtually identical from the front, because there is a lot of common ground between ART and ARTsa (the ARTsa being an single mono ART split into two channels, requiring an extra input driver tube and a second set of inputs and outputs). It may sound strange when discussing amplifiers costing tens of thousands of pounds, but this shared chassis layout helps keep costs down. The chassis is a substantial affair, finished in a deep matt black crackle finish, with the distinctive contrasting gold front panel. The input tubes are encased in a lattice of acrylic wedges, while the four KT120 power tubes per side are each enclosed in their own cover, leaving an almost inch-wide channel down the centre of the top-plate from the end of the input triodes to the beginning of the transformer cover. The net result is actually very attractive in a sort of low modernist architecture style; think what Alvar Aalto or Mies van der Rohe would have done with an amplifier chassis. The one grumble (common to all c-j power amps) is that in order to keep those elegant lines, the power valve covers use spring-loaded chromed screws to secure the cover from the inside, and it’s something of a dark art to learn how to do this without swearing.
Bias, as ever with c-j designs, is adjusted using a small screw and orange LED arrangement; once the amplifier has settled down for half an hour or so, adjust the bias screws on each tube until the LED goes out. It’s a good idea to periodically – but not obsessively – recheck this every few months, because like baggage in the overhead locker, these things can move around in the journey. It’s a simple, but effective method, although like all bias adjustment screws, it’s designed to be a little fiddly, because you don’t want little hands armed with screwdrivers rebiasing an octet of expensive tubes.
It’s the electronic expression of Occam’s Razor: “entities must not be multiplied beyond necessity”. It applies to negative feedback (just 12dB overall, to help linearity and increase the damping factor for today’s reactive speaker loads) and even to the whole circuit itself. It’s essentially just a voltage gain amplifier, direct coupled to a cathode-coupled phase inverter, which drives the output stage. Occam’s razor blunts slightly at the power supply stage; the amplifier sports individual, low impedance discrete DC power supply regulation for both input and phase-inverter, keeping these sections completely isolated from the power feed to the output stage.
The ARTsa and ART are c-j’s flagship amplifiers, and as a consequence both bristle with ultra high-grade components on the circuit boards. Bill Conrad and Lew Johnson must be on Vishay’s Christmas card list, because the ARTsa is packed full of the things, and the same applies to the use of its own CJD Teflon caps, custom built for the company. They are everywhere, and the word ‘electrolytic’ is clearly banned from the ART production line. Even the power supply sports CJD Teflons, in parallel with large polypropylenes. If you add in the cost of those wide-bandwidth transformers, the chassis and even the cost of the terminals and wiring loom and the tubes themselves, the Bill of Materials entailed within every ARTsa is damn substantial.
Whether it’s those components or the circuit itself is unclear, but the result of all this is uncanny, even before you play a piece of music. This is the quietest amplifier I’ve come across. Note that I said ‘amplifier’ not ‘valve amplifier’. You really have to put your ear to the tweeter to begin to hear anything approaching ‘tube rush’, and solid-state designs I’ve used have all had greater self-noise than this. Other parts of the signal chain are noisier than the ARTsa, and this leads to those comedy ‘is this thing on?’ moments.
When you do power it up, and give it half an hour or so to come on song, staring at that quartet of hidden yellow LEDs that wrap around the big front power button in the process, chances are you won’t be spending too much time discovering the absence of background noise. You’ll instead be spending a vast amount of time just enjoying your music collection. The ARTsa has a strange and wonderful effect, the ‘rediscovering your music’ cliché doesn’t apply here. You listen to a piece of music, then reflect on that piece of music, and play another piece of music. Rather than pulling out disc after disc after disc, you kind of know what improvement is on the cards with each piece of music and instead concentrate on the music itself.
The midrange has a quality that is hard to pin down. It’s not liquid, it’s not fluid, it’s sort of at once fruity, yet fast, in the way amplifiers like the Premier 8a always used to be so great at. Perhaps the best track to highlight this is ‘Lazarus Man’ by the late Terry Callier. The performance is sublime in it’s own right, but played through the ARTsa is like direct-coupling the disc to your emotions. The amp gave a sense of a performance, right from the outset, rather than just a band coming in over the sound of water in the background. It’s interesting to hear good recordings, but not the sort of audiophile approved tracks, to see just how good an amplifier like this will behave under realworld conditions, and it works exceptionally well. Curiously on this track, the vocals are back in the mix with the guitars in the foreground. This can fox many systems, either detracting the vocal or overstating the guitar parts. That fast and fruity sound gives everything the right sense of weighting. Callier’s voice is still back in the mix, but it’s an organic part of the recording, not fighting for position.
We are in a state of transition, moving from spinning disc to file-based music replay, and the biggest pocket of resistance to this transition is in the high-end. And often for good reason – many of the best disc spinners are still uncommonly difficult to better in the post-disc domain. The ARTsa eases that transition; not because it smothers the differences, but because it turns your attention away from the differences in file format and back on to the music. Yes, you can here why someone who bought a Zanden or a Metronome or similar is still playing discs through their top-end player, but it also shows how file-based music can sound… and it sounds better than many imagine.
This is the kind of music replay that also befits all genre. It doesn’t suffer from that audiophile disease of ‘slowing under Tool’ – play Lateralus by that well-recorded heavy band and the sound remains just as tight when things get all dropped-D graunchy as it does when it’s all moody chorus pedal and moaning about blood-letting. There’s a distinct drum anchor that is easy to mess up. The drummer Danny Carey is one of the best in the business and some supposedly good systems reduce his playing to something metronomic or bland. This doesn’t. It makes him sound properly.
Similarly, there’s a tendency when dealing with dub lines for the bass line to dominate the presentation at the expense of the mid and top. Not here. Everything has its own space and energy, no matter how complex or deep somethings get. It unveils insights into recordings you know well. Strangely, I’m reminded of those classic little valve amps from British companies of the 1950s and 1960s, only writ large. If you ever wanted to know what a Leak Stereo 20 would have sounded with seven times the power, more resolution and full 20Hz-20kHz bandwidth, the ARTsa is the amp to do it. And compared to what we can do today, those classic Leaks and Quads are found wanting at the frequency extremes (especially the top-end) and in the power delivery stakes. They also made that sweet sound at the expense of some dynamic range and clarity of presentation. None of which detracts from what they do best, but the ARTsa also does what they do best, with none of the downsides. It’s a truly captivating presentation.
In short, the ARTsa gives a presentation that is effortless, simply effortless. It gives effortless dynamics, effortless flow, refinement, sophistication and elegance to the sound. There was simply nothing that could trip it up. It had all the bottom-end grip of a solid-state amp, and even when presented with something truly excellent to get its teeth into (like ‘Un Bal’ from the Munch/BSO Symphonie Fantastique on classic Living Stereo SACD) and enough power in reserve to cope with some dub and dubstep without complaint. It’s perhaps not the first choice for those who only listen to heads-down rock, because they would trade that musical flow for sheer speed of attack, but anyone with more catholic tastes than just a one-genre fan will find the ART sa an excellent performer.
With great power, comes great responsibility. The ARTsa’s magic spell comes at a cost. It’s so resolving that unless the rest of your system is absolutely Shipshape and Bristol fashion, it will make a fair to good sound, but not a great one. This is the destination, not the journey; use this with the superb c-j GAT preamp or similar, good intrinsically neutral choices of cable and good source material and more, and the amplifier will play an enticing and irresistible sound. Play it through a work-in-progress, mid-way through the upgrade path and you’ll find yourself upgrading faster or listening to less music. So, this could be the last product you buy, not only in a round of upgrades, but also in terms of it being the sort of amplifier you could comfortably live with for decades.
That was always c-j’s big strength; although there is always a brisk trade in ‘preloved’ c-j preamps and power amps, the amps are often ‘keepers’ in people’s systems. They make a sound that invites you deeper into the music. But none more so than the ARTsa. It joins a range that points to that harmonically beguiling place the best of all c-j amps always took you, but without any of the lushness or softened leading edges the amps could descend into. Calling this amp the Premier 8a of the 21st Century is a massive compliment, but the ARTsa is so much more than that. This must be heard, as it joins the GAT as one of the world’s best.
Only problem is, now I want to know what the monoblocks sound like and, for that matter, the forthcoming LP125M and LP125sa amps below it. I think its going to be a great year ahead!
Technical specifications
Power: 140 watts per channel from 30
Hz to 15 KHz at no more than 1.5 % THD
or IMD, both channels driven into 4, 8 or
16 ohms (standard setting is four ohms)
Sensitivity: 1.8V to rated power Frequency
Response (at 10 watts): 20 Hz to 20 kHz,
+/- .25 dB
Frequency Response (at 10 watts): 20
Hz to 20 kHz, +/- .25 dB
Hum and Noise: 108dB below rated power
Input Impedance: 100 kOhms
Tube Complement: 1 x 6189, 2 x 6N30P,
8 x KT120
Dimensions (WxHxD): 48.3x18.1x47.6cm
Weight: 37.2kg
Price: £18,995
Manufactured by: conrad-johnson
Design Inc
URL: www.conradjohnson.com
Distributed by: Audiofreaks
URL: www.audiofreaks.co.uk
Tel: +44(0)208 948 4153
by Alan Sircom | Aug 23, 2013
Categories: Tubed power amplifiers | Products: Conrad Johnson ART sa
The company learned its lesson. The big ART monoblock amplifiers have a ‘little’ brother, the ARTsa. In many respects, the 140 watt per channel (rated into four ohms) stereo amplifier is in the sweet spot, especially for European listeners, because it isn’t two large chassis, we seldom require more than 250 watts in our smaller rooms and because it isn’t north of £36,000 a pair. We felt this is the more comfy place for Hi-Fi Plus’ audience.
The two models look virtually identical from the front, because there is a lot of common ground between ART and ARTsa (the ARTsa being an single mono ART split into two channels, requiring an extra input driver tube and a second set of inputs and outputs). It may sound strange when discussing amplifiers costing tens of thousands of pounds, but this shared chassis layout helps keep costs down. The chassis is a substantial affair, finished in a deep matt black crackle finish, with the distinctive contrasting gold front panel. The input tubes are encased in a lattice of acrylic wedges, while the four KT120 power tubes per side are each enclosed in their own cover, leaving an almost inch-wide channel down the centre of the top-plate from the end of the input triodes to the beginning of the transformer cover. The net result is actually very attractive in a sort of low modernist architecture style; think what Alvar Aalto or Mies van der Rohe would have done with an amplifier chassis. The one grumble (common to all c-j power amps) is that in order to keep those elegant lines, the power valve covers use spring-loaded chromed screws to secure the cover from the inside, and it’s something of a dark art to learn how to do this without swearing.
Bias, as ever with c-j designs, is adjusted using a small screw and orange LED arrangement; once the amplifier has settled down for half an hour or so, adjust the bias screws on each tube until the LED goes out. It’s a good idea to periodically – but not obsessively – recheck this every few months, because like baggage in the overhead locker, these things can move around in the journey. It’s a simple, but effective method, although like all bias adjustment screws, it’s designed to be a little fiddly, because you don’t want little hands armed with screwdrivers rebiasing an octet of expensive tubes.
It’s the electronic expression of Occam’s Razor: “entities must not be multiplied beyond necessity”. It applies to negative feedback (just 12dB overall, to help linearity and increase the damping factor for today’s reactive speaker loads) and even to the whole circuit itself. It’s essentially just a voltage gain amplifier, direct coupled to a cathode-coupled phase inverter, which drives the output stage. Occam’s razor blunts slightly at the power supply stage; the amplifier sports individual, low impedance discrete DC power supply regulation for both input and phase-inverter, keeping these sections completely isolated from the power feed to the output stage.
The ARTsa and ART are c-j’s flagship amplifiers, and as a consequence both bristle with ultra high-grade components on the circuit boards. Bill Conrad and Lew Johnson must be on Vishay’s Christmas card list, because the ARTsa is packed full of the things, and the same applies to the use of its own CJD Teflon caps, custom built for the company. They are everywhere, and the word ‘electrolytic’ is clearly banned from the ART production line. Even the power supply sports CJD Teflons, in parallel with large polypropylenes. If you add in the cost of those wide-bandwidth transformers, the chassis and even the cost of the terminals and wiring loom and the tubes themselves, the Bill of Materials entailed within every ARTsa is damn substantial.
Whether it’s those components or the circuit itself is unclear, but the result of all this is uncanny, even before you play a piece of music. This is the quietest amplifier I’ve come across. Note that I said ‘amplifier’ not ‘valve amplifier’. You really have to put your ear to the tweeter to begin to hear anything approaching ‘tube rush’, and solid-state designs I’ve used have all had greater self-noise than this. Other parts of the signal chain are noisier than the ARTsa, and this leads to those comedy ‘is this thing on?’ moments.
When you do power it up, and give it half an hour or so to come on song, staring at that quartet of hidden yellow LEDs that wrap around the big front power button in the process, chances are you won’t be spending too much time discovering the absence of background noise. You’ll instead be spending a vast amount of time just enjoying your music collection. The ARTsa has a strange and wonderful effect, the ‘rediscovering your music’ cliché doesn’t apply here. You listen to a piece of music, then reflect on that piece of music, and play another piece of music. Rather than pulling out disc after disc after disc, you kind of know what improvement is on the cards with each piece of music and instead concentrate on the music itself.
The midrange has a quality that is hard to pin down. It’s not liquid, it’s not fluid, it’s sort of at once fruity, yet fast, in the way amplifiers like the Premier 8a always used to be so great at. Perhaps the best track to highlight this is ‘Lazarus Man’ by the late Terry Callier. The performance is sublime in it’s own right, but played through the ARTsa is like direct-coupling the disc to your emotions. The amp gave a sense of a performance, right from the outset, rather than just a band coming in over the sound of water in the background. It’s interesting to hear good recordings, but not the sort of audiophile approved tracks, to see just how good an amplifier like this will behave under realworld conditions, and it works exceptionally well. Curiously on this track, the vocals are back in the mix with the guitars in the foreground. This can fox many systems, either detracting the vocal or overstating the guitar parts. That fast and fruity sound gives everything the right sense of weighting. Callier’s voice is still back in the mix, but it’s an organic part of the recording, not fighting for position.
We are in a state of transition, moving from spinning disc to file-based music replay, and the biggest pocket of resistance to this transition is in the high-end. And often for good reason – many of the best disc spinners are still uncommonly difficult to better in the post-disc domain. The ARTsa eases that transition; not because it smothers the differences, but because it turns your attention away from the differences in file format and back on to the music. Yes, you can here why someone who bought a Zanden or a Metronome or similar is still playing discs through their top-end player, but it also shows how file-based music can sound… and it sounds better than many imagine.
This is the kind of music replay that also befits all genre. It doesn’t suffer from that audiophile disease of ‘slowing under Tool’ – play Lateralus by that well-recorded heavy band and the sound remains just as tight when things get all dropped-D graunchy as it does when it’s all moody chorus pedal and moaning about blood-letting. There’s a distinct drum anchor that is easy to mess up. The drummer Danny Carey is one of the best in the business and some supposedly good systems reduce his playing to something metronomic or bland. This doesn’t. It makes him sound properly.
Similarly, there’s a tendency when dealing with dub lines for the bass line to dominate the presentation at the expense of the mid and top. Not here. Everything has its own space and energy, no matter how complex or deep somethings get. It unveils insights into recordings you know well. Strangely, I’m reminded of those classic little valve amps from British companies of the 1950s and 1960s, only writ large. If you ever wanted to know what a Leak Stereo 20 would have sounded with seven times the power, more resolution and full 20Hz-20kHz bandwidth, the ARTsa is the amp to do it. And compared to what we can do today, those classic Leaks and Quads are found wanting at the frequency extremes (especially the top-end) and in the power delivery stakes. They also made that sweet sound at the expense of some dynamic range and clarity of presentation. None of which detracts from what they do best, but the ARTsa also does what they do best, with none of the downsides. It’s a truly captivating presentation.
In short, the ARTsa gives a presentation that is effortless, simply effortless. It gives effortless dynamics, effortless flow, refinement, sophistication and elegance to the sound. There was simply nothing that could trip it up. It had all the bottom-end grip of a solid-state amp, and even when presented with something truly excellent to get its teeth into (like ‘Un Bal’ from the Munch/BSO Symphonie Fantastique on classic Living Stereo SACD) and enough power in reserve to cope with some dub and dubstep without complaint. It’s perhaps not the first choice for those who only listen to heads-down rock, because they would trade that musical flow for sheer speed of attack, but anyone with more catholic tastes than just a one-genre fan will find the ART sa an excellent performer.
With great power, comes great responsibility. The ARTsa’s magic spell comes at a cost. It’s so resolving that unless the rest of your system is absolutely Shipshape and Bristol fashion, it will make a fair to good sound, but not a great one. This is the destination, not the journey; use this with the superb c-j GAT preamp or similar, good intrinsically neutral choices of cable and good source material and more, and the amplifier will play an enticing and irresistible sound. Play it through a work-in-progress, mid-way through the upgrade path and you’ll find yourself upgrading faster or listening to less music. So, this could be the last product you buy, not only in a round of upgrades, but also in terms of it being the sort of amplifier you could comfortably live with for decades.
That was always c-j’s big strength; although there is always a brisk trade in ‘preloved’ c-j preamps and power amps, the amps are often ‘keepers’ in people’s systems. They make a sound that invites you deeper into the music. But none more so than the ARTsa. It joins a range that points to that harmonically beguiling place the best of all c-j amps always took you, but without any of the lushness or softened leading edges the amps could descend into. Calling this amp the Premier 8a of the 21st Century is a massive compliment, but the ARTsa is so much more than that. This must be heard, as it joins the GAT as one of the world’s best.
Only problem is, now I want to know what the monoblocks sound like and, for that matter, the forthcoming LP125M and LP125sa amps below it. I think its going to be a great year ahead!
Technical specifications
Power: 140 watts per channel from 30
Hz to 15 KHz at no more than 1.5 % THD
or IMD, both channels driven into 4, 8 or
16 ohms (standard setting is four ohms)
Sensitivity: 1.8V to rated power Frequency
Response (at 10 watts): 20 Hz to 20 kHz,
+/- .25 dB
Frequency Response (at 10 watts): 20
Hz to 20 kHz, +/- .25 dB
Hum and Noise: 108dB below rated power
Input Impedance: 100 kOhms
Tube Complement: 1 x 6189, 2 x 6N30P,
8 x KT120
Dimensions (WxHxD): 48.3x18.1x47.6cm
Weight: 37.2kg
Price: £18,995
Manufactured by: conrad-johnson
Design Inc
URL: www.conradjohnson.com
Distributed by: Audiofreaks
URL: www.audiofreaks.co.uk
Tel: +44(0)208 948 4153
nice to see you here...Wizard put me on to the spot last nite. quite cool. Anyway, will be interesting to hear more about the CJ amps from Joe. Perfectly happy where I am with Gryphon Colosseum and the 'magic' I truly enjoy, but with the right speakers, I acknowledge that 'synergy' of matching the CJ GAT with their monos could bring its own 'magic'.