Copland CTA 408 Vacuum Tube Stereo Integrated Amplifier
It has been seven years since I reviewed the Copland CTA 506 Power amp which I liked very much at the time and is still available today. From my 2012 review of the CTA 506:
The Copland CTA 506 combines classic design with the latest developments in vacuum tubes to create an impressive and attractively priced power amp that seems equally at home across musical genres. It stands up well against the other power amps – tube and silicon based – that have been through my listening room. It doesn't pretend to be the last word in power amps, but it sits at a sweet spot in the market where you'll need to pay a lot more to eke out small performance gains in most systems. It's a looker, and it's a keeper too! You can read more about the CTA 506 here and here as well.
Now we have a new amp from Copland, the CTA 408 Integrated, to replace both the CTA 405A Integrated Amp (KT120 based – 50 Wpc) and the CTA 405 Integrated Amp (6550 based – 50 Wpc). This new CTA 408 is based on the KT150 power tube and offers 75 Wpc with an outstanding bandwidth of 5Hz to 100kHz (-3dB). This tube, the latest and biggest variant on the KT88 design, also features in a number of recent amps such as the ARC Reference 160M Monoblocks ($30,000 a pair), ARC VT80SE ($8900), the Jadis JA500 KT150 Edition and the Jadis JA80 Mk II.
A Look At Vacuum Tubes
KT88 / S5550 Beam Power Tetrode
KT90 Beam Power Tetrode
KT120 Beam Power Pentode
KT150 Beam Power Tetrode
A new KT150 tube will cost you just under $100 but you should really buy them in matched sets of four. You should expect exceptionally long tube life (over 4000 hours) because of two factors – the very gentle power-on sequence in this CTA 408 amp, and the low stress level in this circuit design. The tubes are operated around 50% of their full normal power. Other manufacturers may rate their KT150 based amps at over 100wpc. This tells you a lot about Copland's approach. They want to give you a product that is rock solid rather than finicky, fully enclosed rather than putting bare glass out there to burn any passing kid or pet, and they also want to give you a musical sound with no hint of tubeyness, if there is such a word.
By that I mean the even order harmonic distortions are kept at low levels and the frequency response curve is held essentially flat well outside the bandwidth of many competing tube amps. Copland has deliberately traded maximum output level for responsiveness and longevity. I also commend Copland on the noise level in terms of hum and hiss. Even at maximum volume I could detect only the lowest levels of either at the speaker, although there is a low mechanical buzz that can easily be heard if you stand close to the amp. Fortunately, this noise is independent of volume level and unnoticeable at any reasonable listening position.
Copland's CTA 405 has a slatted front plate design so you can just see the four large KT150 tubes inside as well as the two 6072A/12AY7 tubes and the two 128H7 tubes, but don't sit the amp on the floor as I did or you will miss this impressive sight and the lovely warm glow that comes with it. The front panel has a large round display which indicates which input is in use and the power status of the amp. One large knob on the right adjusts volume, and a similar knob on the left controls input. There are also two smaller buttons – one for a Tape Loop and the other to switch between power on and standby. You can use the simple remote if you prefer, but I found the front dial a lot easier to make small volume adjustments with, and it has a really smooth action that spells quality.
The back panel offers four line level inputs, all unbalanced, tape in and tape out, plus a phono input which can be set to moving coil or moving magnet with an impedance load switch for moving coil cartridges. Copland paid special attention to the J-FET based phono-amplifier, using active RIAA equalization and employing over 100 discrete components in a noise shielding box. Sadly, with my latest move, my vinyl days are behind me so I didn't get to try out the phono section. The driver section of the amp uses MOSFETs to control the tubes, while the massive output transformers are designed in-house specifically to support a full bandwidth without saturation. There are multiple independent power supplies designed to operate with constant power.
The CTA 408 has output taps for 4 Ohms and 8 Ohms. It's best to experiment with these rather than just use the speaker's nominal impedance rating. I found Totem's The One worked best on the 8 Ohm tap and the YG Hailey 2.2 much preferred the 4 Ohm tap. Unusually, there is also a connector on the right side panel, close to the front. This is for your headphones, and if you connect your phones in here, the speaker outputs are automatically muted. The discrete silicon-based Class A headphone amp takes over. All the connectors and switches are to a high standard – Copland does not cut corners.
I fed the Copland with an EMM Labs digital front end – the XDS1 SACD Player, used as a transport, and the new DV2 DAC at full volume (it has variable output) using Nordost Valhalla 2 unbalanced interconnects, all power and speaker cables also being Valhalla 2.
After giving the Copland a couple of hundred hours of burn in, I sat down to listen. First up – headphones. Here my results were mixed. The Copland struggles with my Sony MDR-Z1R phones (impedance 64 ohms) offering restricted dynamics and no real sense of musical drive. But it worked like a charm with the Sennheiser HD800 with their 300 Ohm impedance. So careful matching will be required. With the Sennheisers, phones that require quite a lot of juice to really get going, music got its boogie back, backgrounds were silent and while a little on the dark side, they imaged well and revealed a lot of detail.
But you don't buy a powerful integrated amp just to listen to phones, so let's move on to speakers. I recently reviewed a pre-power pair that costs more than twice the Copland's list but with similar specifications. That combination fared so poorly next to the Soulution 511 Power Amp and the variable output of the EMM Labs DV2 that I was afraid this relatively inexpensive integrated would also prove a disappointment. I'm happy to report that if you take care to select the best output impedance for the speakers you are using, and you don't try using it with extremely inefficient speakers (say less then 84dB/W/m) or play extremely loud, the Copland CTA 408 is a very capable and musical amplifier, and a pleasure to use.
Those caveats are important. The 8 Ohm tap with the Hailey 2.2 did not survive loud crescendos without losing all the inner detail, while the 4 Ohm tap with the Totem lacked the powerful base this small speaker is capable of. (Even worse was when I connected one channel in reverse polarity. I must have been having a bad day.) My listening observations will only cover the properly set-up configurations of course.
The distributor, Tash Goka of Divergent Technologies, was worried about the ability of this 75 Wpc amp to drive a big low impedance speaker like the YG Hailey 2.2. But I knew the Hailey 2.2 involved a redesign from the earlier Hailey 1.2 which made it considerably easier to drive in terms of phase angles and current draw. In practice there were simply no problems that I could detect, and I had no problems either with the much smaller Totem The One. The Totem spec reads 4 Ohms nominal impedance and 87dB/W/m sensitivity, very close to the Hailey 2.2, and this requires an amplifier with balls, which the CTA 408 clearly has.
To Start With...
There's a recording I've given a lot of air time to recently, because I've found it can easily sort the sheep from the goats. On the AliaVox label [AVSA9916 SACD], it features Jordi Savall conducting Le Concert Des Nations (an orchestra of 46 musicians playing on original instruments) in powerful performances of Beethoven in a 1994 recording made in the College of Cardona Castle. The last track on this disc is the Coriolan Overture, seven and a half minutes of dynamism and raw power in the right hands and on the right equipment. There is an explosive chord that I have never heard fully resolved until I recently paired the Hailey 2.2 with the Soulution 311 Power Amp. Everything else has wimped out in some way.
Either the peaks were compressed or the individual instruments became confused and lost their timbre, or the details were shot to hell. It's just too much for any speaker I suspect, especially for the tweeter. But the Hailey 2.2 has the new Billet Dome tweeter, massively expensive and remarkably capable, which can resolve such extremes without sweating, and will expose precisely how well the DAC and amplifier manage the same tough task. The Copland CTA 408 does not sound the same as the über-expensive Soulution 311. It doesn't throw that big an image, and its overall dynamics are not so wide, but what it does do is to maintain its composure and sound entirely consistent with its color and detail at less extreme points in the music. It doesn't flinch, it fully resolves the peak waveforms without collapsing the image, smearing the detail or compressing.
This is a very tough test and it passes with flying colors. Incidentally, if you have superb equipment, I would recommend this CD to you. It includes a remarkable version of the Eroica Symphony. I was extremely fortunate to have dinner with Jordi Savall last year in Toronto, and the warmth, understanding and passion you will hear in this recording exactly matches the man I met. Each new Jordi Savall recording, often tackling music that has been neglected for hundreds or thousands of years, is recorded to the highest standards and released in book format in SACD to stand as a testament for the future. We should be most grateful. Who else is taking such care for posterity?
So much for one powerful moment. Why is this so important? Because if you can reproduce this, with its sudden high intensity attack, maintaining a rich blend of gut stringed instruments with natural decay, then you can probably reproduce anything. And so I found, as I ran through recording after recording.
There is a remarkable new recording by Rachel Podger of Bach's Cello Suites transcribed to the violin [Channel Classics CCS SA 41119]. The transcription is entirely successful, the playing in a class of its own, and the DSD recording is quite extraordinary. The Hailey and the CTA408 gave suitable weight and a fully open sound so that the recording could be enjoyed to the full. The image is large but visceral and tangible. The Totem did not quite scale these heights, lacking the presence and detail of the bigger speaker. It was on this recording I tried the 4 ohm tap with the Totem and I didn't like the results at all. The violin sounded thinner and more distant, losing the excitement I felt on the 8 ohm tap. In fact, I couldn't listen to more than a few minutes without fatigue setting in. So be very careful with your speaker matching on this type of upper-register recording.
That the YG Hailey 2.2 sounded so good has nothing to do with its size, for the Totem is perfectly capable of reaching the violin's lowest registers. It is the superb tweeter in the Hailey 2.2, one that must cost more to make than a pair of Totems speakers, that must take most of the credit here. Gut strings and all, it's no problem for me to listen to all six suites in a single session without suffering any hint of strain. The CTA408 brings rich color, rock stable imaging and sharp reflexes to this music. Yes, the Soulution gives a more solid sound still, with richer detail and a greater sense of ease to the music making, but at a small fraction of the Soulution's price the Copland's showing is very strong.
A number of years back, I heard Bela Fleck playing with the Marcus Roberts Trio in Toronto's beloved Koerner Hall. The music sounded at once familiar and really punchy. It sounded so familiar I thought they must be playing standards. But in fact, all the music was freshly composed by Fleck and Roberts for their album Across The Imaginary Divide [Rounder 11661-9142-2]. I can't recommend this disc highly enough, especially the title track. Rodney Jordon is the brilliant bassist, but it's hats off to the amazing Jason Marsalis on drums for his effortless and highly individual contributions that raise this album, and the concert I attended, to a ten.
To reproduce the infectious atmosphere on this disc you need an amp that swings, tremendously fast reflexes and strong sustain, with the ability to keep each instrument in focus when all four are playing separate lines. The CTA408 can do this, with the black spaces between the notes bringing the band into the sharpest focus. No hint of strain here with either set of speakers, and this time the Totem was in its element, living up to its reputation as a giant killer among small speakers.
There's a huge variety of music, and also quality of music, on the classic White Album by the Beatles. Now remixed by George Martin's son Giles, the double album, more accurately titled The Beatles, has never sounded better. In fact, it's never sounded this good. The CTA408 does just as well here as on the jazz disc of Fleck and Marcus. Again, the imaging is a little shallower than the Soulution 511, the dynamics a little more restrained and the inner detail not so complete, but you don't notice these limitations unless you do some careful A/B switching. The power and the beauty of the music comes through without distortion, and without the image collapsing at dynamic peaks (try Why Don't We Do It in The Road or Back in the U.S.S.R). Paul's big bass lines are clean and strong and seem to go as deep as you could wish, even on the little Totems.
At $10,000 I would say this splendid and imposing amplifier is well priced. But it isn't $10,000 – it's just $7999 and for that price the Copland CTA408 represents a great value. As with any tube amp, just be sure to audition it with your speakers to make sure they are a good match for each other.
Conversation With Copland's Founder Olé Möller
Olé: There are in general two ways of biasing tube amplifiers – Fixed Bias and Cathode Bias. These terms for biasing are somehow confusing. The CTA408 amplifier is a Fixed Bias type amplifier. Fixed Bias actually means that the bias is adjustable. In a Fixed Bias tube amplifier, the bias is adjusted and fixed to a suitable level, it then stays the same until you adjust it again. Inside the CTA408 there are four adjustments – one for each power tube. In a Cathode Biased amplifier, there are usually no user adjustments, the negative grid bias is accomplished by lifting the potential of the cathode using a resistor in series with the cathode. In that way, the grid bias varies according to the size of the resistor and the current through the tube (also called Auto-Bias).
In Cathode Biased output stages, the cathode resistors usually have an electrolytic capacitor in parallel, in order to prevent local AC feedback at this point in the amplifier. The Cathode Bias amplifiers, along with some of its more modern variants using IC servos, can have a sonic tendency towards compression and muddy bass, like other types of DC-servos in audio circuitries. The Fixed Bias type amplifier is usually more power efficient with less compression and deeper, tighter, and free flowing bass reproduction.
Phil: How do you provide long tube life and protect the amp against overload?
Olé: The startup sequence of the many power supplies in CTA 408 is arranged with the aim to minimize stressing the tubes. Furthermore, a safety circuitry protects the power tubes from overvoltage / arcing in the output transformers primary and connected components.
Phil: Any comments on the review?
Olé: I am glad that you recognize the CTA 408 as a fuss free design. Many Scandinavians favor a look that is uncomplicated and naturally bound. Maybe this is a result of the protestant puritanism upon which our culture is built. Although Copland focuses mainly on tubes as active devices in the amplifiers, it has never been my intention to obtain a specific sound that could be related to the use of tubes. Fine amplifiers can be designed with tubes as well as solid stage. While listening, you should not easily recognize which method of design has been used.
Audio amplifiers are basically devices for amplifying voltage while matching impedances. Most theories behind this technology are well understood among audio engineers. However, reproduction of music is a complex field and several compromises are necessary in order for theory to be adopted by reality. The intelligent consideration behind these compromises is a central premise for an audio design to successfully deviate from the conventional.
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