History lessons may bore most of you, but some background is needed to understand the brain-rattling Silver Seven. A lesson in psychology wouldn't hurt either, because what we're looking at here is a response to hurt pride, or ego, or whatever it takes to drive a mass-market manufacturer to produce a four-chassis power amplifier clocking in at seventeen big ones.
Bob Carver, a wizard designer who can't decide whether he wants to be Albert Einstein or Cecil B. De Mille, has the high end in his blood. Founder of Phase Linear, Carver can take credit for being one of the first to manufacturer gigantic overkill transistor amplifiers. The seeds of cost-no-object high end took root in the late 1960s and early 1970s, and Phase Linear was a key player. But Bob's tenure with the company which bears his name has seen only the production of affordable products with no aspirations toward the high end, signified by a mix of genuine innovation and marketing excess. Indeed, some of the Carver notions are so bizarre as to border on the comical, but this hasn't stopped the company from selling many millions of dollars worth of hardware.
Carver has always enjoyed winding up the press with what are known as 'the Carver Challenges'. Three years ago, Bob took on the American high end community -- mainly in the pages of ¬Stereophile¬ -- by suggesting that he could make one of his more affordable amplifiers sound just like whatever cherished high-ender his critics cared to name. The technique he employed was what he calls 'Transfer Function Matching', in which the differences between an input signal and an amplifier's output are used to identify its 'sonic fingerprint'. By inverting an amplifier's output and summing it with the output of a second amplifier, the amplifier can be tweaked to sound like the first. If the two are absolutely identical, then a null will be created by complete cancellation. Any differences will be the distortions or by-products to be removed for tweaking the second amp to sound like the first amp.
Subjective tests followed, apparently supporting Carver's contention, but his victims were less than satisfied with what reached the shops. Stung by this, Carver decided to produce his
own cost-no-object 'statement', returning to what he has described in print as his true love: tubes.
Carver knows his target victims well enough to realize that what he needed to produce was an absolute mother of a tube amplifier which would offer the sound of the classics, the true greats, while being able to emulate the virtues of modern amplifiers in every respect. If it seems like Carver tailored the amplifiers to perform in such a way as to appease certain reviewers, well, that's probably the most pragmatic (if somewhat cynical) approach I've ever heard of as far as hi-fi design is concerned. On the other hand, if you, the reader, believe that Reviewer A is a knowledgeable and honest individual whose opinions are to be valued, then it also stands to reason that the designer who builds an amplifier to that reviewer's exact tastes has made what that reviewer genuinely considers to be a superlative product. In other words, forget the motive, which will always be to sell amplifiers and garner rave reviews (or vice versa). The proof is in the performance.
Carver's Silver Seven Mono Vacuum Tube Power Amplifier is described as a classic circuit benefitting from modern developments. Taking no chances, Carver has incorporated every
known tweak short of Beltism, so the end user need do nothing except install the amplifiers in the system.
The Silver Seven takes the form of two chassis per channel, including a massive power supply connected by a multi-core umbilical cord to an equally massive power amplifier. Starting from the ground up, each hand-rubbed, black lacquered chassis rests on four rubbery Simms Vibration Dampers, which in turn rest on polished granite anti-vibration bases; Carver is taking no chances here on mechanical interference causing microphony and you do save on Isoplats. The power supply chassis, measuring 252x452x245mm (wdh) including the feet and baseplate, sports a large needle-type meter on its front sloped panel, the meter monitoring tube condition.
The slope continues back toward the massive mains transformers, behind which lurk the fuses, the mains and umbilical leads and the on/off and stand-by switches. This is Ergonomic Failing No 1, because -- I don't care how purist you are -- these amps will not be left on at all times once you've experienced either the heat they generate or the way they set your electricity meter into overdrive. Having the switches on the front would make one's life a bit easier. The meter itself does diddly until something goes wrong, so I didn't get to see it dance. It does, however, look cute enough in its retro glory to have inspired Sony to put a similar meter on the front of their top-end amplifiers.
Switch-on from cold takes a good three or four minutes until the 'soft start' relays click and music emerges. At times when you wish to interrupt your listening sessions, you can switch the unit into stand-by; switching back on takes about one minute as the amp has been left 'idling'.
You'll know when the amps are on, believe me. Each 330x485x275mm (wdh) main chassis sports no less than ¬fourteen¬ 6550 output tubes, plus a 6550 as a voltage regulator; KT88s are an added-cost optional extra. A 12BY7 high-gain voltage amplifier pentode serves as the input valve and three paralleled 12BH7A power triodes drive the 6550s, completing the line-up. While the 1930s-mad-scientist styling may be aimed at securing a following in Japan, where such glorious kitsch has real cachet, seeing four chassis and 38 exposed valves is guaranteed to seduce ¬anyone¬ who ever looked at an out-of-date ¬Hi-Fi Yearbook¬ in a lustful manner.
Protecting the four input valves at the very front is a tiny barrier, to the right of which rests a gain control; the mains transformers reside at the back. Beneath these at the rear are two gold-plated input sockets, one for real-world pre-amps and one for pre-amps guaranteed not to leak DC. Playing it safe, I opted for the normal rather than the 'turbo' during the reviewing period, as I don't trust any hi-fi equipment, whatever the pedigree. The hot-rod input is labelled 'Lab Direct' and is DC coupled to the amplifier, while the 'Normal' input is AC coupled through a WonderCap. In a fit of bravery (or stupidity), I gave 'Lab Direct' a bash and will admit to experiencing a shade more transparency, but my cowardice soon had me reconnecting via
Although the 'Seven features automatic biasing, a bias switch on the back comes into play when the valves have aged to a point where the meter shows an idling current creeping above 0.6 amps. Switch to 'high bias' and you extend the life of the tubes, as the plate current will fall back to between 0.2 and 0.6 amps.
Ergonomic Failing No 2 is also found on the back, another touch of 'retro' in the form of gold-plated screw tags for the speaker connections. The Silver Seven allows you to choose from taps of 1, 2-4 or 8 ohms, but screw heads are not that wonderful for grasping two bare cables or even two spade lugs if you're bi-wiring. For #17,000, though, I'd be surprised if Carver said
'No!' to a customer who insisted on five-way binding posts.
The Silver Seven derives its name from the use of silver wiring and silver solder throughout, and seven pairs of output tubes. Carver, eager to have this behemoth dubbed a modern classic, used traditional fully-balanced circuit topology, massive wide bandwidth ultralinear output transformers and the calibre of valves which I didn't think you could find in any quantity. The 14 tubes per side are driven to produce a conservative 375W into 8 ohms, with peak current on the 1 ohm tap of 35 amps; energy storage is 390 joules. Reading the owner's manual and the promotional literature reveals that the unit is tailored to sound vintage, but with such modern touches as ghostly silence, the ability to drive hungry and awkward loads and to offer bandwidth, slam and dynamic capabilities not realised by tube designs of the
HW International left the Carvers with me long enough to allow me to try them with speakers including Apogee Divas (2-3 ohms), Stages (3 ohms), Celestion SL700s (6 ohms-ish) and a host of 8 ohm-plus speakers. As the Silver Sevens are unlikely to be driven by budget components, I restricted the sources to the Basis/SME/Koetsu Urushi analogue front-end and the Marantz CD-12 and CAL Tempest II Signature CD players. Pre-amps included the Audio Research SP-14 and Carver's own C-19 valve pre-amp, which I'll discuss in detail next month.
Read more about the Carver Silver Seven on Page 2.