Given that few people will defend tube/transistor hybrids, how do you go about satisfying the valve-oriented consumer who wants his or her amp to have everything under one cage? And without simply adding to the buttonry?
One of the last of the new-ish Italian companies I'm exposing to you this year, GRAAF (Gruppo Ricerche Audio Alta Fidelta) has as its slogan "Il Suono Fatto A Mano", which I think translates into 'Hand-Made Sound' – about as cool a way of saying 'Lunatic purism' as I can imagine.
It's a monomaniacal vision, a sense of purpose usually associated only with such wonderful Japanese crackpot outfits as Air Tight and Audio Note. Designer Giovanni Mariani looked to one of the oldest, most awkward of purist configurations, output transformerless design (OTL), and yanked it into the present by incorporating all of the best audiophilic developments since the days of the great Julius Futterman.
GRAAF's philosophy consists mainly of excessive, train-spotterish attention to detail and a disregard for component cost. The sense of no-compromise and "Fatto A Mano" is everywhere, from the use of a real glass cover instead of perspex over the pre-amp tubes to the decoupled feet underneath every chassis. But plenty of ultra-conservative manufacturers operate using cost-no-object criteria.
GRAAF's persona is a happy blend of luxo-finish prestige and salivating audio dementia, because GRAAF produces a fully-balanced OTL amplifier which will drive 2 ohm loads without self-immolating. It leaks no strange substances when the chassis turns hot. It has enough safety circuitry to satisfy the Danes. It's the most wayward of hi-fi cult topologies ever offered but now forced to behave like, like, like a super-secure tranny amp! It's one of those blissful contradictions, an exoticar that's easy to drive or a computer that's user-friendly. That it comes from Italy says plenty about why the further development of high-end audio is probably going to be Latinate instead of American or British.
To be specific, GRAAF is based in Modena, the heart of the country's supercar industry. It's no accident that the GRAAF metalwork comes from the same factory as that which produces parts for the new Bugatti. Neither is it an accident that GRAAF is truly performance-oriented like its automotive neighbours. The GM 200 amplifier isn't just fully balanced and OTL and capable of driving something with a lower impedance than that of an LS3/5A: it pumps out a very useable, very real 200W/channel. And you're all hip enough to know that an OTL amp delivering 200W into sub-4 ohm impedances must be sporting a lot of tubes. And it does.
Each channel of this dual-mono amp's power is derived from sixteen PL504s, chosen for their ability to supply high current.
The rest of the circuit is all-valve and tranny-free, including an input stage using a 12BZ7 working as a balanced Class A buffer separator, followed by a 12AV7/5965 differential stage. This section of the circuit was design for good linearity and immunity to noise from the AC line; it also acts as a phase splitter. Voltage gain is provided by a pair of EFL200 double pentodes.
GRAAF's insistence on an all-tube circuit in which the signal handling, offset, bias control and stabilisation are pure tube, with no solid-state components present, extends even to the power meters. They're separate EM81 'magic eyes' for each channel, which glow green and illuminate according to the amount of power the amp is delivering. If you've not been keeping count, the valve tally runs to 42.
Not that you'll have to worry about tube failures, because this unit has been designed with dependability in mind...even when being manhandled by a reviewer. Switch-on, for example is accompanied by a silent period of a minute or so, during which three or four relay clicks indicate that all systems are stable and ready to rock. Beneath each of the PL504s is a 1ohm resistor (cost from Tandy: 3p) which will be taken out before the valves; this might happen, for example, should you not show patience by switching on and off too rapidly. (This demand for restraint is not an inordinate request.
The most modern of all late 20th Century appliances, the home computer, also needs to rest for a minute or two between switch-on-switch-off sequences unless you want to trash your hard-drive.) The only current limiting in the GM 200 is the intrinsic behaviour of tubes to act as current limiters, so audible clipping rather than shut-downs say when it's time to back off a bit.
When you first lift the GM 200 out of its wooden crate, you know it's all business. The unit weighs just under 30kg, even though the chassis measures a compact 445x415x210mm (WDH). Visually, it's 'cleaned-up lab chic', the mirror image layout placing two rows of eight tubes on each side, running from the back to the front. Flanking the centrally-positioned blue on/off button are the EM81s, the EFL200s and the 12AV7s. Above the rows of output tubes are black nickel-finished cages which, when removed, reveal chrome 'barrier' rods reminiscent of the old Radford handles.
Inbetween the banks of tubes are large capacitors and a massive toroidal transformer, the only shared component beside the chassis. All of these parts are made in Italy, to GRAAF specification.
The rear panel contains the XLR-type balanced inputs (there's no unbalanced alternative), beautiful gold-plated Esoteric Audio multi-way binding posts, a mains fuse holder and an IEC mains socket. Removal of the bottom plate reveals the milspec mother board, secondary boards and the balancing-act 12BZ7 tubes. Fit and finish are absolutely flawless, as befits an amplifier retailing for around £6400 back home. (If that's all too frightening, there's a half-power version, the GM 100, for less £3600.)
To drive the GM 200, GRAAF supplied one of its two line-level pre-amps, the GM 13.5B, either model selling for £3200. The one not supplied is the single-ended version, which sports a superior resistor ladder volume control. The GM 13.5B is the fully-balanced version and it contains a more compact but top-of-the-line ALPS pot because the other wouldn't fit; a future model will incorporate both balanced operation and the 'killer' volume control.
Continue reading about the GM 200 on Page 2.
What I was assured, though, (by GRAAF and by others) is that the
balanced mode will contribute more to the overall performance than the
better of the two volume controls, hence the 13.5B being the
better-sounding of the two.
All-black, like the power amp, the GM 13.5 measures 410x320x105mm
(WDH). Its upper edge is chamfered from two-thirds of the fascia's
width, and from head on or at eye level you can just detect the glow of
the six 2C51/5670 double triode tubes. The top plate contains a glass
'window', which extends down the front. To the right are rotaries
choosing playback and record-out for tape, a balanced source and four
RCA line inputs. At the extreme right is the volume control and below
it the on/off switch. 'Round the back, it's gold-plated socketry, a
single set of XLR balanced inputs and another set of XLRs for output,
plus two sets of single-ended outputs, so the GM13.5B can actually
drive three sets of power amps.
The rear-mounted hardware is completed by an IEC mains input, a mains
fuse holder and an earthing post, useful when the company delivers its
all-tube phono stage.
The 2C51 tubes are used for gain and buffering functions, producing a
self-balancing differential pre-amp conceived for maximum linearity
with low distortion. GRAAF has built in extensive amounts of power
supply filtering, so much so that the GM 13.5B was the first and so far
only product I've used which didn't benefit from the Versalab Woodblock
mains filter. In effect, the pre-amp is separated from the AC line so
it can operate optimally with even line variations of +/-15%. GRAAF's
choice of components include oil-paper, polypropylene and electrolytic
capacitors and metal film and wire resistors used according to their
suitability in a given stage of the circuit. The input selectors
feature ceramic switches and the balanced potentiometer consists of
four specially designed sections with 10 brushes to ensure the best
contact and minimum wear. Which makes the absence of the dearer volume
control found in the unbalanced pre-amp less of a hardship.
Although I used the GRAAF pairing in fully-balanced mode with signals
courtesy of the Krell MD-10/Reference 64 CD playing system in balanced
output form, I did try the line inputs, too.
And so good are they that I heard less difference between sources in
single-ended vs balanced mode than I ever expected. Yes, the balanced
input offered quieter background 'silences' and a bit more
transparency, but not so much that I was prepared to forget about that
superior volume control in the other version. But, because of a quirk
with the sample I was reviewing – the volume control was far too
sensitive, hitting 'Way Loud' at under a quarter of a turn – I often
switched to a line input; it cuts back the signal by 6dB and made
volume adjustments easier. This too-hot volume control, I have been
assured, is not typical, but I'm grateful to it for endowing me with a
surgeon's delicate touch.
The GM 200 was connected to speakers ranging from Apogee Divas at one
impedance extreme to LS3/5As at the other. Inbetween were Sonus Faber
Extremas and Minima Amators, Linn Tukans, Wilson WATT/Puppies and Opera
Callases. Why so much variety? I wanted to learn if here, at last, was
an OTL for the real world, one which would work with something other
than old Quad ESLs. And, with only minor caveats, the GM 200 behaved
like a monster solid-stater every time.
Let's get the limitations out of the way first. I was told that if I
insisted on using the GM 200 with Divas or Extremas, I'd be better off
either bi-amping (tell that to the bank manager) or fitting the device
which enables the smaller GM 100 to work with difficult loads and comes
as standard with that unit. The 'toroidal impedance translator',
obviously named by someone for whom English is a second language and
acronyms are not of consequence, is said not to compromise the amp's
OTL virtues, but I've not tried it so I can't comment. Suffice to say,
I could use both the Divas and the Extremas at sane levels without
complaint, but it didn't take too much to demonstrate the sound of
clipping with those speakers – oh, for a second amp!
With others, especially the WATT/PUPPY package and the Minima Amator,
the GM 200 in solo emerged as what I can only describe as the
best-sounding amp I've ever used. Yes, you can read that again. I said
'The best-sounding amp I've ever used.' Not the most accurate, not the
most powerful/dynamic, but the nicest, sweetest, most comforting, most
involving power amp I've tried. It has sonic traits which keep the
adjective 'perfect' in the dictionary and out of this review, but
they're the kind that are so obvious and so understandable that you'll
quickly decide to be pro or anti.
Very simply, they are the sins of tube-ness, and if you don't like
excess warmth, lushness and a bit of boom in the lower registers, then
you'll look elsewhere. Hell, if you don't like warmth and lushness then
you probably don't like any tube amps, let alone one which is all-tube
and directly coupled to your speakers.
Steve Harris noted this immediately and I think it was what the guys
from Linn objected to when they dropped off the Tukans. Other visitors
fell into their respective camps with the same ease. Me? I'm a tube
slut from way back, so I was wallowing, wallowing in the sound.
It's 3D, it's open and it's transparent. There's a sense of clarity and
of immediacy which I can only think of in terms of Steve Harris'
argument in favour of 78s over later forms of sound storage: less
between you and the music.
To dig wa-a-ay back into the pre-politically-correct Hi-Fi Reviewer's
Thesaurus, there's veil removal akin to a full strip tease: G-string,
pasties and all. This is naked sound, the tube artefacts not getting in
the way of the resolution of fine detail or the sense of space. Even
with poorly recorded discs, like the recent live Marvin Gaye set on
Magnum, the GRAAFs managed to salvage a convincing sensation of space.
Which is impossible, right?
We all know that hi-fi can't add what's missing. So it can only mean
one thing: the GRAAFs are letting more through. Admittedly, 'more'
includes the tube traits mentioned above, but the overall sensation was
one of going from a 27in screen to a Barco projector, from plastic
eyeglass lenses to glass, from anything to a Leica.
Or, since we're talking son and not lumiere, it's like post- a Q-Tip
session, or popping your ears as the plane descends.
As befits products from the country which rules in matters operatic,
the GRAAF handles vocals like a cup of lemon-and-honey-spiked tea.
Rasp, sibilance and chestiness, if present, will be by-products of the
speakers, not the electronics. As mid-band performers, the GRAAF
siblings join such greats as Quad ESLs, Koetsu cartridges and, yes,
LS3/5As. The extreme treble, unlike the bass, hasn't been excessively
'tube-ified', in that is neither soft nor absent, so crispness and
speed at one end and a lush tush at the other sandwich what is a
positively fluid and smooth mid-section. But the transitions from bread
to filling are barely perceptible.
I know that I've just described as magnificent what an objectivist
would adjudge a dog's dinner. But maybe words just aren't enough.
Listening to the GRAAF components – despite the
high-tech-meets-vintage, steam-punk concept blending – is, as with
Sonus Faber's Guarneri, an emotional experience no matter how
analytical you try to be about it. That this stuff makes me forget that
I'm reviewing (and therefore working) is all I need to accept it as the
perfect amp for me.
Oops...there's the 'P' word.
But when I saw the grinning, blissed-out look on Steve Harris' face, as
he sat there listening to Lee Dorsey in mono fer goodness' sake, I knew
I'd have no problem justifying the claim.