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REVIEW
HI-FI WORLD
Hot Reference
Audio Research turn up the heat with their new Reference 80S valve power amplifier.
Noel Keywood warms to it.
V
alve amplifiers – you 6SE preamplifier, price £16,998. will fit a 19in rack but the fascia of
have to admit – are There’s good reason for this as I’ll both units measures exactly 19in
wacky and gorgeous. explain later. and is likely to protrude – and
That’s in appearance and You won’t find many reviews of even appears to be chamfered
in sound. Here’s one that the Reference 80S power amplifier to do so. Just think ‘big’ here.
meets both criteria – the because at 28.2kgs (62lbs) it’s “Suitable for the larger home” an
new Audio Research Reference difficult to handle: a two-person estate agent might say. Much of
80S (70W) power amplifier, price lift. Measuring 483mm (19in) wide, the casework is alloy, most weight
£14,998. Built in Minneapolis, USA 470mm (18.5in) deep and 260mm being in the single mains and dual
and aimed at a market more recep- (10.5in) high we were challenged output transformers at chassis rear,
tive to such esoterica than the UK, getting it photographed, tested, beneath a black screening cover.
the 80S is certainly gorgeous, and then into a hi-fi system. Because of The front panel, with its handles,
also wacky too I think – although size, weight and internal complexity is firmly attached to the chassis
I’m sure Audio Research would this is very much a dealer installed by cast alloy brackets in order to
contest that. and maintained item I’d suggest, withstand the load of being used
Importers Absolute Sounds something I’ll also go into further to lift the entire amplifier but we
wanted us to run it with a suitable later. didn’t try this: it was a man at rear
preamp – so it’s reviewed here Because the rear casework and one at front to move it. There
with the Audio Research Reference measures 18.5in (47cm) wide it are plenty of transistor amplifiers
HI-FI WORLD JUNE 2021 www.hi-fiworld.co.uk
REVIEW
around that match or exceed
HI-FI WORLD
this weight – the Musical Fidelity
M8xi at 46kgs for example (Dec20
issue) – but they usually offer more
power.
To develop 70 Watts per
channel Audio Research use the
rugged and reliable KT150 valve
that is to my mind undoubtedly
the most practical proposition
available nowadays, since it offers
a consistently smooth sound,
unlike the higher powered KT90
and KT120 valve that I never got
along with and were, I’m told,
not especially reliable. All the
same, I noted straight away Audio
Research say on their website the
output valves have fuses to guard
against catastrophic failure, as can
happen if run past their suggested
(handbook) life span of 3000 hours,
due to physical distortion of the
electrode structure from thermal
cycling. This phenomenon applies to
all valve amplifiers. The Reference 80S can be run with cover removed. Then
The valves are run in before the "ghost meters" become ethereal. At rear the black case
the amplifier is shipped, necessary screens mains and output transformers.
to catch early valve failures caused
by manufacturing defects. We once whose founder Mike Mathews but give less power, whilst EL34,
had to return an entire batch financed Hendrix into the UK no KT77 and 6L6 types are unsuitable.
of new KT88s at World Audio less. A nugget of important useless The perforated top cover is
Design because none worked information! KT150s are known user removable for a clear view
properly; QC in East European for being consistent and reliable of the valves and to improve
factories was somewhat lacking but Audio Research play safe by ventilation. It’s suggested 8in is
in the 1990s. Audio Research use running them in first. needed above the amplifier to
Russian Tung-Sols, linked to New The Reference 80S is a fully- allow hot air to escape but four
York’s New Sensor Corporation balanced design, Audio Research KT150s don’t run super-hot, unlike
say, for best sound quality. This the Russian 6C33C double-triode
makes it quite a lot different to ‘trawler tube’, even though the
most valve amplifiers that are heaters draw a few more Watts
single-ended (unbalanced) up to than usual. A ‘quiet’ fan is fitted to
the phase splitter stage. There the bottom plate to draw cool air
are however standard unbalanced in from below and help expel it
inputs via phono sockets as per above, but it can be heard to gently
usual, the handbook noting that whir from close up, if not at a
both cannot be used at the same distance.
time. Ideally the amplifier should be Audio Research state the
run from a balanced preamplifier bottom panel should not be
via XLR cables, explaining why removed of course, since it
Absolute Sounds wanted it exposes lethally high voltages. We
paired with the Reference did so for photographic purposes
6SE preamplifier. I used Chord and to check out the fuses but they
Company Epic balanced cables run up to F15 and are not clearly
between them. identified on the circuit board for
Biassing is automatic – in effect rating or function; a service manual
fixed bias that does not need to is needed here – best left to a
be user-adjusted. It compensates dealer.
for changes in valve characteristics The front panel carries
over time, running the KT150s at what the company describe as
65mA. There is a small elapsed “illuminated ghost meters” that
time meter on the rear panel to show power output. Surprisingly,
show how many hours are on the they are traditional analogue
Behind, a KT150 power valves and is user-resetable to zero meters with white needles, lit
output valve. In front a when a new set are installed. The from below by white LEDs. The
6H30 double-triode with handbook states 6550s, KT88s and scales are white too, printed onto
damping rings. KT120s will run in the amplifier clear acrylic background. Behind
www.hi-fiworld.co.uk JUNE 2021 HI-FI WORLD
REVIEW
HI-FI WORLD
At left the 80S power amplifier with perforated grille behind the meters. At right the grille has been removed to
show valves at rear. Two different views, easily set at home.
this clear panel lies a removable gain stage that employs six 6H30 are digital inputs, nor a Phono
perforated cage panel that gives tubes – a Sovtek double-triode stage.
a visually peculiar background I that’s unlike anything else (so no The amount of gain available
thought, but it can be removed to alternatives available) and preferred is also limited to x4 or 12dB from
show the valves behind; I preferred by Audio Research (as they once XLR in/out, or phono in/XLR out.
it removed. only used 6550s). Talking of which, If only the phono sockets are used
The amplifier can be switched they use a 6550 and 6H30 in this then gain falls to x2 or 6dB. This
from Ultralinear mode to Triode preamp within a regulated power gives an input sensitivity value
mode just by pressing a front supply. of 350mV for the preamplifier
panel button. A relay clatters in As you might guess then, the in conjunction with the power
the background and the power Reference 6SE focuses on balanced amplifier – not high, if sufficient for
warning light turns from green to inputs, no fewer than four of them. digital sources. Low gain external
blue. Triode mode always gives less There are two sets of balanced phono stages may need volume to
power, in the Reference 80S 36 outputs, plus fixed-gain Record be turned right up.
Watts per channel, but many prefer balanced outputs. All balanced Warm up after switch on takes
the slightly easier sound on offer, inputs and outputs are duplicated about 45 seconds, after which Mute
unless that is the loudspeakers by unbalanced phono-socket inputs releases. Alongside the right hand
need pepping up. and outputs for convenience, but volume control lies a massive green
The Reference 6SE preamplifier the preamp, like the power amp, dot-matrix fluorescent display that
is specifically suited because it too majors on being a balanced design. runs from 0 to 103 (don’t ask) and
uses balanced circuitry in a single This is its raison d’être. Not fitted a remote control is supplied for
this purpose too. The remote also
switches inputs, alters balance, has
mute, can select mono or phase
invert and even display-brightness.
The preamp has a 12V trigger to
the power amplifier so they can be
switched on together and there’s
an input for an external remote
control sensor for enclosed
use, although with valves always
best not to enclose to avoid
overheating. There are many side
functions such as auto shut-off,
tube hours, volume re-set, input
naming – all aids to use.
The Reference 6SE preamplifier
is as wide as the Reference 80S
power amplifier, measuring 483mm
(19in) across the front panel,
419mm (16.5in) deep and 198mm
(7.8in) high. Behind the front panel
the case is 465mm wide so will
fit into a 19in (483mm) rack. A
weight of 17kg (37.5lbs) makes the
From below the Reference 80S power amplifier board is unit liftable, but it is still weighty.
packed with smoothing capacitors (centre), safety fuses and Inside sits a large C core mains
special parts. At right is the mains transformer (yellow) and transformer as part of its linear
– above and below – output transformers with connection power supply, all visible through the
boards. clear acrylic top panel.
HI-FI WORLD JUNE 2021 www.hi-fiworld.co.uk
REVIEW
HI-FI WORLD
At rear the 80S power ampli-
fier has three loudspeaker
impedance options: 4, 8 and
16 Ohms. A small window
showing hours of use sits
at left of the central power
input. There are balanced
XLR sockets at left and
right, as well as unbalanced
phono sockets.
SOUND QUALITY Audirvana+ software player. of valve sound – not warm, not
The Reference 80S power amplifier Being a balanced analogue languorous, instead speedy and
was connected to our Martin amplifier I had to feed it balanced revealing. There was clean, solid
Logan ESL-X hybrid electrostatic analogue from LP. To this end I used bass free from wallow, because of
loudspeakers through Chord our Timestep Evo Technics SL-1210 the way Audio Research handle
Company Signature Reference Direct Drive turntable, its SME309 feedback around their output
cables. I also hooked it up to the arm with Audio Technica OC9X transformers, explaining our very
Fink Team KIM loudspeaker as a MC connected up balanced to a low bass distortion figures. But you
more conventional but sufficiently Pro-Ject RS2 phono stage whose get the aural benefits of valves all
revealing alternative. balanced output was fed into the the same – the smoothness and
Sources were an Oppo UDP- Reference 6SE preamplifier. the sense of air and space around
205D spinning CD through its I’ll kick off, as I prefer to, by images.
ESS ES9038Pro DAC, connected outlining basic properties – what As I played through a selection
balanced through Chord Company to expect. As with Audio Research of high quality modern LPs, plus
Epic cables. Hi-res and DSD were amplifiers I have reviewed in the older not-so-high-quality ones,
fed into the Oppo over USB, past, this pre and power were far certain traits emerged. Running
from a MacBook Pro running the from many people’s expectations all-balanced sets up a manicured
The Audio Research Reference 6SE preamplifier has a very large green dot-matrix display of
volume level, plus input in use at left. Below are push-buttons for Ultralinear/Triode mode.
Mono, Phase invert, Mute, option Select and Power – all available by remote control also.
www.hi-fiworld.co.uk JUNE 2021 HI-FI WORLD
REVIEW
HI-FI WORLD
sound stage and that’s what I
heard from our audiophile LPs,
such as 2L’s superb recording of
Marianne Thorsen playing Mozart
violin concertos, backed by the
Trondheim Soloists. The sound
stage was wide and open, backing
violins separated from each other
and with distinct lateral position.
Marianne Thorsen’s violin floated
out with sublime ease, smooth,
natural in tone and perfectly
rendered. I could hear the
strings suffering under the bow,
appreciate her ability and effort.
Funny how a communicative
amplifier draws you in and this the
Reference 6SE preamplifier and
Reference 80S power amplifier
did, staring right into what was
happening in this recording.
The sheer clarity and
separation of threads within a
performance was an outstanding
feature and, curiously – perhaps
bizarrely you might think – I got
to hear it in a strange place, my A top view of the 6SE preamplifier with clear acrylic cover
old 12in 45rpm disco singles. removed. At right a C-core mains transformer, and at top centre
These things from the 1980s were 6550 and 6H30 valves to provide power regulation. Six 6H30s
cut at huge levels, as you can do provide balanced amplification.
with a track that lasts 10 minutes
on 12in of vinyl. With Billy Ocean’s – and this is what faced me with Sun (DSD64) fine cymbal taps
Get Outta My Dreams, Get Into the Audio Research combo: less! rang out clearly whilst plucked
My Car the manic mix was better Singers and instruments came over bass laid down a firm backing. Her
sorted – less confused – than I as starkly defined and less hazy, vocals hung in a clear open space
have heard it before. Similarly, for want of a better explanation. it seemed, the whole performance
Carol Kenyon’s Dance With Me This isn’t about dynamic drama having that strong sense of live
was clinically clean yet stabbingly so much as insight and
powerful – not what you might stage composition. In
expect from a 1984 cut. photographic terms, losing
Moving on to digital, Josefine haze and gaining better
Cronholm was put up in clear but image focus.
almost barren form singing In Your In terms of dynamics
Wild Garden (CD) and here the this Audio Research pair
balanced nature of this combo were strengthy if tight and
became even controlled. The Reference
more apparent. 80S delivers fast and clean
Balancing subjec- bass but it is free of wallow
tively strips the or bloat. This took me by
sound to its bare surprise a few times, tracks
bones, or so it like Loreena McKennitt’s
seems. Gone Gates of Istanbul suddenly
is something shaking the room low
you don’t down with its introductory
consciously hear, bass line after a seeming
a subliminal absence of subsonic bass
mush I speculate from preceding tracks. I did
however notice that with
Most LP the Reference 80S was
driving big bass into both
preamplifier
our Martin Logans and the
functions
Fink Team KIMs, so was
are
aware the Reference 80S
available on packs a punch lower down. The 6SE has a valve regulated power
the remote With preened hi-res supply for better sound quality. It
control. recordings such as Cyndee comprises a 6550 power valve (rear)
Peter’s House of the Rising and smaller 6H30 double triode.
www.hi-fiworld.co.uk JUNE 2021 HI-FI WORLD
REVIEW
HI-FI WORLD
Four sets of XLR balanced input
sockets (left) take up space on the
preamplifier's rear panel. They are
accompanied by matching phono
sockets. Two sets of balanced and
unbalanced outputs sit at right,
plus a fixed-level Record output.
presence valves bring.
I found the mono function on
"The Reference 80S delivers
the remote control useful with
John Coltrane’s Easy to Remember fast, clean bass free from
(24/96) as his saxophone is placed
in one channel, backing quartet in wallow or bloat"
the other, which comes across as
a trifle odd – bit like The Beatles is enough for me and most that makes them unusual. Run
early stereo! But the Audio loudspeakers. Volume hovered from balanced sources – as I did
Research combination brought a around 30 on the display for the for this review – they offer almost
magnifying glass to Coltrane’s sax, most part (103 is maximum). unique cleanliness, deep insight
every small breath and keystroke and pin sharp stereo imaging
made obvious. Again there was a CONCLUSION across a wide sound stage. With
washed-clean sense of clarity from Fully balanced amplifiers are rare a good range of facilities, these
balanced working. beasts at present; many now all-analogue amplifiers are highly
In case you’re curious I used have balanced inputs – but they specialised and well worth hearing
Triode mode for the most part, are unbalanced internally. The if you want to know where the
rarely getting past a few Watts Reference 6SE preamplifier and world is going in terms of sonic
on the meters even when playing Reference 80S power amplifier are direction. A fabulous duo from one
loud in a large room; 40 Watts fully balanced throughout – and of America’s top manufacturers.
MEASURED PERFORMANCE
The Audio Research Reference 80S power XLR sockets. Noise -100dB AUDIO RESEARCH
amplifier delivered 72 Watts into 8 Ohms Frequency response ran flat from 3Hz Distortion (10kHz, 1W) 0.01% REFERENCE 80S
and 64 Watts into 4 Ohms, just before to 100kHz at full volume (103) but fell to £14,998
clipping (Ultralinear mode). It is rated at 70 25kHz (-1dB) at 80 then rose to 35kHz
FREQUENCY RESPONSE
Watts into 8 Ohm in the published spec. at 50 and 80kHz at 20. So bandwidth AUDIO RESEARCH
Switched to Triode mode power fell to 36 depends upon volume control position REFERENCE 6SE
Watts. For full output, an input of 0.7V is – not ideal. At normal control positions of PREAMPLIFIER
required via the phono input sockets and below 50 the upper limit was acceptably £16,998
1.4V via the XLR input sockets. above 35kHz. There was minimal noise at
Frequency response ran flat from -100dB and distortion was negligible too,
3Hz to 80kHz (-1dB limits) and distortion measuring 0.01%. OUTSTANDING - amongst
measured 0.25% in the mid-band (3rd The Reference 80S measures well. the best.
harmonic) but just 0.1% at 10kHz and The Reference 6SE preamplifier turns in
VERDICT
0.06% at 40Hz (all 1W). Just below a satisfactory if not impressive measured Washed clean sound with
full output the result was 0.5% at all result due to low gain and bandwidth DISTORTION great composure. Clear and
frequencies, all fairly typical for a valve varying with volume position. NK open too. Breathtaking.
amplifier using fixed bias. Bass distortion
was very low as valve amps go. REFERENCE 80S POWER AMPLIFIER FOR
Power 72W - clean, clear sound
The accompanying Audio Research - spacious sound stage
Reference 6SE preamplifier had a modest Frequency response (-1dB)3Hz-80kHz
- facilities
gain of x2 (6dB) from phono socket inputs
Distortion (10kHz, 1W) 0.1%
Separation (1kHz) 94dB AGAINST
to phono socket outputs and x4 (12dB)
Noise (IEC A) -114dB - large and very heavy
from XLR in-XLR out, or phono in to XLR Sensitivity (phono/XLR) 0.7V / 1.4V - no digital
out. Useful but not large gain values. If the - no phono stage
two units are coupled through balanced REFERENCE 6SE PREAMPLIFIER
XLR cables, as they should be, input Frequency response (+/-1dB) Absolute Sounds
sensitivity is 350mV for both phono and 3Hz-30kHz +44 (0) 20 8971 3909
Gain / overload x4 (12dB) / 72V www.absolutesounds.com
www.hi-fiworld.co.uk JUNE 2021 HI-FI WORLD
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