Ayre | DX-7 | Specifications | Ayre DX-7 Specifications

The AX-5 Story
from Ayre Acoustics
t: 01727 865488
e: info@symmetry-systems.co.uk
March 2014
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 2
Ayre AX-5 Introduction
Featuring Ayre's new Diamond output stage, their
exclusive EquiLock circuitry, and a Shallco solid-silver
contact switch for gain control, this fully-discrete, fullybalanced, zero-feedback integrated amplifier provides a
complete solution for your modern music system.
TYPE: Reference class integrated amplifier
The key to perfecting the AX-5 was to incorporate the
Variable Gain Technology (VGT) of the award-winning Ayre
KX-R preamplifier into the power amplifier section. The
addition of ultra-transparent FET input selector switches
completed the transformation of a basic power amplifier
into a compact one-box solution which will become the
heart of your high-performance audio system.
MANUFACTURER: Ayre Acoustics
IN THE SIMPLEST VIEW,
THE AYRE AX-5 IS AN
AMALGAMATION OF
THE AX-7 AND THE
KX-R. YET IN ANOTHER
WAY, THE AX-5 IS
THE MOST RADICAL
INTEGRATED
AMPLIFIER EVER
DESIGNED.
55 years of preamplifier
history out the window
Words by
Charles Hansen
OUTPUT POWER: 125 wpc 8 ohms / 250 wpc 4 ohms
DIMENSIONS: w 44cm x d 48cm x h 12cm
WEIGHT: 22 kg
WEB SITE: www.ayre.com
UK PRICE: Silver £7,895* (*add £195 for black chassis)
Remember in the Ayre KX-R, we threw 55 years of
preamplifier history out the window and created a new
topology never seen before. In 99.9% of preamplifiers,
the signal comes in at a slightly lower level than the
power amplifier requires. There is a gain circuit to boost
the signal, so that it is large enough to drive any power
amp with any set of speakers. But to keep it from being
too loud, there is also a signal attenuator (volume
control) in front of the signal booster (gain circuitry). It
doesn't take too much of a brilliant mind to figure out
that there must be a better approach than to take the
incoming signal, reduce its volume to the right level with
the volume control, and then increase the volume by a
fixed amount with the gain circuit.
Variable Gain Transconductance
And that is what was so radical about the Ayre KX-R.
Instead of using a fixed gain circuit , the gain of the circuit
was variable (by changing its transconductance), hence
the name VGT for "Variable Gain Transconductance".
There are many advantages of this approach:
a) The signal is never attenuated, which would always lead
to a loss in S/N ratio and also dynamics.
b) With a conventional preamplifier, the noise of the
gain circuitry is fixed. This means that you only reach the
maximum S/N ratio when the volume control is at the
t: 01727 865488
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 3
The AX-5 Story
from Ayre Acoustics
maximum. When you turn the volume control down, the
output signal is reduced, but the noise of the circuitry
remains the same -- therefore the S/N ratio becomes worse
and worse as the volume is lowered. Since most preamps
are used anywhere between -10 dB to -40 dB for an average
listening level, this means that the S/N ratio in actual use will
be 10 to 40 dB worse than on the spec sheet.
In contrast, the S/N ratio of the VGT circuit is always at
the maximum, regardless of the volume setting. So in
real world usage, the S/N ratio is increased 10 to 40 dB
higher than a typical preamp. This results in unparalleled
resolution and retrieval of detail.
Eliminating the Preamp Stage
For the Ayre AX-5, we completely eliminated the preamp
stage altogether and simply made the gain of the power
amp variable using the VGT and added an input selector.
This is the simplest possible signal path in any audio
product ever made. Period.
" Please note that the VGT ONLY works
with circuits that have zero negative
feedback. Since very few designers have
any experience at all with zero-feedback
circuits, we are not too worried about being
copied anytime soon. "
In contrast, 2013 marks Ayre's 20th anniversary, and every
product we have ever made uses zero-feedback audio
circuitry and zero-feedback power-supply regulators.
t: 01727 865488
March 2014
The volume control of a VGT design demands the use
of extremely linear and low resistance switches. FET
switches will not work in this application. Thus the only
candidates for the job are relays and rotary switches.
Foolproof methods
We have a very simple, yet 100% foolproof method for
listening to the sonic effects of various switching devices.
With our method, each device has the exact same
number and type of connectors, wire, and even solder
joints. This allows us to compare the switching element
to a true "straight wire bypass" with no other variables
involved.
By far the most neutral and transparent switching device
we have ever tested is the solid-silver-contact rotary
switches from Shallco. The only change from a "straight
wire bypass" is a extremely small loss of resolution -- I
would estimate it at less than 1%, so you are getting
99%+ the full resolution of the source.
Nearly every other solution sounds broken by
comparison. One of the worst offenders are relays. (This
is especially ironic as almost all modern preamplifiers use
relays for either signal switching, volume control or both.)
The relay
A relay is a truly wretched device to put into the audio
signal path. There is absolutely nothing good about
it. The conductors are bad sounding, having various
alloys mixed in to the copper to make it "springy". The
plating is similarly bad, with almost all small signal relays
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 4
The AX-5 Story
from Ayre Acoustics
March 2014
" I am confident of this to the point that I consider any product that uses relays in the audio signal
path to be unusable as a reference-quality device. At Ayre we use them to short out the signal for he
mute function in some products. But that is as close as they ever come to the signal path of even the
lowest priced of Ayre equipment. "
using gold plated contacts. This wouldn't be too bad if
it were just gold. But the normal gold plating process
leaves pinholes that require a nickel underplate to avoid
corrosion of the copper base metal over time.
It is both expensive and difficult to perform "direct gold"
plating for connectors, and I have never seen it done
in a relay. But the normal technique of using a nickel
underplate leaves a magnetic layer underneath the
gold that the signal *must* pass through on its journey.
Magnetic conductors create signal distortion that is easily
measured with modern test equipment.
A relay also has no "self-cleaning" action such as is found
in a rotary switch. Each time the switch is operated, the
contact of a rotary switch wipes any surface oxides or
other contaminants away leaving a fresh contact surface
Finally the optimal conductor geometry is of no concern
in a relay. Sometimes the conductor is steel so that the
contact is operated directly by a magnet. Sometimes
the conductor has a complex shape that complex and
undesirable impedance variation versus frequency in the
switch. Almost all relays are sealed such that it is virtually
impossible to clean them.
Just listen
The net result from a sonic standpoint is difficult to
describe. I think the best description was given by our
Senior Research Assistant, Ryan Berry. At one point he
asked, "Why not just use a relay?" I told him to go listen
to the best one we had found, an exotic device costing
double the typical price of the a top-quality small-signal
relay. After a half-hour of listening tests, he came back
and I asked him what he thought. He replied, "They just
make the music sound, well, WRONG!"
t: 01727 865488
After the Shallco rotary switches, the best sounding
switching elements we have found are FET switches.
These have many advantages, including relatively low
cost, silent operation, and no moving parts. However
there are many other disadvantages that must be
carefully managed if an acceptable level of performance
to be attained. They are also prone to damage from
static discharge, especially when used as input selector
switches that are connected to external devices, and
their "On" resistance varies with the applied voltage
However, when carefully managed, these are also
capable of truly excellent sound quality, and the latest
generation of devices are also quite robust.
We spent well over a month selecting the highest
performing FET switches for use in the AX-5 that would
provide trouble-free operation for decades in the harsh
environment encountered when exposed to potentially
damaging episodes ranging from nearby lightning
strikes to a high-voltage discharge when connecting
(or disconnecting) cables during the dry winter months
when static shocks are commonplace.
So far we have focused only on controls that are suitable
for use in stepped attenuators. This is because to obtain
the full performance available from a truly balanced
circuit, the level matching between phases of each
channel should be held to less that 0.1%. Devices such as
ordinary potentiometers (volume controls) fail to meet
this standard by a factor of between 200x and 10,000x,
rendering them totally unsuitable for use in a high
performance balance circuit.
A question of balance
As is normal for every Ayre product ever built, the AX-5
is fully-balanced from input to output, and uses zerofeedback circuitry. The advantage of fully balanced
operation has nothing to do with interference pickup
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 5
The AX-5 Story
from Ayre Acoustics
in long interconnect cables (the reason why balanced
equipment is standard in all recording studios., but rather
because just as the balanced circuit can reject hum and
interference on the input cables, it can also reject any
interference in the units power supply. When the day
comes that a totally perfect power supply is developed,
there will be no more need for using balanced circuitry in
home-use applications. Until that time, Ayre will continue
to build the most advanced power supplies possible,
and further improve on their effective performance by
combining them with balanced circuitry.
Regarding the use of feedback in audio circuitry, we
already know that it does not work as advertised. The
idea is that the output of the circuit
is compared to the input signal. Any
differences at all (noise or distortion
of any type) is subtracted from the
incoming signal. But if this process
worked properly, then all amplifiers
would sound identical as they would all
be reproducing the input signal perfectly.
March 2014
Introducing the Diamond circuit
I could never figure out why it was called a “Diamond”
circuit, as it really looks nothing at all like a diamond the
way it is normally drawn. For example, here is how they
show it from Burr-Brown on a now discontinued part see diagram 1.
There are some extra parts shown in here, with the
current sources and some other bits, but there isn’t
anything particularly “diamond-like” about it.
If you take away all of the extra parts and strip the circuit
down to its bare essentials, it looks like this see diagram 2.
Unfortunately reality is somewhat more
messy than is theory. In reality every
amplifier sounds different from each
other. Applying negative feedback does
not help this in any way whatsoever.
There is at least as much variance
between the sounds of amplifiers
employing feedback as those that do not. In fact,
taken as a whole, our experience is that zero-feedback
amplifiers tend to sound more similar to each other than
typical feedback-type amplifiers.
A far better approach is to simply design a circuit that
is inherently linear, to the point where the distortion
contribution from the amplifier is well (eg, 10x) below the
distortion contributed by the loudspeakers. When this
condition is met, there is no reason to apply feedback.
Anyone who becomes familiar with the sound of zerofeedback amplifiers will find it difficult to return to
conventional designs.
t: 01727 865488
Now it is much easier to understand. It is simply a pair
of complementary cross-coupled emitter-followers.
However, it still makes no sense to me why in the world it
would be called a “diamond” buffer. But I am an amateur
historian of audio technology and audio companies. So I
kept digging...
Then I found the original patent for the circuit. It was
invented by a professor at MIT, Richard H. Baker, who is
best known for the “Baker clamp”, a circuit that prevents
problems when a transistor amplifier clips. (Although
Baker patented it and his name is associated with it, the
circuit was actually known for several years before he
applied for the patent.)
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
5
Page 6
The AX-5 Story
from Ayre Acoustics
DIAGRAM 1
March 2014
DIAGRAM 3
DIAGRAM 2
t: 01727 865488
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 7
The AX-5 Story
from Ayre Acoustics
March 2014
" What is different about the diamond buffer from a typical output stage is
that after the signal has been split into two halves to send to each output
device, is that the two half signals are rejoined at ONE single point. There is
NOTHING in between these two half signals. "
Diamond buffer
Back to the “Diamond” buffer. Professor Baker developed
another circuit which he called “The “Diamond Circuit”
in an internal publication for MIT, but on the patent he
called it “A Gateable Bridge Network Having Power Gain”
(attached), with some properties that mad it sort of a
It is commonly used in the output stage of “buffer”
IC’s that have unity voltage gain, but boost the current
to drive heavier loads. Sometimes it is also used with
discrete circuits, where it requires careful matching of the
opposite polarities of parts (NPN and PNP) to minimize
the offset voltages.
It is typically only used in low power
stages, such as preamplifiers outputs
or things of that nature. After playing
around with it for quite a while I came
to understand why this is so. To work
properly, the driver stage needs to use an
identical transistor to the output stage.
An output transistor is a big beast that
typically draws a lot of current at idle and
also has large capacitances between the
terminals. So this means that the driver
stage also has to use a “big beast” and
this stage also needs to draw a lot of
current and is fairly difficult to drive due
to the large capacitances.
hybrid between a digital circuit and an analog circuit. In
the patent application, Baker drew it rather differently
than it is normally drawn and one can now *easily* see
why he called it a “Diamond Circuit” - see diagram 3.
Diagram 3 is simply a rearranged version of the simplified
circuit above, but when drawn in this manner it is
obvious to see why Baker called it the “Diamond Circuit”.
In actual practice it was most useful as a “buffer” -- that
is, a circuit with no voltage gain but a high current
gain, which is precisely what is needed to drive a low
impedance load. Hence it has become popularly known
as a “Diamond buffer”.
t: 01727 865488
Using a diamond buffer as an output stage has two
fairly significant disadvantages:
1) It draws a lot of current and this adds to the total power
consumption (from the wall outlet) of the amplifier, as well
as requires additional heatsinking to dissipate the power
drawn by the driver stage.
2) Since the input transistors of the diamond buffer must be
identical to the output transistors of the diamond buffer,
they are large and rather difficult to drive. This means that
one cannot drive them directly with the typical voltage
amplifier used to provide the gain in a power amplifier
circuit.
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 8
The AX-5 Story
from Ayre Acoustics
To address the first problem means that the amplifier
needs to be larger and heavier, with a more powerful
power supply. To address the second problem means
that one needs to use a more powerful driving source
than the typical amplifier uses.
The large majority of transistor power amplifiers use a
“front end” circuit that provides the voltage gain, and
then an “output stage” with no voltage gain, but that
provides the current gain required to drive the low
impedance of the loudspeakers. (One version of the
Wilson WATT/Puppy dipped to around 0.3 ohms in the
upper midrange. While this is unusual, it is important
that a high-quality power amp won’t be bothered by
loads below 2 ohms or even 1 ohm. Most electrostatic
loudspeakers drop below 1 ohm at frequencies above 20
kHz.)
The typical solid-state power amplifier only uses two
transistors signal path of the output stage. (There may
be more in parallel to provide more current *handling*
capability, but this does NOT increase the current gain.)
A really good output transistor will have a current gain of
around 100x, and the same is true of a driver transistor.
This means that a two-transistor output stage will have
a current gain of 100 x 100 = 10,000x. So if you connect a
4 ohm loudspeaker, the load on the “front end” (voltage
gain stage) will be 40,000 ohms.
While this sounds like a lot, it really isn’t. It is a low
enough load that it puts a strain on the front end and
increases the distortion significantly. The solution
that 99.9% of all designer use is to add loop negative
feedback. Works great on paper, but doesn’t sound so
great.
“ At Ayre, we have always used *three*
transistors in series in our output stage. “
So if the third transistor also has a current gain of
100x, now the total current gain is 100 x 100 x 100 =
1,000,000x. Now if you connect the 4 ohm speaker, it
only puts a load of 4 megohms on the front end and
the distortion drops dramatically without having to use
negative feedback. These extra transistors only add a
t: 01727 865488
March 2014
dollar or so to the Bill of Material (BOM) so unless we
are talking ultra-cheap junk audio equipment, this is
completely negligible.
" Back to the Diamond circuit. If it has these
disadvantages, why in the world would
anyone use it? The short answer is it sounds
better. "
The long answer is that I really don’t know why, which
doesn’t help much as that’s not much of a story to tell,
and writers like to tell stories and people like to listen to
stories. At this point the best that I can do is to speculate.
So here goes nothing....
Before transistors came along (in the vacuum tube
era) there were two types of power amplifier circuits
in common use. One was the single-ended circuit and
the other was the push-pull circuit. In the single-ended
circuit, there is one tube (or possibly more, but they are
simply connected in parallel to act as one larger tube),
and this tube must be “on” all the time or the signal will
be horribly distorted with clipping on either the top or
the bottom (depending on the particulars of the design.
This limits the power to a few watts (“flea-power”) unless
the designer resorts to huge power tubes originally
designed for radio station transmitting tubes. Even then
it is hard to get more than 20 (or *maybe* 25) watts out
of the amp and it draws a ton of juice from the wall,
which is pumped out as heat in your listening room.
So when the push-pull output stage was invented, it
allowed for MUCH more powerful amplifiers to be built
very easily. Instead of a single 6L6 tube putting out
perhaps 5 watts, a pair in push-pull could easily put
out 30 watts. And when they developed bigger tubes
like the KT-88 (6550 in the US), instead of a single tube
putting out maybe 8 watts, a pair could put out 60 watts!
This was just in time for stereo, when all of a sudden
one needed TWO speakers and the small “acoustic
suspension” designs took over the market place. They
needed all that power, as they were so inefficient.
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 9
The AX-5 Story
from Ayre Acoustics
With a push-pull amplifier, the input signal is split into
two halves with opposite polarities with a stage called
a “phase-splitter”. Then each output tube amplifies
one half of the signal, and these two “half-signals” are
recombined by the output transformer.
When solid-state came out, they were able (eventually)
to make two devices that were opposite and
(approximately) equal. So a designer could pull the
same trick of splitting the signal into two parts, one
for each output transistor, and then the output of each
output transistor was combined back into a single
output containing the entire signal without the need
for an output transformer (which is big, heavy, and
very expensive). This type of design is referred to as a
“complementary output stage”.
One can also do the same trick with transistors of the
same polarity by adding an extra transistor to invert
the drive signal to one of the output transistors, and
this is called a “quasi-complementary output stage”,
but it doesn’t change anything fundamental about the
situation.
Specifically, the input signal on ANY modern power
amplifier is split into two parts, sent through an
output stage that has a separate device for each half
of the signal, and then the two half-output signals are
recombined to make one final output signal. This is true
whether it is tube or transistor, uses transformers or is or
not, is truly complementary or quasi-complementary.
March 2014
As you can see, there is *something* between the two half
signals in the traditional output stage. Invariably it is a bias
circuit that sets the amount of output current in the output
transistors. And so the two halves of the signal going
through the two halves of the output stage are slightly
different somehow and when the recombine to recreate
the entire signal out the output of the output stage, it
simply doesn’t sound as good as the Diamond circuit.
In a way, this entire argument makes no sense, because
if you look at the simplified Diamond circuit in the
second figure (near the top) again, there is no connection
whatsoever between to two halves of the signal at the
half-way point through the output stage. That is, at the
input, the signals are identical as they are hard-wired
together, and at the output the signals are identical as
they are hard-wired together. But *in-between* the two
transistors in series, there is absolutely no connection
between the top half of the circuit and the bottom half of
the circuit.
“ But that is the beauty, the mystery, and the
art of audio circuit design. If we knew all of
the answers to everything, then everything
would sound identical and everything would
sound perfect. There is still clearly more
awaiting discovery here. “
A conventional output stage always has *something* in
between the two inputs of the two half-output stages
before they are recombined. Typically it is a bias circuit
of some sort that sets the idling current in the output
devices, but there is *always* something there.
The only other power amplifier that I have ever seen
that uses the Diamond buffer for its output stage is
the original DartZeel amplifier. But it works in a very
different way than does that Ayre AX-5. Remember how
we needed to have *three*stages in the output stage
to properly isolate the loudspeaker from the front-end
circuit, whereas the Diamond circuit has only two?
The diamond circuit is the only commonly output stage
in use that feeds the two half-output-stages from the
same exact point. In contrary, here is a typical twotransistor NON-diamond output stage. (Two transistors
for each half of the signal, for a total of four transistors)
- see diagram 4.
In the DartZeel, they solve this problem by giving some
extra “heft” to the front end of the amplifier circuit by
using three transistors with a feedback loop around
them. This makes them “strong” enough to handle the
load presented by only using two transistors in series in
each half of the output stage.
t: 01727 865488
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 10
The AX-5 Story
from Ayre Acoustics
March 2014
In this simplified schematic (see diagram 5) from the
DartZeel website, I have drawn a red box around the
Diamond output stage (identified as the “Third Stage” at
the bottom of the diagram) and two green boxes around
the two half-stages that amplify the “bottom” and “top”
halves of the signal, using a feedback loop around the
three transistors in each state (identified as the “Second
Stage” at the bottom of the diagram).
DIAGRAM 4
No feedback
Of course at Ayre, we absolutely avoid the use of
feedback in everything that we do. Feedback can only
attempt to correct an error *after* it has happened. It
works great on paper and can be mathematically shown
to be sound (as long as certain rules or guidelines are
followed).
" But to my ear, there is something more
natural and musical about an amplifier that
does not use any feedback whatsoever. "
So we developed a special buffer stage to go in between
the front end circuitry and the Diamond output stage
that has a directly coupled input *and* a directly coupled
output.
In any event this works quite well, as the AX-5 is perhaps
the finest sounding product that Ayre has ever made.
DIAGRAM 5
The Integrated Approach
There are lots of possible variations on combining
separate functions into one box. Some make more sense
to me than others.
In the old days receivers were quite popular, but now
radio is kind of a dead medium. And of course no receiver
could ever match the audio performance of good
separate components.
I think that putting too many things into one box (eg,
phono stage, DAC, preamp, and power amp) would lead
to a product that would be relatively expensive *and*
degrade the overall performance. Amplifying microvolt
level MC phono signals in a box that is also delivering
t: 01727 865488
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 11
The AX-5 Story
from Ayre Acoustics
tens of amperes to loudspeakers is not conducive to high
performance. Similarly, putting complex digital circuitry
in the same box with analog circuitry is going to cause
problems. The RFI from the digital circuits is going to
contaminate the analog signals.
" So to my way of thinking the best route to
reducing the overall number of boxes in your
system is an integrated amp (combining the two
analog components into one box) and then a
separate box for the digital (either a disc player
or a DAC). "
But even putting a phono stage into an integrated is
problematic. Although everything in the box is still
purely analog signals, just the problem of having a huge
power transformer for the amp section is going to make
it difficult to avoid introducing hum into a phono stage.
It’s hard enough to put a small, super-shielded power
transformer in the same box as a high-gain phono circuit,
but just about impossible with a huge transformer
required for a power amp.
Toroidal transformers tend to have less stray magnetic
fields than E-I (square) transformers, but in my opinion
they don’t sound as good. A toroidal transformer
t: 01727 865488
March 2014
generally has a really wide bandwidth that couples the
RFI on the power line into the audio circuitry.
Our preamps from the 90’s (the K-1 and K-3) had phono
card options, but to avoid problems with hum had
external power supply boxes. So you end up cutting off
your nose to spite your face, because you still end up
with two boxes.
Now that digital is the dominant source for most
audiophiles, we only offer phono stages as separate
components. The way I figure it, people into turntables
these days are a dedicated bunch and really want to get
the most performance possible. After all a good ‘table,
arm, and cartridge is going to cost at least $2,000 and
more like $5,000 to $20,000 for something really nice.
To make a phono stage in the $1,000 range means it has
to be single-ended only and use IC’s. In my opinion this
won’t give the level of performance that we want to offer
in our products.
" I think that an integrated amp makes the most
sense for combining two functions into one box. "
One could make a case for combining a DAC (ie, a digital
preamp) with an analog preamp and then having a
separate power amp but to me this is much more of
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 12
The AX-5 Story
from Ayre Acoustics
March 2014
“ I guess the bottom line is that to me, what you are asking for is not really an
‘integrated amp’ so much as an “integrated system. ”
a performance compromise than having one box for
digital and one for analog. I think that combining the
volume function with a DAC can make a lot of sense for
an all-digital system, but not so much if one has any
analog sources.
Obviously at least one of the components must have
a volume function, but to my way of thinking the best
place to put it if you are combining boxes is with the
power amp. Then one is not limited to a digital-sourceonly system when going for maximum performance.
Digital sources with volume control
But there is probably a big enough customer base for
digital-source-only systems that some day we may build
a DAC with a volume control. One big advantage of
doing this is that one can make a high quality volume
control for significantly less cost. The reason is that a
purely digital volume control is practically free, but it
degrades the sound quality
more and more as the
volume is reduced. But with
only digital sources, one
could make a hybrid volume
control. A good approach
would be to have (say) six
small (eg, 1 dB steps) digitally.
cheaper than (for example) the 60-position switch we use
in our KX-R analog preamp.
Another problem with putting too many functions into
one box is the lack of ability to upgrade. For example,
Linn makes some boxes that have everything in them
but the speakers. This is a nice solution for a less-thanmaximum performance system, such as a second system
for the bedroom or office. But then there are severe price
constraints.
We will surely offer more integrated amps in the future
besides our current AX-7 and quite possibly a DAC with
a volume control for digital-source-only systems, but I
don’t foresee us ever building an integrated system.
A very long-winded answer, but I hope that helps you
understand where we are coming from. So there is a
(very long-winded) explanation of why our integrated
amp still retains the basic feature set of a traditional
integrated amp, and why we
don’t include digital inputs,
or phono stages, or whatever
strange combinations of
things that some customers
ask for.
" We also continue to pay attention
to all of the other “little” things that
we always do that other makers
seem to ignore. For example, more
and more manufacturers are using
“touchscreen” control panels on their
products now. These are nothing
more than flashy gimmicks designed
to appear sophisticated, yet in reality
degrade the sound significantly while
raising the cost considerably - the
worst kind of trade off in my book. "
Then the maximum
degradation would only be
one bit. In a 24-bit system
this would still leave 23 bits
of performance, which is
more than enough. (Any
real-world system is limited
to only 20 or *maybe* 21
bits of resolution.) Then the
analog volume control would
only need coarse steps of 6
dB. This means a 12-position
switch would be more than enough, and that is a *lot*
t: 01727 865488
e: info@symmetry-systems.co.uk
I’m not saying that those
aren’t valid for some
situations or that they won’t
make some customers happy.
I’m just saying that they
don’t meet the requirements
that Ayre is aiming for and
that if they are looking for
something like that they
should look at other brands.
Back to the design of the
AX-5.
OK, so now we have created
an integrated amp that is
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 13
The AX-5 Story
from Ayre Acoustics
truly revolutionary in its concept and execution. We
have described how the input selector works and why
we have chosen FET switches (properly implemented) to
achieve the most transparent input selection short of the
Shallco rotary switches but managed to save thousands
of dollars off the retail price by making only a *very, very*
small sacrifice in the sound quality.
It's the little things
that make all the difference
At Ayre, we have always used front panel displays that
don’t generate ANY electrical noise. Instead, they are
typically either single LED’s or segmented LED’s that are
always on. The exception is the display in the KX-R which
is a special dot-matrix display that is capable of creating
Japanese Kanji characters, or even simple graphical icons.
Typically these work by addressing the pixel via a row by
column address. In order to keep an entire row or column
from lighting up, the pixels are lit in a sequential fashion,
turning on and off very rapidly - so rapidly that to the eye
they appear to be continuously illuminated.
However they cause a subliminal fatigue, and even
worse they generate a large amount of high-frequency
switching noise in the audio band. When a touchscreen is
added to this the position sensors work in the same way,
and they typically generate at least double the amount of
electrical interference. We have a computer monitor like
this at the factory that we bought to use with computer
audio systems. It is pretty much a disaster as it degrades
the sound quality significantly to have it even turned on
in the same room.
Special dot matrix display
The Ayre KX-R uses a special form of a dot matrix display
where the illuminating phosphors are deposited directly
on top of small transistor switches with one switch
for each dot. With this mechanism, the dots are lit
continuously and the only time that they switch on or off
is when the display is changed (eg, when changing the
volume setting). Of course everything is a trade off and
the trade off here is cost. What would be a simple $10
part in the standard multiplexed configuration suddenly
becomes a $200 part to achieve noise-free operation.
t: 01727 865488
March 2014
That is why that is reserved for the ‘R series’ products,
which cost considerably more than the more mainstream
5 series products. Here we use 7-segment LED’s to
indicate the numerical volume control and 14-segment
LED’s to indicate the alpha-numeric characters that
display the input names.
The only Ayre products that use the electrically noisy
multiplexed displays are the products based on DVD
players, including the C-5xeMP universal audio player.
But on these products there is always a button on the
remote control that allows the users to turn the display
completely off for critical listening, and it automatically
turns back on for a few seconds when it receives any
command, whether from the front panel controls, the
remote handset, or the AyreLink communication system.
Sleep mode
And of course the same degree of care is taken with
the microprocessors that control the advanced features
that are expected on modern products. The control
processors are always in “sleep” mode, whereby the
master oscillator is completely turned off. When a
command is received, it is detected, and this “wakes
up” the µP, turning on its clock (which is essential for its
operation as it carries out its instructions step-by-step. As
soon as the command has been executed, the processor
returns to “sleep” mode and the oscillator is turned off
once more.
" As more and more manufacturers have
followed Ayre’s lead of making balanced
components, four of the six inputs on the
AX-5 are balanced. "
If a customer requires additional single-ended inputs,
Ayre sells high-quality single-ended to balanced
adapters. But the converse can only be made with
expensive and imperfect transformer coupling. So we
have chosen to include a full complement of balanced
inputs.
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 14
The AX-5 Story
from Ayre Acoustics
Ease of use
To simplify the use of the system, the inputs may be
named - either from an extensive list of pre-loaded
names, or by generating a custom three character name.
Each input is only active when it is named. In this way the
customer need not scroll through several unused inputs
to reach the desired one, as the inactive inputs are simply
skipped over. This effectively turns the AX-5 into an
amplifier with a custom number of inputs, to match the
number of sources the customer owns (up to a maximum
of six).
Custom remote
The included remote control is our custom metal remote.
This has a slew of great unique features. One is that the
keypad is back lit for easy operation in a darkened room.
Using a single LED to illuminate the entire front panel
via a system of optical fibres, the button to activate the
illumination is physically off by itself so that it can be
found simply by feel even in a pitch-dark room.
The handset also has controls for a disc player or
transport. It is easily configured to operate the CX-7 CD
player (Philips RC-5 codes), D-1, DX-7 DVD players, C-5xe
universal stereo player (Pioneer codes), or DX-5 universal
audio engine (Oppo codes).
" Finally it has Ayre’s exclusive Battery Saver
function. If the handset becomes wedged in
the couch cushions and one of the buttons is
accidentally pressed for a long period of time, it
will not drain the battery. Instead after any key
is held for more than ten seconds continuously,
the internal µP will go to “sleep” and save the
batteries. "
EU compliance
To comply with the recent low-power regulations
enacted by the EU, the unit has a combination master
power switch and magnetic circuit-breaker. No more
looking for replacement fuses when the shops are all
closed. Furthermore the breaker chosen for the AX-5 is
t: 01727 865488
March 2014
not the commonplace thermal breaker that has nonlinear metal alloys chosen for their thermal expansion
properties. It is a hydraulically-damped magnetic circuit
breaker, where the AC mains power is fed through a
coil of pure copper wire. Excessive current draw creates
a magnetic field that opens the electrical contacts,
providing not only the best sound quality, but also the
most reliable and repeatable protective action.
Low-power consumption mode
The right-hand front panel button has two functions. A
short press places the unit into mute mode, indicated
by illuminating the decimal points in the LED display.
Pressing and holding the button for more than three
seconds, places the unit into “low-power consumption
mode”, indicated by the green LED ring on the push
button.
In this state, the bias is removed from the output
stage, reducing the power consumption by a factor of
approximately 10x, the audio is muted, and the display
is turned off. However, the AyreLink function are still
operable, as are the tape out connectors. In this day and
age, the tape out connectors will more commonly be
used to connect the source components to a headphone
amplifier, thereby allowing the preamplifier functions to be
controlled while the power amplifier section is effectively
turned off. However the voltages remain applied to the
audio circuitry allowing for a quick warm-up.
Ayrelink
Pressing and holding the right-hand button also sends
a signal out on the AyreLink connectors on the rear
panel. Levinson was probably the first to introduce
a communication system so that a stack of separate
components could be configured to act as one
large system. But the AyreLink system takes this to a
completely new level.
For starters, the connecting cables are two-line
telephone cables (available at any RadioShack in just
about any length and in three different colours for only
a few dollars). Sometimes these are not used in other
countries, but we include something with every AyreLink
product and are happy to get anything specific that you
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 15
The AX-5 Story
from Ayre Acoustics
may need. Next, there are two connectors on each unit.
Each connector has both an input and an output, so they
are completely interchangeable. The system is connected
in a “daisy-chain” fashion, and the component that
generates the command transmits it on both connectors.
As it travels down the line, any component that is
supposed to react to the command does so and re-sends
the command down the line. If it does *not* need to
act on the command, it simply re-transmits it until all
of the units have received the command. There are no
requirements for connecting things in a certain order or
configuring anything -- just plug’n’play.
March 2014
About Ayre
Ayre Acoustics, Inc. has been designing and building
superior quality, award winning audio and video
equipment since 1993.
They are recognized as a world leader in the industry,
and our full line of audio and video components sets new
standards in innovation, design, and performance.
Discover Ayre and lose yourself in the moment…
intimately experiencing music and cinema that is
perfectly timed and
But the best thing about the AyreLink system is that
each input has an opto-isolator. This means that adding
the AyreLink cables will never cause a ground loop, nor
couple any high-frequency noise from one component
to another. There is absolutely no degradation of the
audio signal from using the AyreLink system - just added
convenience.
No product is perfect
And customers, dealers, and reviewers have always
appreciated the Ayre products for what they do well,
which is to present a musically coherent and naturally
involving recreation of their favourite music. But they
may have also had reservations about the things that the
Ayre products have not done so well.
One of the reservations that some people have is that
the Ayre amplifiers (or perhaps all Ayre products, I’m
really not too sure) do not have enough power or impact
in the bass. Or stated another way, I have never heard
anyone accuse an Ayre product as being “bass heavy”
or “ponderous” or “thunderous”. Much of this naturally
depends to which system the component in question is
connected and a large variety of other factors. But all of
that is changed with the AX-5.
t: 01727 865488
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Page 16
The AX-5 Story
from Ayre Acoustics
March 2014
9 Features
AX-5 Specifications
- VGT for "Variable Gain Transconductance" circuit
Power Output
125 watts per channel continuous into 8 ohms
250 watts per channel continuous into 4 ohms
- Ayre’s new Diamond output stage
- Ayre’s exclusive Equilock circuit
- Linear analog power supply
- Zero-feedback, fully-balanced discrete circuitry
- High-speed circuit board material
- Custom developed audio-grade resistors
- Ayre Conditioner power line RFI filter
- AyreLink communication system
Gain
26 dB
Input Impedance
1 MΩ unbalanced inputs
2 MΩ balanced inputs (1 MΩ per phase)
Frequency Response
DC - 250 kHz
Power Consumption
48 watts in low-current consumption mode
230 watts in operating mode, no signal
Dimensions
17.25” W x 18.75” D x 4.875” H
(44cm x 48cm x 12cm)
Weight
48 pounds (22 kg)
t: 01727 865488
e: info@symmetry-systems.co.uk
w: www.symmetry-systems.co.uk
Symmetry, Suite 5, 17 Holywell Hill, St Albans, Hertfordshire AL1 1DT
Download PDF

advertising