Specifications

5
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 eective 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
dierences at all (noise or distortion
of any type) is subtracted from the
incoming signal. But if this process
worked properly, then all ampliers
would sound identical as they would all
be reproducing the input signal perfectly.
Unfortunately reality is somewhat more
messy than is theory. In reality every
amplier sounds dierent 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 ampliers
employing feedback as those that do not. In fact,
taken as a whole, our experience is that zero-feedback
ampliers tend to sound more similar to each other than
typical feedback-type ampliers.
A far better approach is to simply design a circuit that
is inherently linear, to the point where the distortion
contribution from the amplier 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 zero-
feedback ampliers will nd it dicult to return to
conventional designs.
Introducing the Diamond circuit
I could never gure 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.
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” buer. 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 amplier 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.)
t: 01727 865488 e: [e-mail] 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 March 2014