Circuitry
All of the line stage and phonograph circuitry in the
Concerto is discrete; that is, made up of independent
transistors, capacitors, and resistors. No IC operational
amplifiers are used in these signal paths. All of our
circuits are as simple as possible, in order to minimize
distortion. Each and every circuit is class-A, and free of
negative feedback loops (except benign degenerative
feedback - see our white paper for the difference). All
passive components are selected for their outstanding
sonic quality and reliability. These include polypropolene
capacitors, 1% metal film resistors, gold plated RCA jacks,
and gold plated, mil-spec, bifurcated gas-tight connectors.
Line Stage
The line stage provides just over 4X, or 12 dB, of gain.
The input to the line stage is unbalanced, the output is
balanced. The unbalanced output is taken from the non-
inverting output. No additional circuitry is required to
produce balanced signals from your Cantata. Therefore,
the balanced outputs are every bit as pure sounding as the
unbalanced outputs. This is often not true, even with
expensive preamplifiers.
Power supplies
We have found that power supplies are a fundamental
determinant of superb sound. Given a reasonably well
designed circuit, the power supply design and execution
will ultimately determine how well music is re-created.
We also feel that a power supply must be designed to the
specific needs of different circuits; there is no one "best".
The power supply configurations in the two stages of our
Cantata amplifier, and the two major circuits in the
Concerto, are all at least slightly different in conception.
This is the result of hundreds of hours of listening, and
correlating designs to the most musically faithful sound.
All power supplies in the Concerto are locally regulated
using discrete components.
Plug-in circuitry
Both the line stage, and the optional phono (RIAA & gain)
stages are provided on plug-in circuit boards.
Since its circuitry is contained on plug-in boards, your
Concerto may be upgraded or customized easily and cost
effectively. You need purchase only those circuit boards
which you wish to use, and can make cost-effective
upgrades as your needs changes, or as our research and
development yields significant breakthroughs in the future.
Balance
Two adjustment knobs are provided which attenuate each
channel independently. This arrangement is the purest we
know of: it adds only a single metal film resistor to the
signal path, as apposed to the carbon or plastic
potentiometers used by almost everyone else. Each trim
selector provides twelve settings. The first setting is a
direct connection or "by-pass". Successive counter-
clockwise settings attenuate the signal in the following
steps:
#1 -0.0 dB (Full On)
#2 -0.5 dB
#3 -1 0 dB
#4 -1.5 dB
#5 -2.0 dB
#6 -3.0 dB
#7 -6.0 dB
#8 -9.0 dB
#9 -12.0 dB
#10 -15.0 dB
#11 -18.0 dB
#12 -24.0 dB
Input Selector
The input selector determines which input you will listen
to, and/or record on tape. Much research, listening, and
evaluation has gone into the selection of this critical
component. We tested, listened to, and ranked nearly a
dozen of the best rotary switches available before
discovering these swiss jewels with silver contacts. This
switch, the first in the critical signal path, uses self wiping
silver contacts to provide a clean, sonically excellent
connection every time.
The five line inputs are labeled "CD", "Tuner",
"AUX 1", "AUX 2", and "AUX 3". These labels are for
convenience only, all "line" inputs are standard and can
accept most low-level audio signals from tuners, VCRs,
televisions, tape decks, etc. The maximum gain
(amplification) from these inputs to the amplifier outputs is
12 dB unbalanced, 18 dB balanced. The overload level is
greater than 5V r.m.s.
In addition to the line inputs, there is provision for a
turntable to be connected. The "Phono" input can only be
used if you install a phono circuit card.
