The Quad
II-Classic Integrated
The
rekindled interest in 2 channel analogue hi-fi been remarkable to witness. The
popularity of vinyl has grown steadily over the last years and now represents a
significant proportion amongst real music enthusiasts. Quad has been at the
forefront of this trend with its development of some of the world's most
stunning amplifiers loudspeakers and
phono stages. Creating a compact audiophile integrated solution for LP and
Vintage Hi-End Audio lovers while working in collaboration with one of the
industry's edteemed legendry figures, Tim DeParavicini.
Through his
contemporary designs based on Qad's novel amplifier technology developed over
half a century ago for his invention of the first Quad II Mono Amplifier
introduced in 1953, our classic range of amplifier and speaker componenets
represent far more than a nostalgic trip down memory lane. Each product
represents as significant a design statement as their original counterparts.
The new Quad
II Classic Integrated Amplifier is
perfectly balanced and completely integrated amplifier system to resolve system
matching and offer exceptional performance nd value within a relatively compact
and classically styled chassis.
Performance
as you would expect from one of the most famous names in hi-fi, is nothing
short of breattaking. The 25 watt per channel specified, belies their power and
ability to drive even the most difficult loads. The remarkable output
transformer design is characterized through its speed, agility and ability to
convey the genuine passion of live performnce.
Design and
Engineering
The KT-66
output valves, in push-pull configuration are visually stunning, even when
safely secured within the cage tht protects them. Each valve produces around 25
watts per channel output in "Pure ClassA" which allows a suebrbly
refined sound that appropriately matches modern as well as contemporary
loudspeakers.
The package
had to retainn the retro look of it famous preamplifier predecessor with th
epower amplifier and transformers blended into a modern compact look. It has an
understated elegance which lies beneath its smooth curves and lustrous finish
because it uses a circuit dating back over fifty years to the time when vacumm
tubes ruled the electronics industry and peter Walker was considered by many to
be the master of audiophile design.
All Quad
products are expected to last a lifetime - even longer. Many Quad customers
still derive immense pleasure listening to products built over fifty years ago.
The new Quad II Classic Integrated Amplifier is no exception, and with periodic
servicing and a caring hand, you can expect its performance to continue for
decades to come.
The Quad II
Classic Integrated Amplifier operates in Pure Pentode (Beam Tetrode) output
with partial cathode loading, this being more linear than so called
ultralinear. It is a pure Class A operation, whereas its push pull operation's
efficiency can only rach 50% max and its power supply is the usual capacitor
filter with diode bridge rectifier, AC 6,3 volts heaters to the valves that is
shared between both channels.
Equipped
with a bi polar transistor phono amplifier that uses 4 transistors per channel
with low feedback to provide correct RIAA equalisation. Also has a gain switch
for moving coil caartridges, 0,25 mV at 1 kHz , a circuit which operates from a
regulated 36 V derived directly from th emain HT valve. It ensures a very high
overload performance from rcords.
The phono
circuit is housed in a shielded compartment providing low noise RF proofing
within th emain package.
Amplification
Process
The Quad II
Classic Integrated Amplifier output is 25 watt per channel Integrated Amplifier had to obey Peter
Walker's Philosophy of cathode loading
of the output stage and simplicity of design.
Upon Input,
a selector switch routes the required signal to the volume control then on the
first of 3 small driver valves. This first valve is an ECC83 acting as a
differential balance circuit that is a phase slitter.
The output
going into a pair of ECC88 valves that both operate as a cascode circuit for
high gain and wide bandwidth directly drives the output valves (KT 66) via
capacitors.
The circuit
had to have high gain than a normal power amplifier to offer a nominal 250 mV
input sensitivity on the various inputs.
Push pull
feedback is arranged from the cathodes of the output back to the ECC88 valves
to provide low distortion and noise with consistent performance.
Specificastions
Stereo Power
Output: 25 W per channel into 8 Ω
Total
Harmonic Distortion: 0,06% (at 15W
&700 kHz )
Signal-to-Noise
ratio: better than -95 dB (ref 25 W into
8 Ω)
Frequency
Response: 20 Hz - 20 kHz +0 dB -0,5 dB
Crosstalk:
better than 75 dB
Gain : 34 dB
Noise: -98 dB (275 mV input)
Valve
Type: 4 x KT66; 4 x ECC88; 2 x ECC83
Input
Channel: 3 x Line Level; 1 x MM/MC Phono
and Tape monitor
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