Spectral DMC30SC
 Design Qverview
The DMC-30SC
Reference Preamplifier
It required years of painstaking research and develop-
ment and exhaustive listening trials to create the renoun-
ed DMC-30SV ‘Super Veloce’ Reference Preamplifier.
The DMC-30SV succeeds the classic DMC-30SS
reference preamplifier, for eight years our most popular
product and one of the most highly regarded audio
components in the high-end audio industry. Developed
over the course of three years, the DMC-30SV is the
fourth generation of the DMC-30 family which music
enthusiasts worldwide have come to regard as the gold
standard in state-of-the-art performance and top value.
The DMC-30SV utilizes new Spectral exclusive tech-
nologies and componentry to raise the bar in signal
control and amplification to a new level of precision.
With the stunning success of the DMC-30SV reference
preamplifier, Spectral customers have clamored for a
simplified preamplifier utilising the new SV technology.
To meet this challenge, Spectral engineers have devised
a new ‘straight-line’ DMC-30 which utilizes single-end-
ed operation for inputs and outputs. This single-ended
DMC-30 is called the DMC-30SC. It offers the sing-
ular performance of the benchmark DMC-30SV in a
new ultra high-value preamplifier.
Since the establishment of our company in the 1970s
and the introduction of our very first audio component,
high performance preamplifier design has occupied the
highest engineering priority at Spectral. Our special
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focus on high-end preamplifier development over the
years is based on the major design challenges which
low-level amplifier and control circuitry can represent.
At these critical signal levels minute amplifier distor-
tions and signal control colorations are passed on and
magnified by power amplifiers to dominate the sonic
signature of the best audio systems. Spectral engineers
have spent the last four decades pursuing ideal perfor-
mance and signal transparency in audio preamplifiers
to realize ultimate fidelity in high-end music systems.
The Super Veloce Technology
In the DMC-30SV and DMC-30SC preamplifiers our
engineer have evolve the renowned DMC-30 topology
with our most advanced amplification circuits to date.
Utilizing recent breakthrough understanding in high-
speed transistor behavior, new semiconductor designs
exclusive to Spectral address historic limitations in
amplifier linearity and banish low-level distortions to
previously unattainable levels. These devices are utilized
in our new generation high-speed, wide-band preamp
output sections with unprecedented results.
Thermal Memory and Super Transistors
For years Spectral engineers have investigated the
fleeting signal memory distortions found in certain
semiconductor devices known as “thermal tails”.
These elusive non-linearities occur at high speeds in
transistors during switching as junction behavior
changes as a function of heating and cooling. This
change in semiconductor switching behavior affects
amplifier circuit linearity until the device recovers
from transient heating. This “thermal memory” dist-
ortion has long been a recognized phenomena in high
tech amplifiers circuits for RF and microwave but is
ignored by conventional audio engineers. In high res-
olution audio amplifiers, however, we find low-level
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transistor distortions problematic as they compromise
signal linearity and transient settling. Having isolated
and observed these distortions in our own high-level
driver circuits, Spectral engineers first addressed their
elimination in our reference standard amplifier designs.
Solving these subtle distortions which blur transient
waveforms requires uniquely precise test and measure-
ment systems and specific semiconductor designs
which do not change their linearity under transient sig-
nal conditions. The results of this development are the
finest performing amplifier circuits we have designed.
Now our goal in Spectral preamps is to successfully
apply the benefits of the new semiconductor technology
for the first time.
The SHHA Generation 3 Analog Line Modules
Just as the preamplifier is the essential heart of the
finest music systems, the ‘Spectral High-speed Hybrid
Amplifier line module is the essential heart of our
high resolution preamplifiers. For this reason, the
modular architecture of Spectral preamps has been
developed to accommodate the design evolution of our
SHHA technology with convenience and ease. Now
the new SHHA G3 line module takes our wideband,
fast-settling discrete circuitry to a new level of refine-
ment and signal resolution. Spectral engineers have
continued to optimize the dense surface-mount Fet
topology of the SHHA module with new ultra premium
custom semiconductor devices and new circuit innov-
ation and refinement.
The input cascode of the SHHA G3 module utilizes our
own proprietary Fet technology. These new dual J-Fet
devices developed for Spectral, provide higher gain
with ultra-fast transient settling. In addition, Teflon
SMT precision film capacitors provide ultimate signal
transparency in critical circuit locations. Custom ultra
low value polystyrene film capacitors and Teflon film
trimmers adjust each module for ideal transient respon-
ce and wideband stability. These and other advances in
the SHHA G3 module assure uncompromising sonics
and extended reliability. Musical results include
higher resolution, greater dynamics and improved
ssussssvauv vu JCture. Vastly improved imaging and focus
have resulted from the elimination of these transistor
thermal-tail distortions.
THe Case for Uncompromising Attenuation
Certain devices in a high-end preamplifier fundament-
ally determine the ultimate performance possible in
the component. Since a preamplifier basically amounts
to an adjustable line amplifier, the role of the volume
control or gain attenuator system is especially critical
and will have a strong influence over the final sonics
of the component. Most of today’s high-end preamps
incorporate various digital and IC based attenuator
systems to control gain, while a minority still use
mechanical controls, potentiometers, switches or relay
arrays. In our experience, all these approaches have
serious compromises which limit signal transparency,
dynamic range, step resolution or reliability.
Today, digital based IC attenuators are ubiquitous in
modern audio design. But even the most exotic of
these digital and solid-state attenuators color the sound
in various ways. Since digital attenuators are not soni-
cally transparent and stepped resistor attenuators have
step size, contact life and dynamic range limitations,
the ultimate gain control would have to be a variable
potentiometer or fader. Unfortunately, no pot or fader
currently available is transparent or linear enough for
the most critical gain adjustment applications in audio.
The Spectral Super Fader Technology
To solve the problems of existing gain control systems
Spectral engineers work with a leading aerospace con-
tractor. Out of a multi-year design effort comes an
extraordinary ultra-precision gain control. The
Spectral ‘Super Fader’ combines mechanical precision,
advanced materials science and unrestricted use of
exotic materials to create a level control that behaves
like an infinite number of theoretically ideal resistors.
Inside, the critical moving parts are precision machined
from solid precious metals. These wipers have many
surfaces that contact micro-polished optically flat
resistance elements. Exemplary mechanical design and
alignment is used to prevent localized heating from
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circulating currents. Ultra-pure contact metal eliminates
solid-state or junction distortions which occur from
plated parts in other controls. When such precision and
material commitment are combined, noise and error is
unmeasurable and performance is very near to ideal
thermal accuracy limits. The ‘Super Fader’ potentio-
meter outpreforms all existing gain control systems with
virtually infinite service life. We hear a transparency,
as if a wire has been substituted for the control.
The DMC-30 Floating Power System
Key to the performance of the DMC-30 is a most
advanced powering system and regulator topology we
call the ‘Floating Power’ system. It offers extreme
isolation from environmental and ac line interferences
while powering sensitive signal circuits in a remarkable
silient envelope. This floating power or battery-like
regulator was developed for the SDR-4000 Reference
CD Processor and it has demonstrated a superior isol-
ation of noises that occur from power line, audio/video
and digital switching sources. Its combination of dense
physical size and electrically open circuit design, can
out perform batteries and other devices to provide pure
floating power. Amplifier circuits within the DMC-30
receive highly regulated voltages as if from many small
batteries. But unlike batteries, the floating shunt regula-
tor isolates both low and high frequency noise contami-
nation so circuits are not subject to outside noise, nor
pass residue from amplification of audio signals. This
enviromental isolation improves performance from
complex sound systems as well as assuring unhindered
perfrmance from the DMC-30 itself. The Spectrtal
‘Floating Power” regulator is a superior approach to
powering and noise isolation. By integrating supply
regulation with noise supresion it outperforms ac line
isolation products which impose their own colorations.
The DMC-30SC Reference Preamplifier-
Uncompromising Performance and Value
We are pleased to see more and more music enthusiasts
are coming to understand that no music system can be
any better than the performance of its preamplifier.
There is growing sophistication in regards to absolute
performance and price. At a time when ultra high price
preamplifiers are routinely introduced at several times
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the cost of Spectral, the thoughtful music enthusiast is
left to wonder exactly what benefits these lofty prices
bring? We believe the sohisticated customer will find
the answer in the uncompromising DMC-30SC.
Few preamplifiers at any price can boast the designer
credentials and unrivaled component quality of the
DMC-30SC. Edge-of-the-art amplifier technology
and advanced custom component design are utilized
throughout the DMC-30SC to a degree rarely seen
in stratospheric components. This is because Spectral
engineers have identified those key components that
most determine instrument stability and sonic trans-
parency and have invested agressively. When careful
investment in superior circuit performance and signal
path components becomes the design priority over elab-
orate metalwork sculpture, state-of-the-art clarity and
signal resolution can be achieved with affordably and
and high value.
The world renouned Spectral DMC-30SV has redefined
preamplifier performance and signal resolution in the
most ambitious music systems. Now the DMC-30SC
reference preamplifier offers enthusiasts the advanced
“Super Veloce” amplifier technology introduced in the
DMC-30SV in a remarkably affordable single-ended
DMC-30 design.
The stunning clarity of DMC-30 preamplifiers is not
achieved by accident but was accomplished through
painstaking engineering and listening care based on
our forty years of preamplifier design experience.
The DMC-30SC brings the breakthrough performance
and instrumentation quality of the DMC-30 family to a
wider audience, offering a new level of musical realism
and exceptional value previously unknown in the audio
industry. Compare our new DMC-30SC reference pre-
amplifier against the most costly and ambitious high-
end preamps. We are confident you will discover the
important musical difference Spectral's superior engi-
neering and design innovation can make in your listen-
ing experience,
| Dealer Interviews
Q/A: The DMC-30SC Reference Preamplifier
1) What is it?
The DMC-30SC is the new foundation preamplifier from Spectral. Like all DMC-30 preamplifiers, it features
very high performance with ultra value. It offers the finest performance yet achieved at its price point.
2) Why was it created?
Spectral has built high-performance / high-value preamplifiers since the 1970’s. Until 2000, all of these
preamplifiers operated with manual controls to achieve the most uncompromised performance. The recent
DMC-15SS followed this straight-line manual tradition with tremendous success worldwide. After analyzing
the market we decided to base its successor on the remote controlled DMC-30 platform. The high-end customer
has changed, with many clients finding manual control operation simply too awkward to relate to. The DMC-30
platform solves this dilemma with an uncompromised signal path and the convenience of a full remote
operation. The DMC-30SC replaces the DMC-15SS as our highly affordable foundation reference preamplifier.
3) How is it different from DMC-30SV?
The DMC-30SC is our foundation preamplifier and as such offers single-ended output amplifiers and single-
ended inputs like the DMC-15. The topology for the output section comes from the DMC-30SS and uses the 301
output board. The DMC-30SC continues with the passive component technology of the DMC-30SS, whereas the
DMC-30SV utilizes fully balanced model 304 and 301A modules.
4) Haven’t we offered a single-ended DMC-30 before?
Yes, twelve years ago Spectral built the DMC-30S Reference preamplifier which was a single-end version of the
DMC-30. This preamplifier also offered extreme performance / price ratio and was very successful for Spectral
5) What are the applications for the DMC-30SC
Customers seeking the highest performance for the price and do not have a requirement for balanced I/O
interfacing will find the DMC-30SC ideal. Spectral has proven that single-ended operation and interface offers
exception performance in our preamplifiers and most of our clients chose to use them this way. Those requiring
ultimate, state-of-the-art performance with balanced source components and balanced cable interface will prefer
to consider the unsurpassed DMC-30SV.
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6) How is it a Reference preamplifier?
The DMC-30SC shares its core technology and topology with the DMC-30SV, uncompromising features like the
DMC-30 “super fader’ and “silent control architecture “are common to both.
7) Does the DMC-30SC use the Gen 3 SHHA modules?
Yes it does. The DMC-30SC uses two of the G3 SHHA modules in combination with the model 301A output
board which was used in the DMC-30SS.
8) Is it intended to be upgradeable like the DMC-30SV?
Possibly. That option will be considered at a future date if there is a demand.
9) Who will be offering the DMC-30SC?
All Spectral dealers can offer the DMC-30SC, however, we developed the DMC-30SC specifically with the
Spectral Foundation dealers in mind.
* Full feature remote control operates all functions.
* Indicator displays are clearly visible from a distance.
* New generation high-level line output section topology.
* Improved SHHA G3 ultra high-speed hybrid amplifier modules
with ultra precision compensation components.
* 80 volts peak-to-peak output voltage for unprecedented dynamics.
* Relays allow signal control selection at the optimal point in the circuitry,
maintaining the shortest signal path.
* Microprocessor "sleep mode" and silent display architecture.
* Cost-no-object discrete custom component technologies.
* Custom ultra-precision mil-spec studio audio attenuator.
* Ultra low-noise "silient power" supply system, with floating ground shunt regulation.
* Three-tiered architecture takes the signal path off the power supply circuit board.
* Fully symetrical architecture takes maximum advantage of differential operation.
* Optically isolated protection systems for maximum signal purity.
* Optional balanced input and balanced output modules.
Input Compliment:
Output Compliment:
Control Compliment:
Output Attenuation
Output Balance
Mute Switch
High Level Trim
Mode Switches
Input Select
Output Level Display
Output Balance Display
Input Impedance
Output Impedance
Recording Amplifiers:
Input Impedance
Output Impedance
Protection Circuit
Protection Mode
Chassis Temperature
Frequency Response
Slew Rate:
Rise Time:
Output Voltage:
Output Current:
Remote Control:
7 inputs - 5 normal, 1 balanced (optional), tape monitor
3 outputs - normal, balanced (optional) , tape
Motorized custom fader conductive plastic, modified log taper
Relay attenuator system with center position bypass
0, -20 dB attenuation
0 and -12 dB attenuation for all high level inputs
Stereo/Mono, Absolute Phase
6 position, and tape monitor
50 step LED
50 step LED
15K ohms
100 ohms
20 db unbalanced, 26db balanced
11K ohms, 100 ohms minimum load
2K ohms
DC offset, oscillation
Crowbar output relays
20 mV continuous DC
Approximately 10 seconds
Internal 48° C @ 25° C room temperature
DC to 5 MHz, -3 dB
DCto1 MHz, -.10dB
Any level to 36 V RMS
1000 V/us or greater
70 ns
Less than .005 % THD and IM
Greater than 92 dB
105 dB A Weighted, ref 100 mV @ 1 KHz
1.6 VRMS, 100 V peak to peak maximum
1 Amp maximum per channel, balanced out
operates all front panel functions, level and balance rates,
display brightness, and system reset
48.3 ст (19") W, 10.4 em (4.1") H, 31.1 cm (12.25") D
11.8 kg (26 Ibs) net.
ctral Audio Incorporated www.spectraiaudio.com
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