The Circuit Description:
The Linestage I is an active linestage using vacuum tubes as the gain device. Vacuum tubes
are also used in the regulation of the power supply. A class A triode circuit is employed in a
most straightforward design, with emphasis on keeping the design as simple as possible.
This is in accordance to our design philosophy plus the added benefit of very high reliability
(the simpler the design equates to fewer parts, equates to less parts to fail). The purity of the
signal is kept as intact as possible as it travels through the preamplifier. As the signal enters,
it goes to the selector switch, into the gainstage (the vacuum tube), into the attenuator, and
out. Quick and short, minimizing the possibility of signal degradation by eliminating one or
more stages in the signal path. This is the most straight forward design possible for this
Hertz to 250K Hertz, +0, -3db
than 0.4% at 2V
than 91 db below 2V
than 15 db at 1 kilohertz
6DJ8 or comparable, 2 OA2
main outputs, one tape output
chassis: 18" W x 14" D x 5.5" H
8" W x 13" D x 5.5" H
Paramount Statement: 159 lbs.
Paramount: 81 lbs.
Presence Deluxe 4.0: 78 lbs.
Presence Deluxe: 57 lbs.
Click here for information on ACHIEVING OPTIMUM SONIC PERFORMANCE
The Components and Parts:
The External Power Supply:
The Linestage I is included with an external power supply. It is connected via a
dedicated umbilical cord. The power supply is removed from the main chassis to
improve on the performance aspect of the unit. A power transformer emits different
kinds of spurious radiation that could impede in the uninterrupted flow of the music signal
and thus have a degradation in the performance. Removing the power transformer away
from the main chassis prevents this from occurring. Though implementing an external power
supply is much more expensive, it nevertheless ensures the purity of the signal from
spurious radiation from the power supply.
The ON/OFF Switch:
The on/off switch of the Linestage I is actually an electromagnetic circuit breaker. It functions
as a regular on/off switch and also as a replacement of your regular A.C. fuse. The
electromagnetic circuit breaker provides for a solid contact for the A.C. to go through in
comparison to the little thin wire normally found in A.C. fuses. Furthermore, all the
connections in the electromagnetic circuit breaker are direct soldered rather than having
quick disconnects, ensuring full contact in the electrical junction.
Current Rating of the Bridge Rectifiers:
The current requirements of the Linestage I is relatively small at less than 1 amp. The current
rating of the bridge rectifier is at 4 amps. With the optional power supply upgrade, this current
rating goes up to 12 amps! Such overkill is not by accident but by design. Aside from having
great safety margins in using overly large current ratings, this again ensures the unimpeded
flow of electrons to their destination, resulting in a power supply that is quick, instantaneous
and responsive to the needs of the music. The bridge rectifiers are made from discrete parts
using high quality fast recovery diodes. This translates into a focused, effortless and natural
performance with clear and defined presentation at the musical extremes.
Computers Grade Electrolytic Capacitors:
These large 2.0" x 4.125" capacitors provide for vast amounts of power reserves for the
Linestage I. Totaling to greater than 180,000 mfd in capacitance, these capacitors ensure
that an enormous amount of power is always ready to provide when called for. Having overly
large supply of capacitance provides stability and filtering in the power supply, coupled this
with the high ampere ratings of the bridge rectifiers provides for power reserves that would
seem unfathomable. Computer Grade Electrolytics are choice capacitors for this particular
application where large power capacitance, low ESR and high ripple current are needed.
Two of these capacitors are found in the external power supply and eight are on the main
chassis. The massiveness of the power supply as a whole is perceived with the lowering of
the noise floor, creating a space for the music to unfold that is as black as space itself; no
grain, milkiness or electronic haze. Rather, just the music itself with all its intricacies and
The transients extends to the highest high and the lowest low with blazing speed and
recovery. Bells and cymbals are recreated with such realism that you can almost see the
thickness of the instrument and smell the brass. Bass plunges to the very bottom depths with
such speed, authority and weight while retaining the very subtle nuances, giving such
texture and delineation to the bass notes you never have thought you would be able to
The Dedicated Umbilical Cord:
Measuring at almost 3/5 ths of an inch, the dedicated umbilical cord uses four pairs of twisted
wire with each air having a full 100% shield and a drain wire plus an overall shield and a
drain wire. Using high quality copper ensures signal purity as well as proper physical
characteristics for the intended application. The 100% shield prevents signal loss and
provides coverage for optimum protection against radiated emissions and ingress at audio
and radio frequencies. The shielding ensures that the power from the external power supply
would remain as pure and undiluted as possible from the spurious radiation in the
environment. The individual shielding for each twisted pair of wire further ensures that each
pair would not contaminate each other.
The Main Chassis:
The main chassis is made out of .06 inch thick cold rolled steel. It is then plated with copper
all over as per MIL-C-14550B Class 2 specification. The combination of steel and copper
provides for the best protection against spurious radiation in the environment. In such a
protected environment, the audio circuitry can perform to its maximum potential and not be
subject to any degeneration from the external spurious radiation. Furthermore, copper
plating lowers the resonant frequency of the steel chassis to a level that does not detract
from the harmonics of the musical signal.
Dual Mono Construction:
The Linestage I incorporates a true dual mono construction on the main chassis. This means
that all controls and components are repeated for both the Left and the Right channels. This
approach greatly enhances the channel separation. Separating the components for the left
and right channels decreases the possibility of the crosstalk between channels. Crosstalk
can lead to poor focus and stability of the presentation. It can further degrade the soundstage
presentation, making the soundstage both narrower and shallower. It can also lead to smear
and grain and inability to have clear delineation of the different instruments and their location
in the performance. Having great channel separation is one of the key aspects to great sonic
performances. The minimizing of the crosstalk is essential. Though relatively rare in the High
End industry, true dual mono construction is effectively the best way to minimize crosstalk.
Separate Mounting Platforms:
In adherence to the true dual mono construction philosophy, the Linestage I employs
separate Left and Right Mounting Platforms. These are made from the same material as the
chassis and is also plated with copper. These platforms are shaped in an L figure with one of
the planes held vertically to provide for further shielding from the other channel. It houses the
separate circuit boards in its underside (for further shielding) and attenuators and selector
switches, along with the other computer grade electrolytic capacitors.
Short Signal Path:
As one would look inside the Linestage I, four long stainless steel rods would be apparent.
These rods extend the controls for the volume and selector switches which are located at the
very back of the unit. Keeping the switches at the back helps maintain very short signal path
in the unit. The shorter the signal path, the less possibility of sonic degradation from various
sources, including the wire itself. Even on the circuit boards, the copper traces are kept to a
very minimum length.
The Use of Damping Materials:
The use of damping materials is employed on the main chassis, its cover, the external power
supply and its cover. Circular damping materials along with other vibrations absorption
devices help tune the units’ overall performance. Vibrations can play a significant role in a
chassis sonic signature. The Linestage I is no exception. Extensive listening test were
conducted to determine where and how much damping material would be needed to
produce the overall balance in the chassis.
High Grade RCA Connectors:
These gold plated solid body RCA connectors provide performance levels that are truly in
the very High End. The solid body construction ensures that there is no gap or breach in the
flow of electrons. The gold plating provides for superior contact and resistance to oxidation.
These High Quality Gold RCA’s are chosen primarily for their sonic performance, edging out
even more expensive counterparts.
The Use of High End Wire:
The Linestage I uses custom wire from High End Wire Manufacturers. The Linestage I
employs various sized gauges in the signal path. These wires provide for exceptional
performance over regular O.E.M. wire manufacturers. Specific gauge wire from specific wire
manufacturer is used in specific areas of the signal path. In particular parts of the circuit, up
to 12 gauge size are used! Their high level of performance compensates for their relatively
Extensive Grounding Network:
The grounding topology used in the Linestage I is directly derived from the First Sound
Passive Unit. This particular grounding technique is unique to the whole electronics industry
and can only be found in the First Sound passive and Linestage I products. Such extensive
topology provides for quieter backdrop for which the music can unfold in its entirety. It further
establishes the quick and controlled bass response and the full bodied expression of the
high frequency. Within the grounding topology, ground wires reach up to a maximum size of
9 gauge! The ground leg of the signal has not been neglected and given meticulous
attention in its implementation. The importance of proper grounding cannot be over
emphasized. There is a delicate balance in the relationship between the positive and
negative legs of the signal. With the experience gained from the extensive wiring topology of
the First Sound Passive, the Linestage I has stretched the limits of grounding networks for
linestage applications beyond state of art.
The Linestage I uses an array of discrete resistors on a switch to set the volume level. This is
called an attenuator. These hand made attenuators are superior to any volume
potentiometer (commonly known as a "pot") with regards to the manner of providing
attenuation. The resistance in a pot is done through having a film of carbon spread over a
plastic film. The thickness of the carbon would vary from one end to the other thus providing
the means of attenuation. An attenuator on the other hand has discrete resistors with specific
values to set the attenuation level. The performance of a specific resistor is infinitely better
than having carbon on a plastic film. The switch used in the attenuator of the Linestage I is
the same switch used to select the inputs. This switch is a very massive, having a current
carrying capacity of 25 amps! The very high rating ensures the uninterrupted, low loss
delivery of the signal in the full frequency spectrum. Only premium quality Holco metal film
resistors, along with Vishay thin foil resistors are used. Though these are among the most
expensive resistors available, they are used primarily because of their sonic excellence. In
the construction of the attenuator, each resistor is looped once through the solder lug then
crimped. After which it is then soldered. The extra step of looping the resistor leads through
the solder lug ensures mechanical reliability and optimum contact between the surfaces. The
tedious process of hand assembling each attenuator is rewarded by the clear and focused
delivery of the performance. The lack of grain, searing, rounding of the edges and loss of the
inherent subtlety of the musical instruments are some of the obvious aspects achieved when
using an attenuator.
These resistors were specifically chosen for their sonic performance. In this particular
application, there are very few other resistors that could outperform them, often costing 20-40
times more. Their outstanding musical qualities are gaining notice in the High End industry
as more companies discover their qualities. Holco resistors are made with no ferrous
material. Utilizing the closely controlled production process, the metal film is vacuum
deposited on a ceramic substrate whose ends are gold plated. This is then joined to the
copper end caps and leads. These resistors are used for the attenuators discussed above.
Caddock and Vishay resistors:
These premium brand name resistors, though very expensive, are at the top of their field.
Using metal film foils as the resistive element provides for an unparalleled performance. Due
to their excellence, these the only resistors employed in the main circuit. Using anything less
would result in a sharp decrease in sonic performance.
These are used throughout the unit.
The First Sound Linestage I has various options available to its owners. From the starting
model Presence to the top of the line model Ultimate Paramount, various options are
available as upgrades. The owner of the Presence model can continually add on options
that raise the level of performance all the way up to the Ultimate Paramount level of
performance. This provides a gradual and convenient path for attaining a desired level of
performance without having to have to sell current unit at hand. This further provides for an
opportunity to see the difference between each level of options/performance, giving an
added dimension in developing ones high end system.
We at First Sound are very proud of our products. If there are areas of the product that
has not been covered or leaves certain questions unanswered (or raised new ones), please
feel free to contact the factory. We would like to assist you in the best way possible to help
you make an easier and intelligent decision for your next linestage purchase.
You are cordially invited to listen to a First Sound Linestage I at a dealer nearest you.
Give yourself an opportunity to witness the sonic presentation of the culmination of all that
has been discussed in these pages.
Information herein are subject to change without notice.