Coda 1 Users Manual FET PREAMPLIFIER 01

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TECHNOLOGIES INC.

ADDRESS

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SAFETY PRECAUTIONS

INSTALLATION CONNECTIONS

INTRODUCTION

DETAILED INSTALLATION

DESIGN PHILOSOPHY

TECHNICAL DATA

CARE and HANDLING

WARRANTY

WARRANTY REGISTRATION

OPERATION MANUAL

FET PREAMPLIFIER 01

!

CAUTION

CAUTION

WARNING

WARNING !

SERVICING TO QUALIFIED SERVICE

CAUTION: TO PREVENT ELECTRIC SHOCK,

DO NOT REMOVE COVER. NO USER

SERVICEABLE PARTS INSIDE, REFER

PERSONNEL.

THIS SYMBOL IS INTENDED TO ALERT

YOU OF THE PRESENCE OF IMPORTANT

OPERATING AND MAINTENANCE

INSTRUCTIONS IN THE LITERATURE

ACCOMPANYING THE UNIT.

THIS SYMBOL IS TO ALERT YOU OF THE

PRESENCE OF UNINSULATED DANGER-

OUS VOLTAGE WITHIN THE UNIT'S

ENCLOSURE THAT MAY BE OF SUFFI-

CIENT MAGNITUDE TO CONSTITUTE A

RISK OF ELECTRIC SHOCK.

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SAFETY PRECAUTIONS

WARNING: TO PREVENT FIRE OR SHOCK HAZARD, DO NOT

EXPOSE THIS UNIT TO RAIN OR MOISTURE. TO

AVOID ELECTRICAL SHOCK, DO NOT OPEN THE

UNIT. REFER SERVICING TO QUALIFIED PERSONNEL.

Never install or remove the power cord from the chassis

unless it has been disconnected from the AC power source

first.

Never pull on the power cord when removing it from an AC

power source. Grasp it by the plug.

Do not leave the power cord connected to an AC power

source unless it is connected to the unit.

It is recommend that during extended periods of nonuse

that the units power cord be unpluged from its AC power

source.

Route the AC power cord so that it will not be damaged or

walked on.

CAUTION -

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This preamplifier is a precision device, designed in an effort to provide the listener with

unmatched sound quality, design, and construction. In order to operate your preamplifier

properly and to realize all of the capabilities of the FET PREAMPLIFIER 01, we recommend

that you read this entire manual carefully.

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INTRODUCTION

AC LINE INPUT (SEE BOTTOM) GROUND

LEFT

PHONO / LINE

RIGHTRIGHTRIGHTRIGHTRIGHTRIGHTRIGHTRIGHT LEFTLEFTLEFTLEFTLEFTLEFTLEFTLEFT RIGHT

COMPACT DISCTUNERVIDEOINRECORD ONEOUTINRECORD TWOOUTOUTPUT

LEFT RIGHT

BALANCED OUTPUT

RECORDER TWO

The first section of the installation instructions for the FET PREAMPLIFIER 01 is a diagram of

the basic configuration required to bring the preamplifier into an operating mode. These

brief steps will allow you to begin operating your system. Make sure during installation

that the level control is turned fully counter clockwise, all other components are off, and

AC power connections are interrupted to the preamplifier. While the diagram may be

self explanatory, we strongly recommend that you read the detailed instructions

following this introductory section.

POWER AMP

POWER AMP

INPUT OUTPUT INPUT OUTPUT

PHONO / LINE

COMPACT DISC

TUNER

RECORDER ONE VIDEO

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INSTALLATION CONNECTIONS

Ω

Ω

Ω

ΩΩ

Ω

Ω

Ω

22 22

47 47

100 100

1000 1000

1000 PF 1000 PF

200 PF 200 PF

100 PF 100 PF

50 PF 50 PF

ON

ON

I. Set up and Installation

1. If the phono stage has been incorporated in the preamplifier it will be necessary to set

the gain as well as the loading for each channel prior to installing the unit. With the unit

unplugged, remove the cover using the supplied Allen key. The default value for the gain

is “Low", such as would be used with a high output Moving Coil or a Moving Magnet

cartridge. The “High” setting will provide an additional 20dB of gain, if necessary, for

lower output cartridges.

2. In order to set the input loading, it will be necessary to toggle the DIP switches which

are located on the main board of the preamplifier. Each one of these switches connects

a resistor or capacitor in parallel with the input and so adjusts the load value. The default

values are 47k Ohms and 50pF. Refer to the diagram below, which is repeated inside

the unit, to determine the values which need to be switched in for your cartridge.

Replace the cover after setting the switches.

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DETAILED INSTALLATION

LOW

HIGH

LOW

HIGH

PHONO STAGE

WARNING: NEVER OPERATE THIS UNIT WITH THE TOP COVER REMOVED. NEVER MAKE ANY

INTERNAL ADJUSTMENTS WHILE THIS UNIT IS CONNECTED TO AN AC POWER SOURCE.

3. The balanced outputs are equipped with switchable phasing due to differences in the

USA/EUROPEAN standards. The default setting is EUROPEAN, but may be switched

according to the following diagram.

Note: These switches may also be used for selecting absolute phase .

XLR BOARD XLR BOARD

4. Position the FET PREAMPLIFIER 01 in the space which you have chosen, leaving enough

space to connect the ancillary components of your audio system, and the AC power

cord for the preamplifier. Although the FET PREAMPLIFIER 01 has the ability to reject

external fields that produce system noise, it is recommended that the unit not be placed

near any sources of strong electromagnetic energy.

5. Before installation, make sure all of the power switches of any associated components

are switched off. If any of your other audio components do not have power switches,

make sure they are unplugged from their AC power source.

LEFT RIGHT

BALANCED OUTPUT

LEFT RIGHT

BALANCED OUTPUT

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+

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+

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1

2

3

1

2

3

1

2

3

1

2

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2

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1

2

3

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DETAILED INSTALLATION

USA EUROPEAN

Note: The Operating Voltage of the FET PREAMPLIFIER 01 is convertible

in order that it may be used worldwide. Contact your dealer to

arrange altering the operating voltage.

AC LINE INPUT (SEE BOTTOM) GROUND

LEFT

PHONO / LINE

RIGHTRIGHTRIGHTRIGHTRIGHTRIGHTRIGHTRIGHT LEFTLEFTLEFTLEFTLEFTLEFTLEFTLEFT RIGHT

COMPACT DISCTUNERVIDEOINRECORD ONEOUTINRECORD TWOOUTOUTPUT

LEFT RIGHT

BALANCED OUTPUT

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DETAILED INSTALLATION

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6545321

II. Source-Output, and Power Connections

The input and output connectors are clearly marked on the rear lip of the top cover. It

is important to remember the correct left or right channel orientation. The function and

channel markings on the rear panel correspond to the front panel controls and their

signal paths.

1. The GROUND post should be attached to the ground wire from a turntable.

2. The PHONO/LINE inputs should be attached to either the outputs of a turntable, or

if using the bypass option, may be treated as another line level.

3. The CD, TUNER, and VIDEO input connections are all line level inputs, requiring only the

insertion of the RCA plugs.

4. The RECORD ONE and TWO inputs should be attached to the OUTPUTS of the

corresponding recording device; alternately, they may be used as additional line inputs.

5. The RECORD ONE and TWO outputs should be attached to the INPUTS of the

corresponding recording device.

6. The OUTPUTS (unbalanced) should be attached to the amplifier inputs either directly,

or through a crossover or processor, as appropriate to the application.

7. The BALANCED OUTPUTS should be attached to the balanced inputs of the amplifier,

either directly or through a crossover or processor, as appropriate to the application.

8. The AC LINE INPUT should be attached to the power cable provided with the pre-

amplifier. After making the appropriate connections and rotating the level control fully

counter clockwise, insert the three prong safety plug into an appropriate AC power

source. Once properly connected, the LED on the front panel will light. At this point, you

may switch on your chosen ancillary components including the power amplifier.

III. Front Panel Control Functions

1. The INPUT SELECTOR control selects the source which will be presented to the

unbalanced OUTPUTS and BALANCED OUTPUTS.

2. The RECORD SELECTOR control selects the source which will be presented to both of

the record outputs. Because of the independent controls, one source may be monitored

while a second, different source is being recorded.

Caution: Do not attempt to activate the record mode of a recording device when it is

selected as a recording source. This is an illogical state and may cause oscillation of the

recording device. If the monitor control is set for this device, the oscillation may produce

damaging levels at the unbalanced outputs and balanced outputs.

3. The MODE control allows selection of stereo and reversed stereo, as well as mono

(summed) output.

4. The BALANCE control works by attenuating the right channel when being rotated from

the detent in the counterclockwise direction, and conversely, the left channel for

clockwise rotation.

The element is conductive plastic. Adjustment is continuously adjustable allowing for

infinitesimal adjustments to match channel gain, which is impossible with stepped

controls.

5. The OUTPUT LEVEL control is a precision tracking, audio taper, conductive plastic

potentiometer used to adjust the voltage level at the outputs and balanced outputs.

Clockwise rotation, of course, increases output.

Select a source with the INPUT SELECTOR switch and advance the OUTPUT LEVEL control

to the level you wish. Keep in mind that your input sources will vary in level which can,

when switching from one input to another, abruptly yield uncomfortable sound pressure.

Note: If a power interruption occurs to the system, reduce the OUTPUT LEVEL control gain.

The resumption of power will cause no noise pulses in the FET PREAMPLIFIER 01. However,

some sources may produce high output voltages on turn on, which may cause damage

to an amplifier or speakers .

REVERSE

STEREO

MONO

PHONO/LINE

COMPACT DISC

TUNER

VIDEO

RECORD ONE

RECORD TWO

INPUT SELECTOR RECORD SELECTOR BALANCE OUTPUT LEVELMODE

FET PREAMPLIFIER 01

DETAILED INSTALLATION 7

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DESIGN PHILOSOPHY

I. Design Philosophy and Approach

The circuitry utilized in your FET PREAMPLIFIER 01 is the result of an advanced and

complete design process combining innovation and proven fundamentals. This process

avoids both the limitations of total adherence to convention and the flaws resulting from

inappropriate application of clever circuit gimmicks. Our approach demands painstaking

consideration of every facet of each design choice regardless of how small. Analytical,

as well as subjective techniques are all applied in an open-minded fashion with “no

compromise” musical perfection as the goal. The resulting refinement of the product

escapes simple explanation. With this in mind, we present here a few design highlights

and concepts.

All voltage gain is derived from FETs. While careful design can yield good results from any

device type, FETs consistently seem to have the edge in voltage gain and interface

applications. This is borne out by superior sonic qualities observed in subjective testing.

FETs are inherently transconductance devices, meaning that an input voltage controls

an output current. In other words, it “senses” the audio signal without drawing current

from the source to provide an output. This eliminates complex interactions with the

source allowing maximum performance from each system element and greatly reducing

the chance of cable characteristics altering the sound. The absence of input current in

FETs also allows high bias currents for linearity and speed without sacrificing DC parameters.

While excellent capacitors for coupling use exist, there can be no doubt that a signal

path free of coupling caps yields the best possible signal integrity. The DC stability of the

circuit eliminates the need for any questionable DC servo circuits or coupling capacitors.

We make no AC compromises for DC performance, however. Our key design choices

provide not only inherent DC stability, but also optimized AC performance throughout

the audio region and well beyond. These choices include the use of top quality dual FETS

in differential configurations for all voltage gain. Because the signal in these stages is

handled in a balanced manner, rejection of unwanted noise and modulation from

external sources is extremely high. This rejection extends even to noise which may

originate within the circuit from support circuity such as current sources. Stray RF signals

are also rejected well.

In the phono stage where the necessary equalization requires the use of capacitors, we

use only high grade film types. These and other equalization components were carefully

chosen to maintain response to within .2dB of RIAA standard. An additional subsonic

rolloff at 14 Hz serves to reduce IM Distortion.

Noise is kept low by paralleling input devices, careful selection of circuit impedances,

and pre-screening of devices.

The class A complimentary followers used to drive the preamp output are of such speed,

linearity, and low output impedance that no feedback correction is required or used. The

advantage of this is that the circuit’s perfect stability and transient response are

preserved into a wide range of difficult and unpredictable loads. Variation in sound

which could occur through interactions with interconnect cables and other system

elements are thus avoided. A simple, very high performance inverter provides a fully

balanced output on the preamplifier which allows the user to take advantage of the

balanced inputs on many power amplifiers. The most commonly acknowledged

advantage of this is rejection of stray noise pickup, but improvements in distortion and

bandwidth may occur also.

While many manufacturers intentionally omit recording buffers on the grounds of signal

path simplification, the potential advantages of their use were worth an investigation.

The resulting experimentation ended with the development of a circuit of such simplicity

and performance that its transparency was guaranteed. The circuit is simply a direct

coupled, class A, FET follower. Because of the FETs inherent characteristics, the buffer

provides total isolation of the recording system from the main signal. In addition, it

provides a relatively high, purely resistive load to the source, and a relatively low, purely

resistive drive to the recording system. This assures consistent stability and freedom from

interactions, including cable effects.

DESIGN PHILOSOPHY 9

The requirements of a power supply for flawless audio reproduction are straightforward

but important. The supplies in the FET PREAMPLIFIER 01 take a very direct approach to

high performance. First, a top quality shielded toroid transformer with plenty of reserve

current capability is used. The shielding eliminates strong fields which could induce hum

into sensitive circuitry. About 20,000 uF of capacitance with very low ESR and inductance

provides good passive filtering. A reference voltage is developed by delivering a

constant current to zener diodes. The resulting voltage is heavily filtered and delivered

to each stage through independent class A followers which completely decouples the

stages. The resulting non-reactive low impedance over an extremely wide bandwidth

yields a perfect power source for the individual circuits. The simplicity and absolute

stability of the supplies removes the chance of unpredictable interactions which may

occur with the more elaborate, high feedback circuity often used.

Most companies in the upper end of the audio industry use either sheet metal or formed

aluminum. By contrast, the FET PREAMPLIFIER 01 has all structural parts made of machined

extruded aluminum. The advantage of this over an all stamped chassis is that the

machined metal can be worked more precisely allowing us to work on tighter tolerances

and use PC mounted parts more easily. Moreover such a design allows easier servicing

either for repair or for future upgrading. From the standpoint of appearance, a

machined surface can be contoured in a far more precise manner, giving the final

product a more seamless appearance.

II. Parts' Quality

1. Finishes - All exterior and interior metal parts are anodized. While paint may be more

impact resistant, the anodized surface is more resistant to solvents and prevents corrosion.

Moreover, the anodized parts' appearance can be enhanced by either graining or

bead-blasting the surface.

2. Circuit Boards - Circuit boards are fiberglass epoxy with gold plating over a tin/nickel

barrier. This gold layer will not corrode, while the barrier plate prevents the gold from

migrating to the lower copper layer and detracting from its appearance.

3. Resistors - All are high reliability metal film 1% resistors.

4. Capacitors - All capacitors have been eliminated where possible on the basis that “no

cap is better than the best cap.” Where they are used in the active part of the circuitry,

they are high quality film caps. The only electrolytics used are in the power supply where

large numbers provide enormous filtering capacitance for the supply.

5. Semiconductors - There are no integrated circuits (IC) to be found in this product. Very

high quality dual FETs are the only source of voltage gain and were selected for their

superb noise performance and precision matching. The remaining semiconductors are

also of very high quality, each possessing parameters ideally suited for the specific

application.

6. Potentiometers - The volume controls are conductive plastic. These pots track with little

error and are totally neutral.

7. Connectors - Coda employs a standard RCA configuration with a gold plated case.

The balanced output connectors are Neutriks from Switzerland. These are black chrome

finished with gold contacts.

8. Wire- All signal wire has been eliminated whenever possible. Where wire is used, Coda

employs silver plated copper, 141 strand, 18 gauge wire with a silicone insulation.

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DESIGN PHILOSOPHY

HIGH LEVEL

Frequency Response: DC to -3dB @ 200kHz

Distortion: <.01 percent from 10Hz to 40kHz @ 6 Volts peak into 600 Ohms or

higher, shunted by 1000pF or less .

Gain: 14dB unbalanced

20dB balanced

Maximum Output: 12 Volts peak

Noise: >100dB referenced to 1 Volt output

Input Impedance: 20k Ohms

Output Impedance: 15 Ohms non-reactive unbalanced

30 Ohms non-reactive balanced

Crosstalk: 70dB @ 20kHz

PHONO STAGE

Frequency Response: +/- .2dB of RIAA with an additional subsonic rolloff at 14Hz

Distortion: <.01 percent from 10Hz to 40kHz @ 3 Volts peak output

Gain: 37dB @ 1kHz (Low)

57dB @ 1kHz (High)

Maximum Output: 12 Volts peak

Noise: >85dB referenced to 1 Volt output

Input Impedance: 22 Ohms to 47k Ohms

50pF to 1050pF (see Set Up)

Crosstalk: 70dB @ 20kHz

BUFFER

Frequency Response: DC to 1 MHz

Distortion: <.01 percent from 10Hz to 40kHz @ 3 Volts peak into 20k Ohms

Gain: 0 dB (Unity Gain)

Maximum Output: 12 Volts peak

Noise: >100dB referenced to 1 Volt

Output Impedance: 1k Ohm non-reactive

DIMENSIONS

Height: 1.75" Faceplate, 2.35" Overall

Width: 19.0" Faceplate, 17.0" Chassis

Depth: 9.75" Overall

Weight: 15 lbs. Shipping

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TECHNICAL DATA

CARE and HANDLING 12

The interior of the unit requires no special care, due to the use of sealed controls and gold

plating on contacts. If it becomes necessary to clean the exterior, a simple dusting may

be all that is required. If a cleaner is necessary, any dilute commercial ammonia based

product will be appropriate. NEVER use any abrasive rags, cleaners or chemical solvents

on the preamp.

When removing the cover to set the loading switches or otherwise handling the unit, take

care not to mar the aluminum. Aluminum is a medium hardness metal and can be

scratched by the harder tool steels.

Avoid exposing the unit to direct sunlight, and keep it away from sources of intense heat.

If you wish to rack mount your FET PREAMPLIFIER 01, it is advised to place nylon washers

under the heads of the mounting screws to avoid scratching the anodized finish.

Do not throw away the carton or associated packing material. They are ideal if you need

to pack the unit for moving and in the unlikely event that servicing is needed, they will be

necessary for safe shipment.

Be sure to provide adequate insurance when shipping.

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WARRANTY

I. Warranty- Any failure of the FET PREAMPLIFIER 01 to operate or to meet specifications,

applicable at time of manufacture, due to a manufacturing defect or component

failure, will be corrected by Coda Technologies, Inc. without charge for parts, or labor

for a period of ten years from date of original purchase. Coda Technologies, Inc. will

provide for surface transportation to and from the factory from an authorized Coda

Technologies, Inc. dealer for a period of one year from date of purchase.

II. Procedure- If the FET PREAMPLIFIER 01 should require service under warranty take it,

with proof of purchase date, with its carton and packing material, to a Coda Technologies,

Inc. dealer. The dealer will arrange for service. Direct shipments to the factory will be

accepted at the discretion of the company. Coda Technologies, Inc. products

purchased outside of the U.S. will be covered by those warranty conditions extended by

the importing distributor which may differ in some respects from those given above.

Warranty service, if required, is the responsibility of the importing distributor. If a Coda

Technologies, Inc. product is removed from the country of original purchase, Coda

Technologies, Inc. distributors or dealers are not obligated by the conditions of this

warranty and repairs will be affected at their discretion.

III. Exclusion of Coverage- At the sole opinion of Coda Technologies, Inc. the following

situations are specifically excluded from coverage:

1. Any FET PREAMPLIFIER 01 not operated in accordance with the instructions contained

in this manual, or otherwise subjected to abuse, tampering, modification, accidental

damage, or serial number defacement.

2. Damage to other property caused by any defects in this product, damages based

upon inconvenience, loss of use of the product, loss of time, commercial loss, or any other

damage whether incidental, consequential, or otherwise.

3. It is Coda Technologies, Inc. policy to extend coverage when reasonable doubt exist;

however, freight charges will be billed for any units returned under warranty and found

by the company to be operating according to specification.

This warranty gives you specific legal rights, and you may also have other rights which

vary from state to state.

Coda Technologies, Inc. continually researches new techniques, designs, and

construction methods and so reserves the right to introduce refinements into current

product lines without notice or obligation. The company may offer product modifications

to make these refinements available to earlier production units.

WARRANTY REGISTRATION

MODEL DESIGNATION:__________________________________

SERIAL NUMBER:______________________________________

DATE OF PURCHASE:

PLACE OF PURCHASE

Dealer:___________________________________________

Address:__________________________________________

City:_____________________ State:____ Zip:__________

Phone:____________________________________________

PURCHASER

Name:_____________________________________________

Address:__________________________________________

City:_____________________ State:____ Zip:__________

Phone:____________________________________________

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NOTES:

Fill in and retain this copy of the warranty registration sheet for your records .

MODEL DESIGNATION:__________________________________

SERIAL NUMBER:______________________________________

DATE OF PURCHASE:

PLACE OF PURCHASE

Dealer:___________________________________________

Address:__________________________________________

City:_____________________ State:____ Zip:__________

Phone:____________________________________________

PURCHASER

Name:_____________________________________________

Address:__________________________________________

City:_____________________ State:____ Zip:__________

Phone:____________________________________________

WARRANTY REGISTRATION 14.5

Please fill in and send this copy of the warranty registration sheet to Coda Technologies,

Inc.

NOTES:

ADDRESS

Coda Technologies, Inc.

9941 Horn Road Suite A

Sacramento, CA 95827 USA

Phone: (916) 363-4653

Fax: (916) 363-4627

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