Coda Stereo Amplifier 02b User Manual

FET PREAMPLIFIER 02b  
OPERATION MANUAL  
T
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SAFETY PRECAUTIONS  
INTRODUCTION  
1
2
INSTALLATION CONNECTIONS  
DETAILED INSTALLATION  
DESIGN PHILOSOPHY  
TECHNICAL DATA  
3
4
7
10  
11  
12  
CARE and HANDLING  
WARRANTY  
WARRANTY REGISTRATION  
ADDRESS  
13  
14  
 
INTRODUCTION  
2
This preamplifier is a precision device, designed in an effort to provide the listener with  
unmatchedsoundquality,design,andconstruction. Inordertooperateyourpreamplifier  
properlyandtorealizeallofthecapabilitiesoftheFETPREAMPLIFIER02b,werecommend  
that you read this entire manual carefully.  
 
INSTALLATION CONNECTIONS  
3
The first section of the installation instructions for the FET PREAMPLIFIER 02b 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.  
AC LINE INPUT  
FOR CONTIMUED PROTECTION AGAINST  
SHOCK OR FIRE HAZARD,DO NOT EXPOSE  
THIS UNIT TO RAIN OR MOISTURE.  
~
BALANCED OUTPUT  
UNBALANCED OUTPUT  
LEFT RIGHT  
OUT  
RIGHT  
RECORDER  
IN  
VIDEO  
TUNER  
UNBALANCED DISC  
LEFT RIGHT  
BALANCED DISC  
SEE SERIAL TAG FOR  
!
POWER REQUIREMENTS  
LEFT  
RIGHT  
LEFT  
LEFT  
RIGHT  
LEFT  
RIGHT  
LEFT  
RIGHT  
LEFT  
RIGHT  
BALANCED DISC  
UNBALANCED DISC  
POWER AMP  
TUNER  
POWER AMP  
OUTPUT  
INPUT  
RECORDER  
VIDEO  
 
DETAILED INSTALLATION  
4
I. Set up and Installation  
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.  
1. Position the FET PREAMPLIFIER 02b 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 02b 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.  
2. Beforeinstallingthepreamplifiermakesureallofthepowerswitchesofanyassociated  
componentsareswitchedoff. Ifanyofyourotheraudiocomponentsdonothavepower  
switches, make sure they are unplugged from their AC power source.  
Note: The Operating Voltage of the FET PREAMPLIFIER 02b is convertible in  
order that it may be used worldwide. Contact your dealer to arrange  
altering the operating voltage.  
!
 
DETAILED INSTALLATION  
5
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.  
They are:  
1.TheBALANCEDDISCinputsshouldbeattachedtothebalancedoutputsofacompact  
disc player or phono stage. The balanced XLR pin configuration is as follows; ground is  
pin 1, positive is pin 2, negative is pin 3.  
2. The UNBALANCED DISC, TUNER, and VIDEO input connections are all line level inputs,  
requiring only the insertion of the RCA plugs.  
3. The RECORDER inputs should be attached to the outputs of the corresponding  
recording device; alternately, they may be used as additional line inputs.  
4. The RECORDER outputs should be attached to the inputs of the corresponding  
recording device.  
5. The unbalanced OUTPUTS should be attached to the amplifier inputs either directly, or  
through a crossover or processor, as appropriate to the application.  
6. The BALANCED OUTPUTS should be attached to the balanced inputs of the amplifier,  
eitherdirectlyorthrougha crossoverorprocessor,asappropriatetotheapplication. The  
balanced XLR pin configuration is as follows; ground is pin 1, positive is pin 2, negative is  
pin 3.  
7. 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. OncetheFETPREAMPLIFIER02bisproperlyconnected,theLEDonthefrontpanel  
will light. At this point, you may switch on your chosen ancillary components including  
the power amplifier.  
7
6
5
4
3
1
2
AC LINE INPUT  
FOR CONTIMUED PROTECTION AGAINST  
SHOCK OR FIRE HAZARD,DO NOT EXPOSE  
THIS UNIT TO RAIN OR MOISTURE.  
~
BALANCED OUTPUT  
UNBALANCED OUTPUT  
OUT  
RIGHT  
RECORDER  
IN  
VIDEO  
TUNER  
UNBALANCED DISC  
LEFT RIGHT  
BALANCED DISC  
SEE SERIAL TAG FOR  
!
POWER REQUIREMENTS  
LEFT  
RIGHT  
LEFT  
RIGHT  
LEFT  
LEFT  
RIGHT  
LEFT  
RIGHT  
LEFT  
RIGHT  
LEFT  
RIGHT  
 
DETAILED INSTALLATION  
6
III. Front Panel Control Functions  
1. The INPUT SELECTOR control selects the source which will be presented to the outputs  
and balanced outputs.  
2.TheRECORDSELECTORcontrolselectsthesourcewhichwillbepresentedtotherecord  
output. Because of the independent controls, one source may be monitored while a  
second, different source is being recorded.  
3. TheBALANCEcontrolworksbyattenuatingtherightchannelwhen beingrotatedfrom  
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.  
4. 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.  
1
2
3
4
INPUT SELECTOR  
RECORD SELECTOR  
BALANCE  
OUTPUT LEVEL  
BALANCED DISC  
UNBALANCED DISC  
TUNER  
RECORDER OFF  
VIDEO  
TUNER  
VIDEO  
UNBALANCED DISC  
BALANCED DISC  
RECORDER  
FET PREAMPLIFIER 02b  
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 02b.  
However, somesourcesmayproducehighoutputvoltagesonturnon, whichmaycause  
damage to an amplifier or speakers .  
 
DESIGN PHILOSOPHY  
7
I. Design Philosophy and Approach  
The circuitry utilized in the FET PREAMPLIFIER 02b 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  
inappropriateapplicationofclevercircuitgimmicks. Ourapproachdemandspainstaking  
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  
sourceallowingmaximumperformancefromeachsystemelementandgreatlyreducing  
the chance of cable characteristics altering the sound. The absence of input current in  
FETsalsoallowshighbiascurrentsforlinearityandspeedwithoutsacrificingDC 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  
circuiteliminatestheneedforanyquestionableDCservocircuitsorcouplingcapacitors.  
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.  
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.  
To accomplish balanced inputs and outputs, the FET PREAMPLIFIER 02b uses simple  
very high performance inverters. The most commonly acknowledged advantage of this  
is rejection of stray noise pickup, but improvements in distortion and bandwidth may  
occur also.  
The FET PREAMPLIFIER 02b controls provide an off position for the recording output. This  
completely disconnects the recording system from the main system to prevent possible  
interactions which may affect sound quality.  
 
DESIGN PHILOSOPHY  
8
Therequirementsofapowersupplyforflawlessaudioreproductionarestraightforward  
but important. The supplies in the FET PREAMPLIFIER 02b take a very direct approach to  
high performance. First, a top quality shielded toroid transformer with plenty of reserve  
current capability is used. About 28,000 uF of capacitance with very low ESR and  
inductance provides good passive filtering. A reference voltage is developed by  
deliveringaconstantcurrentto zenerdiodes. Theresultingvoltageisheavilyfilteredand  
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 02b 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  
tolerancesandusePCmountedpartsmoreeasily. Moreoversuchadesignallowseasier  
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.  
 
DESIGN PHILOSOPHY  
9
II. Parts' Quality  
1. Finishes - All exterior and interior metal parts are anodized. While paint may be more  
impactresistant,theanodizedsurfaceismoreresistanttosolventsandpreventscorrosion.  
Moreover, the anodized parts' appearance can be enhanced by either graining or  
bead-blasting the surface.  
2. Circuit Board - 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  
capisbetterthanthebestcap". Theonlyelectrolyticsusedareinthepowersupplywhere  
large numbers provide enormous filtering capacitance for the supply.  
5. Semiconductors-Therearenointegratedcircuits(IC)tobefoundinthis 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-Thevolumecontrolsareconductiveplastic. Thesepotstrackwithlittle  
error and are totally neutral.  
7. Connectors - Coda employs a standard RCA configuration with a gold plated case.  
The balanced connectors are Neutriks from Switzerland.  
8. Wire - All signal wire has been eliminated whenever possible. Where wire is used, Coda  
employs silver plated copper, 141 strand, 18 guage wire with a silicone insulation.  
 
TECHNICAL DATA  
10  
CIRCUIT SPECIFICATIONS  
Frequency Response: DC to -3 dB @ 200 kHz  
Distortion:  
< .01 % from 10 Hz to 40 kHz @ 6V peak into 600 Ohms or higher,  
shunted by 1000 pF or less .  
Gain:  
with unbalanced in and unbalanced out 14 dB  
with balanced in and unbalanced out 14 dB  
with unbalanced in and balanced out 20 dB  
with balanced in and balanced out 20 dB  
12 Volts peak  
> 100 dBA referenced to 1 Volt output  
unbalanced 20 k Ohms  
Maximum Output:  
Noise:  
Input Impedance:  
balanced 20 k Ohms  
Output Impedance:  
Crosstalk:  
15 Ohms non-reactive unbalanced  
30 Ohms non-reactive balanced  
70 dB @ 20 kHz  
POWER SUPPLY  
independently regulated with shielded toroidal transformer and  
28,000 uf of capacitance  
DIMENSIONS  
Height:  
Width:  
Depth:  
Weight:  
1.75" Faceplate, 2.35" Overall  
19.0" Faceplate, 17.0" Chassis  
9.75" Overall  
14 lbs. Shipping  
 
11  
CARE and HANDLING  
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 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 02b, it is advised to place nylon  
washersundertheheadsofthemountingscrewstoavoidscratchingtheanodizedfinish.  
Do not throw away the carton or associated packing material. They are ideal if you  
needtopacktheunitformoving, andintheunlikelyeventthatservicingisneeded, they  
will be necessary for safe shipment.  
Be sure to provide adequate insurance when shipping.  
 
WARRANTY  
12  
I. Warranty- Any failure of the FET Preamplifier 02b 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-IftheFETPreamplifier02bshouldrequireserviceunderwarranty, takeitwith  
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 02b 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  
uponinconvenience,lossofuseoftheproduct,lossoftime,commercial loss,oranyother  
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  
productlineswithoutnoticeorobligation. Thecompanymayofferproductmodifications  
to make these refinements available to earlier production units.  
 
WARRANTY REGISTRATION  
13  
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:____________________________________________  
NOTES:  
 
WARRANTY REGISTRATION  
13.5  
Please fill in and send this copy of the warranty registration sheet to Coda Technologies,  
Inc. Include copy of proof of purchase.  
MODEL DESIGNATION:______________________________
SERIAL NUMBER:____________________________________
DATE OF PURCHASE:  
PLACE OF PURCHASE  
Dealer:___________________________________________  
Address:__________________________________________  
City:_____________________ State:____ Zip:_________
Phone:___________________________________________
PURCHASER  
Name:____________________________________________
Address:__________________________________________  
City:_____________________ State:____ Zip:_________
Phone:___________________________________________
NOTES:  
 
ADDRESS  
14  
Coda Technologies, Inc.  
9941 Horn Road Suite A  
Sacramento, CA 95827  
Phone: (916) 363-4653  
Fax:  
(916) 363-4627  
 

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