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CAD 300 SE Signature
Vacuum Tube Audio Amplifier
NOTE: Before installing your new component, please read this manual carefully
as it will inform you of the product specifications, proper installation and correct
operating procedures for your unit. Also included in this manual are guidelines
on how to service and care for your new Cary Audio Design product.
INTRODUCTION____________________________________________________
Congratulations!
You have purchased one of the most exotic vacuum tube audio amplifiers available. Within its power
range, the CAD 300 SE Signature offer the most realistic sound reproduction one could desire for a "high-
end" home audio system. Careful design, parts selection and proper circuit topologies contribute to
incredible reliability and enjoyment.
For the technically minded, a review of the circuit is in order. Your new CAD 300 SE Signature operates in a
Class A single-ended mode utilizing fixed negative grid voltage on the 300B triode output tube. The input
stage utilizes two 6SN7 dual triodes. The output transformer in the CAD 300 SE Signature is the most
important component in the amplifier and has been specifically designed by Cary Audio for use in the
300-SE Signatures. The output transformer is an air-gap design with a commercial continuous rating of
200% duty cycle. The CAD 300 SE Signature output transformer is an E/I laminate, silicon impregnated,
grain oriented steel design. The windings are wax vacuum impregnated and the entire transformer is
potted in high temperature wax. The power supply is a full wave center tap configuration running a CV-
378 (heavy duty 5AR4) vacuum tube rectifier. The rectified 430 VDC is fed to a pi-L filter network. The filter
capacitors consist of two (2) 1200 MFD and one (1) 100 MFD computer grade electrolytics for a total of
over 230 Joules of energy storage. Each electrolytic capacitor is by-passed with a low impedance .22
polystyrene capacitor. The power transformer is also a 200% duty cycle rating on the CAD 300 SE
Signature. To avoid AC hum, both the 6SN7 and 300B tubes have DC voltage on the filaments. This will
prevent AC ripple voltage from capacitively being coupled to the elements in the tubes.
Additional Design Thoughts
A great deal of attention during design of your new CAD 300 SE Signature was concentrated on the
"overload recovery" ability of an amplifier to instantly recover from clipping is much more important than
is commonly believed. In the power war of amplifier manufacturers the mentality is focused on high and
then even higher power output to solve the clipping problem. When in reality the most critical aspect is
how fast a recovery and amplifier can achieve after overload. With the incredible dynamic range of live
and in turn recorded music even 2000 watts of power is not enough power. Most of the music being
listened to in an average listening room is only requiring about 3 watts of power. It is on the transients of
loud low frequency program material that tremendous signal voltages will appear at the input of the
amplifier. It is in this situation that the overload recovery ability of an amplifier is of critical concern. The
single-ended CAD 300 SE Signature extols its merits in the ability to handle transients and instantaneously
recover from brief or even extended overloads. The CAD 300 SE Signatures will overload symmetrically at
any frequency in the audio band pass. The CAD 300 SE Signatures will also yield faithful reproduction of
extremely low frequencies at full output levels. Power transformer, power supply regulation and output
transformer design and careful shaping of the overall frequency response curve all play a very important
part in the ability of the CAD 300 SE Signature to recover quickly when overloaded. If one were to monitor
the high voltage rail voltage (420 VDC) of a CAD 300 SE Signature during soft and loud music passages it
will be found there is no more than a volt or so change from soft to loud passages.
Another technical feature of your new CAD 300 SE Signature is amplifier stability. The CAD 300 SE
Signature may be operated with no load (without speaker) without damage to the amplifier, output
transformer or tubes.
2
The most exciting feature of the CAD 300 SE Signature, aside from how compact and gorgeous it looks, is
the delightful, sensual beauty of the music it recreates. The first thing that will strike you about your new
CAD 300 SE Signature amplifiers is the incredible transparency and resolution of detail of the music. The
CAD 300 SE Signature's sensual nature is best revealed in the sense of life it displays in female vocalists.
Your new CAD 300 SE Signature presents music with such presence and directness; you'll be drawn into
the music hour after a musically satisfying hour. This is the result of single-ended circuit techniques, which
eliminate and crossover notch at low levels and also contributes to the freedom from listening fatigue. The
CAD 300 SE Signature will draw you in even further as you realize how lucid and utterly uncolored
neutrality reveals delicate nuances in the sound stage.
Enjoy the music!
SPECIFICATIONS ___________________________________________________
This section describes the basic specifications of the CAD 300 SE at the time of printing. Specifications are
subject to change without notice or obligation. When the following cautionary terms are used in this
manual, these definitions apply:
WARNING
Electrical hazard! Misuse or failure to follow instructions properly may result in personal injury
or death!
CAUTION
No risk or personal injury; however, misuse or failure to follow instructions may result in
damage to equipment.
NOTE
No risk of personal injury or equipment damage; however, misuse or failure to follow
instructions may prevent proper performance of the equipment.
........................................................................................................................................................................................................................
CIRCUIT TYPE
Single-ended Amplification in Class A
........................................................................................................................................................................................................................
POWER OUTPUT
1 kHz sign wave
6.5 volts RMS across 4 ohms = 10.5 watts
9 volts RMS across 8 ohms = 10 watts
........................................................................................................................................................................................................................
INPUT SENSITIVITY .75 volt for full output
........................................................................................................................................................................................................................
INPUT IMPEDANCE 150,000 ohms
........................................................................................................................................................................................................................
NOISE AND HUM 80 dB below rated output
........................................................................................................................................................................................................................
FREQUENCY RESPONSE
20 Hz to 23,000 Hz + 0/ - .75 dB (at one watt output)
3
........................................................................................................................................................................................................................
TUBES
1 - 6SL7 input tube
1 - 6SL7 driver
1 - 300B Triode output
1 - 5U4-6B Rectifier tube
........................................................................................................................................................................................................................
TRANSFORMERS
1 - EI laminated core power transformer
1 - Special air gap output transformer
200% duty cycle on all transformers
........................................................................................................................................................................................................................
RESISTORS 1% metal film
........................................................................................................................................................................................................................
CAPACITORS Oil filled
........................................................................................................................................................................................................................
POWER SUPPLY CAPACITORS 2-1200 MFD 450VDC, 1-100 MFD 450VDC
........................................................................................................................................................................................................................
AC CORD
........................................................................................................................................................................................................................
AC POWER REQUIREMENTS 120/240 volts AC @ 50/60 Hz
........................................................................................................................................................................................................................
3 conductor shielded
CONSUMPTION
125 watts – Operation
50 watts - Standby
........................................................................................................................................................................................................................
WARM-UP TIME 3 minutes
........................................................................................................................................................................................................................
BREAK-IN PERIOD 100 hours of music playing time
........................................................................................................................................................................................................................
FINISH Nickel chrome plated stainless steel
........................................................................................................................................................................................................................
DIMENSIONS 7" H x 5 1/2" W x 19" D
........................................................................................................................................................................................................................
WEIGHT 32 lbs.
........................................................................................................................................................................................................................
4
FEATURES __________________________________________________________
Front Panel
........................................................................................................................................................................................................................
AC-ON TOGGLE SWITCH
........................................................................................................................................................................................................................
STAND-BY/ OPERATE Turns B+ high voltage on in the "up" position. Right Blue LED comes on
Turns AC power on in the "up" position. Left Blue LED Comes on
........................................................................................................................................................................................................................
Rear Apron
........................................................................................................................................................................................................................
INPUT
Signal input connection via shielded interconnect cable
........................................................................................................................................................................................................................
OUTPUT
Copper 5-way binding posts provide the output to the
speaker system. Red = +, Black = -
........................................................................................................................................................................................................................
BIAS POTENTIOMETER Screwdriver adjustment for 300B bias
........................................................................................................................................................................................................................
BIAS JACK 1/4” mono jack to measure bias
........................................................................................................................................................................................................................
AC 3 conductor shielded power cord to AC power mains
........................................................................................................................................................................................................................
FUSE
AC power fuse. Never replace with any other fuse than
2 AMP SLOW BLOW! 250 VOLT
........................................................................................................................................................................................................................
TUBE FUSE Never replace with any other fuse than ¼ AMP FLAST BLOW!
........................................................................................................................................................................................................................
CAUTION
EQUIPMENT DAMAGE MAY OCCUR WITH IMPROPER FUSES.
NEVER REMOVE / INSERT AC LINE CORD WHEN THE UNIT IS ON.
WARNING
MAKE NO ATTEMPT TO PUT THE CAD 300 SE SIGNATURE AMPLIFIER IN SERVICE WITHOUT
THE BOTTOM PLATE ATTACHED - CONTACT WITH VOLTAGE IN THE UNIT CAN BE FATAL.
5
INSTALLATION _____________________________________________________
This section describes the unpacking and installation procedures for your new component.
Unpacking
All Cary Audio Design shipping containers have been specially designed to protect their contents and
special care has been taken to prevent damage under normal shipping conditions. Mishandling should be
evident upon inspection of the shipping container. If shipping damage is found after visual inspection,
take care not to destroy the evidence. If necessary, document the damage with photographs and contact
the transport carrier immediately.
Carefully remove your new component from its packing carton and examine it closely for signs of shipping
damage. We strongly recommend saving all original packing cartons to protect your amplifier from
damage should you wish to store it or ship it for after-sales service.
Warranty Card
IN THE USA: If you are the original purchaser of a new unit from an AUTHORIZED CARY AUDIO DESIGN
DEALER, please fill out the enclosed warranty registration card and return it to Cary Audio Design within
15 days of your purchase. Cary Audio Design also suggests that you keep your original packing cartons in
case you ever need to ship the unit when moving to a new home. Warranty restrictions apply. Consult the
warranty section at the end of this manual for details. Please be certain to keep a copy of the original sales
receipt from your AUTHORIZED CARY AUDIO DESIGN DEALER to validate the warranty if ever needed. The
warranty is for the original purchaser only and does not transfer to any subsequent owner.
OUTSIDE THE USA: Your local Authorized Cary Audio Design Distributor will make his own warranty policy
for your country. Please check with them for the terms of warranty for your new amplifier.
Placement
In general, the location of your new CAD 300 SE Signature amplifier is not critical. The best placement in
your system is near the speaker system with short lengths of speaker cables. Certain precautions must be
taken to ensure optimum performance. Avoid extremely hot locations such as near radiators or other
heating units. Keep the top of the CAD 300 SE Signature clear of books, paper or other equipment to
protect against overheating.
Power Requirements
The CAD 300 SE Signature is designed to operate from house current mains. The design voltage is 117
VAC at 50/60Hz. (Foreign units 234 VAC at 50/60Hz)
Cables
The speaker cables from the output posts of the CAD 300 SE Signature to the speaker system can be any
convenient length your set-up requires. Select speaker cables of sufficient size to preserve the outstanding
performance capabilities of your CAD 300 SE Signature. Heavy gauge #16 wire is suitable for distances up
to 10 feet; #12 for 25 feet. Most audio dealers will have proper speaker cable in stock for this purpose.
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OPERATION ________________________________________________________
Signal input connection is made via the input jacks on the rear of the CAD 300 SEI located next to the
output binding posts. The interconnect cables from the output of the preamplifier can be any convenient
length your set-up requires. The choice of a high quality interconnect cable is important. Once again, your
audio dealer will have the proper cables in stock for this purpose.
Your new CAD 300 SE Signature's are ready for operation after the speaker, interconnect cables and the
three tubes have been installed.
AC On Power Switch
Simply push the AC rocker switch up to the ON position (the BLUE LED will light).
Stand-By Switch
This is a most convenient feature on the CAD 300 SE Signature amplifier. This switch is located on the front
of the amplifier. In the "up" position, the amplifier is ready to operate. In the "down" position (provided
the front panel AC switch is in the "on" position), only the tube filaments are operating. You may wish to
leave your CAD 300 SE Signature amp turned on in the stand-by mode 24 hours a day. When you wish to
listen to music, simply flip the stand-by switch in the "up" position. Under these conditions the CAD 300 SE
Signature's are always warmed up and ready for peak performance.
Break-In Period
The tubes, capacitors and output transformers take approximately 100 hours of music playing to fully
settle in for peak performance. The CAD 300 SE Signature's may seem sterile or thin sounding right out of
the box. After the first couple of hours you will notice increased depth and tighter bass. This break in
period defies all engineering theory, but is true with most audio amplifiers.
WARNING
MAKE SURE AMPLIFIER IS UNPLUGGED FROM AC MAINS BEFORE SERVICING.
7
SERVICE AND CARE ________________________________________________
The chassis may be cleaned with a soft towel and Windex® or a similar window cleaner. Spray it on the
cleaning cloth to moisten it, not on the component. Do not use solvents or harsh chemicals to clean the
preamplifier. They may remove the labels from the chassis. The frequency and need of cleaning will be
governed by operating environmental conditions. Avoid letting the component become dusty or wet. A
‘feather duster’ type cleaner will also work well for cleaning the component.
Tube Replacement
If it becomes necessary to replace the tubes in the CAD 300 SE Signature amplifier, a matched set of tubes
of the same brand should be used. A new tube kit is available from Cary Audio Design, Inc. You should get
years from the 300B output tube with everyday usage and many, many years of use from the 6SN7 input
tubes and CV378 rectifier tube.
Factory Service
Careful consideration has been given to the design of this product to keep maintenance problems to a
minimum. If the problem is not easily solved, we suggest that you contact our Customer Service
Department by phone at (919) 355-0010, 1–5 pm Eastern Standard Time, to describe your problem in
detail. DO NOT return the component to the factory without a Return Authorization Number (RA) from
the Customer Service Department.
Cary Audio Design assumes no responsibility if the transportation company refuses to pay a damage claim
due to your improper packing or lack of insurance should the unit be lost in shipment. We strongly
suggest using the original packing cartons for shipping any Cary Audio Design component.
Non-Warranty Repairs
Cary Audio Design will provide repair service for its products charging on a time and expense basis. At this
time, the standard non warranty service bench fee is $125 with all parts used for repair charged extra. This
may change with time and is not a quote for service. Please call us at 919-355-0010 for more information
about out of warranty service and repair fees.
WARNINGS
MAKE NO ATTEMPT TO PUT THE CAD 300 SE SIGNATURE IN SERVICE OUTSIDE OF THE
CABINET. CONTACT WITH HIGH VOLTAGES FOUND IN THE UNIT CAN BE FATAL.
COMPLETELY REMOVE AC POWER PLUG FROM THE WALL AND ALLOW 30 MINUTES FOR THE
HIGH VOLTAGE CAPACITORS TO DISCHARGE THROUGH BLEEDER RESISTORS BEFORE
ATTEMPTING TO CHANGE TUBES OR CLEAN THE INSIDE TO THE PREAMPLIFIER.
CAUTIONS
NEVER REMOVE / INSERT AC PLUG WHEN THE UNIT IS ON OR THE AC POWER SWITCH IS IN
THE ON POSITION. OBSTRUCTION OF THE TOP PORTION OF THE CAD 300 SEI WILL RESULT IN
TUBES OVERHEATING.
8
UNITED STATES LIMITED WARRANTY ______________________________
Cary Audio Design warrants to the original United States purchaser for use in the United States that Cary Audio Design
vacuum tube or solid state power amplifiers, surround sound processors or preamplifiers shall be free from defects in
parts or workmanship for three (3) years from the date of the original purchase. Vacuum tubes, if any are used in the
component, are offered a 90 day from purchase date exchange policy against defects with the exception of the CAVT
300B vacuum tube which has a (1) one year from purchase date exchange policy. Any digital drive design, whether a
Cary Audio Design CD or SACD player or a Cary Cinema DVD player, has a limited one year parts and labor warranty
against defects in manufacture. This is a limited warrant, for the original purchaser only and does not transfer to any
subsequent owner. During the limited warranty period, Cary Audio Design or an authorized Cary Audio Design service
facility will provide free of charge both parts and labor necessary to correct any defects in material or workmanship.
To obtain such warranty service, the original purchaser must:
1. Complete and send in the warranty Registration Card within 15 days of purchase.
2. If claiming service the owner must send a fully filled in copy of the original sales receipt along with any unit
sent in for service showing the AUTHORIZED CARY AUDIO DESIGN DEALER’S name, the new selling price, the
buyer’s name, e-mail or phone number and address on the receipt. Blank receipts will NOT validate the
limited warranty for service.
3. Notify Cary Audio Design as soon as possible after the discovery of a possible defect and submit the
following information to determine eligibility for warranty:
(a) The model number and serial number;
(b) A fully filled in copy of the original sales receipt showing the original selling price, purchasers name and
address filled in by an AUTHORIZED CARY AUDIO DESIGN DEALER with the original date of purchase shown
on the form;
(c) a detailed description of the problem.
4. Deliver the product to Cary Audio Design or the nearest authorized service facility or ship with all freight and
insurance charges prepaid, in its original packing container or equivalent, to Cary Audio.
Correct maintenance, repair and use are important to obtain performance from this product. Therefore, please
carefully read the Operating Manual. This warranty does not apply to any defect that Cary Audio Design in its sole
discretion determines is due to:
1. Improper maintenance or repair, including the installation of parts or accessories that do not conform to the
quality and the specifications of the original parts.
2. Misuse, abuse, neglect or improper installation.
3. Accidental or incidental damage.
WARRANTY DISCLAIMER
Except for the express warranties stated herein, Cary Audio Design disclaims all other warranties including, without
limitation, all implied warranties of merchantability and fitness for a particular purpose. The foregoing constitutes Cary
Audio Design’s entire obligation with respect to this product, and the original purchaser and any user or owner shall
have no other claim for incidental or consequential damages. Some states do not allow the exclusion or limitation of
incidental or consequential damages, so the above limitation and exclusion may not apply to you. This warranty gives
legal rights and you may also have other rights, which vary from state to state.
EXCLUSIVE REMEDY
Notwithstanding the foregoing, the purchaser’s exclusive remedy for any breach of warranty, express or implied, is
limited to the repair or replacement of the defective unit or the refund of the purchase price, at the option of Cary
Audio Design. Under no circumstances is Cary Audio Design liable for incidental or consequential damages. Any
implied warranties imposed by law terminate one (1) year from the date of purchase.
INTERNATIONAL PURCHASERS (Export markets)
Cary Audio Design warrants its merchandise to purchasers within the United States exclusively for use within the
United States of America. It provides no other warranties, expressed or implied. If you are living outside the USA,
please consult with your local dealer or distributor to determine the details of your local warranty.
9
CARY AUDIO DESIGN
1020 Goodworth Drive, Apex, NC 27539
phone 919-355-0010
fax 919-355-0013
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