Cary Audio Design CAD 808 Stereo Amplifier User Manual
Contents
1. 200 mA reading simply pull out the plug from the bias jack You may hear a slight click in the speaker This is normal Bias levels will change with time of day and power usage in your home In fact during the summer months when the air conditioner is running you may have less AC line voltage available and in turn the bias will be slightly lower This is not critical In fact the Rocket 88 R is designed to operate in the range of 180 to as high as 240 mA DC current The best sound will generally be produced in the 195 to 225 mA region You may wish to experiment if you desire NEVER ADJUST THE BIAS SETTING WITH A VOLTMETER SET TO THE VOLTAGE POSITION Break In Period The tubes capacitors and output transformers take approximately 100 hours of music playing to fully settle in for peak performance The Rocket 88 R will sound good fresh out of the box However after the first couple of hours you will notice increased depth and tighter bass This break in period is normal for tube based components and with high performance audio components SERVICE AND CARE WARNING MAKE SURE AMPLIFIER IS UNPLUGGED FROM AC MAINS Care and Cleaning The chassis of the Rocket 88 R may be cleaned with a soft rag and Windex or a similar window cleaner A dry feather duster is also good for cleaning the chassis Tube Replacement If it becomes necessary to replace the tubes in the Rocket 88 R amplifier a matched set of tubes of the same brand should be2. Setting Your new Rocket 88 R bias adjustment has been factory set prior to shipping Please keep in mind that the bias will vary from location to location depending on the AC line voltage The design of the Rocket 88 R is such that you may start listening with the factory set level DO NOT TURN THE BIAS ADJUSTMENT SCREW WITHOUT WATCHING LEVELS ON A DC mA CURRENT METER The type of meter used must be a DC current meter or a volt ohm meter with a DC milliampere current scale A digital multi meter is very inexpensive and available at a local Radio Shack or ACE hardware store Included with your shipment of the Rocket 88 R is a black and orange patch cord with a _ male plug and two clips This is the bias adjustment cable To check and or set the bias simply place the red clip lead on the positive meter lead The black clip lead will hook up to the black negative lead of the test meter The meter must be placed in the DC current mode If the meter has a selectable scale use the one that measures 0 to 300 ma DC current With the Rocket 88 R turned on and operating for about 10 minutes you will have the resting current level indicated This measurement should be done without any music playing A nominal level of 200 milliampere mA is standard for the Rocket 88 R If the level is lower advance the bias adjustment to the clockwise direction Higher readings turn the bias control to the left counterclockwise direction After you have established a
3. two conductors wound at the same time will yield the closest balance and coupling of any design currently utilized in vacuum tube output transformers The E I laminates used are silicone impregnated hipersil steel contributing to the extremely low loss of the Rocket 88 R output transformer The above process is similar to the single ended air gap design found on the Cary single ended output transformers A balanced drive signal is applied to the control grids of the KT 88 output tubes from the I2BZ7 phase inverter driver tube This tube is configured in a dual differential network that operates in the following manner The first section of the dual triode I2BZ7 tube is direct coupled to the input RCA or XLR jack on the rear apron of the amplifier The drive signal is amplified through this first section in a class A grid driven circuit with the output signal inverted 180 out of phase at the anode and then coupled to one half of the push pull bank of KT 88 s At the same time the second half of the dual triode I2BZ7 is cathode driven in a grounded grid non inverting class A gain stage coupled to the other half of the push pull bank of KT 88 s With this network the balance is a perfect plus and minus dual drive signal to drive the final KT 88 s in a balanced push pull configuration The I2BZ7 cathodes are direct coupled to the anode sit on top of the EL 84 in an infinite current source configuration The EL 84 stage takes the place of the conventiona
4. used A new tube kit is available from your Cary Audio dealer You should get 2 5 year s from the output tubes and even more years of use from the I2BZ7 and EL 84 tubes with everyday usage Factory Service Careful consideration has been given to the design of your Rocket 88 R amplifier to keep maintenance problems to a minimum However it is possible that some problems may arise which cannot be cured by tube substitution At this point we suggest that you contact our Customer Service Department from to 5 PM East Coast Time phone number 1 919 355 0010 to describe your problem in detail Do not return the amplifier to the factory without a return authorization number from the Customer Service Department Cary Audio Design will assume no responsibility if the transportation company refuses to pay a damage claim due to improper packing or lack of insurance should the unit be lost in shipment Cary Audio Design 1020 Goodworth Drive Apex North Carolina 27539 www caryaudio com info caryaudio com Tel 919 355 0010 Fax 919 355 0013 WARNINGS MAKE NO ATTEMPT TO PUT THE ROCKET 88 R INTO SERVICE OUTSIDE OF THE CABINET CONTACT WITH THE HIGH VOLTAGES FOUND INSIDE THE UNIT CHASSIS CAN BE FATAL COMPLETELY REMOVE THE AC POWER PLUG FROM THE WALL AND ALLOW 30 MINUTES FOR THE HIGH VOLTAGE CAPACITORS TO DISCHARGE THROUGH THE BLEEDER RESISTORS BEFORE YOU ATTEMPT TO CHANGE THE TUBES OR TO CLEAN THE INSIDE OF THE AMPLIFIER CAUTIONS NEVER
5. CIENT oindio Design CAD 808 Rocket 88 R Stereo Vacuum Tube Power Amplifier INITIAL SET UP and OWNERS MANUAL NOTE Before installing your new power amplifier please read this manual carefully as it will inform you of the specifications proper installation procedures and operation procedures Also included in this manual are guidelines on how to properly service and care for your new Rocket 88 R 1 Dear Audiophile Friend would like to take this opportunity to personally thank you for purchasing a Cary Audio Design Rocket 88 R stereo power amplifier have spent many many hours designing and voicing this latest iteration of our very popular Rocket 88 In fact have had tremendous fun listening to the new Rocket 88 R during and after the design phase There are several design projects that stand out to me in the recent past The three design projects that immediately come to my mind are the new CAD 805 10th Anniversary Edition single ended triode mono bloc power amps the new V 2 R stereo power amp and now the new Rocket 88 R Designing and releasing the new Rocket 88 R has been a real treat to me and hope it is for you as well It combines our superb Cary Audio Design sound and build quality at a surprisingly modest price We believe it is a truly a Best Buy stereo vacuum tube power amplifier The basic premise started with on the Rocket 88 R was to develop a truly linear wide bandwidth stereo vacuum tube powe
6. IS OF THE ROCKET 88 R CAN BE FATAL Unpacking All shipping containers have been specifically 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 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 Rocket 88 R amplifier from its packing carton and examine it closely for signs of shipping damage It is recommended to save 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 Fill out the enclosed warranty registration card and return it to Cary Audio Design within 10 days of original purchase Keep your original sales slip with the packing cartons should you ever need it for reference Failure to register warranty will limit the warranty to one year Amplifier Placement and Set Up In general the location of your new Rocket 88 R 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 hot locations near radiators or other heating units Keep the top of the Rocket 88 R clear of books paper or other equipment to protect agains
7. REMOVE or 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 ROCKET 88 R WILL RESULT IN THE TUBES OVERHEATING PLEASE OBSERVE ALL THE SAFETY DIRECTIONS IN THIS OWNER S MANUAL TO AVOID RISK OF PHYSICAL HARM
8. e position from the other a channel imbalance will occur There is dB more gain in the Ultra Linear position BIAS This screw driver adjustment is used to set the proper DC bias current for the KT 88 output tubes REMEMBER THIS ADJUSTMENT MUST BE ADJUSTED WITH A METER READING DC mA CURRENT TUBE FUSE This is a fast blow _ amp fuse to protect the Rocket 88 R amplifier should an output tube fail CAUTION USE OF ANY OTHER PROTECTION FUSE CAN DAMAGE UNIT BIAS JACK This _ two conductor jack is used to plug in the supplied meter cable This is a shorting jack In other words when the plug is removed the circuit is automatically connected You may plug in the test plug while the unit is playing You may hear a slight click in the loudspeakers when inserting or removing the plug This is normal SPEAKER These switches change the 4 and 8 ohm output taps from the output transformer to the speaker posts on the rear of the amplifier They maybe operated with the amplifier in operation EYE TUBE There are two of these They set the green eye tube intensity You may set to any desired level for your listening room The control does not change any of the sonic characteristics of the amplifier INSTALLATION This section describes the unpacking and installation procedures for the Rocket 88 R amplifier WARNING MAKE NO ATTEMPT TO PUT THE AMPLIFIER IN SERVICE WITHOUT THE BOTTOM PLATE ATTACHED CONTACT WITH VOLTAGE INSIDE THE CHASS
9. l dropping resistor network found in conventional gain stages The power supply transformer is designed to operate at 200 continuous commercial service at the full rated 80 watt output level The high voltage power supply section is a full wave center tap configuration not some cheap voltage doubler as used in many competitor s amps to a dual PI network with two filter chokes This high voltage section feeds the final output KT 88 tubes An additional choke filter network serves as the power supply for the I2BZ7 phase inverter tubes Another supply is the negative DC grid bias and current source voltage for the EL 84 s A great deal of attention during design of your new Rocket 88 R was concentrated on the overload recovery ability of the amplifier The ability of an amplifier to instantly recover from clipping is much more important than is commonly believed In the output power war of some amplifier manufacturers the mentality is focused on high and then even higher overall power output levels to try to solve the clipping problem In reality we believe the most critical aspect is how fast a recovery an amplifier can achieve after overload With the incredible dynamics range of live and recorded music even 2 000 watts of power is potentially not enough Most of the music being listened to in an average home listening room is only requiring about l 3 watts of power It is on the transients of loud low frequency program material that treme
10. ndous 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 Rocket 88 R extols its merits in the ability to handle transients and instantaneously recover from brief or even extended overloads The Rocket 88 R will overload symmetrically at any frequency in the audio bandpass It will also yield faithful reproduction of extremely low frequencies at full output levels The power transformer the power supply regulation and the output transformer design and careful shaping of the overall frequency response curve all play a very important part in the ability of the Rocket 88 R to recover quickly when overloaded If one were to monitor the high voltage rail voltage of the Rocket 88 R during soft and also loud music passages it would be found there is no more than a volt or so change from soft to loud passages Another technical feature of your new Rocket 88 R amplifier is unconditional circuit stability The Rocket 88 R maybe operated with no load without speaker without damage to the amplifier output transformer or tubes Operating the Rocket 88 R stereo amplifier is a simple procedure since each unit is designed for long term stability in virtually any home operating situation Therefore if the unit is operated outside the parameters outlined in this owner s manual damage may result Please read this manual carefully before putting your new R
11. ocket 88 R amplifier in operation The following definitions are applicable to this manual These definitions must be followed explicitly WARNING HAZARD PRESENTS PERSONAL INJURY OR DEATH Caution EQUIPMENT DAMAGE MAY OCCUR BUT NOT PERSONAL INJURY Note Proper performance of the amplifier cannot be ensured if disregarded Specifications Rocket 88 R Stereo Power Amplifier DIMENSIONS WEIGHT CIRCUIT TYPE POWER OUTPUT INPUT SENSITIVITY INPUT IMPEDANCE NOISE AND HUM IO W x 18 D x 6 H 25 4 cm x 45 7 cm x 15 2 cm 45 Lb 20 4 kg Push Pull Triode Class A Ultra linear Class A B 30 Watts Triode 60 Watts Ultra linear 1 2 volt for full output 150 000 ohms 87 dB below rated output FREQUENCY RESPONSE 10 Hz to 82 000 Hz 0 3 0 dB watt TUBES TRANSFORMERS RESISTORS 2 12BZ7 Dual Triode Phase inverter gain stage I2AX7 2AY7 2 EL 84 Current source or 6BQ5 4 KT 88 Output tubes or EL 34 6550 KT 66 KT 77 KT 90 2 1629 Green Cat Eye indicator tubes El laminated core power transformer 2 Special interleaved output transformer 3 Filter Chokes 200 duty cycle on all transformers 1 0 metal film CAPACITORS Polystyrene and polypropylene oil filled optional POWER SUPPLY CAPACITORS AC CORD AC POWER REQUIREMENTS WARM UP TIME BREAK IN PERIOD FINISH 2 560 uFD 450 VDC 3 10 uFD Film and foil 600 VDC l 47 uFD 450 VDC Detachable 3 conduc
12. oth 30 watt Class A triode and 60 watt Class A B ultra linear pentode mode Full speaker control with complete coverage of the frequency extremes is the result of the changes just can t imagine it any better Please read the complete operating manual before turning on your amplifier and get ready for the musical time of your life Thank you once again for your interest and continued support for Cary Audio Design Dennis J Had President Cary Audio Design THEORY OF OPERATION For the technically minded a review of the circuit is in order Your new Rocket 88 R operates in push pull triode Class A mode and in class A B ultra linear mode The output stage KT 88 tubes are biased with a negative fixed bias voltage for low distortion and maximum output capabilities In the triode mode the Rocket 88 R is the most linear and yields the most musically satisfying presentation The output power is 30 watts of triode power per channel and 60 watts per channel in ultra linear mode The output transformers on the Rocket 88 R are the most important component in the amplifier They have been specifically designed by Cary Audio for use in the Rocket 88 R We have taken the approach in the output transformer design not too dissimilar to the single ended amplifiers we design and produce The primary and secondary windings on portions of the output transformer are wound in a bifilar process with the two inductors interleaving sixteen times The bifilar wind
13. r amplifier Also in direct response to Rocket 88 owner s comments about input sensitivity we wanted to harmonize the input sensitivity level of the amplifier to match other components used in an audio system was seeking an amplifier design that would precisely mimic the input signals up stream from the source signals while being more sensitive In the design the front end stage EL 84 tubes are used as current sources for the high gain I2BZ7 driver stage and phase inverter tubes with one used for each channel I2AX7 or I2AW7 tubes may be substituted for the I2BZ7 The EL 84 s do not do any of the amplification They allow the 2BZ7 phase inverters to operate in an equal balanced fashion From the first incarnations of this project to the final result it was an intriguing concept to say the least We found that changing the input circuit to accept the 12 series vacuum tubes caused a dramatic drop in total harmonic distortion Overall circuit dynamics and frequency bandwidth improved with the new driver tubes as well We have come to the conclusion that the limiting factor in the previous Rocket 88 design was the 6922 tube we used in the front end stage The 12 series tubes certainly fixed that realize you may think am rambling but am just so excited about the Rocket 88 R amplifier Imagine listening to a compact stereo tube amplifier driving a pair of B amp W 801 Nautilus 15 woofer loudspeakers to thunderous levels in b
14. t overheating Power Requirements The Rocket 88 R is designed to operate from house current mains The design voltage is 117 VAC at 50 60 Hz Export models are 117 or 240 VAC at 50 60 Hz depending on destination Cables The speaker cables to the speakers can be any convenient length your setup requires Please choose speaker cables of sufficient size to preserve the outstanding performance capabilities of your Rocket 88 R Heavy gauge 14 AWG wire is suitable for distances up to 10 feet 12 AWG for 25 feet Our recommendation for best sound is to place the Rocket 88 R in between the stereo pair of loudspeakers Use heavy duty loudspeaker cables with a length to reach from the Rocket 88 R to the speakers Avoid long lengths that have excess slack If your loudspeaker has the facility for bi wiring then by all means use separate cables or bi wire speaker cables Your Authorized Cary Audio Design Dealer will have proper speaker cable in stock for this purpose Signal input connection is made via the input jacks on the rear of the amplifier located next to the output binding posts The interconnect cables from the output of the preamplifier can be any convenient length your setup requires Through the years we have found that using tube amplifiers like the Rocket 88 R it is better to have short loudspeaker cables and long interconnect cables to the preamplifier The choice of a high quality shielded interconnect cable is important Once again
15. tor 14 gauge 117 volts or 240 volts AC 50 60 Hz 300 watts operate 3 minutes 100 hours of music playing time Black Epoxy powder coat Anodized Aluminum face plate Specifications are subject to change or improvement without notice or obligation Front Panel Features AC ON ROTARY SWITCH Turns AC power on in the on position GREEN CAT EYES Indicate audio power output fully closed eye at maximum power Rear Apron Features INPUT Signal input connection via either RCA or XLR shielded interconnect cables Pin 1 is the shield 2 positive phase signal on XLR connector INPUT SWITCH Push in direction of the type of input to be utilized RCA or XLR OUTPUT The 5 way speaker binding posts provide the output to the speaker system Red posts positive connections Black posts negative connections AC 3 conductor detachable power cord AC POWER FUSE Use only a 3 Amp 250 V slow blow fuse Rocket 88 R Top Panel BIAS LED These indicators will light when there is the proper bias voltage operating for the EL 84 current source tubes along with the proper DC grid bias voltage for the final output tubes If these LED s fail to light discontinue use and place a call to the Cary Audio service advisor TRIODE UL SWITCH These switches change the operation of the Rocket 88 R between triode class A to Ultra Linear class A B These two switches maybe switched during operation If one channel switch is in the opposit
16. your dealer will have the proper cables in stock for this purpose The tubes used in your new Rocket 88 R have gone through a 48 hour burn in process and testing with your individual Rocket 88 R They are matched and labeled on the tube boxes Look at the top panel of the Rocket 88 R for the proper placement of the tubes Be careful to insert the tubes in the proper sockets with the key way in order At the end of this manual you will also see a block diagram of the tube layout Your new Rocket 88 R is ready for operation after the speaker interconnect cables and the vacuum tubes have been installed AC Power Switch Simply turn the AC power to the ON position the red bias LED s will light After 30 to 60 seconds observe that all tubes are lit filaments and the green eye tubes are illuminated Should you not observe the above conditions turn off the amplifier and check the power cord and AC socket Triode Ultra Linear Switch On the top of the chassis behind the KT 88 output tubes is located a chrome handle switch With the handle pushed to the rear of the amplifier the mode of operation is ultra linear In the forward position the mode will be in triode class A mode This set of switches maybe switched during listening A slight click maybe heard in the loudspeakers This is normal Usually the triode position will provide plenty of power and is the most preferred position by most audiophiles and the designer of the Rocket 88 R Bias
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