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 (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 12BZ7 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 12BZ7 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 12BZ7 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 12BZ7 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 conventional 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 12BZ7 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

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Cary Audio Design Rocket 88 R, CAD 808 specifications Theory of Operation
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CAD 808, Rocket 88 R specifications

Cary Audio Design has long been known for its high-end audio components, and the Rocket 88 R and CAD 808 amplifiers exemplify the brand’s commitment to excellence in audio performance. The Rocket 88 R is a tube amplifier that combines classic design with modern technologies, making it a popular choice among audiophiles who appreciate the warmth and character of tube sound. The CAD 808, on the other hand, is a solid-state powerhouse that brings to the table unparalleled clarity and power, providing a perfect counterpart to its tube-based sibling.

The Rocket 88 R is built around a unique dual mono configuration that allows each channel to operate independently, minimizing crosstalk and enhancing stereo imaging. This amp utilizes a pair of 6550 power tubes, delivering an impressive output of up to 100 watts per channel in push-pull mode. The result is a rich, harmonic sound that brings music to life, allowing listeners to experience their favorite tracks with an emotional depth that only tubes can offer. Additionally, the Rocket 88 R features Cary Audio’s proprietary Ultra-Linear and Triode switching modes, providing audiophiles with the flexibility to choose between a more powerful, dynamic sound or the intimate, lush qualities of triode operation.

The CAD 808 amplifies the experience even further with its advanced solid-state design. Featuring robust power supply and output stages, the CAD 808 is capable of delivering a staggering 200 watts per channel, ensuring that it can drive even the most demanding speakers with ease. Incorporating state-of-the-art technologies such as high-current output transistors and a fully discreet output stage, the CAD 808 minimizes distortion and maximizes input sensitivity, resulting in crystal-clear audio reproduction. Its low negative feedback design not only enhances the overall sound quality but also improves the amplifier's transient response, providing listeners with a more dynamic and engaging listening experience.

Both amplifiers boast beautifully crafted chassis with a blend of classic aesthetics and modern functionality. The Rocket 88 R is complemented by its glowing tubes and polished finishes, while the CAD 808 showcases a sleek, contemporary look with a user-friendly interface.

In conclusion, the Cary Audio Design Rocket 88 R and CAD 808 amplifiers stand out as exceptional choices for audio enthusiasts seeking both tube warmth and solid-state clarity. With their unique technologies and remarkable design characteristics, these amplifiers promise to elevate any audio system, ensuring an unforgettable listening experience.
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