RED - Integrated Stereo Amplifier
Output power RMS: 25W into 4 or 8 ohms (dual taps)
4 inputs (500mV RMS input for full power output)
Tube complement: per channel PCF80 (driver stages), GU29/829 (output stage)
RED is a minimally designed (only 2 tubes per channel), topologically a push-pull tetrode output stage amplifier – and this is where all similarity with classic designs ends. RED was designed with audiophiles in mind, desiring to try the benefits of tube amplification for the first time and likely as an upgrade in a system more suited to solid state amplifiers. Great care has been taken to insure that the rated power can be delivered into speakers with medium sensitivity that are not necessarily tube-friendly, in other words, the typical speaker found in most systems. While minimalism is often used as an excuse for lack of technical sophistication, usually while mentioning that tube amplification has been around for more than a century, we view this history as a vast collection of unusual and advanced techniques to be used for sonic benefit, that we carefully selected and used in RED.
* Input signal selection is implemented using hermetically sealed relays with precious metal contacts, right at the input connectors. This reduces the number and length of wires carrying the audio signal to a minimum.
* Specially designed toroidal output transformers insure that the amplifier can deliver full rated power throughout the 20Hz to 20kHz audio bandwidth. Although this technology is often used to obtain an unusually extended high end response, we have decided to optimize our transformers for best low end extension so that the available output power can be delivered in every circumstance, while maintaining a full octave of bandwidth beyond 20kHz.
* Pseudo-triode operation of the output stage is achieved using a mostly unknown (because it is not practical with traditional designs) method of applying local feedback, which is nevertheless very efficient and does not have the drawbacks of similar concepts like the ultra-linear connection. It offers a synergy of characteristics which are applied in the design of RED, for example a drastic lowering of global feedback which is usually the bane of tetrode and pentode output stages. Red only uses a minimal amount to establish precisely equal gain for both channels.
* Hyperbolic class AB operation is used in RED to gain all of the desirable characteristics of class A operation without excessive power consumption and heat. This is possible through pseudo-triode operation of a carefully selected output tube type and it’s operating point. Crossover distortion is completely avoided, while maintaining the high power output and tube lifespan of class AB operation.
* The GU29/829 dual power tetrode tube has inherently well matched systems due to it’s original specification targeted at transmitters. A system of static and dynamic balance of the output stage guarantees minimum distortion. The output tubes are a rugged design targeted at much more difficult operating conditions than present in RED, in addition the input stages employ a sophisticated operating point stabilization mechanism. Together these methods insure long term operating stability and tube longevity, which makes it possible to include the tubes in our 3 year warranty.