Features
| Brand | Cary Audio |
|---|
Product Description
The Cary Audio CAD-300SEI Valve Integrated Amplifier is a single-ended triode design with outstandingly detailed sound. The output valve is a 300B triode, this is a very famous valve first produced in 1938. The valve is operated in class A where one valve handles both sides of the audio signal.
As a result, some of the most fatiguing distortions are eliminated. The power output of Class A is lower. In this case 15 watts per channel. This is more than compensated for by the extremely quiet background, where you can hear the tiniest detail.
The frequency response is 23Hz to 23kHz. It is to be noted that Cary recommends a hundred-hour running in period before optimum performance is reached.
Exemplary Build quality
Traditionally valve amplifiers were made using point-to-point wiring, as is the Cary Audio CAD-300SEI Valve Integrated Amplifier. Point-to-point wiring is considered to be more reliable. However, it is very labour-intensive to use this method.
Therefore, in the 1960’s PCBs started to be used. These are not ideal for valve circuits as valves generate a lot of heat. The heating and cooling cycle leads to cracked solder joints and overheated boards. Hence the best modern valve amplifiers do not use PCBs.
Another issue is the output transformers, these have to be carefully designed to provide the best audio quality. Moreover, Modern methods of construction provide far superior results over older types of transformer.
Transformers are needed because the output of the valve is at a high impedance and this has to be reduced to 8 ohms for the speaker. The transformer also stops any high voltages from being present on the speaker terminals.
Connectivity
There are three RCA inputs with the Cary Audio CAD-300SEI Valve Integrated Amplifier. These are controlled by a rotary switch on the front and labeled, CD, aux 1, and Aux2. Speaker outputs are by standard binding posts that are situated at either end of the back plate. The front is kept simple with just the input selector, volume, and balance control. There is also an on/off switch and a 6.3mm headphone output.
About valves
Valves are thermionic devices, in that they emit electrons from a heated cathode. The earliest type of valve was the triode invented in 1908. This is also used as the output valve by the Cary Audio CAD-300SEI Valve Integrated Amplifier. The triode was the first device that could amplify a signal. Triodes have three terminals as well as a heater.
The heater normally runs at 6.3 Volts and heats a cathode. The cathode emits electrons from a special coating. The other main electrode is the anode. Additionally, there is a control grid. The anode is held at a high voltage while the grid is kept slightly negative of the cathode.
As a result, electrons are attracted to the positive anode, and a current flow is generated. If an audio signal is applied to the grid an amplified version appears at the anode.
A word about capacitors
An important part of a valve amplifier, such as the Cary Audio CAD-300SEI Valve Integrated Amplifier, is the coupling capacitors. Their main function is to couple the audio signal between stages while stopping DC from getting to the grid. Up until the 1960s capacitors had a paper dielectric.
These tend to fail over time. As a result, they became electrically leaky. Modern capacitors are made of polypropylene or polystyrene and do not deteriorate over many decades. Notably, if a positive voltage gets onto the grid it causes the valve to be turned fully on potentially burning out the cathode.
