Triode & Ultra Linear Switchable Modes
High power valve output stages are push pull. In this design the input signal is split into two halves via a phase splitter. Each half of the signal goes to one output valve and the signal is combined in the output transformer which is then coupled to the loudspeaker.
The triode push-pull output stage is the choice of many audio purists. The drawback is that because triodes are inefficient the output is limited and insufficient to drive many modern low sensitivity loudspeakers to high volumes.
A basic diagram of our triode output stage is given here. By connecting the screen grid to the anode a beam tetrode valve effectively becomes a triode with all its benefits and drawbacks
For many years the beam tetrode output stage was relegated to public address amplifiers because of its inherent non linearity and high distortion. Many attempts were used to improve tetrode operation but their output transformers were complicated and expensive.
Enter the Ultra Linear Output Stage. By connecting the screen grid to a special tapping on the output transformer a local feedback loop is incorporated around the output valves, lowering their output impedance, linearising the output and massively reducing distortion. The result is an amplifier with most of the advantages of the triode combined with the efficiency and power of a multi-grid valve.
Negative Feedback (NFB)
Overall Negative Feedback is a process where a percentage of the output of an amplifier is fed back to the input in reverse or negative phase. This lowers the output impedance, reduces distortion and improves frequency response. This bring obvious benefits to sound reproduction.
On EKCO amplifiers, NFB can be toggled on or off, with benefits for each setting. If you have, for example, horn loudspeakers you may find that triode operation with low NFB is suitable. With conventional loudspeakers (particularly low sensitivity models), ultra linear operation with high NFB offers the best operating mode.
We feel it is preferable to have a relaxed generous soundstage which you can enjoy over long periods of time. Experiment with different sources and at different volume levels before changing modes and you can then use the one which offers the best result. I's all about enjoying the music, suited to your tastes.
Flexible system controls & settings
Ekco amplifiers are designed to be flexible and easily changed to suit different sound sources and music. Aside from adjustable negative feedback and different valve configurations, users can also toggle between different speakers with an A/B switch. The EV55DP CD Player, DAC and Preamp also offers a Solid State and Valve output stage switch, again to tailor the listening experience for the user and music. The EV55DP also implements high quality P10 DAC circuitry, enabling audio resolution playback up to 24bit / 192kHz file resolutions.
Each EKCO product does not just offer superior realism in sound reproduction, but a height of quality in its craftsmanship too.
Each chassis is made of protective grilles finished with a proprietary high temperature black paint to protect the valve tubes. The sides of the chassis are fitted with matched pairs of hand crafted solid Deep Louro Preto wooden panels. The panels are hand finished using a multi-layer piano lacquer finish completing its elegant and retro charm.