Concero 25 Monoblock Tube Amplifier

Our first Prestige Series amplifier is the Concero Direct Heated Tube Monoblock amplifier.

Using top of the line design, material and building techniques, we have managed to get pretty close to our Reference line amplifier performance, but in a more manageable design, as regards funds and size.

We endeavoured to produce a design that has all the sonic virtues of only the best of the best Single Ended amplifiers, but with absolutely none of their shortcomings. We strongly believe we have succeeded.

Driving the output tube is a major task, which almost all SET amplifiers fell short, using tubes not adequate to the task. Tubes with high Rp and small current swing capabilities. What we choose to use is a small amp, consisting of the special quality Siemens E280F super-tube, with its own power and bias supply.

This ultra wide-bandwidth/ very high trans-conductance tube is transformer coupled to the grid of the output tube using a very wide-bandwidth inter-stage transformer. No RC coupling is used in any of our amplifiers.

The output is rated @ 30W, via a massive output transformer, with 4 and 8-ohm taps.

The output transformer weighs more than many SET amplifier’s total weight. The highest quality massive core of the output transformer used in the design is mandatory for delivering true undistorted higher and lower bass and driving any speaker through complex musical content. Many SET amplifiers get distortion when driving speakers with complex music, because of core saturation. Our output transformer can easily take 60W at 20Hz, so at 25W intermodulation artefacts are next to zero.

Separate power supplies are used throughout our design, using 4 toroidal transformers rated at over 1100VA total. Separate toroidal are used for driver stage, output stage, filaments and bias circuits.

Driver and output is ground-choke regulated and energy banks are over 4000 joules per channel.