“Single Ended Triode (SET) amplifiers in our opinion present music in a sonically pure form, with an enormous amount of emotion and timbral accuracy quite unmatched by any other type of amplifier. The presentation is truly special, and for some – once heard, there is no going back. We have invested thousands of hours in the lab developing a comprehensive range of SET amplifiers. The Concero 65 series, with it’s sheer power and size, takes SET performance to the highest level possible. These amplifiers are big, bold and very dynamic, with treble details and purity, and a liquid midrange as we would expect from the very best SET designs. In our case, the Concero 65 also has rock solid bass control and bass detail unmatched by any other SET design available today.” - Stavros Danos, Designer
 
 
The Concero 65 Series
 
The Concero 65 monoblock power amplifier series come in 3 versions, the Reference, the Signature and the highest level – the Limited Edition.
 
The Concero 65 Reference and Concero 65 Signature are both smaller versions of the Exsequor monoblock power amplifier, which is our top level 814 driving 813 circuit topology.
 
The Concero 65 Limited Edition is a different breed, and descends from our Legend Series Achilleas amplifier, based on our 813 driving 813 circuit topology. The Limited Edition version uses the same 813 directly heated triode on both the driver and the output stage, thus being a ‘one type’ tube amplifier.
 
The 813 Tube
 
The Concero 65 Limited Edition uses a parallel pair of RCA 813 tubes in the output stage, with a further 813 a the driver stage. So 813 driving an 813 topology. As an output tube, we believe this tube is one of the most linear tubes ever built. Triode curves quality are unmatched even by the most linear 300B tubes for example. And of course most bigger triodes like the 833 are far behind in both linearity and sonic performance.
 
This 813 big bottle tube never seizes to impress us whenever we compare it in our labs with ANY power tube used today, and is our weapon of choice when designing SOTA SET amplifiers.
 
Driver Stage
 
The driver stage is housed in a separate chassis, and has it’s own massive tube rectified power supply units and special biasing circuits. The driver stage is built like a small SET amplifier driving the output stage, and uses a unique interstage transformer. An example of the driver’s capabilities is the fact it can deliver 18W of power if needed.
 
Output Stage
 
The output stage is driven in absolute fidelity to the input signal. Having the same type of tube in the driver stage as in the output stage, and using a carefully designed biasing scheme, we can use what is called harmonic distortion cancelling. This occurs in special cases where a cascade of tube stages using the same tube type are used.
 
Filament Supplies
 
All three Directly heated triodes, both output and driver, are using triple PI filters with a total capacitance of 700,000uF, providing a completely ripple and noise free filament current. In the Concero 65 Limited Edition all filaments are inductively isolated from their power supply units.
As in all circuits using directly heated triodes, the filament power supply units are part of the signal circuit. This in turn means filament current supply is critical to the end sonic result. Having a very low noise PSU is mandatory. In the Concero 65 Limited Edition we took the extra step of isolated the PSU from the signal using specially designed inductors.
 
Driver & Output PSUs
 
All PSUs in the Concero 65 Limited Edition are independent using their own transformers,chokes and our proprietary Super Capacitors. The driver stage power supply unit is tube rectified, and uses a pair of high current damper tubes.
 
As energy storage we use our unique Super Capacitors. This unique type of film capacitors present a set of specifications unprecedented in capacitors used in audio, such as ESR and ESL values 100 times lower than electrolytics, as well as a maximum current surge measured in kiloamperes.
 
Biasing
 
Both driver and output stage bias can be monitored and set/adjusted on the fly, with the use on the built in digital monitors, paired with biasing adjusting knobs. Users can adjust the bias on the fly even while music in playing! This is a highly flexible feature and the sonics can be tweaked based on the settings.