Exsequor Tube Reference Amplifier

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Working in Class A1, the Exsequor amplifier can deliver more than 65W in 8ohm or 4ohm loads. With it’s unsurpassed clarity, 3D imaging and breathtaking transients, with enough power to drive almost any floorstanding speaker, this SET amplifier is a class of it’s own.


We believe that SE non feedback amplification stages deliver the best overall sonic performance to the listener. Yet, almost all SET amplifiers do not have sufficient power to drive the majority of modern loudspeakers. One way of delivering enough power from a SET amplifier, is the use of many parallel mainstream tubes like KT-88, EL34 or big bottle tubes like 845 and the 805.

Direct heated triodes with their super smooth sound are the way to go. The tube of our choice is the 813, a 50W thoriated Tungsten filament tube with it’s 125W plate dissipation rating and probably the best big bottle tube sound we have ever tried in our labs, leaving far behind any version of 845 and 300B tubes we ever tried. Almost all tube amplifier manufacturers with their light, slow and weak power supplies, give a distinct flabby sound to the majority of these amps. They get things worst by trying to drive the big output valve with small signal tube like 12AXXs e.t.c. As a result, the output tube, is underdriven with the known results of limited frequency response and lack of acceptable transient response..
We chose to differ…

. The Exsequor monoblock tube amplifier is our opinion of how a SET amplifier without compromises should sound and how tube amplification should be implemented.

 

Specifications:
- Max Power Output : 65W (A1)
- Power Consumption (idle) : 490W
- Power Bandwidth (@ 60W) : 15Hz-45Khz(-3db)
- Weight (each, unpacked) :160KG


Dimensions: 780mmH X 520mmD X 630mmW

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    Driver stage : Most SET amplifiers, use a small signal tube, usually RC coupled to the output stage. As a result, the final stage is well under-driven, compromising the sonic performance, giving the SET amplifiers their usual distinctive mellow sound. In order to drive a pair of big tubes with large grid capacitance the driver stage must be a small amp by itself.

    We decided to built an amplifier inside an amplifier, so the output stage is driven without any compromise. Using the 814 tube, a Direct Heated Thoriated Tungsten tube, we are capable of delivering >14W in class A operation to the grid of the 813s, more power than many SET amplifiers deliver as their output. Power from the driver tube is delivered to the 813 tubes by an amorphous double-c core, bifilar winded inter-stage transformer with exceptionally wide bandwidth and low distortion.

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    Output stage use full-bridge tube rectification, using the 6D22s damper tubes. With 1A peak current capability we avoid any problems using standard rectification tubes.

    No electrolytic caps are used throughout the power supply. A double choke CLCLC filter is implied, using polypropylene in oil caps, and three film SuperCapacitors(3kg each,100 times less ESL/ESR than any Electrolytic technology),delivering lightning fast energy storage with a total of almost 1000joule energy reserve. Separate power transformers are used to power the filament supplies. A soft start module is used to avoid any line problems when the total of 850VA power transformers are switched on. The output stage is using a pair of 813 tubes, biased with a separate adjustable bias power supply.

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