DESIGN

​The Arcus vacuum tube amplifier has been designed from the ground up to provide the discerning listener with an exceptional musical experience, while remaining relatively compact and easily integrated into a living space.

 

In many cases, this approach would lead to a toned down version of higher-end separate components but not here: the Arcus was conceived with an uncompromising approach despite its compactness. A true dual mono supply, a precision resistor ladder volume control and a computer controlled power output stage that is capable of both Class A and Class AB operation put it in a category of its own.

 

With the combination of an all-tube amplification chain, very high quality components and an innovative feature set we're convinced that the Arcus amplifier will satisfy your highest expectations.

FEATURES SPOTLIGHT

ALL TUBE AMPLIFICATION

​COMPUTER CONFIGURABLE POWER STAGE

The Arcus amplifier uses only tubes and transformers in the signal path with no other active devices performing audio signal amplification.

 

The balanced inputs are handled by high quality amorphous core line input transformers, offering extremely good common-mode noise rejection over a wide frequency range.

 

Voltage and power amplification stages are connected through an additional interstage transformer using a push-pull topology with a precision current mirror for precise driver tubes biasing.

 

Finally, output power transformers connected in an ultra-linear topology provide the smooth and detailed sound signature of the Arcus amplifier.

 

​One of the most distinctive capabilities of the Arcus amplifier lies in its ability to let the user select the supply voltage and bias current of the output stage through multiple tube profiles.

 

This feature allows the use of all tubes from the 6L6 family such as the 6L6,-G/A/B/C, 5881 or Russian 6P3S, and operate them in optimal conditions. Class A and AB profiles are also available providing complete tube operating conditions control.

 

The precise bias control also has the beneficial side effect of providing zero maintenance push-pull balance, thus ensuring the output transformer operates in ideal conditions over the entire tube lifetime.

 

Rounding up the flexible output stage, six WBT speaker binding posts offer the choice of two output impedance ranges: 4/8Ω or 8/16Ω, allowing optimal impedance matching.

 

​FLEXIBLE FILAMENT VOLTAGE SUPPORT

TWO CHASSIS DESIGN

For tube enthusiasts, the Arcus amplifier adds the ability to support signal amplification tubes using either 6.3V or 12.6V filaments. No manual adjustment is necessary and the correct filament voltage will be applied automatically based on the inserted tube.

 

This opens up the possibility to install new and NOS tubes from both the 6SN7 as well as the 12SN7 families, vastly expanding the usable NOS tubes range.

 

For the dedicated tube rollers, a simple Loctal to Octal socket adapter allows 7N7 and 14N7 tubes to be used for even more NOS tube options!

Designed as a no-compromises dual mono architecture from the ground up, the Arcus amplifier uses a separate power supply chassis housing dedicated power transformers for each channel.

 

In addition to offering fully DC regulated filament, high voltage and bias voltage rails, the power supply has been designed to limit RF interference from entering the circuitry through systematic use of common-mode chokes and filtering capacitors.

 

The end result speaks for itself: a pristine background for music to unfold on.

PRECISION RESISTOR LADDER VOLUME CONTROL

​Contrary to many integrated amplifiers employing inexpensive volume controls, the Arcus deploys one of the most direct and transparent implementations: a relay-controlled precision resistor ladder volume control. The circuit uses low noise metal film resistors to offer volume control in 1dB steps with almost perfect channel matching.

 

For ultimate user convenience, during volume changes the audio path is switched to a professional grade VCA (voltage controlled amplifier) circuit enabling smooth and continuous volume adjustment until the desired sound level is reached. Once this is done, the pre-amplifier ciruitry will switch the audio signal back to the passive volume control.

 

Like everywhere else: no compromises.

 

GALLERY

Images ©2017 A. Sautebin

SPECIFICATIONS SUMMARY

​The Arcus amplifier offers several tube operating conditions and combinations making it impossible to measure all the permutations. For simplicity, the specifications below apply to standard new production 6SN7 and 6L6GC tubes as supplied from the factory.

 

Internal auditioning tests have also produced exceptionally good results with NOS tubes from US and Russian origin.

 

Please visit our Accessories section for available tube sets.

AMPLIFIER SECTION

POWER SUPPLY

  • ​Vacuum tube only signal path with inter-stage and output transformer coupling and no negative feedback.
  • Push-pull drivers and push-pull ultra-linear output stage with choice of Class A or AB operation.
  • Computer controlled, analog tube bias control and voltage control with user-selectable tube profiles.
  • Precision current sensing for perfect push-pull bias current balance requiring no manual adjustments.
  • Transformer coupled balanced audio inputs feeding a hybrid resistor ladder volume control / analog VCA.
  • Lundahl interstage and Hashimoto output transformers.
  • Six speaker binding posts allowing two different output impedance ranges (two out of 4Ω, 8Ω or 16Ω)
  • ​Dual mono design with individual power transformers for each channel.
  • Fully DC regulated heater, high voltage and bias supplies.
  • Separate digital circuits supply (with its own power transformers) to avoid interference into the analog circuits.
  • Common-mode choke filtering on all rails to drastically reduce noise and RF interference entering the amplifier.
  • Lundahl C-core power transformers.
  • Ultra long life film power supply capacitors.

Input

Amplifier Dimensions

Input impedance
(balanced)
27
Attenuation Range -63..0 dB
Sensitivity 2 V rms
Voltage gain 14 dB

Output

Bandwidth
(+/- 1dB)
20..20000 Hz
Rated power
(1kHz, 8Ω)
A 27.5
AB 30.0
W
Distortion
(1kHz, 1W/8Ω)
A <0.2
AB <0.5
%
Distortion
(1kHz, Rated power)
A <1.2
AB <2.5
%
Output tube balance
(automatic adjustment)
<500 μA
Outside dimensions
(L x W x H)
298
298
200
mm
Weight 13.5 kg

Power Supply Dimensions

Outside dimensions
(L x W x H)
298
298
200
mm
Weight 17.5 kg

Power Consumption

Standby <0.5 W
Idle 160 W
Maximum 200 W

DOWNLOADS

Please click on the links below to download the desired files.

Arcus Integrated Amplifier

Immerse yourself in music.

Nimbus Audio

 

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