ATLAS images coming soon!

The Atlas represents what we can do with minimal size, weight, and budget constraints.  The Atlas is an amp for typical speakers and offers a staggering amount of output power with a sonic signature that is exceptionally clear and extended.

The 833 is a very large transmitting triode that was used primarily for AM transmitters, but was largely impractical for use in a high fidelity audio amplifier.   To overcome the challenges of using an 833, a very quiet 10V/10A filament supply is required, as is a very large output transformer.  We worked with Monolith Magnetics to develop an output transformer for this specific circuit, as we do not require the enormously high primary impedance that most 833 SET amplifiers do, nor did we push the plate voltage up all that high.  In fact, each Atlas amplifier has a power supply that's roughly equivalent to what you'd see in a stereo 845 amplifier.  Building upon the technology present in our other amplifiers, we are able to use a 5K output transformer rather than the 10K-12K transformers typically used, and this is done with no global feedback.  Quiet heating of the filaments was resolved by the rapid development and improvements to switch mode power supplies, and one 12V 200W power supply set to output 10V works marvelously for this purpose and offers modular replacement options in the future if necessary. 

The circuit uses similar topology to our smaller amplifiers, but employs an 807 input tube which drives a 6HV5 choke loaded cathode follower that's directly coupled to the 833 grid.  A single 6KD3 damper diode ensures that the power supply comes up in a gentle manner, and internal high voltage fusing is present to protect all of the expensive components in the amplifier.  Circuit developments and revisions focused on parts reduction and prioritized simplicity above all else.  The result of this effort is an 833 amplifier that produces substantial power at far lower levels of distortion than expected, especially compared to other offerings on the market.  Gain is kept reasonably low to prevent an excessively sensitive system in the current market where source voltages are extremely high.

Power (Sino 833A):

72W 3% THD 1kHz

80W 5% THD 1kHz

81W 10% THD 1kHz

72W 5% THD 35Hz

79W 10% THD 35Hz (the 5A mains fuse can blow under these conditions, caution is advised)

Output Impedance: 2 Ohms on the 8 Ohm Tap

Bandwidth: 

-3dB at 9Hz and 89kHz

Gain:

15dB at the 8 Ohm tap

Noise:  About 3mV of LF noise on the 8 Ohm tap