Ypsilon Aelius II Mono


The Aelius II is a push-pull hybrid monoblock power amplifier using only two gain stages with no overall feedback providing power to drive real world speakers with unmatched transparency and musical involvement.  

The first gain stage is implemented with a valve, operated in single-ended class A , transformer coupled to the output stage. By using a transformer we avoid using an additional gain stage, so transparency and purity of the signal is maintained.

For this purpose a wide bandwidth (10 Hz – 75 KHz) transformer is made, developed under extensive listening tests and measurements. The bandwidth of the transformer defines also that of the amplifier.

In Aelius II a recently developed input transformer is added that extends the purity of the signal path even further. It also gives the opportunity of a balanced input in the amplifier, adding versatility of using longer interconnect cables.

The output stage uses components of the same polarity (N-channel), working in the same topology.  The output of the amplifier is symmetrical so both output connectors, plus, minus, carry signal in opposite phase.

Great attention was paid also in the power supply design. It uses high current inductors for smooth and quiet filtering.

Aelius II is most certainly a revolutionary product having a unique set of features, refinement and transparency with power and control over the speaker.


Output Power Before Clipping200W rms @ 8 Ohm
350W rms @4 Ohm
Bandwidth11Hz -75KHz -3dB
Output Impedance0.25Ω
Input Impedance47kΩ
GainX30 (29,5dB)
Power Consumption250W @idle
Dimensions425mm x 425mm x 230mm (WxDxH)
or 17 x 17 x 9.1 in (WxDxH)
Weight45kg or 99.5 lbs each

Other Resources

Sound purity, endless power, outstanding design, unmatched build quality. This is AELIUS II monoblock hybrid push-pull amplifier. 

Matej Isak, Mono and Stereo, 2016

The Aelius amps were just right if you like a tight, fast, nimble top-to-bottom ride, if you like sounds so transparent it’s almost alarming, convincingly yet not analytically precise transients, and three-dimensional imaging—all without paying the high price of too-sharply-defined edges or a clinical, soulless, harmonically bleached sound.

The Aelius is yet another spectacular sonic and technological achievement from Ypsilon Electronics. I remain impressed by everything they do.

Michael Fremer, Stereophile, 2013

Ever go shopping for a winter scarf? I like to test the “hand” of each offering, noting quality and price. The acrylic one would do the job, but it doesn’t feel so nice. How about the wool or the cashmere blend? Silk, maybe? Any one of these materials would do the job and each has its own “hand.” 

Don’t we go through the same process with components? In this analogy, the Ypsilon Aelius Mono Amps are the equivalent of the finest silk-cashmere blend. They have the nap of lux on your ear; their sound feels good there. 

This is my third taste of Ypsilon componentry and it has been consistent. Within that spectrum, I’d place the PST 100 Preamp and VPS 100 Phono Stage together on the musical side in their voicing; the Aelius mono amps tack closer to neutral. 

Whether the Aelius was paired with the matching PST 100 or my Trinity Preamp, the verdict was the same. These products are communication specialists. Everybody enjoyed them. 

I was very tempted to hold on to them and make them my new reference. That would have been a radical jump from my Soulution 710 Stereo Amp. Yes, they’re that good.

Marshal Nack, Positive Feedback, 2014