Vitus sia 025 vs d'agostino momentum

leo6473 posts07-02-2016 5:35pmDodo try the gryphon Diablo 300
i swapped my Vitus sai025 for one
chalk and cheese imho
leonard

How exactly is it chalk and cheese? The EU price certainly doesn’t suggest so. The Diablo 300 is €17,600, whilst the SIA-025 is €21,000. Both amps are high bias Kl.A/B amps, dual mono with wide bandwidth and ZNF. But there are fundamental differences in the PSU’s. Vitus are using a special UI-core transformer which took 8 years to develop which is extremely efficient & sounds especially liquid/tube-like. The current SIA-025 is outputting 25 watts Kl.A & 150 watts Kl.A/B @8ohms, but Vitus’s power specs are ridiculously conservative. My slightly older SIA-025 outputs 100 watts Kl.A/B and controlled my Magico S5’s in my medium size room without breaking a sweat.

leo6473 posts07-02-2016 5:44pmOne issue with the excellent Vitus amps was that they need to be left powered up as they take 3 to 4 days to reach their transparent sound
my Diablo 300 takes 30 minutes although I do leave it on standby

Maybe stone cold out of the box, but here is what Chris Thomas said in his review of the SIA-025 for Hifi Plus "From stand-by, straight into class A I would say that you are looking at a half hour before it really begins to sing and then it just seems to keep getting better. Even after a solid afternoon and evening’s listening I would swear that the amplifier was growing more fluid, textural and resolute with better dynamic contrasts, tonal shading and the delicacy of its musical message just seems to become more profound." No mention of 3 to 4 days because that is absurd. And I own an SIA-025, so I know from whence I speak.

After owning several excellent high end amps and now the momentum I would say that at this level another amp, in this case Vitus, might sound a little different but better is unlikely. Just different.. Would feel the same way if you reversed the question. At the top level IMO it's a matter of nuance. Listening to a Krell Chorus amp right now and couldn't really say what change in sound I might want. IMO again, high end gear is just really good nowadays. 

The current SIA-025 is outputting 25 watts Kl.A & 150 watts Kl.A/B @8ohms, but Vitus’s power specs are ridiculously conservative. My slightly older SIA-025 outputs 100 watts Kl.A/B and controlled my Magico S5’s in my medium size room without breaking a sweat.

Are you sure about 150 watts in A/B mode? My dealer is still quoting 100 watts A/B. I think the UI transformer contributes significantly to the 42kg weight.

I was also told to keep it on all the time because the magic starts after 72 hours of operation. I don't actually do this, just switch on 1 hour before use.

This is ridiculous - 72 hours before reaching the peak performance. What were they thinking? 

@cyclopse, Yes I am 100% sure about the power specs of the current Vitus SIA-025. Vitus increased the power output from 100 to 150 watts in Kl.A/B about 18 months ago. Class A power is the same. By Hans Ole's own self admission, there are several inconsistencies with the spec sheets and even user manuals right now. That is one of the projects that Hans has 'in the queue'. If in doubt, you could contact Vitus directly and confirm that.

Regarding maintaining optimal thermal conditions. I would refer you to the commentary from reviewer Chris Thomas in my earlier post. But fyi, this is from the SIA-025's owner manual which comes on cd..

"3. Standby mode. In this mode the controls of the SIA-025 are deactivated.
The SIA-025 does not shut down in Standby Mode in order to maintain an optimal working temperature"

You could also ask Bob at Rhapsody in NY who is a Vitus dealer. He had this to say on Audioshark forum about the SM-102 & SM-011 mono's - "One last point is that like most amps, but especially with the SM102's they take at least an hour playing in Class A mode to really strut their stuff. The SM011's take some time to warm up as well, but not as long as the SM102's. They are both VERY listenable from the get-go but after an hour in Class A with the 102's then you understand what they are all about."