Vitus SIA-025 review

[bzr]

Originally Posted by yuh

Hi David, I would like to say thanks for a great review.

I'm new to the forum, and interested in this amplifier as an upgrade into hopefully what could be my end game set up.

Currently i'm running a pair of Parasound JC-1s into Paradigm S8s. The JC-1s have the nice class A sound and is highly biased into class A for the first 25W (and class AB for the rest of the 400W). I was wondering with the Vitus, in class A mode, does it do the same thing, ? ie move automatically from class A to AB, or is 25W the limit? Which would make me worry about clipping into distortion etc.

Whilst the S8s are quite efficient speakers, I would want to upgrade them as well in the near future, perhaps to Evolution Acoustics MMMiniTwos or Magico S5 / Q3. That is if i can ever find a dealer in Sydney that can demo them...

Give Jeff Knox a call, Knox Audio. Either that or cal Absolute HiEnd in Melbourne & talk to Boris, he's the importer, only $95 for a flight!

[yuh]

Indeed i have been to Knox audio and have made some purchases there in the past. I've demoed some Evolution acoustics and Vitus Audio (though not this particular amp) there in the past and they sounded great.

No Magicos that i can find in Sydney though. Might have to make that trip down to Melbourne some day.

[4RE]

Great review, out of real world situation.
Seems to be acknowledged time and time again that Vitus, Accuphase and Soulution gives a great match with any Magico.
Thank you for sharing, great read!

What I cannot possibly concur to is this sentence, quote:

The treble is somewhat softened and the lower midrange slightly emphasised, giving the amp a sound resembling good vinyl.

Originally Posted by yuh

Hi David, I would like to say thanks for a great review.

I'm new to the forum, and interested in this amplifier as an upgrade into hopefully what could be my end game set up.

Currently i'm running a pair of Parasound JC-1s into Paradigm S8s. The JC-1s have the nice class A sound and is highly biased into class A for the first 25W (and class AB for the rest of the 400W). I was wondering with the Vitus, in class A mode, does it do the same thing, ? ie move automatically from class A to AB, or is 25W the limit? Which would make me worry about clipping into distortion etc.

Whilst the S8s are quite efficient speakers, I would want to upgrade them as well in the near future, perhaps to Evolution Acoustics MMMiniTwos or Magico S5 / Q3. That is if i can ever find a dealer in Sydney that can demo them...

Thanks for your kind words Yuh. Your Parasound JC1's look like well engineered amps. They have a similar amount of class a bias as my previous Classe Cap-2100 & look like they have a lot of power. Hopefully I can offer some insight as my previous amp was a Boulder 1060 which is similarly well behaved and powerful.

Coming from the big Boulder to my current Vitus, I was keen to see if the Vitus would have enough power and control for my S5's which are an 88db/4ohm load with a 2.4ohm dip. Overall the S5's are a moderately difficult load. Firstly, Vitus quote their power specs very conservatively. Secondly, I tend to look at the weight of an amp as an indicator of how beefy the power supply is, since the majority of the amp's weight is taken up the transformer(s), and the Vitus weighs 42kg (92.5lbs). By comparison, both Parasound mono's combined weigh less than the Vitus which tells you something. Thirdly, the Vitus is a very high current amp. And fourthly, Vitus use a huge Vitus-designed 1.4kVa UI-core tranny in the 025 which is up to 25% more efficient than a normal audiophile grade toroidal tranny, so that 1.4kVa tranny feels more like a big 2kVa tranny as I mentioned in my review.

Regarding mode of operation, at power up the Vitus defaults to class A/B. When you switch from class A/B to class A mode the amp will operate in class A up to its full rated power and does not switch to Class A/B as one reviewer speculated. Otherwise what would be the point to switchable modes of operation? It would be simpler in that case to design a highly biased Class A/B amp.

Taking into account my amp & speakers are still under 200hrs, at this point my view is the SIA-025 has plenty of power and control to pressurize my medium size room, and in practice should further open up and go deeper in the bass by the 500hr mark. That said, the most important thing to me is system synergy, and there is no doubt the SIA-025 has great synergy with the S5's and Q1, though I haven't heard it paired with the Q3.

If it would further assure you, at the Munich High End Show a couple of years ago, Vitus was driving German Physiks speakers which are 87dB and other speakers at 83dB sensitivity using an SS010 (which only has the 25W at all times) in a 300m2 room with 4m to the ceiling. So yes I am very confident it will have no issue - in Munich it was running in class A mode all the time.

Cheers,

[yuh]

Thanks for the detailed reply and many useful points, David. I have no doubt the Vitus is a much better sounding amp than my parasounds, which is why I'm strongly considering them as my next upgrade.

Originally Posted by Bodhisattva

Coming from the big Boulder to my current Vitus, I was keen to see if the Vitus would have enough power and control for my S5's which are an 88db/4ohm load with a 2.4ohm dip. Overall the S5's are a moderately difficult load. Firstly, Vitus quote their power specs very conservatively. Secondly, I tend to look at the weight of an amp as an indicator of how beefy the power supply is, since the majority of the amp's weight is taken up the transformer(s), and the Vitus weighs 42kg (92.5lbs). By comparison, both Parasound mono's combined weigh less than the Vitus which tells you something.

The lowest sensitivity speakers I'm considering are the MMMiniTwos which are 86db into 6ohm load, which isn't too far off the S5. Just a slight error, but the Parasounds JC-1s do weigh 29kg (64lb) each monoblock and that's not including any preamp.

Originally Posted by Bodhisattva

Regarding mode of operation, at power up the Vitus defaults to class A/B. When you switch from class A/B to class A mode the amp will operate in class A up to its full rated power and does not switch to Class A/B as one reviewer speculated. Otherwise what would be the point to switchable modes of operation? It would be simpler in that case to design a highly biased Class A/B amp.

Just my thoughts (and i could be completely wrong here), I would have thought that having switchable modes of operation could be useful with respect to heat output. ie in class AB, there is no bias into class A at all and hence very low heat. And class A mode is the mode with bias of 25W into class A.

If the class AB mode is biased into A up to 25W, it would make almost as much heat as a pure class A 25W amp, would it not?

Originally Posted by Bodhisattva

If it would further assure you, at the Munich High End Show a couple of years ago, Vitus was driving German Physiks speakers which are 87dB and other speakers at 83dB sensitivity using an SS010 (which only has the 25W at all times) in a 300m2 room with 4m to the ceiling. So yes I am very confident it will have no issue - in Munich it was running in class A mode all the time.

That is indeed reassuring. I like the fact that I can get all this in an integrated amp and have one less set of ICs and power cables to worry about (not to mention rack space/isolation).

[yuh]

I got an email reply direct from Vitus Audio.
Class A mode: is 25W class A and then goes into class AB up to 100W.
Class A/B mode: is approx 7W class A and then class AB up to 100W.
Values for into 8 ohms RMS.

No worries about clipping then. Why they didn't just call it high and low bias, i have no idea. Would have saved the confusion. Well that finalises it for me, I know what i'm getting as my next amp

Originally Posted by yuh

Thanks for the detailed reply and many useful points, David. I have no doubt the Vitus is a much better sounding amp than my parasounds, which is why I'm strongly considering them as my next upgrade.

YW Yuh. The thing about the Vitus is it's wonderful purity and musicality. Btw, Vitus updated the modules in the SIA-025 in Q1 2012. They optimized multiple areas of the amp - but with most focus on the modules in both pre and power amp part. Basically it gives a bit more of everything - higher resolution and better power handling.

Originally Posted by yuh

The lowest sensitivity speakers I'm considering are the MMMiniTwos which are 86db into 6ohm load, which isn't too far off the S5. Just a slight error, but the Parasounds JC-1s do weigh 29kg (64lb) each monoblock and that's not including any preamp.

I had a look at the current specs on the MMMiniTwo's. They are a 9ohm, 86db load with an impedance variation of +/- 1.5 Ohms, although given they have an active sub, I would be confident the Vitus would not be stressed operating in KLa mode. In general, the SIA-025 has good synergy with ceramic drivers as it tends to tame their edginess and offer warmth and richness which those drivers need.

Ah, sorry I got the weight wrong on the JC-1's. That changes things a bit and suggests they have robust power supplies which deliver plenty of control. The main difference moving to Vitus is likely to be the sound which should have excellent synergy with any of the speakers you mentioned.

Originally Posted by yuh

Just my thoughts (and i could be completely wrong here), I would have thought that having switchable modes of operation could be useful with respect to heat output. ie in class AB, there is no bias into class A at all and hence very low heat. And class A mode is the mode with bias of 25W into class A.

If the class AB mode is biased into A up to 25W, it would make almost as much heat as a pure class A 25W amp, would it not?

The SIA-025 only gets warm to the touch in Class A/B mode, and very warm to perhaps mildly hot running in Class A mode. But just to correct you, in Class A/B mode, the amp still has a similar amount of Class A bias to my previous Classe Cap-2100 (which operated in Class A for approximately 20% of it's output). By way of reference, the Classe consumes 125W at idle, whilst the Vitus consumes 100W at idle in Class A/B mode. That equates to around '16 watts' in Class A @8ohms before moving to Class A/B. I emphasized 16 watts as again those power specs are very conservative.

Originally Posted by yuh

That is indeed reassuring. I like the fact that I can get all this in an integrated amp and have one less set of ICs and power cables to worry about (not to mention rack space/isolation).

Those were my exact thoughts before I decided to reduce my box count and take the plunge on the Vitus. My philosophy is quality over quantity and to fully optimize your system.

[4RE]

Roughly devide the draw current by 5 and you have approximately Class A in watts.

As example 100 watt current draw it would approximately be around 20 Watts Class A but likely some less.

There are many misconceptions about "Pure Class A" and Nelson Pass has written a great article on this, you may download it from his webpage.

There is no 'switching' involved. almost all amps ( also the so called Pure Class A) are in fact Class AB.
Nelson Pass used to build Pure Class A amps which are Single Ended. These were so hot you could frie eggs on it. There is a picture to be found on the internet where two eggs are fried in a steelpan on top of -if i'm right- an Aleph 2 stereo.

Performance of any amp lies for great part in its power transformer / power supply.
Vitus has this worked out beyond any doubt, and that is what you hear.

I do think Class A is not the one and only way to get great sound.. Love my PR350SA
and it might be biased to 5 Watt Class A only. 5 Watt is sufficient for 90% of listening habits concerning one has around 88 Db speaks.

Ask any Accuphase owner about how many Watts are randomly used and shown at the Vu meters! hmm this may be new topic start.

Hi 4RE, thanks for your insight. I discussed the points you and Yuh raised with Hans Ole and you are mostly correct. I said "mostly" having regard to Hans' response below..

"well they are kind of right

in pure kl. a the sia025 is biased to give a full 25W into 8 ohm in kl. A but still runs into 100W ab - with no switching

when switched into ab mode - the bias is lowered to about 5w kl a simply to save power

there is not such thing as "pure kl. a" as such

the SM-102 is a 100W kl A / 100W kl. AB amp - so that is what we mean by a pure kl a amp"

I have to admit my understanding of the SIA-025's biasing scheme was not correct, although I did correctly state in my earlier post that in class A mode the amp will operate in KLa up to its full rated power and does not switch to Class A/B as one reviewer speculated (since there is no switching).

I prefer VA amps, but respect Nelson Pass, so I will make a point of reading that article you mentioned . I agree 100% with your comment that an amp's PSU is largely responsible for the performance, and ultimately the sound the amp produces. Companies like Audio Note (Ongaku) and VA understand this and invest great amounts of money and resources into developing their own very high grade psu's.

Btw I agree that so called pure class A design is not the only way to achieve good sound. I used to own a Boulder 1060 which operates in KLa biasing up to 17 watts before switching to class a/b, and the sound is great! Boulder go to a lot of trouble to notch out crossover distortion to maintain linear operation. I asked Rich Maez from Boulder about KLa amps and this is what he had to say -

"Class A biasing is beneficial when it comes to sound quality, but there are many, many other things that it affects, most notably reliability: constant thermal cycling leads to failures. Our 2000 Series products are pure Class A up to full rated power output, but we go through a lot of effort to maintain thermal stability and eliminate rapid cycling, all of which is very, very expensive to implement - and by this I don't mean shiny metalwork."

On your last point about how many watts KLa we actually use at normal listening levels, Rich commented - "Another fundamental to think about is this: how often do you think you exceed that 17 watts of power output? Do the math with your particular loudspeaker and you'll find that it's much less often than you think." And since the Vitus is conservatively delivering up to 50 watts KLa @4ohms, given a moderate speaker load such as the Magico S5, or even easier Q3 it is unlikely you would leave class A operation at normal listening levels .

[yuh]

4RE, yes you are right, KLa mode is still Class AB, highly biased with at least 25W class A. I think that's better than a 'pure class a' anyway as there is less concern for clipping.

Thank you all for your contributions. I will likely be ordering one of these amps in the near future.

Please note, because i'm a new member, my posts appear on the thread several hours after i've posted them as they need to be checked by a moderator. Hence, my last post with the official reply from Vitus Audio may have appeared after you had posted your replies.