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ATC SIA2-150 Mark 2 Integrated Amp Review

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With a little luck the ATC SIA2-150  review will be completed this weekend.  It has been on hold for several weeks now as things popped up that robbed me of time or energy but it seems at least half of this weekend will be free so I'm going to step on the gas and see if I can get this one finished and written up.  I know there's at least one SNA'er waiting on it.



It isn't a large amp, reasonably weighty though at 20kgs, but it can pump some serious power.  As demonstrated at Terry's place it was one of the few amps that we tried on those VA Concert Grand speakers of his that took control and made the speakers perform.  This places it in the same category as the Sansui 907 NRA, 907 Limited, ME-240, and Zeus Integrated.  And that is some pretty decent company to be in.


The ATC suffers a little in my home system in that it doesn't impress as much as it did at Terry's place.  I think this is one of those amps that reacts well to being asked to work harder so it will step up on lower impedance speakers.  Since my Lenehans are fairly benign in impedance I believe the ATC is coasting a little.  Still a very good amp but not quite as "Wow inducing" as it was on those VAs of Terry's.


Details to follow once my washing machine has finished it's job and quietened down a bit.


There is more info on the ATC SIA2-150 on page 5 of the thread Terry and I started, link below.  Some rather nice pics too.



Edited by Cafad

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I guess that SNAer would be me?  I agree with your assessment on benign loads.  On my SCM40 passives it didn't seem to work all that hard but it also seemed to run out volume at higher levels.  This was compared directly to the active version so possible not a fair comparison.

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I've been lucky enough to clock up a few miles listening to ATC gear in recent years- Scm19, 40, 150 active towers, Scm100 active classic, SPA2-150 and P1 power amps, the CDA2 Swiss army knife, CA2 preamp. All that electronic stuff plays very nice with other brands too.

ATC gear has a house sound that should have very broad appeal but they are determined to let the products speak for themselves rather than foist it on to us via cosmetic enhancement and slick marketing. ATC refuse to plug in to audiophile neuroses to make a buck. They're not sell outs.

That's why you can ring ATC up and talk directly with happy technical people, they love talking about what they do and have nothing to hide.

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As it is an English amp the ATC does run a little on the warm side.  That's why I cut up some pine and made little chocks for each of its feet, just to make sure it had enough height underneath it to get some unrestricted air movement over those heat sinks.  Unfortunately the 9 volt battery from my heat gun was recently used to get one of my smoke detectors back up and running so I can't tell you exactly how hot it gets, all I can say is that it was still cool enough to hold my hand on indefinitely.


Let's get the associated gear paragraph out of the way shall we?

Source in use was my trusty YBA Heritage cd 100, connected via Aurealis all copper dragon interconnects to the ATC.  Speakers were my just as trusty Lenehan S2R stand mounts and speaker cables were Redgums "Audio Pipeline" 7 gauge "you could tow a ute with them" cables.


There we go, all done.  Now for a little more about the amp itself.


I like the fact that ATC have an integrated amp that is all analogue and all unbalanced.  No frills, no added bling, just a true and tried design with a serious power supply.  Let's not forget the separate torroidal for the preamp section as well, (or possibly just the DC motors) always a good thing in an integrated design, IMO. 


Much of the 20kg weight is due to the heat sinks but that main transformer is solid enough to make the whole unit just a little front heavy.


Now usually I separate out an amp review and write about the top end, mids and bass, vocals and so on.  This one is going to be a bit different for reasons I'll get into.  You see, most amps treat the different regions of the treble, mid-range and bass differently.  So while an amp may have nice clean mids it may back those up with tight or warm or understated bass and the top end may be rolled off or extended or a little hard or sweet.  Basically they can all sound a bit different to each other and this is not so unusual. 

But not the ATC SIA2-150, it plays no favourites at all.  So when I say that the top end does not seem rolled off at all but at the same time it isn't softened, it is just well detailed and not harsh to listen to.  As is the mid-range and the bass.  No favourites.  None!

To elaborate on that, the top end is at the same time as hard and harsh and ragged as it needs to be but it is still not too much of any one to make it sound unpleasant.  I seem to have coined a term here "well detailed", the sort of detail that is considered by the ear to be supplying all the detail that is needed to be heard but doing it in a way that carries very little in the way of anything that could contribute to listening fatigue.  Add a character that I can only describe as, slightly on the warm and earthy side of neutral and you've got the SIA2.

I do have to say more about the bass because the bass region takes much more power to make it work well than the mids or the top end and power is something that the SIA2 has plenty of.  Bass is fast and tight but also full and well weighted.  Drums are  So!  Damn!  Good!  Even better than the Luxman 507u and that is some serious praise right there.  I've awarded scores of 8.75 for the top end, 8.5 for the mids and another 8.75 for the bass.


Vocals are also brutally honest in their reproduction.  The SIA2 does not give any singers any assistance at all, no extra breath or warmth to be found.  Depending on your preferences this could be a bad thing but you have to recognize that this could be invaluable in evaluating the rest of the audio chain.  I like it, and I certainty appreciate it, but it does make awarding a score rather difficult.  I'm going to go with a flat 8.0 for both but I'll reserve the right to increase that upon further consideration.


I just have to talk separation, the SIA2 has it in spades.  Every instrument is kept well and truly away from every other one, vocals are separate too and this lets you hear so much more detail in the performance of every one of them.  The 2D sound stage assists greatly with this effect.  

I just have to say, on having listened to the SIA2 I feel like it has gotten something correct that most other amps have not managed to as it not only separates everything out but it does so in such a way as to enhance both the musicality and the dynamics of the music.  


There's more that I want to say but I think I may be tired enough that I'm not expressing myself as well as I would like.  I think I'll pick this up in the morning with a fresh head.  TBC.







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I really enjoyed the ATC when it was hooked up in my system, easily one of the best integrated amps I heard, it was that good that after reading reviews I started looking at their powered speakers as a option but as it’s very hard to find any to audition it is to much of a leap of faith to lash out and buy them.


The only downside for me when we played it in my system was it was one of the very few amps that actually sounded worse when hooked up to the Superchargers, and when I say worse it was not nice at all, go figure.

Other than that which means very little as Superchargers aren’t exactly a common component the ATC was very nice, if I was looking for another Integrated this would be on my short list.


cheers Terry

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OK, I'm late (my week was terrible, not much of an excuse however it happens to be the only one I've got) but I'm determined to finish this review so I'm going to dive back in to it.


I did forget to say something about the top end above.  I've almost always made mention of triangles in my reviews with mention made of how they sound, glittery, hard, bright, muffled, etc.  Well triangles with the ATC sounded spot on, so detailed that they somehow sounded more refined than usual (as if the triangle model I was listening to was the third or forth generation of design so the metallurgy had been improved and refined and so too had the resonance) and then there is the spacious 3D effect.  Often triangles on Wagner's "Ride of the Valkyries"  seem to move horizontally from right to left (that's from back right towards center, or at least they do on my system), sometimes they move from high on the right and move downwards towards the center and sometimes they sound like they are muffled and far away.  Listening with the ATC the triangle sounds like it is circling the right hand speaker, it's quite an entrancing effect.


Now where was I?  I think I've covered performance integration since I've mentioned how it doesn't play favourites with freqency ranges and doesn't let any one aspect of the performance dominate unless the music calls for it.  I have made mention of a slightly warm earthiness in my post above but I'll just make it again here to be certain it takes.  

And now I'm thinking that at least one reader out there is going to come to the conclusion that the ATC sounds a bit like a farm in north Queensland smells a day after it's been ploughed in late spring or early autumn.  Oh well, at least it's a nice metaphor.


Ability to Emote:  8.5

But it doesn't make you think, 'Wow that singer's a crooner/songstress so I want to listen to them all day.' the way a Heed Elixir or a Perreaux Audiant would.  The ATC is much more about giving you instrumentals that sound so good individually and mix so well together that you get dragged into listening to the song because it sounds fresher and cleaner than you are used to and therefore reminds you of the first time you listened to it.  

Almost as if the SIA2 is giving you as much of the micro as you can take but still focusing on the macro as well.


Electric Guitar Test:  8.5.

Big, bold and solid.  It made me smile.  Didn't quite manage to spark those little shivers up and down my spine but I'm sure I could kick them into gear with some extra volume if I so desired.


80's Rock Test:  9.0 for honesty, only 7.5 for implementation.

Those street rock albums that are a bit on the lean, thin and metallic side, well with the ATC they are bit more on the lean, thin and metallic side than usual.  So those unauthorized live albums that you already know sound pretty bad, yeah they're probably going to sound even worse on the ATC.  But that's OK, honesty isn't always good for everything.


So, the short version is that the ATC SIA1-150 is a small powerhouse that specializes in honesty.  It is an absolute delight of an amplifier to listen to and it certainly deserves all those positive reviews floating around out there in internet land. 

I have heard tell that the active ATC speakers sound even better than the passive ones powered by this amp and that both impresses and concerns me.  I'm impressed because that means that the active speakers must be damn good but concerned that they can possibly sound better than they do when powered by one of the best integrated amps around.  

Edited by Cafad

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I’ve been so looking forward to this review. Cafad really does know his way around integrated amps and more so reviews.

This particular amp was mine, bought on a whim to run some passive atc Scm40 mk2’s. Previously these speaker have been powered by a big Primare A32, ME240, 850 and even a 1500, most of which were borrowed. I even gave them a run with RRP $22k Moon amp.  All of these worked well with the ATC the equal in most respects apart from maybe power in the case of the bigger models.


I also own active scm40’s which are the same apart from the obvious lack of crossover and addition of designated amps for each driver.


I’ve had the passives for some years now and the actives not as long.   The SIA came along only last year and was just to have a play with and to power the rear passive atc’s in my home theatre set up. Excessive? Definitely.


When I first set up the SIA and the passives it had been a while since I’d listened to anything, days if not a week or so. Audio memory not so strong. 


Each system was set up in the same room with speakers next to each other. Same source and the actives had the ATC CA1 as the pre.  The passives were first and entertained me for quite a while.  I was at the point of thinking I’d be selling the actives and save the money.  Eventually I swapped systems. It took but a few seconds, everything the passive system did well the actives did better. Everything was there in the passive system but the actives seemed to sharpen everything up without making themselves obvious.  


Ultimately it came down to the thing that paralyses all of us in this silly game, it’s the little improvements that takes us, too hard to resist. The SIA is a great amp, certainly pound for pound and dollar for dollar right up there with anything I’ve had.


In the end the one movie a month powering rear HT speakers didn’t justify the money sitting there. I knew Cafad was keen on one so he had first dibs.  For some time I thought he didn’t like it as it hadn’t made it into one of his reviews.  Little did I know what an impression it made although I suspect he’s still taken with the big Sansuis.


I really enjoyed my time with the SIA and would gladly own it again if I wasn’t madly saving for some active ATC’s further up the range, either 50’s or 100’s.  Unfortunately anything ATC is addictive, the more you spend the more you get. 

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