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.