All tube aficionados know McIntosh, a marriage of timeless looks and beautiful sound. Like others, in the 70's McIntosh abandoned tubes. To their credit, their solid state products sounded warm and good too, though not as good as their older tube products. Of course, more recently they have gone back to tube products, though they still make solid state ones too.
McIntosh MC-1700 You can find info on the MC-1700 stereo receiver in the wonderful Roger Russell Page. Study the various models and you shall understand McIntosh's evolution. The 1965-67 MC-1500 was an all-tube receiver. The 1967-1973 MC-1700 was its replacement, and belongs to the transitional age - while its tuner section is still tube, the rest is solid state. Its replacement, the 1973-78 MC-1900 began the all solid-state era. If you ask me, look-wise the MC-1700 is the best. Last retail price was USD 599 in 1973. That was a lot of money. According to the Inflation Calculator, USD 599 in 1973 had the same buying power as USD 3,181 in 2012! Of course, I couldn't afford it then; my unit was acquired in the late 80's for a song, but these have steadily increased in second-hand value.
This shall be a brief and limited Overview. ATC is well known by sound industry professionals, its history briefly chronicled in its Official Page. When I came back to HK in the early 90's ATC was enjoying its first flowering in the consumer market. I got to hear every model in the original range, some many times over the years.
ATC is most famous for their proprietary soft-dome midrange driver, the technology of which have been extended to the bass units of the smaller 2-ways. The model names indicate the volume of the enclosure. Thus SCM10 = 10 liters; SCM20 = 20 liters, and so forth. The original models have very heavy and damped cabinets. These models have had many "revisions" and "special editions", reflecting changing tastes - usually the later ones have more prominent treble. What I mention here are all original models, without any suffixes behind the numerical number. In recent years, these have virtually disappeared from the second-hand shops in HK - most have been scavenged by buyers from the PRC.
SCM20 (info here; 1990 review here) Likely the best known and loved of the range. I owned one for many years (original, single-wired, fabulous rosewood) and had truly enjoyed it. Mine came with Sound Anchor stands. It casts a huge soundstage, plays with authority even with the most complex music (say, Mahler). It is detailed, but nothing sticks out. Indeed, it sounds natural and, yes, like a much larger speaker. It has a reputation of being hard to drive, which led many people to use high-powered ss amps. I have used a Bryston 4B (original, partnered with a tube preamp of course) to satisfaction, but I am sure they sound their best with a good tube amp. Not anything would do, but a vintage Marantz 8B surprisingly can drive it with ease. Even juicier was the ARC D-115. I think its even load (8 ohm) is friendly to amps. The half as big SCM10 has a very similar sound but it is even more difficult to drive.
SCM50 and SCM100 These larger 3-ways using the original soft-dome midrange driver are much coveted. They are quite a bit easier to drive then the 2-ways. The sound of course is even better, particularly in the bass. I have actually visited someone using 300B for the SCM100 (of course, just near-field), but I wouldn't recommend that.
SCM7 The smallest in the newer commercial range, which have lighter builds and are easier to drive than the classic models. I used to own one, the original version. It was much easier to drive than the earlier A7 (see below) and has more treble content, but I felt the sound was a bit on the light side. Later this range changed to have protruding baffles, which are ugly IMHO.
A7 This was an oddity, without the SCM designation and an early commercial foray. It looks like a reduced SCM10 and is a forerunner of the SCM7. There are good reviews in soundonsound and hometheaterrevie. There was a floorstanding version called the A7T.
A7 vs SCM7 For a time I had both and compared them. Although they are similar in size and cabinet volume, the A7 is a bit heavier. There are significant sonic differences. The drivers look similar, but there is little question the SCM7 is easier to drive and has a crispier sound (spec has only a 1 db difference, 84 vs 83 db). Part of this is due the SCM7's reduced woofer size (5" vs the A7's 6"). The A7 tends to be a little rolled off at the top (probably needs more power). Indeed if you look at the spec's the A7 and SCM7 differ quite a bit (with the treble -2db points at 12kHz and 16kHz, respectively). Sonically, I feel it is a double-edged sword: the SCM7 is easier to drive but has a lighter sound; the A7 is more inefficient but has more authority and what I think of as the classic ATC sound. If you partnering gears are up to it, I feel the A7 shall come out ahead, closer to the performance of the SCM10.
The McIntosh has only 40 watts per channel, but its power supply is beefy. I knew it would not be a perfect match, but I also knew it would not be totally embarassed either, despite the A7's inefficiency. That was because many years ago when I first bought it, I took it to my friend Tanuski's home, where he had an old pair of Proac 3-way (not EBS, probably an old Studio) that nothing could handle satisfactorily, including Jadis JA-80. But to our great surprise, the MC-1700 did a very good job! I wrote about this in 2004 in my yahoo group of the same name:
"...I think it is UNLIKELY that it (Ed: Proac EBS) is tube amp friendly. Older Proac's are rather difficult to drive. Actually Tanuski had some old Studio bookshelves. We couldn't get satisfactory sound out...finally on the day he sold them I hooked it up to a Mac 1700 ss receiver and bingo the sound was so much better. The EBS should be even more difficult..."
Sound (Line) In my 300 ft room, perched high up the A7 gave a well rounded and familiar ATC sound. My friend Boylah said it was surprising that the old receiver was up to it at all. For the uninitiated the slightly dark sound masks a little the great amount of detail on offer, and the midrange and bass had a fullness that belied its size. It is best to give it a high output source. The CD's buffered output worked better than the iPod's earphone out (of course).
FM Tuners section IMHO this is a VERY good tuner. Warm sound and reasonably good sensitivity.
Phono section The humble Technics SL-1200 Mk II with an el cheapo Audio Technica 5625AL cartridge gave a very good performance. Quiet!
- The McIntosh MC-1700 is a very solid performer, worth every penny of its cost. With an even load it performs beautifully.
- The ATC A7 has more than a tinge of the classic ATC sound, though it needs some care in partnering with ancillary equipment. The more you give it, the better it sounds.