How do we remember 1970s amplifiers?


I would be curious to hear some of the memories and impressions associated with the following short list of 1970s amplifiers:

- McIntosh "first generation" SS amps, MC2105, MC2505, MC2300, MC250, MC2100
- Dynaco Stereo 400 and Stereo 120
- Phase Linear 400 and 700
- Bang & Olufsen "slide rule" receivers (i.e. especially blackface Beomaster 4000)
- Original Ampzilla (not Son of Ampzilla)

I've chosen this list mainly because they cover a wide range of approaches to solving the issues of early semiconductor technology, and they were all pretty mainstream products in the U.S. I'm excluding the Japanese receivers/amps not out of predjudice; it's simply that the circuit designs varied quite a bit with each model, and thus harder to broadly classify their characteristics.

I'm interested in impressions of both sonic and non-sonic attributes, and a preferred ranking of the above, if you like.
kirkus
SAE was also founded by James Bongiorno who founded G.A.S. and also co-designed the Dynaco 400.
I thought Bongiorno was just one of several people who designed different SAE products (not one of the founders), but I may be wrong. I had forgotten his connection to the Stereo 400; thank you.

One thing about the Dyna 400 and the GAS products was that they didn't skimp on the quality of the silicon . . . these were all fully-complementary output stages that used the transistors' characteristics very effectively. The GAS amps extended the complementary-pair thinking through to the input and voltage-amp stages, which IMO deserves respect for its conceptual elegance, even though there are some fundamental problems with its implementation. This fully-differential approach is also a hallmark of many of John Curl's designs, though I would hesitate to imply that the Levinson designs bore influence from the GAS.

But the Ampzilla was hugely influential . . . it did start out as a project amplifier with the schematic published in a magazine, and like the Williamson amp published 25 years or so before, bits of it seem to turn up everywhere. The current crop of McIntosh SS amps (from approx. the mid-1990s) use a front-end that strongly resembles Ampzilla's, with a few refinements.
Currently my #1 power amp is just past the '70s--the 1981 Heathkit AA-1600. I got it used for $239 and it makes my jaw drop. Just two years into the '80s, it is so far beyond the amps of the '70s. It reminds me a lot of the 1990-ish Jeff Rowland Design Group amps.
I remember these from the Heathkit catalogs, and dug up a schematic . . . and from the way it looks on paper, I'm not surprised that you like the way it sounds. It's kinda like a simplified Dynaco 400, but with the biggest flaws fixed (esp. the intermediate stage with its current-mirror).
I remember my dad replacing his Fisher receiver (complete with built-in tape deck) and Fisher speakers with a new McIntosh 4100 receiver, DCM Time Window speakers, and a Nakamichi cassette deck. The difference in power and sound was incredible and formed the basis for my interest in audio. I have since moved the Mac/DCM combo to a second home, and it still sounds great.
I had a couple of NAD 3020(bought new for the princely sum or $200.00 each)and never had a problem.

Maybe I was lucky, but then I've never had problems with any of my gear.

The cost to performance of the Nad was it's biggest selling point.

It also got lots of rave reviews and if I can remember, was one of very few components to ever get positive press from all the audio rags back then.

How would it perform today?
I think there is a comparison of the old 3020 to a present day unit, and the reviewer tended to still find quite a few nice things to say about it.

Sorry if it measured so poorly on the test bench or had such inferior parts, but we are talking $200.00 new.
I would presume the better measured gear with the superior parts also cost more, so really all that you can compare is how the sound of the parts used compared, and to my ears back then on Rogers Ls3/5A speakers and later Mission 770 speakers, the Nad was good enough to not warrant any updates for a couple of years.
Even then I used the pre as a phono stage and then used the two units I had as dual mono pre amps with a single power amp.

I later got into Conrad Johnson MV75A-1 and Premier Twp pre amp,and Acoustat medallian 3 stats, and onto my first foray into the High End of that era.

This was the early 80's, the gear was better no doubt about it to my ears,and yet the Ls3's are still quite well regarded and fetch more used today than I would have ever imagined back when I bought them new for $400.00 bucks.

Yes the good old days,when $600.00 bought you a decent integrated amp and a pair of speakers.

But in keeping with the OP, I still remember 70 amps as being feature laden ,pricey units that could be bettered sound wise by simpler units costing far less.

There was a thickness to the sound of some of those receivers, like my 100 watt Pioneer or thinness like the Yamaha A-1,that never really clcked with me.

The sound of 70's amps was all over the map, so pick your colouration and sing the praises.

Time marches on things get better, and there are still some sonic bargains to be had.Those who think that great sound is only available to the rich who can afford $75,000.00 amps, and turn to vintage gear for solace, needn't do so.

I really am quite impressed with my 2 Watt DecWare Zen Select amp.

It is the spirit of the 3020 today.
I have a mint Phase Linear 400 Series 2, in which I installed DC protection circuitry a couple of years ago. I have all new electrolytic caps waiting to do a total recap, I just haven't gotten around to it yet. To my ears, it is not a bad amp at all. Not the finest, but better in some ways than some other amps of that era that I've had in my collection.
Lacee, you're probably right that I was a bit too harsh on the 3020 . . . NAD's manufacturing quality steadily declined through the 1980s, then plummeted under the ownership of KH America in the early-1990s . . . and this is when I serviced them. It seemed that the late-1980s stuff failed at least twice as often as that from the early-1980s, even though they were newer. The current product of the time (I'm thinking of the 505 and 705) had out-of-box failure rates of at least 25%.

The 3020 was indeed cheap and it did have a nice phono preamp, this was probably the best part. And after two failures in two years with my 3225PE bench amp, I added a pair of 0.33-ohm emitter resistors and switched to 2SC3281/2SA1302 output transistors, then re-biased. It completely transformed the performance . . . the distortion was reduced by something like 75% leaving overwhelmingly even-order products. The little NAD then sounded quite nice with my KEF C25 bench speakers . . . which I guess was exactly the kind of setup for which it was intended.

Still, I don't know whether to praise the design because it didn't take many changes to make it a nice little amp, or to be really annoyed because these changes would have cost less than $2.00 per unit in production . . . probably cheaper if you factor in volume pricing of the day and the better reliability during the warranty period. With the Phase Linear 700 it was far more clear-cut -- the circuit was wholly unsalvageable. The best thing for one of these is to use the case and heatsinks (but NOT the transformer) for a project amp.