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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
rleff
1,065 posts
 
I had fun building the hafler pre and power amp kits;dh101 and the dh500 power amp.At this time of my early audio hobby the dh500 I thought was just awesome and produced the best sound driving my infinity speakers;the 500 still surfaces now and then with mods from musical concepts;
it was a pretty good performer for its time.
eldartford
4,262 posts
 
The DynaKit 120 circuit is a preamp on steroids. Output through a big capacitor: no transformer. Its sound quality was critisized until they come out with the conventional 150, which made the 120 sound good. I had both.

The Kenwood L-07M is a direct-coupled amp, input to output. It is really an analog-programmable DC power supply, with response time fast enough to play music. Response is DC to 100KHz. You have never heard bass until you try the L-07M.
inpepinnovations
134 posts
 
Siliab, I am still running the 630,620, 600 Nakamichis. Bought them in 1977 and using Totem Mani's as speakers and Oracle Alexandria MKIII with B&O EN20 cartridge.

All sound great in my room, still!

Salut, Bob P.
johnnyb53
3,510 posts
 

11-29-11: 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.
You're right. I knew he was involved; I thought he had founded it, but that was Morris Kessler, with whom I'm not familiar. It looks like Bongiorno was an early advocate for bigger power supplies and wider bandwidth for better behavior into reactive loads and better dynamics. Bascomb King was also a collaborator on Ampzilla, according to a conversation I had with his son. It may explain the rave review Bascomb gave Ampzilla in Audio Magazine at the time.

--->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'm stunned every time I listen through it as I am right now. There is none of the edginess or midrange/treble harshness that described the typical '70s big power amp.
transaudio
96 posts
 
So few remember the whole David Halfer kit thing. The Dynaco's were so good, Halfers were equally good to their time in SS. Hafler did OK but eventually got bought by Rockford Fosgate, who also owned Accustat. I forgot his name that designed all those Accustat TransNova amps, but (memory fuzzy) he was involved with Halfer later, wasn't he? I had an interview with Halfer in the 90's (they were all pro by then), in Tempe Arizona.

Hey anyone remember when Summer CES (high end suites) was at Hotel Congress in Chicago? That was about the early 80s and all those folks would be there.....the big companies where all at McCormick Place. In winter, it was Vegas and the Riviera for the high end and everything else was at (a much smaller) LV convention Center.
Brad
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