How do we remember 1970s amplifiers?

Strongly agree Apt Holman pre-amp and matching amp (I have that pre-amp driving two of their amps running as mono-blocks).

Kirkus - truly great thread here.  Enjoying reading all about this 70's gear.  This was a little before my time getting into high end.  Back in the 70's, I was still with my HK 330c receiver not getting into separates until in the mid 80's.

Actually an interesting neighbor let me hold onto his Dyna MKII amp, Mac C22 pre, MR71 tuner, and Thorens TD124 TT w/SME tonearm in the late 70's.  Not knowing a thing about tubes back then, I turned it on and wondered why it didn't come on immediately and why it sounded so terrible after 5-10 seconds and ran so hot.  I gave my girlfriend the TT and she said, "what is this POS?"  If only we knew......

Wish they had a long discussion like this about 1980's gear.  That is my go to era in audio and when I made lots of purchases......

chuxhifi,

Doesn't surprise me. A friend ran two D-500's bi-amping a pair of the original AR-9's.  Sounded amazing. I could easily live with my old Phase Linear gear.  Enjoy the 700.  It's a wonderful little amp.

The damping factor on the 700 is 1000.  Your woofers love that type of control.  

N.

I had a  Rotel 1412 integrated that could be used as a pre or power amp. Sounded great with JBL monitors.

I know it sounds crazy, but the PL700 I recently purchased out of curiosity (original series, w/factory-recommended mods done in the late ’80’s), fed directly from my Sony DVP-S9000ES SACD and running my Dunlavy IV’s, just wipes the floor with my Threshold S500 S2. PRAT is off the charts; it makes the Threshold sound dull and lifeless in comparison. I’m hearing subtle details in the music that the Threshold doesn’t reveal. Dead quiet amp. No sibilance or harshness, even at high volumes. This amp just makes beautiful music.

Bettered my VTL ST-125 as well. Very similar to my VTL TT-25’s in the mids and highs (and that’s high praise indeed).

I wonder how many people who go around poo-pooing these amps in some of the PL threads have even heard one in a decent system in the last forty years?

And FWIW, I’m a semi-professional trombonist, not some hack with wooden ears...

Crown DC-300A Power Amplifier
Also Heathkit did make some good equipment 

g_nakmoto,

I have to say that back in the 70's I was a Phase Linear user and was surrounded by others who used Phase Linear.  I remember the sound being wonderful, fast and clean. Amps that I owned were the 400 series's One and Two. Never a problem. My friends owned 400s, 700s and one used two D-500's. We ran them hard and never had a problem not ever. 

I even used a 400 to run a PA system for my band. Now it wasn't built like my McIntosh MC-2300, but then nothing at the time was. Still all this Phase Linear bashing?  A Phase 4000 preamp and any of the above mentioned amps makes a sweet little system that will drive anything. With regard to frying speakers, I can't remember that happening either. 

I like most have moved on but I know if I had too I could live with any of my old systems, Phase, Mac, GAS, Citation, Levinson etc. I have re-discovered my Sansui 9090db a few years ago and haven't been listening to anything but it. Seems to do everything just about right. 

N

i heard that the phase linears were the king of frying speakers!!

I had a set of Fulton J-Modulars as well. For a long time I ran them with dual modified Dyna ST-70s monostrapped until I got my own amp going. Fulton was a local so I spent time with him at Bob Fredere's house in Minneapolis, which is where I first met Bill Johnson of ARC (I had a D-51 for a while also...).

I also ran the Rabco- an ST-7 that I had modified with a new servo circuit and a carbon fibre rod for the arm tube (hi tech back in those days), mounted on a Technics SL-1100.

I liked the Tandbergs. THese were among the best I recall hearing in those daysin terms of overall clarity and listenability. Even the tr2080 receiver's amp that I had up until a couple years back had a lot of top notch positive attributes. Its limitation was current delivery into more challenging loads, but this was a receiver not a separate power amp. I would like to own a vintage Tandberg amp in good working order again someday.

Salectric, I must say that I heard them when Fulton visited a local deal when I lived on Long Island. He played them with his "amp in a trunk." They were great, but the amp never became a product. I ended up with three pair of Luxman 3045 mono block amps, which had to be rebiased hourly. I gave up and bought double Quad 57s. Before I moved to Texas I had an offer to sell them, which I did.

Yes, I was going through equipment quickly at that time and finding little that satisfied me.

Tbg, I would have loved to own a set of Fulton J-Modulars or the later Premiers, but they were way out of my limited budget.

Salectric, Your speakers sound like the Fulton Premiers which I had in the late '70s.

My system in 1976 would probably still sound pretty good by today's standards. Here's the lineup:

Table #1--Rabco ST-4 with ADC XLM
Table #2--Thorens TD-124 with homemade pivoted arm and Decca Mk 5

Phono---homemade based on Trevor Lees circuit (supposedly a copy of the Paragon 10)

Linestage--homemade passive (pot in a box)

Power amp (100 Hz and above)---Dyna 70 with extensive mods

Power amp (below 100 Hz)--Williamson Twin-20 (Audio Amateur magazine project)

Speakers---KEF B200 in homemade transmission line; Fulton FMI-80 for mids; RTR ESR-6 electrostat tweeter

I had a Dyna stereo 120 which had substitute transistors and never blew up. I used them on Rectolinear III speaker. I had the Phase Linear 700 with the Dayton Wright Electrostatics and the Watson Labs Model Tens. I also had the Ampzilla with Infinity 2000As. It is hard to say which of these gave the best sound. Probably the Watson Labs and PL 700. I never had any problems with the Phase Linear. I sold it to a disco and they blew it up in less than a month.

You neglected to add the Stereo 70, the Audio Research Dual 50, 51, 75A, 76 amps, and the Paoli 60M amps. The Dual 75A and Paolis were great on my Infinity ServoStatics. I keep this combo for five years.

This was a fun period for me with young kids, Hobie racing, and great sea food in addition to some good audio.

I also work in the hi-fi business and have been fortunate enough to change bits and pieces as I went. My very first system was an Apt Holman preamp / HK Citation 19 amplifiers (a pair bridged mono 220w/ch), a Micro Seiki MB15 / Micro Acoustics entry level cartridge with a pair of Yamaha NS100 monitors. I spent quite a lot of time listening to music back then!

Times have changed as well as the sophistication of my systems but the 70's was a fantastic time in audio! Loads of fun. Thanks for the trip down memory lane.

Well, my Flame Linear blew up, as did my dyna 120.
Having worked my way thru the dyna line, and going by their reputation only, I rushed to sell my Mk 3's for the newer better solid state - big mistake, the magic went.

I've owned the MC250 - the industrial looking 50WPC amplifier. It uses autoformers and actually sounds fairly tubey. Good bass, a little muddy in the mids, and a not very detailed treble. It had a bit of a grainy smear to the sound - at least with the speakers I had at the time. But still, it was a very enjoyable and musical amplifier, just not very high-end.

I've also used a (rebuilt) Dynaco ST-80. Like the ST-120, it's actually capacitor-coupled to the speaker, so some of the faults could be attributed to the bad electrolytics of the time. The only I rebuilt had modern caps and sounded half-decent. Certainly not world-class, but a nice little dorm amp or something for a second system. Again, it just had a slight grain and a slightly forward/etchy treble.

Hi Lacee...

You are most likely right about the "we left it behind" and should really not go back there. But with that said my new DDX 1000 (after a lot of upgrades) sounds
fantastic, although it cost me thousands of $$$ to get there..LOL
My new speakers are coming in a few weeks and I'll decide if vintage is the smart
way to go... :-)

- Acoustic Research integrated with AR5s. Solid state sound hard and glarey. Gave SS a bad name (which it deserved)
- Dynaco ST 120 - more of the same!
- Crown IC 150 and D150 driving Infinity 2000As - World class speakers even today and beautiful looking pre and amp but op amps and boatloads of negative feedback = bleeding ears + empty wallet!
- Phase Linear 700B- Much better but still electronic
- Phase 400 - better still and actually nice with beefier power supply caps. driving T-1Ds (needed ARC!)
- Hafler 100 & DH200 - actually not bad and better pooged.

I remember going from a Dyna 416 to a David Berning ea 150 to use with Magneplanar Tympani 1-C speakers and being blown away with the difference. The shrillness of the dyna compared to the Berning was unbelievable. I still have that amp and it is competetive with a lot of modern amps.

Peter53, will finding those old amps not just be an attempt at capturing lost youth?

Nostalgia for any of the gear that gave us our first glimpse at what was really hidden in the grooves I think is more like it.

Because a certain speaker or amp was a milestone,somehow some folks think it still will be today.

I have friend who has gone that route, thinking the best was all behind him.

He set out on a journey to replace all his newer gear with gear that he used to own.
Hoping to find audio nirvana once again.

All he found were the reasons why he let that gear go many years ago.

It was 1978, (in Sweden) and I just got my first job cooking in a restaurant.
No debt, and nothing to spend my cash on "Forced me" to check out the stereo store in the neighborhood. Wow I loved it, the smell of warm amps and the big
VU-meters pulled me in to it's warm embrace. I think I spent more time in the store then the owner for the next six months....LOL
One day the owner come up to me and said, why don't you buy a system and you can enjoy some tunes at home. I walked out with Magneplanar Tympani 1D's,
two Sansui BA3000 amps and matching pre-amp, and the turntable was the
Micro Seiki DDX1000 with two tonearms.
I still remember how fab that system sounded, and I just bought the DDX1000 a month or so ago to revisit my youth. If I can only find two Sansui
BA3000 in mint condition I'll be in heaven :-)

Peter

Eldartford brings up an interesting subject in that many of the amplifiers with more humble aspirations in the 1970s were capacitor-coupled . . . Johnnyb53 mentioned that his Altec integrated stereo had issues with reduced power output at 20Hz, which is a strong indicaion that it had an output capacitor. Most self-respecting "high-end" amplifiers, on the other hand, were DC coupled, possibly taking this to an extreme in the Kenwood L-07 that actually passes DC, and has DC gain.

Crown was proud of this in the late-1960s; I think that the DC-300 got its moniker because it was "DC Coupled". And nowadays, this power-supply configuration is standard, and an output capacitor is an anachronism . . . ah, progress. But wait a minute . . . a quick re-examination of the current path in a typical "DC coupled" power amplifier (including even the L-07M), and the speaker is still coupled via capacitors - it's just that now they've moved from the positive side of the speaker terminal to the negative, and we call them "power supply filter capacitors". If their only purpose was to smooth ripple, there could be just one tied between the + and - rails . . . but then there'd be no way to return the loudspeaker current to the supply. The power-transformer's center tap does this in the case of faults and on startup (and for extreme subsonic noise/content on the L-07M), but most power amps can in fact purr along nicely with this disconnected, and no DC ground for the power supply at all.

It's true that the "DC coupled" topology doesn't (or at least shouldn't) suffer from nonlinearities associated with the coupling/supply capacitors, the reason is that they are effectively inside the feedback loop, whereas in the "Capacitor coupled" topology they typically aren't. In the "DC coupled" scenario, there's still usually an electrolytic grounding the feedback loop (keeping DC gain to unity), and this can be a measureable source of distortion.

So that leaves me wondering a bit why it was cheaper to build a capacitor-coupled amp in the 1970s? The extra cost of front-end transistors is tiny. You still need two big electrolytics, or three for a stereo amp, so it's actually more expensive in that regard. There is a bit of savings in the lack of an output relay and protection circuit, but that doesn't seem like enough to offset the extra big capacitor.

This leads me to the conclusion that the real big chunk of cost was the talent to design an input stage with good offset characteristics, and perhaps the production technician to adjust the offset on every single amplifier, making up for the inconsistency in the semiconductors of the era. With an output capacitor, the whole thing is much more tolerant of both substandard parts and design mistakes. Now that transistor quality has improved dramatically, and there are plenty of existing designs to plagarize . . . those costs are much less significant for inexpensive systems, and capacitor-coupling has fallen by the wayside.

Some of those old designs were pretty good and while the art has moved forward on a lot of amp features (protection, thermal and short monitoring, metering) sound was quite good in many of them.

Indeed it was . . . and the idea of swapping in fancier parts to "improve" them to today's standards has some appeal. There's of course usually plenty of room for sonic improvement by simply correcting the ravages of 30-40 years of age, and technology and manufacturing of all electronic parts has moved forward innumerably in the past few decades. But the parts themselves are certainly NOT the real story, and the real improvement to be have comes from applying a modern design perspective to the older circuits, and making major or minor tweaks as needed. Some of them end up being pretty amazing just as they are, and others . . . well there simply aren't enough Black Gates and teflon caps in the world to help.

Some of those old designs were pretty good and while the art has moved forward on a lot of amp features (protection, thermal and short monitoring, metering) sound was quite good in many of them. Just listening to an old mac amp is a good example of this. That Audio Research (tube) amp line in the late 70's was darn good. Dynaco's too.

I think long term amps will mean less to the market as active speakers become more and more important over the next years. Older preamps will likely gain in importance-for the front end will be ever more obvious.

Brad

I loved my Kenwood...KA-7100 of the late '70s.

Good with my 12" 3-way JBL 4311 clones from RSL....(SoCal Boutique brand) and later with my first panels...some MG-1s.
Since I was poor, I did a snip/snip....solder/solder and attached cables with RCA male ends and used just the preamp for another couple years with my first bit of hi-power amp, my old Carver Cube. Worked fine as a preamp.....

I still know where the amp is. I gave it away to someone who NEVER used it. I'm going to ask for it back. If they haven't used it in 20+ years, it'll never get used. Maybe a recap of the PS would be in order before pluggin it in?

"It's quite possible that some highly regarded "high end" amps are essentially "Haflers" or "Dynacos" with different parts." Amen.

Either Hafler, or Dynaco could be transformed into true "high end" amps by simply substituting their existing parts for the best parts available today.

Successful businesses were created doing just that. When "Black Gate" capacitors were available, I replaced every electrolytic in every piece of equipment I own with Black Gates. That was with the exception of huge capacitors in power amps, but all other lytics in everything from reels to DACs were replaced with Black Gates.

If the replacement of a single part can upgrade a piece of equipment, imagine how replacing all of the parts would affect that piece of equipment. It's quite possible that some highly regarded "high end" amps are essentially "Haflers" or "Dynacos" with different parts.

Curious....how is the Kenwood ka 6000 by modern standards?

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

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.

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.

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.

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.

Pubul57, aside from tons of repair and modification, my audio design experience revolves mostly around small-volume or one-off custom stuff for pro audio applications . . . various iterations of analog and mixed-signal "preamp"-type stuff. This has included mic preamps, electronic crossovers, long-line drivers and receivers, active bandwidth-limiting filters, small low-noise mixers, etc. etc., and various combinations of these building blocks combined into a single chassis. I used to get a lot of requests like "We need these PA systems to be at least 8dB quieter at the inputs to the mid- and tweet-amps, and get rid of that 'clippy sound' in the bass when it's really loud. Can you build something to do that?" And I would . . . and all kinds of similar stuff in FM broadcast and recording.

But I'm not an EE - my education is in classical music, and the way we learned about harmony, part-writing, counterpoint, form, etc. was to study the works of the masters (and the also-rans, too). I tend to take this approach to the study of audio design . . . since it's much more informative to analyze the harmony in Schumann's "Ich grolle nicht" than a silly textbook example, I'd rather listen to i.e. a DC-300 or whatever, then measure it and study its circuit design, than simply read about hypothetical circuits (and equations simply for their own sake) in a typical undergraduate EE text. The repair process is a natural method for analysis and measurement, and since I like to listen to music while I work . . . I've always kept a well-set-up amp/speaker system on my test bench, so I'm always trying to correlate what I hear to what I see and measure.

And I'm also generally a sucker for history, and love hearing/reading people's stories and narratives . . . hence this thread. Again, thanks to all for the contributions!

Alot of the collectable 70s pioneer/sansui mega receivers have an overly bass dominant sound...some would say 'tubby' quality...far from nuetral but kinda fun in a muscle car way...I didn't come into my own till the early 80s...when luxman and hk still made decent stuff...the hard part was finding good 2 way monitors ala BBC types...which are far more readily available today...but from a purely cosmetic and build quality standpoint...the vintage stuff has some merits...this is a crude generalization...but the low to moderate power offerings always seemed to perform better...the 70s amps listed above didn't hit my radar still much later...

Lacee , so pleasant to read your comments, they are so parallel to my own. The store I worked at was a little place called Wack Electronics in Milwaukee Wisconsin-from 1975 to about 1977-then to a sound contractor, then back to the store until I became a rep in 1980. You are right about the tube stuff, it WAS better even then. (McIntosh too, but I wasn't a dealer) As a rep, I reprsented Jon Dahlquist, NAD, the folks at Crown, and Joe Grado- Proton too when it arrived. It was quite a time in hifi, I was a little late to party, there was so much business, so many hobbyists buying stereos in the 70s. By 1980 it was changing, rack systems where coming to big box stores, reel to reel was fading as Nakamichi took off. I so remember that Advent cassette recorder! There many very nice people in high end hi fi in those days, I think its still this way.

A DC300 in 1975 was a different beast compared to the competition than in 1980. Flame Linears in 1978 or so where the first company to meet the "dollar per watt" ideal, and at 399, the best bargain going. But boy they didn;t like to messed with. Crowns would work and work. But on something like an electrostat? Yuck! The Audio Research was smooth as could be.

NAD< what wonderful stuff in the time of the 3020, the 7020. That stuff STILL sounds good. A NAD 3020 and pair of little Fried speakers was fantastic

I eventually got more into pro, learning about live sound and installed sound where Crown eventually migrated when hi fi dried up. By the 90s it seemed high end hi fi stores where reduced to one per 1M market. "Listening to records" was no longer the cool hobby!

By the way, I just bought a Stromberg Carlson 1939 AM tube radio I found on ebay, with the acoustical labyrinth system, the very first transmission line bass system. VIntage Hi FI is still just as cool as it was new!

I lucked into owning, perhaps the sexiest components of all time, the Nakamichi 600 cassette deck, 620 100 wpc amplifier and 630 tuner/preamp. Spinning the tuning wheel of the 630 was a particularly sensual experience, as was the light show of the center-tune indicator. The system also featured a Philips 312 table with a Signet TK9E cartridge, and A/D/S 300 speakers with an M&K subwoofer. This system was very good with the classic rock I was mainlining at the time but considerably less good with the Jazz I was beginning to become fascinated with. I remember acoustic bass sounding particularly hollow and disembodied through this system. In retrospect, it was most probably the tendency toward one-note bass of the subwoofer that was mostly to blame.

Economic necessity led to my parting with the 620 and the 630, but I still have the 600, which still sounds great when properly setup. It didn't take long to find components that sounded considerably better, but I have yet to own anything nearly as great looking.

Mostly I remember my speakers (Kef) and 'tables (several). My only memorable electronics were SS models from Audire - the Diffet pre and a power amp which I can't recall the model designation of. Purchased cheap at Crazy Eddie, a large New York discount chain that somehow got the Audire line.

IIRC, they sounded quite good. Of course, that's a damn big "IF" in the IIRC. Not too much later I bought a pair of the earliest production Quicksilver mono amps which - I think - were simply great amps (of their type).

Marty

My AR receiver gave me many years of joy, but the sound is only in my imagination now. I was seventeen; it was a very good year...

Kirkus, do you design gear? Seems like you know a lot about it.

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.

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.

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 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.

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).

Dynaco Stereo 300 / QSA300 Power Amplifier



--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

Description:

Specifications:

Rated 4-channel Power Output: 75 watts continuous average power per channel into 8 ohms (40 watts per channel into 16 ohms) 20-20,000 Hz, at less than 0.25% total harmonic distortion. Distortion reduces at lower power outputs.

Available 4-channel Output Power:

20-20,000 Hz, all channels driven, 0.25% maximum THD:

75 watts continuous average per channel @ 8 ohms;
100 watts continuous average per channel @ 4 ohms;
40 watts continuous average per channel @ 16 ohms.
Stereo Operation Available Output Power:

Low Impedance Mode Connections:

80 watts continuous average per channel @ 8 ohms;
150 watts continuous average per channel @ 4 ohms;
200 watts continuous average per channel @ 2 ohms;*
High Impedance Mode Connections:

80 watts continuous average per channel @ 16 ohms;
150 watts continuous average per channel @ 8 ohms;*
* 5 minutes sustained full power limit without a fan.

Power at Clipping, 1 of 4 channels, 2500 Hz, less than 1% distortion:

90 watts @ 8 ohms;
130 watts @ 4 ohms;
45 watts @ 16 ohms.
Power at Clipping, Each Stereo channel, 2500 Hz, less than 1% distortion:

Low-Z mode:

95 watts @ 8 ohms;
160 watts @ 4 ohms;
240 watts @ 2 ohms.
High-Z mode:

160 watts @ 8 ohms;
90 watts @ 16 ohms.
Intermodulation Distortion: Less than 0.25% at any power level up to 75 watts rms per channel into 8 ohms with any combination of test frequencies. Distortion reduces at lower power levels.

Half-power bandwidth: 37.5 watts per channel at less than 0.25% total harmonic distortion from 5 Hz to 50 KHz into 8 ohms.

Frequency Response: +0, -1 dB, 10 Hz to 40 KHz @ 1 watt into 8 ohms; ±0.5 dB, 20 Hz - 20 KHz @ 75 watts into 8 ohms.

Hum and Noise: Greater than 95 dB below rated output, full spectrum.

Input: 35,000 ohm load; 1.0 volt for 75 watts into 8 ohms.

Semiconductor Complement: 52 transistors, 40 diodes.

Slewing Rate: 7 volts per microsecond.

Damping Factor:

Greater than 80 to 1 KHz into 8 ohms;
Greater than 50 to 10 KHz into 8 ohms.
Channel Separation: Greater than 70 dB by IHF standards.

Connectors: Inputs: phono jacks. Outputs: Color coded 3-way binding posts with standard 3/4" spacing.

Dimensions: 18-1/4" wide, 14-1/2" deep;, 7" high panel, 17-1/2" wide. Add 1/2" for feet.

Shipping weight: 58 lbs. Net weight: 52 lbs.

Power Consumption: 120 VA quiescent; 10 amps maximum; 50/60 Hz, 120/240 VAC.

Designed by:

Harry Klaus

Year Introduced:

1976

Price:

$269.00 kit
$399.00 assembled

Comments:

Basically two ST-150 units in a single chassis, with separate power supplies. Usable as four independent channels or as a bridged stereo amplifier with 300 watts per channel. The MC2/MC3 meter kits provided output monitoring.

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

This page created and maintained by Greg Dunn.
Copyright © 2000 Greg Dunn

I originally purchased this as a 4 channel amp which I used with my "Quad" Phase Linear 4000 pre. At that time, I thought it was "hot stuff".

Now, it is in use as a bridged stereo amplifier with 300 watts per channel. It sounds like what it is, "A big powerful mid fi amp". It works fine in our entertainment room where at least three conversations are always going on at the same time.

My first stereo was an Altec-Lansing 911A compact in 1972 for $419 (about $2160 in today's money). It aspired to rare heights for a compact--it incorporated a (slightly de-tuned) Altec 44 wpc receiver, Garrard SL95B (their top line consumer deck until the Zero 100), Shure M93ED, and Altec 887A speakers, an 8" 2-way sealed cab. The tuner section was excellent and the amp section wasn't too shabby either.

A couple years later I was working at a hi-fi store in SoCal where our amps were Phase Linear (we needed their 700 to power the Ohm F's), Accuphase, Marantz Pro (a good lie at the time), Crown, and a few SAE's left over.

One day We hosted a Marantz clinic where an audio engineer would measure (for free) power and distortion on any unit you could lug in. I proudly brought in my Altec 911 and was disappointed to find that its 44 wpc at mid-band dropped off to 27 wpc at 20 Hz. Turns out Altec had shrunk the power supply (compared to the receiver it was based on) to fit it in the cabinet with the turntable.

There was an orphan pair of entry-level SAE components back in the storeroom--the Mk XXX preamp and the Mk XXXIB power amp. I picked those up and started using them instead. The amp was rated at around 50 wpc but the tests at the time indicated it put out more like 70, but the cool thing is it had textbook square wave response (even better than the Crown) in the bass. You could really hear that--any speaker it powered had cleaner, tighter, more extended bass with this thing than with a receiver.

SAE was also founded by James Bongiorno who founded G.A.S. and also co-designed the Dynaco 400. As I remember it, however, the treble was a bit hot. Still, I wonder how much our perception of the separates of the time is influenced by the way we used them. We had no awareness of a "burn-in" period, let alone a warmup period for solid state. We plugged things in and immediately started evaluating them. Now I never turn my power amp off, and it was pretty edgy when I first plugged it in and turned it on.

I also had the privilege of meeting John Iverson and spending a day with him as he demonstrated his incredible A-75 class A power amp into his own speakers. Until that day I'd never known that hi-fi could do *that*!

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.

The music was so much better back then that we didn't know the equipment was lousy, and a good time was had by all.

Since everything is relative, and none of us had rigs much better or much worse than the next guy; we all thought our rigs were killer at that time.

Lacee, thanks for bringing up the little 20W NAD . . . this is the perfect 1980s equivalent of the Phase Linear amps. I serviced these back in the day, and even had the "Power Envelope" decendent (3225PE?) as a test-bench amplifier for several years. In contrast to the big, "all technical" 1970s aesthetic, it was small, lightweight, low-powered, and simple-looking. But like the Phase Linear, it was cheaply made and unreliable . . . and the sonic signiture was filled with exactly the opposite types of problems.

I will say that the preamp sections were pretty decent, maybe even good considering the low price . . . but the power-amp section was an absolutely atrocious piece of engineering. The key "feature" was that it didn't have emitter resistors on the output transistors, and I assume that this was an attempt to reduce notch distortion. But even if this had been a good idea (which it wasn't) . . . they then chose the absolutely cheapeast big power transistors available (2N3055/MJ2955) that have poor linearity even by 1970s standards. The result is that even with enough idle current to make it run pretty toasty, it was still really operating in underbiased Class B, and put out a whole slew of nasty harmonic and intermodulation distortion products. This may have been "redeemed" somewhat by the single-transistor input stage, which guaranteed a big helping of even-order distortion as a big sugary coating for that rancid-piece-of-meat of an output stage.

Not as good or as pleasing a sound as the tube stuff, but still better than the solid state amps I had been using in the 1970s.

This is the reason I find the new fascination for 70's solid state stuff so perplexing.
From someone who was there and listened to that stuff when it was new and all the rage, and then moving on to better things,I just can't see the interest in any of it.

Well, selective memory seems to work both ways . . . we overwhelmingly shun what was in vogue in some eras, and romanticize others. One of the reasons why I mentioned the 1970s B&O receivers was because (like the NAD amps of the 1980s) they offered a modestly-powered, domestically sensible alternative to the "high knob-per-dollar" mainstream aesthetic. They were vastly better engineered than either the Phase Linear or the NAD, but had a few quirks of their own (esp. cultural?) . . . I'm wondering whether they're remembered similarly to some of the more high-profile [sic] pieces of the decade.