Who made the best quasi class A receivers in the early 80,s

thesurfer

I always liked the Pioneers, and early Denons, what say you folks.

F1nut

I spit on receivers.

F1nut from years ago.

thesurfer

Ah, that's nice F1nut, how bout those who don't spit on them, as the question was not directed at receiver haters such as yourself, but thanks for your input anyhow.

BlueFox

Out of curiosity, what is ‘quasi class A’?

treitz3

Oh, I need to shut up.
Tom

thesurfer

That would be anything that's not pure class A, say like Yamaha CA 1010. or R-9.

TroyD

Awwww....c'mon, it was funny. It's a line we dig up from time to time and have been doing so for years. Lighten up a bit.

That said, other than cool factor.....Most, but not all fer sure, vintage receivers performance can be bested easily and inexpensively....and pure Class A, imo, is no guarantee of anything except heat.

Just my .02

mhardy6647

Quasi Class A is like Quasi Virginity.
Class A = output devices biased to a fully "on" condition 100% of the time. (Tubes or transistors, doesn't matter)
If nothing else, crossover distortion is eliminated.
There is probably some effect on the spectrum of harmonic distortion products operating at Class A bias, too.
Any other bias scheme = NOT Class A.

There where myriad sliding bias schemes and other rigmarole used in an attempt to mimic Class A distortion parameters in a more efficient amplifier topology. It was, indeed, a big deal in the late '70s/early '80s (there were "Energy Crises" in those dark days, and inflation and energy costs were sky-high). They've pretty much all gone away. So... there you go.

If one wants high power, low distortion (in the audible frequency range) and high efficiency, pulse-width modulation ("Class D") will get you there, and even inexpensively.

If one wants Class A amplification -- get a Class A amplifier.
That's what we roll here at the ol' casa (FWIW).

DSC_4281 (2) by Mark Hardy, on Flickr

mhardy6647

thesurfer wrote: »

That would be anything that's not pure class A, say like Yamaha CA 1010. or R-9.

Nothin' quasi about the CA-1010.
Yamaha CA-1010 will operate in Class A if the little switch on the front is set to Class A. In Class A, the CA-1010 is good for either 10 or 15 wpc (I forget... but I think 15) and of course will run quite hot, as the output transistors are dissipating full power all of the time (even at zero signal).
If the switch is thrown the other way, it is a normal Class AB1 amplifier (albeit a pretty good one).
Oh. Don't throw the switch with the amplifier turned on. Bad juju.

I don't have a 1010, but here's a (small) photo of the 2010 that's here. You can see the "Operation" toggle switch to the right of the speaker selector.
DSC_6689_z by Mark Hardy, on Flickr

Here's a better photo illustrating the same function on the older and smaller CA-800. This one is 10 wpc in Class A.

DSC_0180 by Mark Hardy, on Flickr

Panasonic/Technics "New Class A" is one example of the "quasi Class A" schemes of the late-70s and early-80s.


https://worldradiohistory.com/hd2/IDX-Audio/Archive-Audio-IDX/IDX/80s/Audio-1981-01-OCR-Page-0061.pdf#search="technics new class a"

SeleniumFalcon

In my semi-humble opinion the best sounding transistor receivers were made by Sherwood, Heathkit, Harmon Kardon and the Sony V-FET models (good luck finding those) and I have spent lots of time listening to them on a wide range of speakers. I don't think any of them used a type of class A operation, possibly the better Hitachi designs would be worth considering for their transistor capability? They do know their way around doping.

TroyD

When I was in Korea....I ran across a big, honkin' solid state Luxman integrated amplifier that one of the shop owners that I frequented had. Now, I didn't listen to it enough to know if it was the Luxman or the rest of the chain....but it certainly sounded good.

SeleniumFalcon

My first component stereo was when I got to Okinawa: Luxman tube integrated amp (there's only one FM station on the island "A-Farts" actually Armed Forces Radio was its real name, but nobody called it that). A pair of Coral brand speakers and a Garrard SL95 changer with Shure M75 cartridge. Oh boy! I can still remember opening the boxes (the turntable's base and dust cover came separately).

SeleniumFalcon

This is supposed to be a sought after model:

SeleniumFalcon

The problem that was trying to be addressed, at that time, was that output power transistors that could produce higher amounts of current tended to be a bit sluggish in switching on and off. This sluggishness resulted in fairly high amounts of crossover notch distortion. This kind of distortion is caused when the transistors producing the positive part of the waveform aren't completely shutoff as the transistors producing the negative part of the waveform begin turning on. There ends up being a kind of "notch" in the smooth sine wave's zero point. A pseudo or sliding class A amplifier has the ability to vary the type of bias the output stage is operating under as a function of power demand. At higher playing volumes crossover notch distortion is less noticeable so the amplifier performs in class AB operation. When less power is needed and the audibility of crossover distortion is more apparent then the amplifier "slides" into class A output (the transistors remain conducting, not being switched off). This is kind of the best of both designs, lower distortion when things are the most discernible and less expensive when full power is required.
However, as transistor development improved throughout the '80's and '90's more powerful transistors with faster on/off capabilities were available at reasonable prices so the "pseudo" class A designs were no longer in vogue. Of course there are many other factors in what makes up a good sounding audio component, such as negative feedback design, slew rate, transient intermodulation distortion (TIM), power supply design, surrounding device contaminations (all those meters and light bulbs) just to name a few.

mhardy6647

SeleniumFalcon wrote: »

This is supposed to be a sought after model:

The Class G amplifier topology was (and still is) a dual DC rail design that essentially gives transient access to double the "RMS" (continuous) output power. There are still Class G amplifiers in production (but I'll have to do some web browsin' to offer specific examples). The amplifiers operate at Class AB bias point(s), though.

HitachiSR2004 by Mark Hardy, on Flickr

Soundscraftsmen used a similar but somewhat more sophisticated variable DC HV power supply scheme that was (is) dubbed "Class H", FWIW.

TroyD

SeleniumFalcon wrote: »

My first component stereo was when I got to Okinawa: Luxman tube integrated amp (there's only one FM station on the island "A-Farts" actually Armed Forces Radio was its real name, but nobody called it that). A pair of Coral brand speakers and a Garrard SL95 changer with Shure M75 cartridge. Oh boy! I can still remember opening the boxes (the turntable's base and dust cover came separately).

Armed Forces Radio Television Service = A-Farts

SeleniumFalcon

Ah, thanks!

F1nut

A-Farts being discussed by old-farts....only at Club Polk folks.

ALL212

I didn't mind receivers, just never really got into radio. There was a gradual decline in build quality starting in the very late 70's and progressively got much worse into the 80's. I was (still am) a Sansui and Yamaha fan boy.

Clark AFB in the Philippine's had a decent audio section but the Subic Bay (Navy) store was much better but I only got there once.
My first amp was a Sansui AU-919 that was quickly replaced with the G9700 as it had twice the power and the Bose 901's I was running at the time really liked mo' power. The G9700 found its way back to the US with me, got lost and one day my brother mentioned he knew where it was. Both that and the 901's resurfaced. Both were sold a bit later. (Carver...I think, got the $$ from those sales).

Once the Yamaha line hit the x20 or xx20's things began to gain a lot of plastic and the next generation of x40, xx40's were pretty much crap (IMO - it ain't humble..). I did pick up the very interesting CR-1000 and owned that for a bit. I own the CA-800 with matching CT-800 (from @SCompRacer ) with no intention of letting those go. For a short period of time I also owned the CA-810.

I lost track of the Sansui line going forward from the G9700 but over the years I've owned the much older (and HUGE'r) AU-999 integrated amp and TU-999 tuner, then the AU-9500 integrated and TU-9500 tuner (still own the tuner). The AU-9500 weighed in at about 50 lbs and doesn't fit in any modern cabinet. Great amp though - mega controls if you like the "many buttons and switches" look. Somewhere here is an AU-222 and an AU-3900...somewhere... Both recapped if I remember correctly.

If you're digging the early 80's receivers and go Yammy I would never get a x40 or xx40 and would seriously doubt owning the x20, xx20 line. Prior to those amps - fantastic.

Receivers in general are a bit more complicated to work on. 1st you've got to work around/document the string layout for the tuning dial movement. Then you've got the tuning section to be careful of. And, as I mentioned, I just never really got into radio.

mhardy6647

ALL212 wrote: »

I didn't mind receivers, just never really got into radio. There was a gradual decline in build quality starting in the very late 70's and progressively got much worse into the 80's. I was (still am) a Sansui and Yamaha fan boy.
...

I knew there must be some reason why I like you...

Noted in passing: I would not mind owning a Sansui AU-717, even at this late date.

The CA-800 and CT-800 are very, very nice components, belying (did I spell that right?) their middle of the line heritage.

ALL212

Pretty sure I should have hung on to the 919…

Proof of packratism…

F1nut

thesurfer wrote: »

That would be anything that's not pure class A, say like Yamaha CA 1010. or R-9.

One is an integrated amp, the other a receiver. BIG difference.

SCompRacer

That amount equates to $2,596.62 today.

mhardy6647

(borrowed, needless to say)

I -- ahem -- I wouldn't mind having an R-9 either... truth be told.
Don't revoke my audiophile cred card, though... please.

I mean... as some of you may recall, lately I've been using this monstrosity (which wouldn't know Class A if it tripped over it) for two-channel. Quite a bit.
Not for any particular reason... other than, perhaps, that I like its latter-day Yamaha aesthetics, its amber display, and its sheer bulk.

DSC_7020 (2) by Mark Hardy, on Flickr

OK, maybe it is time to kick my cred to the curb.

DSC_0635 (2) by Mark Hardy, on Flickr

JayCee

ALL212 wrote: »

Ahhhh, the good old day's of "Layaway". As a $$ challenged highschool brat I purchased many a 35mm gear using the BX Layaway plan.

No disrespect intended...all this talk of Sansui...when I repped for Matsushita (Technics/Panasonic) at Mainz Kastel in the mid 80's, the running joke amongst rival reps was calling the Sansui gear "Sansewage". Regardless, the rep was super hot and she was always in the top 10% in sales for the audio club.

nooshinjohn

Sansui G30000, period.

jbreezy5

mhardy6647 wrote: »

SeleniumFalcon wrote: »

This is supposed to be a sought after model:

The Class G amplifier topology was (and still is) a dual DC rail design that essentially gives transient access to double the "RMS" (continuous) output power. There are still Class G amplifiers in production (but I'll have to do some web browsin' to offer specific examples). The amplifiers operate at Class AB bias point(s), though.

HitachiSR2004 by Mark Hardy, on Flickr

Soundscraftsmen used a similar but somewhat more sophisticated variable DC HV power supply scheme that was (is) dubbed "Class H", FWIW.

I believe recent Arcam amplifiers/receivers run Class G. Not sure of anyone else.

Are you familiar with Class T amplification? My Lepai desktop amp says it is this type.

mhardy6647

I don't know if Arcam's class G amps are the only current ones, but they certainly could be, for all I know

Class "T" was Tripath's implementation of a PWM ("class D") scheme.
The Tripath chipset amps were a big deal for a while. TI (IIRC) bought Tripath, or maybe they just folded -- I don't think there any 'real' Tripath chips any more.

This little monster supposedly has one of the Tripath chipsets. Supposedly.

Lepai and friend by Mark Hardy, on Flickr

Current production versions use a TI PWM IC.
https://www.parts-express.com/Lepai-LP-2020TI-Digital-Hi-Fi-Audio-Mini-Amplifier-with-Power-Supply-310-3000

Depending on one's frame of mind, the little Lepai is either irredemable junk or not bad for the $. I (still) tend to fall into the latter camp. It is a great test/"cannon fodder" amplifier for the bench.

That's all I've got.

Oh -- Class D is a) not digital and b) isn't terribly new in the great scheme of things.
Sir Clive Sinclair was a pioneer of (more or less) commercial PWM amplifiers (?!) in the mid 1960s
see, e.g., http://www.vk6fh.com/vk6fh/sinclair x10.htm
http://www.vk6fh.com/vk6fh/sinclairX20.htm





EDIT: Oh, the EQ smile in the Lepai photo above was meant to be ironic.

no smilies by Mark Hardy, on Flickr

TroyD

Cool and educational.......I look forward to anything Doc posts....

mhardy6647

... and I look forward to typing, cutting and pasting, and trespassing on others' copyrights.
Oh, and pontificating. Pontificating makes my day.

OleBoot

Pontifficating