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amplifier class in vintage receivers?

George W

George W

Active Member
Reading about experiences with vintage receivers, much is said about musicality and quality of reproduction. Was there a general design feature of vintage receivers that could help identify the class of amplifier used? I"ve become intrigued by Sansui products from the 70s. I would expect that a Class A amplifier would be a prominent feature advertised about a product, so would a class AB represent the typical quality receiver from the 1970s? Thank you.
 
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Almost everything would be class AB. IMO, it might come down more to what kind of input and output stages they used, diff amp or simple single, and quasi comp or full comp, and whether the output was cap coupled or not. You have to be careful with generalizations as there's a wide range of vintage receivers with varying degrees of sound quality. Then, don't forget the various phono stage designs and tone control designs.
 
Receivers crowd several components in one chassis and real class A amps give off tremendous amounts of heat, not a good combination. The only receiver that comes to mind that could run in class A is the Yamaha R-9 from around 1985.

But what makes an amp or receiver good is a much more complex question than what class it is.
 
Technics had a line of Class A receivers in the '80s of which I owned one myself. Typical of Class A, it would become very hot at idle.

I also recall Hitachi having a series of "Class G" amplifiers and receivers as well - sometime in the '70s IIRC.
 
62caddy said:
Technics had a line of Class A receivers in the '80s of which I owned one myself. Typical of Class A, it would become very hot at idle.

I also recall Hitachi having a series of "Class G" amplifiers and receivers as well - sometime in the '70s IIRC.
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Yamaha may have made a few that could run Class A, but not too many. R9?

http://www.manualslib.com/manual/773694/Yamaha-R-9.html?page=19#manual

Button top right

Yamaha%20R9%201.jpg


http://www.chrisinmotion.com/MyFavoriteReceivers2.htm
 
Is there any way to just look at a unit and decide which amp class it is, without looking at a schematic?
 
Plug it in and turn it on (no source, no signal, no volume, but power amp "on"). If it gets hot even with zero signal -- it's probably biased to Class A (or maybe it's got vacuum tubes or something really wrong with it) :-)
 
Thank you all for your knowledge. Raynald & Bubo, it's ironic you mention the R-9 since I see there is one on the auction block at GW currently. It looks pretty dusty, and the pictures do not appear to show it powered on. You'd think the least they could do is wipe a piece down at a little bit.
 
The R-9 is very impressive. It has speaker A/B/C switching, a great tuner section with .01 fine tuning, MM/MC phono, 125 wpc, Yamaha's great variable loudness and a midrange control in addition to bass and treble.

However, it is surprisingly lightweight at around 26lbs with all of those features. My later RX-1130 is around 32lbs and my earlier CR-2040 is 46lbs. I would love to have one as it is rather unique, but I would not pay big bucks. You have to consider if it was left in class A for long periods of time without adequate ventilation it may have suffered. Some Marantz and Musical Fidelity class A integrated amps are famous for cooking themselves over time.
 
Raynald said:
You have to consider if it was left in class A for long periods of time without adequate ventilation it may have suffered. Some Marantz and Musical Fidelity class A integrated amps are famous for cooking themselves over time.
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I have started putting USB powered DC fans on top of all of my gear blowing in from the top, they now remain cool to the touch.

Blowing in, with a quiet fan, the case acts as a muffler but not 100%.

Give the age of the R, I would think a complete recap and cleaning and tuner alignment are required. So if purchased for $150, expect $350 for recap and align.

What else could you buy for $500 that compares?
 
Check out the R-9 before purchase. The FM function can be intermittant especially when hot. There is also the "glue" that becomes corrosive. The preset station memory cap will likely need to be replaced. Make sure the remote is included.
I really like my R-9, but I really can't tell the difference between Class A and AB except that it gets too hot to touch when in Class A. The remote is convenient and it looks good. I wish it had a pre-out so a sub could be more easily added in. It does have an accessory out, but it is before the volume control.
I have considered recapping it, but it may not be worth it if the FM fails. I listen to it about 10-20 hours per week and don't see much need for an upgrade.

Edit: Looking at the pic above I just realized that my signal meter is partial out. I don't have the bars lit up, only the green led at the top of each bar works, so I get a line graph instead of a bar graft. Hmmm.
 
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Aspen said:
Check out the R-9 before purchase. The FM function can be intermittant especially when hot. There is also the "glue" that becomes corrosive. The preset station memory cap will likely need to be replaced. Make sure the remote is included.
I really like my R-9, but I really can't tell the difference between Class A and AB except that it gets too hot to touch when in Class A. The remote is convenient and it looks good. I wish it had a pre-out so a sub could be more easily added in. It does have an accessory out, but it is before the volume control.
I have considered recapping it, but it may not be worth it if the FM fails. I listen to it about 10-20 hours per week and don't see much need for an upgrade.

Edit: Looking at the pic above I just realized that my signal meter is partial out. I don't have the bars lit up, only the green led at the top of each bar works, so I get a line graph instead of a bar graft. Hmmm.
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Contact BetheKing he frequently posts in the Yamaha section.

I like him from what I've seen

Anyway he runs a repair shop and enjoys a good rep, also likes Yamaha stuff.

I think he is a couple of hours from your location.
 
Bubo said:
Contact BetheKing he frequently posts in the Yamaha section.

I like him from what I've seen

Anyway he runs a repair shop and enjoys a good rep, also likes Yamaha stuff.

I think he is a couple of hours from your location.
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I know of him, but Ottawa is about 7 hours drive from me. I have a local tech who can refurb it once I am ready.
 
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