Rate my vintage amp by todays standards

[KEW]

There's no mention of 4 Ohm loads at all.
It cannot be bridged mono (though imagining 5-7 of those behemoths running a HT is interesting).

The convention for power specification was mandated by the FTC. They had to give frequency range, THD level and minimum RMS Watts per channel at 8 ohms all as one spec.
This was a good thing after previous years with Soundesign and Julliette (cheap stereo consoles) rated at 800 Watts IPP (that is Instant Peak Power)!

Although a 4 ohm rating would have been good, I am disappointed that manufactures are no longer held to reporting a consistent standard as they were then.

The amp allows for connection of two sets of speakers, but has the caution that you should not run two pairs unless the impedance is greater than 8 ohms for each speaker. I would interpret this to mean stable down to 4 ohms, but not below 4 ohms.

I just don't think bridged mono was done back then. High Figh is probably right about it being capable with slight mod, but I don't remember bridged mono in specifications.
Cheers,
Kurt

 

[highfigh]

The convention for power specification was mandated by the FTC. They had to give frequency range, THD level and minimum RMS Watts per channel at 8 ohms all as one spec.
This was a good thing after previous years with Soundesign and Julliette (cheap stereo consoles) rated at 800 Watts IPP (that is Instant Peak Power)!

Although a 4 ohm rating would have been good, I am disappointed that manufactures are no longer held to reporting a consistent standard as they were then.

The amp allows for connection of two sets of speakers, but has the caution that you should not run two pairs unless the impedance is greater than 8 ohms for each speaker. I would interpret this to mean stable down to 4 ohms, but not below 4 ohms.

I just don't think bridged mono was done back then. High Figh is probably right about it being capable with slight mod, but I don't remember bridged mono in specifications.
Cheers,
Kurt

Most consumer electronics customers didn't know what 'bridged mono' was back then and that's a good reason they had that stupid power race with receivers. The Pioneer SX-1980, Sansui 9090DB and others like them were huge boat anchors that really don't sound all that great, but when the market says it wants 270W/ch (SX-1980), they jumped to it. For the price of those things, separates were far better.

I thought Symphonic, Juliette and SoundDesign used JBF and WLS for their power ratings. (In case you never saw it, 'JBF' stands for "Just Before Fire" and 'WLS' stands for "When Lightning Strikes")

 

[KEW]

The caps did leak and I would definitely replace them because of that. Caps are relatively cheap and it's good insurance. The photos show mostly metal foil resistors and by the time that was made, carbon composition resistors had been largely replaced by what yours has. OTOH, if this was a vintage guitar amp, most people would recommend keeping the old carbon comp resistors if they were within tolerance or replacing with new ones to maintain the vintage sound. I have one guitar amp that's from 1958 and another that's at least 70 years old- people have commented on how quiet they are and I have replaced two resistors on the '58 and none on the older one.

I seriously doubt you have any bad resistors and if you want to find out if any need to be replaced, switch it to an unused input (other than phono) and turn the volume up. If you hear loud hissing or crackling, you may have a bad resistor but if it's quiet, they're fine. I wouldn't crank it wide open- that kind of crackling can toast tweeters.

Enjoy it. Being older doesn't mean it's bad- there are many people who love old equipment that's hardly great but they don't care. Yours is far better than that what I have seen people fawn over.

Great info. Thanks!

 

[KEW]

Most consumer electronics customers didn't know what 'bridged mono' was back then and that's a good reason they had that stupid power race with receivers. The Pioneer SX-1980, Sansui 9090DB and others like them were huge boat anchors that really don't sound all that great, but when the market says it wants 270W/ch (SX-1980), they jumped to it. For the price of those things, separates were far better.

I thought Symphonic, Juliette and SoundDesign used JBF and WLS for their power ratings. (In case you never saw it, 'JBF' stands for "Just Before Fire" and 'WLS' stands for "When Lightning Strikes")

LOL That is about the truth of it.
My very first stereo (paper route money) was a Juliette. I watched my dad build Heathkit for his stuff and put insulation in the speaker boxes. I stuffed my Juliette speakers with old rags and could not believe how much it tightened up the sound! That was the real advantage of POS stereos, they were easy to make better!

 

[zvardanian]

Was not my intent to be critical, just impart some experience.

 

[KEW]

Was not my intent to be critical, just impart some experience.

I wasn't referring to anything you had said, I was anticipating that things could get out of hand after I posted photos. I just didn't want unfair criticism of a simple repair job not done with the love and care an obsessive audiophile would apply.

Do you see anything else I should get a quote to have replaced other than the black caps in the third photo?

Thanks!

 

[zvardanian]

When you see that orange gunk below a cap it means the material has leaked out. Electrolytics don't have long usage or shelf life, so when the material leaks out, the capacitor loses its value. I believe the load can become resistive. If you checked each one, you'd probably find that orange material throughout the stereo. If it works, keep using it. If you listen closely and hear humming that's most likely a cap that's died. If you feel the sound isn't quite "right", it's probably because of the caps.

I'm not an engineer, so anyone else chime in .

If you have any inclination to recap yourself, buy a solder kit and practice first. The actual cost of the caps are probably pretty cheap...just use some Panasonic FM or FC's. Anything will be better than what they came with. For the power caps, Panasonic TSHA's are pretty good. I've used Nichicons too.

You'd probably be looking at 60-70 in caps (the main power supply caps are about 8 bucks each).

Ok, I went off on a tangent. I guess what I'm saying is, if you are going to replace the caps that have leaked, you might as well go all the way and replace them all.

 

[KEW]

Thanks.

I guess I need to compare it to a modern unit and see if I can hear a difference, then figure out whether or not to rejuvenate it.

 

[zvardanian]

It can be a fun project.

 

[highfigh]

Thanks.

I guess I need to compare it to a modern unit and see if I can hear a difference, then figure out whether or not to rejuvenate it.

Electrolytic caps often cause hum when they go bad because they fail in a way that's like they aren't even there. Their purpose is to conduct any AC voltage present after the rectifier in the power supply to ground (the rectifier converts the AC from the power transformer to DC voltage, which is what transistors use). If the cap fails open, it does nothing so you'll hear hum and if it shorts, it'll likely pop or blow a fuse. If the voltage exceeds their rating, they pop, sometimes very loudly. If you can't hear loud humming, the rest of the electrolytics are OK and unless it does something else that's not normal (normal meaning not going into protection and not sounding bad), about the only thing I would recommend is cleaning the switches and controls. Once these are done (if needed), if you like the way it sounds without comparing it to something else, just enjoy it. You probably won't be comparing two or more amps on a regular basis anyway, so you'll be able to decide if you like the sound. Good or bad specs make no difference when something sounds good.

 

[3db]

Electrolytic caps often cause hum when they go bad because they fail in a way that's like they aren't even there. Their purpose is to conduct any AC voltage present after the rectifier in the power supply to ground (the rectifier converts the AC from the power transformer to DC voltage, which is what transistors use). If the cap fails open, it does nothing so you'll hear hum and if it shorts, it'll likely pop or blow a fuse. If the voltage exceeds their rating, they pop, sometimes very loudly. If you can't hear loud humming, the rest of the electrolytics are OK and unless it does something else that's not normal (normal meaning not going into protection and not sounding bad), about the only thing I would recommend is cleaning the switches and controls. Once these are done (if needed), if you like the way it sounds without comparing it to something else, just enjoy it. You probably won't be comparing two or more amps on a regular basis anyway, so you'll be able to decide if you like the sound. Good or bad specs make no difference when something sounds good.

Carefull with the polarity of Electrolytic specs. Get the polarities mixed up and they explode or burn briefly which can cuase damage.

 

[highfigh]

Carefull with the polarity of Electrolytic specs. Get the polarities mixed up and they explode or burn briefly which can cause damage.

Good point- they're marked but if the cover has disappeared, measurements must be made to find out which leg goes to + and -. Another point, they're not all marked the same way- some have the arrow on the - and some on the +.

 

[pearsall001]

I bought this amp in 1980.
The two links below give a pretty good overview.

http://www.vintageaudio.com.au/Amps/Sansui/Sansui AU-717 Integrated Amp.htm
http://www.sansui.us/images/Manuals/au717_spec.JPG

For you guys who know the ins and outs of good amplifiers, how does it compare with modern gear? Are there some major omissions by today's standards?
TIA

That is one gorgeous piece!!! I too have found that vintage gear from that era is still going strong & sound wonderful. I fell into by accident a "Mint" Nikko Alpha VI amp about a year ago & it's now sitting pretty smack dab between my mains! It's a beast...300w (8ohm...340w 4ohm) dual mono design that was actually designed & built by Luxman for Nikko back then. A & B speakers terminals, headphone jack & individual gain control. Everything functions like brand new.

I tried posting some pics but I can't get them to work. I'll give it another shot.