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First Sansui! Au 555A ...and underwhelmed.

toneriderMUC

toneriderMUC

Active Member
I finally scored my first Sansui. An Au 555A in PRISTINE condition. Apart from one minor scratch on the wood, this little sweety looks basically like new. It is all original and has never been serviced.

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Its not only in mint condition, it also came along with all the original papers in unused condition, including warranty card and bill from 1/5/1974:

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So, i have say, after unwrapping, I was floored. Such a beauty.

i couldnt wait to hook it on my Yamaha NS 690's. And then...

...could it be..?

...it sounds... mediocre?

I was expecting a full, rich, warm and dynamic presentation. The much quoted "tube like" sound of those early Sansuis. My 555A does not sound like that. It sounds:
- rather bright
- slightly harsh
- dull / flat
- bass is really flat and undefined
- the overall sound is bright and flat and lacks punch and dynamics. Even switching on loudness doesnt change a lot

I can A/B compare it to a Pioneer SX 525 (which is the same age and also completely stock) and a 1984 Luxman L210. Both play much more dynamic and musical. Especially the SX 525 has a much deeper, more detailed and wider soundstage.


So, whats wrong? :-(
I guess, my 555A does not play to its actual potential. Technically there is nothing obviously wrong with it. Its dead quiet, all knobs are quit. no hiss, no humm.
One thing though: when switching it off, its not instantly silent, but "fades out" for 3-5 seconds. Does this indicate bad caps?

It hasnt been used for a couple of years now and judging from the incredible optical condition, hasnt been used much in his lifetime at all.
My guess: caps beyond their lifespan / or just not used enough in the past years? Does it maybe need some break in to catch up in sound qualitiy?

Is a recap likely to bring back the desired sound quality?

Looking forward to your input :-)

Cheers, Robin
 
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I just restored one of these and recommend a recap. It will make a huge difference even if your example is mint it's still forty years old.

The 2sc871 transistors also get noisy I suggest you replace those with 2sc2240 or ksc1845

Cap brands is personal preference Elna simic are highly regarded I used these throughout other than nichicon gold for the output coupling caps

There are much better amps out there than a 555a however it's still a very good performer I'd describe a restored version as well balanced and controlled classical jazz and vocals really shine with this amp if you prefer heavier music I'd go with another amp that's dc integrated such has the au-717 which is ten years newer much more advanced and more power hope that helps
 
Should note it's normal to have music slowly fade out after a switch off it's just the caps draining

Also the CDC 8002 and 9002 transistors aka flying saucer transistors are known to cause issues and should be replaced ksc2690 and ksa1220 are good substitutes.
 
According to the serial number, 833030269, that amp was manufactured in March of 1973 so it has just had it's 44th birthday. When you think about it, it's remarkable that it works at all. It may be in perfect physical condition but the electrolytic capacitors dry out over time. It would be a whole different sound with new caps.

- Pete
 
It could also be running a too low bias - your description indicates that it is performing well below potential. A well running 555a, even stock, has a good amount of low end gusto, combined with a open spatial sound that is very very listenable, even if it's not textbook correct. In short, it should sound pretty darned good and after a rebuild, it is up there with the best In its low powered category.
 
quadmatrix82 said:
There are much better amps out there than a 555a however it's still a very good performer
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I second this. I consider the 555a (fully restored) to be a good introduction to Sansui, and your perception of the sound can really depend on the quality of whatever amp you were using before. This is probably a generalisation but I many people may be impressed by the sound of this amp when they hear it for the first time, if they are used to the sound of fairly average amplifiers. This was the first sansui that I heard, previously I was using a fully modded Quad 303 poweramp (which I then quickly got rid of......)

Yes it will need a full service as stated above. Characteristics of this amp once fully modded are a wide soundstage with powerful bass. Well projected but fairly grainy mids & highs.

Recapping is a must but replacing the existing flying saucers transistors will also do wonders, as stated above.
 
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Cap-coupled Sansui amplifier sections when freshened up will give most any low wattage gear a real run for their money. You have a real gem there and well worth rebuilding.
 
Thank you all for your input. I think it boils down to one question: will a recap likely improve sound and the answer seems to be yes.

I just the thread about Patfonts restoration and all those sound attributes I just dont find in my example:
- fat and punchy bottom end - bottom end is flat and almost non-existant. I dont like heavy bass, but my 555a almost has no bass
- lively and detailed mids - mids are the worst actually. They are muffled and dull. Especially crunchy guitar music (Neil Young, Stevie Ray Vaughan, etc) sounds awful, to be honest. The amp seems to be struggling reproducing that kind of music.
- Highs actually sound fine, I like the voice reproduction!


Despite these shortcomings, I can see the actual potential underneath. So i think I will do the recap.
I am aware, that the 555A is not an AU11000 or something else high end. But also think comparing it to a Pioneer Sx 525 is fair, they should be in a similar league. I dont need a detail king. I dont mind trading some "incorrectness" for overall sweetness.

You also mentioned BIAS and Offset. I can do the recap myself but I dont have the equipment to set those, so I will take it to a technician to get that one. Would you do that BEFORE or AFTER the recap?
 
Absolutely that is the first place to start, if those values are far enough out of spec the sound quality will suffer.
Best practice is to diagnose the unit's health before one starts to rebuild, otherwise one does not know what needs to be addressed and you could end up with more issues than you start with.
 
Overundr1 said:
Absolutely that is the first place to start, if those values are far enough out of spec the sound quality will suffer. Best practice is to diagnose the unit's health before one starts to rebuild, otherwise one does not know what needs to be addressed and you could end up with more issues than you start with.
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+1 and if you do the 'recap' properly - to include any trimmer resistors, then you will definitely need to recheck/reset DC offset and Bias. Even if you don't replace the trimmers the other replacement components often have a significant effect on those settings.
 
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ALWAYS "fix it first"--otherwise you may NEVER find the "real issue"--do the calibrations and get it as close to spec as you can. With ageing components, you may not be able to get it up to spec, but that will give you a clue as to where to start. Blindly embarking on a full restoration can confound what is really going on/wrong.
 
savatage1973 said:
ALWAYS "fix it first"--otherwise you may NEVER find the "real issue"--do the calibrations and get it as close to spec as you can. With ageing components, you may not be able to get it up to spec, but that will give you a clue as to where to start. Blindly embarking on a full restoration can confound what is really going on/wrong.
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Thing is.. I cant do the bias adjustments myself and will have to pay a tech. If it will need adjustment after adding new components anyway, I might as well save the money and take it to tech after replacing caps and maybe ufos.
Otherwise I'd have to pay twice.

Or would that be a really bad idea...
 
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If you get a reputable tech involved the initial adjustment diagnoses should be part of the understanding that those funds would be applied towards a full on rebuild, at least that's the way most of us here at AK handle this in my opinion.
 
toneriderMUC said:
...has never been serviced.
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There is your answer. Probably need rebias and recap, as others have mentioned. It's especially strange that you say the loudness switch hardly improves the situation; this should give a hefty boost to bass unless your volume knob is turned up high. I expect it needs at least a basic service. 50% of amps I get that sound 'okay' have serious technical issues that become obvious only when i hook up to scope. Do not assume everything is working up to spec if it makes okay sound and looks physically good.

It is also possible that the amp is in fine condition and the sound is just not to your tastes.

PS. Beautiful unit and paperwork!

[edit] If you can do the recap, you can definitely work out how to do the bias and center voltage /balance (not really DC offset on this as it is output cap coupled design). You just need a screw driver and a multimeter. Post here if you need further instructions on how to do that. i would do it before recap, to check if it isn't just woeful settings throwing things off.
 
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No bass signals dried up caps to me, that could also be bias.

If you feel confident enough to do the recap yourself then there's probably no reason why you could also setup the bias and DC offset levels afterwards, totally over to you of course. But all you need is steady hands, a small screwdriver and a digital meter.
 
I had an AU-555A. The bass was boomy and it popped now and then. I replaced the bad transistors and recapped the entire unit.
The first thing I noticed was that the bass was not boomy any more, at all. It was much tighter, and could give the impression of a lack of bass.

So it wont have that bloated 300hz hump that the Pioneer has, but should pretty accurately reproduce the bass notes.

As far as the mids, they should not sound muffled, but the highs may be a bit bright. Nothing turning the treble down a notch or two can't fix.

Rob
 
What an absolutely beautiful amp! 'Sorry to hear that it doesn't sound as great as it looks.

The lack of bass is strange. Could you perhaps have hooked it up with the speakers out of phase? Just a thought.
 
After recap, my old unit was fantastic to my ears! If I had not picked up a 777a I wouldn't have ever sold it. I actually have another 555a coming my way.... I'll give it the full treatments. I love capacitor coupled amps.....
 
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