Restoration/Upgrade Of Scribby31's Sansui AU-9500

[highcut28]

If only you could ship it .

My sick AU 111 is now on its way to London where a fab fellow AKer has kindly taken on its resuscitation, yup Malaysia to UK.
Mad ? Yes:yes:

Another heavy old AU to Canada would be too much.

 

[Soundphile]

Leestereo,
Your clear and sharp pics of each individual board with cap numbers make it easy to follow the resto works done. Congrats, thanks and keep the posts coming.
Robert.

 

[Boussole]

Beautiful Job! Best information I have Sean in long time , this is what Internet communications should be used for
Five star

 

[ConradH]

Very nice! As I've mentioned in other posts, the AU-9500 may be the nicest amp I've had the pleasure of listening to. The build quality is astounding, especially considering its power output isn't in the hundreds of watts category.

 

[vuman]

Very nice! As I've mentioned in other posts, the AU-9500 may be the nicest amp I've had the pleasure of listening to. The build quality is astounding, especially considering its power output isn't in the hundreds of watts category.

Is that keep you tapping your feet every hours of listening. That what it did to me? very musical

 

[quadklipsh]

In my experience, improving the preamp stage typically has a large impact on the sound of an integrated amplifier and that was the case here. Possibly due to the circuit topology requirements for larger signal path capacitors, the AU-9500 preamplifier stage reverted to the use of polarized electrolytic capacitors (as compared to the preamplifier stage of the earlier AU-999 which used primarily film capacitors). Fortunately, due to the miniaturization of film capacitors, during the restoration, all of the signal path electrolytic capacitors in the AU-9500 preamplifier stage were replaced with better film types and the single original polyester film capacitor was upgraded to a polypropylene type. Similarly, the main amplifier stage of the AU-9500 utilized polarized electrolytic capacitors in the input and feedback loop whereas the AU-999 had a film capacitor and a bi-polar capacitor, respectively, in these positions. The restoration of the AU-9500 main amplifier stage used a film capacitor and bi-polar capacitor in the same manner as in the main amplifier stage of the AU-999. Of course there were many other changes made during the restoration of the AU-9500, but the aforementioned are worth highlighting as they are probably responsible for the majority of the sonic improvements.


Awesome work lee,
Im an admirer of your work....BRAVO.......I followed this link to help my friend restore my 9500.
the description of your pre restoration is somewhat different from my amp. In MY case, the sound of this amp was all muddy and strangulated . with very poor HF and overall performance .
after an overall , the sound of this amplifier brought me an ear to ear smile ..... never tiring , never losing any detail.
i was slightly discouraged by Mr kevzeps comments that were not going much in favour of this amp as he preferred his G series amps,but thats OK , nevertheless , i went on with this recapping and replacement of many components as per your suggested ones and am happy to say iv never had a more musical amp in my 15 yrs of listening experience with HIFI .

I have a few questions if you can answer to , ill be delighted ......
The first is the use of film caps in pre-amp stage which i DID NOT do.
Do you prefer the sound of the original 9500 with its polarized electrolytic capacitors OR the sound with the film caps ....plz explain the differences in HF or lows .
I may add to this that i don't prefer the sound of the "Sansui 907 iMOS limited" which i sold because of its very neutral sound.

 

[rocknroller]

Tone Control Block (F-2019-1)

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Immediately following the volume control, the signal passes through the input high-pass filter capacitors (C701, C702) which were 0.47µF tantalum types; these were replaced with 0.47µF stacked film types.

So I don't understand - the Stacked film caps have no polarity correct? But the original Tantalum caps did. Is that not an problem?
What voltage did you use?
Will any stacked film cap do or only a certain one?
I'm looking to replace these tantalum and could use some guidance on what exactly I should be using to replace them with. Thanks!

 

[quadklipsh]

Except for the film caps my tech followed leesteeos lead. I am listening to my 9500 2hrs every night..... Never stopped loving it.

 

[quadklipsh]

Wont the film caps make the sound drier and harder compared to the electrolytics?
I like the laid back sweetness of these vintage guns. If the film caps alter the sound to the extent that it will ,
Make the 9500 sound like a mosfety , then I wouldnt wana go that route.
educate me, thanks

 

[Hyperion]

Wont the film caps make the sound drier and harder compared to the electrolytics?
I like the laid back sweetness of these vintage guns.

If anything, the film caps will enhance that 'laid back sweetness'.

If the film caps alter the sound to the extent that it will, Make the 9500 sound like a mosfety , then I wouldnt wana go that route.
educate me, thanks

No, the film caps won't do that at all.

 

[smurfer77]

My personal experience is that replacing electrolytics with same value film caps often results in audible improvement when in audio path. However, I always find it suspicious when people say 'metal' resistors or 'metal' caps sound.....'metallic' (or 'cold', since metal feels thermally cold???). Pretty sure much of that is knowledge bias and most haven't done blind A/B etc. If the caps are same value you shouldn't hear any more high frequency (which people associate with dry/cold) coming through than with the electrolytic. A plus is that film caps are non-polar which is great for signal path, but using those electrolytic polar caps in signal path usually isn't a problem since signal is so small amplitude.

I do think film caps can sound better, but the effect is typically subtle unless I replace them in entire audio path, then I can really start to notice it when I blind A/B with stock unit. I do replace electrolytics outside of audio signal path where I can fit them too, mainly due to long-life of such caps compared to electrolytics.

Oh, and once you start getting familiar with schematics you will start noticing a lot of tweaker threads (especially on cd play 'mods' etc etc) where people change one or two electrolytics for films, in positions that have very little absolutely nothing to do with the audio signal, and will claim the frequency response other features changed drastically... I like films caps a lot, but don't believe everything you hear. Similar rant applies to the issue of boutique caps (which are often worse compared to no frills caps)... IMO.

All this comes from a guy (me), who spends a lot of time replacing caps in amps that others wouldn't bother with... I do think there are good reasons to use film caps where possible, no they don't sound dry or cold unless something is wrong with them (which has happened to me, but that is not a uniquely film cap issue)... and they last for a longgggggg time.

 

[stereofun]

I am with Smurfer77 - film caps are a good choice when in the signal path - but don't expect drastic or dramatic differences, these things are subtle and something you will only notice when you listen on your own rig with your usual test sources. On many of the older sansuis, AU-505, 555(a), 666, 999 - Sansui did use film caps (mylar) in the C801 position (power amp input cap) - then in the highly regarded, no cost cutting, Eight/Eight deluxe they went back to electrolytic, even when they easily could have fitted a mylar in that 1uf/50v position.

 

[quadklipsh]

thanks a lot smurfer,stereofun and hyperion . ill now ask my tech for the use of film caps in the signal path. but now the amp is up and running and my tech is 100 miles away .

 

[Final_Baton]

Congrats Scribby, happy to know you now have an AU-9500 that plays to it's full potential must sound oustanding!

 

[quadklipsh]

i now have the film caps for the signal path board . the little 4.7uF and 0.47uF ones that i have are blue and red coloured ....they look like tiny bricks. im sending the images .. As my tech is 80 miles away and my sansui is serving me pretty well, i will not send it and save myself of the hassle ,ill do this recapping funda myself some bright day .....the board has been recapped using nichicons and rubycons some 2 months ago.... i mean please tell if this replacement using the film caps will make a difference or not worth the effort (on my part of-course )

 

[quadklipsh]

 

[Hyperion]

What value capacitors are you replacing? - the one in the large picture labelled 4700/100 is a value usually only found in tone control circuitry as it is 4700pF,100V (or 0.0047µF). 334J = 0.33µF, 474K = 0.47µF and so on.

 

[quadklipsh]

0.47uf is what ill be using . and some 4.7uf too

 

[Pilsern]

Excellent thread!
I will try to resurrect my nearly dead AU9500 in the coming holidays.

I will change the 2SC1313 and 2SA726 transistors with KSA1845 and KSA992,
Farnell list two different KSA992 transistors - which one do I choose for the au9500 ??




(KSA1845 from Farnell is listed with 300 hFE)

Thanks in advance,

 

[ZOOM]

Both are the same, fta comes on tape, fbu is bulk (loose in a bag). Avoid the tape as the glue on it corrodes the legs after a year or so.