Sansui AU-999 restoration

[pete_mac]

Hi all,

I've previously shared a few Sansui restos so I thought I'd post up another.

A friend wanted this AU-999 fully restored and enhanced wherever possible, along with the addition of proper 5 way binding posts.

The 999 is one of Sansui's best amps from the early 70's, punching out 50WPC and exhibiting excellent quality and a high standard of industrial design. Nice touches include the resistor ladder network stepped attenuators for the bass, midrange and treble, and very high quality switchgear.

Decent quality capacitors were used throughout, including lovely Nichicon Super Through power supply filter caps, Elna Silmic II, Nichicon Muse ES, Panasonic FC and Nichicon HE.

The troublesome original 'flying saucer' small signal transistors have all been replaced with modern equivalents for improved reliability and lower noise.

http://i1307.photobucket.com/albums/s587/petemacsna/473e9567-effa-407b-b374-935e5d3c3f56_zps82bad523.jpg (http://s1307.photobucket.com/user/petemacsna/media/473e9567-effa-407b-b374-935e5d3c3f56_zps82bad523.jpg.html)

The preamp, phono and tone control boards are all modular and easily removeable.

http://i1307.photobucket.com/albums/s587/petemacsna/999recap3_zpsd2173d95.jpg (http://s1307.photobucket.com/user/petemacsna/media/999recap3_zpsd2173d95.jpg.html)

The reason why recapping vintage gear is essential... this cap appeared fine when viewed in-situ, but was leaking:

http://i1307.photobucket.com/albums/s587/petemacsna/999recap5_zps0d76b8aa.jpg (http://s1307.photobucket.com/user/petemacsna/media/999recap5_zps0d76b8aa.jpg.html)


These amps feature 'crowbar' protection circuits which are intended to blow fuses if there is a fault, but instead they often blow the output transistors! As a result, this circuit is removed. Likewise, the subsonic filter circuit has a significant undesirable impact on the bass response, and is also removed.

http://i1307.photobucket.com/albums/s587/petemacsna/au999subsonicandcrowbar_zps22c577bb.jpg (http://s1307.photobucket.com/user/petemacsna/media/au999subsonicandcrowbar_zps22c577bb.jpg.html)


The original sprung speaker terminals are replaced with 5 way binding posts:

http://i1307.photobucket.com/albums/s587/petemacsna/au999bindingfirstlotdone_zps8260f792.jpg (http://s1307.photobucket.com/user/petemacsna/media/au999bindingfirstlotdone_zps8260f792.jpg.html)


Two modifications are made to the preamp boards to improve headroom (the preamp distorts too early otherwise) and to the bass tone control circuit.

And... finito!

http://i1307.photobucket.com/albums/s587/petemacsna/au999boardsfinished_zpsc8fb3123.jpg (http://s1307.photobucket.com/user/petemacsna/media/au999boardsfinished_zpsc8fb3123.jpg.html)

http://i1307.photobucket.com/albums/s587/petemacsna/au999phonoboard_zpsb44570b7.jpg (http://s1307.photobucket.com/user/petemacsna/media/au999phonoboard_zpsb44570b7.jpg.html)

http://i1307.photobucket.com/albums/s587/petemacsna/au999finishednaked2_zps6ad63ad9.jpg (http://s1307.photobucket.com/user/petemacsna/media/au999finishednaked2_zps6ad63ad9.jpg.html)

http://i1307.photobucket.com/albums/s587/petemacsna/au999finishednaked3_zpsb0844351.jpg (http://s1307.photobucket.com/user/petemacsna/media/au999finishednaked3_zpsb0844351.jpg.html)

http://i1307.photobucket.com/albums/s587/petemacsna/au999finishedfront_zps3013d7dd.jpg (http://s1307.photobucket.com/user/petemacsna/media/au999finishedfront_zps3013d7dd.jpg.html)


She sounds very nice indeed. I could easily live with this amp as my main amp. The sound quality post-recap and post-mods is distinctly better than standard, with improved resolution, detail and bass depth. The sound stage isn't quite as detailed as my AU-X701 and there also isn't quite the same clarity overall, however the 999 really shines with how it delivers in the midrange. Vocals are an absolute treat.

All in all, it's a brilliant amp which should hopefully last for another 40 years.

[Rare Bird]

Nice one Pete, i did an old 1960's Trio 'TK150' amp begining of the year, really is one nice sounding amp now..

I'd be looking into swapping out all those green Polyester caps (they look like) for say something like Wima Polypropylenes if they will fit, keep it all nice neat & uniform..

[pete_mac]

Nice one Pete, i did an old 1960's Trio 'TK150' amp begining of the year, really is one nice sounding amp now..

I'd be looking into swapping out all those green Polyester caps (they look like) for say something like Wima Polypropylenes if they will fit, keep it all nice neat & uniform..

Indeed, it's something that I would do if it were my own personal amp. In this case, the friend that I restored it for is happy to stick with the polyesters.

They are all fairly small value caps too (eg. 0.47uf and 1uf) so replacing them would be pretty cheap. Heck, you could even throw in some 'boutique' axial caps like Solens or AXONs which would be around $1-2 each for these values.

I'd imagine the swap to polyprops would definitely be worth the expense. I wouldn't be surprised if this amp comes back to me in future for this upgrade.

[John]

Lovely work to a great amp

[walpurgis]

You don't see many of these about now. Lovely amp!

I seriously lusted after one when they were on the market, but I was nearly broke, so I bought a Rotel RA-611 instead. That turned out to be rather a 'goodie'.

[Rare Bird]

You don't see many of these about now. Lovely amp!

I seriously lusted after one when they were on the market, but I was nearly broke, so I bought a Rotel RA-611 instead. That turned out to be rather a 'goodie'.

Aye i think the 'RA-611' was a Japanese made unit..I have the older 'RA-610'..

Just looking at those slot in Sansui cards, they are very well made & very well laid out :thumbsup:

[Audio Al]

MMMmmm :eyebrows:

Very nice :)

[pete_mac]

Thanks for the kind comments all. I have some detailed build/resto info on other nice vintage amps which I will post in future - eg. the Kenwood KA-8006, Yamaha CA-1010 and a treasure trove of Sansui stuff. They make for good reading and viewing!



Just looking at those slot in Sansui cards, they are very well made & very well laid out :thumbsup:

Yeah, the cards which deal with both channels are 100% symmetrical and nicely designed.