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Thread: Sansui AU-517 and AU-719 restorations (lotsa pics!)

  1. #1
    Join Date: Dec 2011

    Location: Sydney, Australia

    Posts: 142
    I'm Pete.

    Default Sansui AU-517 and AU-719 restorations (lotsa pics!)

    Sorry in advance for the multitude of pictures!

    My father and I are Sansui nuts (over 50 units between us!) and the pride of place in my current system is taken by a restored Sansui AU-719 which has been fully recapped/restored. I also have a AU-517 which I've recapped. The 517 sounds great but the 719 takes things a bit further. It is one of the Super Fidelity models with the Diamond Differential driver boards. The improvement in clarity, accuracy and resolution vs the 517 is quite obvious to my ears.

    The 719 is 90WRMS/ch vs 65WRMS/ch for my AU-517, which is not a huge difference. The physical layout is very very similar to the AU-517, but with a simpler control amp section, a more complex/sophisticated power supply board, and the Diamond Differential circuitry in the driver boards.

    As you can see from the internal shots, the 719 didn't have the same build quality standard as the 517/717 wich were all black inside with internal trim/cover panels etc. The transformers are also bare with no black cladding. I do wish this amp had the same black finish as the others, and I was tempted to strip the whole amp down and paint the chassis... but a painted chassis doesn't make an amp sound any better, so I decided to leave it as-is.

    The caps used throughout are Panasonic FC series, Nichicon Muse bipolar, Elna Silmic II for signal path applications, and also some small Panasonic and Epcos stacked film capacitors for the 1uf capacitors. All of the MV12 diodes (same as the VD1212) were replaced with a series pair of 1N4848 diodes, and the notiorious 'black flag' ceramic caps were replaced with silver micas. As part of the 'Stage 1' recap I retained the original PSU filter caps, so I also added 1uf 100V bypass caps across them as per the other Sansuis of this era.












    I also replaced the original binding posts with proper 5 way units which allow the use of speaker cables with banana plugs. Thankfully the 719 already has binding posts as standard, so the rear panel has circular cut-outs. This made the retrofit much easier.

    I'm actually contemplating at least the top row of speaker binding posts with higher-quality solid copper binding posts, rather than gold plated brass. Not sure whether I will notice the change, but it is bugging me nonetheless. I also want to change the RCA sockets for the AUX input to solid copper sockets.












    A quick comparison of the build quality of the 517 vs the 719 (the 517 is far superior in this regard):






    The front panels are damn similar:




    Some 719 info:




    A few photos of the 719 with a few of its family:






    Listening comparison between 517 and 719 (with my old Dynaudios... I still miss them sometimes) :





    Stage 2 of the mods (completed last weekend!) involved the installation of new power supply filter caps. Epcos 15000uf 63V are very well regarded, nicely spec'd caps which should comfortably out-perform the original 32 year old caps.

    They are slightly narrower but taller than the originals (35mm x 105mm vs 40mm x 80mm) so I needed to make up some spacers to suit the original 40mm capacitor clamps. Dad (skippy124) had done this in the past using some PVC pipe painted black. Insead of painting some pipe, we sourced some black spekaer ports which were 35mm internal diameter and I cut some 1/2" sections with a split to allow the spacer to slide over the capacitor. I did some test-fits in the pictures below:









    The original caps in-situ:






    Here is a comparison of a new Epcos capacitor vs an original Elna:

    [/QUOTE]

    Here are the new capacitors installed with some Arcotronics 2uf polypropylene bypass caps which I had lying around. I used some ring crimp terminals and stripped off the plastic outer covering for better access and solderability.










    So, how does it sound after the big filter cap replacement? I might be imaging things (and it's obviously impossible to do a direct A/B comparison) but I feel that there is slightly more detail and the sound is tighter and punchier overall - and this was during a low-level listening session last night. Tomorrow I'll get the opportunity to open the taps a bit and see how it performs. The amp sounds even more refined than it previously did. Definitely no audible adverse impacts upon sound quality as a result of moving from 12000uf to 15000uf capacitors. I think this is well worth doing if you're restoring your amp and intend keeping it for many years to come.

    Stage 3 will be the aforementioned binding post and RCA socket upgrade, also fitting a new power cord with Belden 19364 cable (the original stuff is twin core figure 8 cable!) and a nice Martin Kaiser mains plug. I may also rewire some of the smaller internal signal-carrying wire and larger speaker terminal wire too.
    Logitech Squeezebox Touch > audio-gd NFB3(2014) w/ E9018 > fully recapped/restored Sansui AU-X701 and AU-719 > a healthy sprinkling of expectation bias > PMC GB1i speakers > Aurealis and Audio Principe cables

  2. #2
    Join Date: May 2008

    Location: Cricklewood

    Posts: 9,081
    I'm ILOB.

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    Lovelly work and you will be rewarded with another 20 to 30 years of life
    I love old Sansui's but only have one in my system
    Loves anything from Pain of Salvation to Jeff Buckley to Django to Sarasate to Surinder Sandhu to Shawn Lane to Nick Drake to Rush to Beth Hart to Kate Bush to Rodrigo Y Gabriela to The Hellecasters to Dark Sanctury to Ben Harper to Karicus to Dream Theater to Zero Hour to Al DiMeola to Larry Carlton to Derek Trucks to Govt Mule to?

    Humour: One of the few things worth taking seriously

  3. #3
    Join Date: May 2008

    Location: Lancaster(-ish), UK

    Posts: 16,964
    I'm ChrisB.

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    Very nice job, well done.
    There'll always be a soft spot in my heart for Sansui kit.

  4. #4
    Join Date: Feb 2012

    Location: Greece

    Posts: 63
    I'm Panayotis.

    Default

    Well done! Superb! I love vintage audio and audio restoration. Machines of that time had excellent sound and they are timeless. I wish you lots of ours of musical joy! Thanks for sharing!

    Sansui was the Hi-end of that time.

  5. #5
    Join Date: Dec 2008

    Location: Yorks

    Posts: 16,649
    I'm Nobody.

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    2uF bypass ! i use 4.7uF + 0.01uF Bypass for each cap that size..

  6. #6
    Join Date: Dec 2011

    Location: Sydney, Australia

    Posts: 142
    I'm Pete.

    Default

    Thanks for the comments gents!

    Quote Originally Posted by F307 View Post
    2uF bypass ! i use 4.7uF + 0.01uF Bypass for each cap that size..
    Yeah, I was contemplating something along those lines, but decided to stick with the values that Sansui used from the factory (they fitted 2.2uf bypass caps to 15000uf caps, so the 2uf is pretty close). I do have a bunch of 0.01uf caps so I can alway try these with the 2uf.

    If I decide to experiment a bit, I also have a big supply of ITT PMC 2R and ITT PMT 2R 4.7uf polypropylene capacitors in a beige-coloured moulded plastic case. These could be good candidates...
    Logitech Squeezebox Touch > audio-gd NFB3(2014) w/ E9018 > fully recapped/restored Sansui AU-X701 and AU-719 > a healthy sprinkling of expectation bias > PMC GB1i speakers > Aurealis and Audio Principe cables

  7. #7
    Join Date: Jan 2009

    Location: Essex

    Posts: 17,888
    I'm openingabottleofwine.

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    Don't apologise for the photographs Pete. We love photos here on AoS, and yours are superb.

    Congratulations on the refurbishment. Your hard work will pay dividends and give you many happy hours of listening pleasure.

    Well done!
    Have you listened to this month's choice in the Album Club?

    Barry

  8. #8
    MartinT Guest

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    Very nice refurbishment and those big Sansuis must give great pride of ownership.

  9. #9
    Join Date: Jan 2012

    Location: Hampshire, England

    Posts: 722
    I'm Martin.

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    Wow, those amps are beautiful - I want one!

    Martin
    Martin

    Source: Sonos CONNECT DAC: Rega DAC Amp: Rega Brio-R Speakers: Neat Motive 2.

    My system photos

  10. #10
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,591
    I'm Simon.

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    When changing the values of bypass caps or attempting multiple bypasses you really should scope them out for ringing, it's all to easy to over do it. They likely sound better because the old caps will have had much higher ESR due to their age.
    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

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