Sansui AU 555 A

[Claus H]

Hi

Been thinking for some time to do a full recap on my Sansui AU 555 A.

I`ve been looking for the right Cap type to use, and information on this by reading, on this forum and other sites.

There are several post, and different opinions. Since I know that I will keep my AU 555 A, it`s important to me to, have the sound as close to original or even better than now. The price range on the components doesnt matter much, but of course within reason 100 $ or so without shipping is acceptable - Most important is to keep the sound.

Is Elna Silmic II for everything except Output Caps and Power supply cap the way to go ? I would like to use no more than 2 brands.

I will be exchanging the 4 trims on the main board with Bourns multi turn, since my experiance iwth these are good.

Greetings from Denmark.

 

[Hyperion]

There are many choices here and you will get a different answer from each person who responds.

The Elna's are fine - and personally I would try to use Nichicon KG types for the PSU and output capacitors - it is OK to increase the values/voltages of these to 'fill the clamps' if you wish. I you are not sure, ask here when you have made your choices for clarification of any increase selected. (do not increase the values of any other capacitors).

For example if the output capacitors are 2000µF for example, it is not unheard of to increase to 4700µF. As for the PSU capacitors, this is a different story and thought should be given to the increased strain put on the power switch and rectifiers by the proposed increase. The reason for increasing value and voltage is partly for 'how it looks', and partly for performance, you could leave the values the same and 'pad' the (smaller) replacements with foam strip or similar.

Have fun.

 

[Claus H]

Thank you for your reply Hyperion I will take a look on the KG types.

There are 2 x Low leak types on the tone control board - ELNA RN ( orange color ) types, can these be replaced ny normal ELNA Silmic II type, think I read somewhere that it would be ok, because of the technology difference since the 1970 ?

 

[Hyperion]

Regarding low leakage capacitors, this is generally thought to be the case - 'ordinary' capacitors today having similar leakage figures to the 'low leakage' capacitors of old.

However, if it were me I would seek out low leakage replacements - I think Nichicon UKL are one such range of top quality low leakage capacitors. Of course if the value is low enough (less than 3.3µf?) you could replace them with film capacitors.

 

[slimecity]

I just fully recapped my 555a - due to $$$ limitations - I used Panasonic FCs throughout - the results are pretty impressive, this amp sounds fantastic. I also used higher-value powersupply caps than the former ones. I'd also recommend upgrading the rectifier diodes as well, this cleaned-up the sound in my amp.

 

[stereofun]

Hi Claus - greetings from another Dane.....living in the Arizona desert. I recommend beefing up the supply cap and output caps both to 4700. I am pretty sure the rectifier diodes are the same as in the larger 777a that comes stock with a 4700 supply cap, at any rate I have had no issues doing so. For filter/output caps I use cornell dubilier 380 or 381 lx series. Those caps are rock solid and have very good ripple current specs, the added capacitance helps making the 555a produce some surprising low end without strain. For the remaining caps I'd stick to Nichicon UK series. On a recent rebuild, very similar amp, I tried silmic II's in the preamp, including the input coupling caps on the main board. My impression is that this gave the amp a softer mid and high registry - very pleasing sound -, but in turn took away some of the crisp spatial definition that I like about nichicons. Here you may want to consider the other components in the chain.

If the amp produces a decent amount of background hiss, You should replace the signal transistors in the preamp as well - fairchild ksc1845's will work well to reduce the noisefloor and bring out more micro detail.

held og lykke til. Hilsen Thomas

 

[Claus H]

Hi Slimecity and Thomas

Thank you for the reply`s. I replaced the 4 transistor in the EQ board allready because of an AUX problem. I do have some KSC 1845 ready, they are great
If its not to much to ask can you indicate component number on the rectifier, i wonder if I should up the 2200 uF to 4700 uF. ( if you have a full list of everything you are free to share it )

You know Danes are simple people,, so if I could get all these items at Mouser og Digikey it would be great thank you.

Hilsen fra -det knap så varme Nord.

 

[ConradH]

IMO, if you want to keep the same sound, don't change values by much. Don't change anything to film that wasn't film to begin with. I'd also do one small section at a time and spend some time listening before moving on to the next. Otherwise, if you suspect something changed you'll have no easy way to find out what.

Now, being somewhat fearless, and not placing much stock in the "sound" of different capacitors in most locations, I'd just use good quality parts, change things to polypropylene (not polyester) where I could, get rid of noisy transistors and make sure everything was working per the original design.

I could also argue that the amp isn't old enough to warrant a full recap. If it passed a careful visual inspection, caps checked good in-circuit and met all it specs, a recap would be wasted money and carries a certain level of risk.

 

[stereofun]

Here is a link discussing diode replacement for the 555a http://www.audiokarma.org/forums/archive/index.php/t-533780.html

Regarding bigger psu/output caps - it is always an option you can test for yourself following a stock rebuild. All my cap coupled units have been upgraded in these positions and the different was imidiatly apparent, especially with the larger supply cap. Keep in mind this is a single supply, split rail config all sucking from the same resevoir.

In 1972 I would imagine that caps were more expensive ? -certainly a lot bigger, perhaps the production choice of the large caps were based on space available in cabinet and cost as long as they would do the job, rather than being the optimal solution. Guilty of speculating :scratch2:

As for replacing the caps, I firmly believe you should even if they measure at spec. On a recent recap I measured the capacitance on the 40 year old supply cap of an Au-505, convinced it would be limping along. No it was right at spec, 2200, a little over even. Doing what Conrad says, I just did that and the supply board, then tested. The change was more than apparant - it was like a new amp. I did use a 4700 here.

Hilsener fra 25-30 graders varme

 

[Claus H]

Thank you all for the pointers. I will make a list for the components and post them here, before buying them.

Take One board, at a time, and adjust the bias and output, listen and continue step by step. I Will try to explain the differens how I hear it, maybe it Can be of some use for other People in the future.

14 grader idag og sol.

 

[ConradH]

...In 1972 I would imagine that caps were more expensive ? -certainly a lot bigger, perhaps the production choice of the large caps were based on space available in cabinet and cost as long as they would do the job, rather than being the optimal solution. Guilty of speculating :scratch2:...

Actually, the choice in can-style caps was larger, and they were dirt cheap compared to today. The price of replacement PS caps today boggles the mind for some of the larger amps. As for technology, today's stuff is smaller, but performance of the general purpose caps is similar. It's the leaded radials where all the action seems to be, with switching supplies and LED lighting driving size, esr and life. The manufacturers don't seem to have much interest in can caps or axial lead caps. My only caution is that cap design seems to be a trade-off. I've noticed that caps optimized for HF performance and esr can have higher DC leakage current than some newer general purpose types. Apparently nothing comes for free.

To the OP, personally I'd go with what Tom did. Upgrade where it will make a difference. If the sound changes, it will change for the better, and you'll soon get used to it. If reliability can be enhanced, so much the better.

 

[stereofun]

Thanks Conrad for clarifying the cost issue back in the day. Compared to later models like the 517 with its combined supply reservoir of 60K or the Eights 16K I always wondered why these single supply amps would have such small cans in comparison, even at their lower output.

@ Claus: If you dont have a scope - there is an alternative way of adjusting the amps center voltage. Being cap coupled there is no off-set adjustment as in a DC amp. Let us know.

 

[jedlejedi]

Hi, I am recapping a Sansui AU 555A as well. There are a few caps on the PSU: 1 x 2200uF, 1 x 1000uF and 2x470uF. So it looks like a few people have upgraded the 2200uF to 4700uF. What about the other 3? Does it make sense to upgrade them as well?

 

[jedlejedi]

I found the answer to my question here: http://audiokarma.org/forums/index....storation-upgrade-of-a-sansui-au-555a.816754/
Thanks @Leestereo