Sansui AU-888 - Now What....?

slimecity

Super Member
Have completed a recap and refurb of a 888. It was pretty cheap as it had no knobs...(now I need to find some of those somewhere...!) Did a full recap - including some with Silmics, also replaced all the 8002s and 9002's with MJE340 and 350. The only other non-factory change I made was install a new bridge made from 4 x MUR860s and replaced C737 on the driver boards with a poly cap.

Are there other mods that I can make to this? Would the Kevzep mods for the 999 work on this? How about replacing some of the paralleling ceramic caps on the driver board with polystyrenes (another sucessful 999 mod).

Overall Im pretty impressed that it took a lot less work than refurbing a 999 to make this amp sound this good. Its very neutral and has heaps of "space." Nice detail and its very revealing with recordings. More bottom end than a standard 999 too.
 
It is possible some ceramics could be replaced with polystyrenes. But you need to be careful, some ceramics are positioned for stability where their characteristics and construction are crucially important.

I don't think any of the AU-999 specific mods are applicable here.

As for the knobs - patience and ebay are your friends.

Well done on the trouble free completion of the recap :thmbsp: the AU-888 is a particularly nice Sansui amplifier.
 
Hi Slimecity - congrats on the 888 - that is one amp I really want to get. It is gorgeus. The pre-amp layout is 100% identical to the 999, having said that I haven't studied the voltages nor the individual resistor values. If it seems to have plenty of headroom I wouldn't worry about Kevzep's preamp mod. In the 999 however, it makes a HUGE difference. Here, keep in mind that the 888 is a more modern version of the 999 as it came out later, so likely some adjustments were made across the board.

I still think some mods may work, particular in on the driver boards where the feedback proper and differential pair set-up looks identical - but here it really comes down to what you hear and what sounds right to you. If it sounds like your describe, I wouldn't mess with. Assuming the design indeed is very identical to the 999, you have a design that can be very spatial and detailed, lush, and with an awesome stereo perspective, but on my 999 I really had to tweak it to get it to where I went "wow".

Cheers !
 
Thanks guys - yea like I said earlier - this amp is well worth having a crack at. Pretty amazing sound. I am getting more and more satisfied with it the longer i listen to it. I also had to slave away at my 999 to get it sounding really good, but now Im happy with that amp.

Another potential change to my 888....lets say that I were to consider replacing the 2SA640's with another type...strictly theoretically speaking of course......what is a good modern replacement? The favourite choice in previous years was the ZTX795A - this now seems to be obsolete...any other similar Zetex type anyone can recommend? I also have heaps of 2SA992's lying around but presume that any improvement in audio quality may be negligible with such a change regarding this latter transistor...? cheers!
 
I'll let the noise floor decide. Having said that, four of my amps have 1845 as signals, it always lowers the noise floor, but not quite what the ztx did on the 999, that thing went to the grave. Digikey still has 3000+ and mouser 3000 on order, so not completely obsolete yet.

Strictly on a theoretical level of course :) - you could replace just the differential pair with some matched 795a's, followed by 2 matched emitter metal film resistors and a source resister and then see if it helps. If not you can swap the old parts back. The 795a's have twice the bandwith (50/100 mhz) and are rated at min. 250hfe vs the 640's min.100 - all good metrics for a differential pair.
 
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