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smsl 1955+ DAC....opamp eatting monster
Jul 21, 2013 at 11:10 AM Post #16 of 37
Hey, I thought I did something wrong by putting a discrete opamp on it, but like you said: it is eating opamps. I have tried several and they all went south. :mad:
 
Aug 3, 2013 at 7:04 AM Post #17 of 37
When mine broke I did change the 2 identical op amps. The dac seemed to work for few minutes and then started to distort sound again.
 
And I didn't quite understand what the cause of this problem was in fuens (#4) reply which he got from the seller or manufacturer. One of the capacitors? The no name blue 3300uf one maybe or the purple Sanyo labeled ones? I bought mine in dec 2012 so it could be relevant.
 
Thanks for any input you can give.
 
Aug 4, 2013 at 1:53 AM Post #18 of 37
My unit was defective on arrival. 7.5db channel imbalance. Currently awaiting an exchange. Fwiw, it sounded pretty good using an external psu. The stock wallwart is garbage.
 
Aug 4, 2013 at 4:58 AM Post #19 of 37
Hi mates
My knowledge is, some units has a defect (how they said, the last december had a problem with a defective Sanyo capacitors), and a lot of ones have problems with his power supply unit.
Try to use another psu.
If not, try contact with the seller for the guaranty, and explain the situation (in concrete for the date of buy and the matter of Sanyo capacitors)
Best wishes.
I'm waiting forward
 
P.D.(my SD 1995 still work perfectly, clear and detailed. I bought in april.)
 
I hope you understand me, my english is not good :p
 
Aug 4, 2013 at 6:01 AM Post #20 of 37
Hi fuens, thanks for your reply. No sense in trying to warranty it as its so expensive to post it back I can almost buy a new one for the same money. And I am not sure if I anymore have the original blown op amps left either.
 
Its quite inexpensive to try to repair it. I have 2 purple Sanyo caps on it, maybe I will test and change them next and see what happens.
 
EDIT: tried with a another power supply. The result is the same: sound is very silent and there is a very high pitch sound on top of everything. Now it doesn't distort sound like it did few months ago when it originally broke.
 
Aug 5, 2013 at 11:24 AM Post #21 of 37
Update: I today replaced the Sanyos with Nichicon KA -series with same values. I also replaced the big 20V 3300uf one just because it looked cheap, didn't find 20V 3300uf so I used 25V 3300uf. And I replaced the op amps with BB 2134s and TI 5532. And I also used a new power supply. Now it plays music again and sounds pretty good! :) I hope it will last. If it does I will try upgrading the 5532 too.
 
I also ran the Sanyos and Nichicons in my cap tester. the 47uf Sanyo came out 22uf, the 330uf Sanyo was 400+uf. Nichicons were spot on to their rating.
 
Sanyos out, Nichicons in: http://i43.tinypic.com/11bnqqd.jpg
Also the big one changed: http://i40.tinypic.com/b6rl8h.jpg
Test run: http://i40.tinypic.com/p25oj.jpg
 
Aug 6, 2013 at 5:17 PM Post #23 of 37
On this forum the people is talking about op amp combinations.
Also talking about replace different caps
 
http://www.htforum.com/vb/showthread.php/190740-troca-de-OpAmp-(DAC-SMSL-SD-1955-rev-B)-OP275G-algumas-duvidas
 
cheers
 
Aug 6, 2013 at 5:42 PM Post #24 of 37
Yeah, I actually bought the lm4562 to match with the opa2134s. But I first try if it works with the 6.4 times cheaper 5532dd without frying. If ok after couple of weeks ill plug the 4562 in.

To make sure overheating wont be a problem I did some minor cooling mods: I added cooling fins to the op amps with heat conductive glue and then I drilled 3 holes to the top and bottom of the box to allow hot air out and cool air in. Might be unnecessary if indeed the root of the problem is the Sanyos but doesn't hurt either.

Like this:
IMG
 
Aug 7, 2013 at 6:53 AM Post #25 of 37
Could somebody measure the voltages on pins 4 and 8 of the opamps? For me they were +-7.5V. which is too low.
 
I added an external power supply of +-15V for the opamps only and it was much better.
 
see here: http://abload.de/img/img_8355bgfluo.jpg
 
 
It's a really bad design anyway. The signal from the USB input chip is not routed to the DAC directly, but the S/PDIF is taken from the USB chip and sent to the S/PDIF receiver DIR9001. So how can USB be better than S/PDIF input?
 
Aug 7, 2013 at 7:50 AM Post #26 of 37
In all honesty, I reckon you guys should bin this rubbish and get a DIY DAC that is properly made.
 
Aug 7, 2013 at 9:21 AM Post #27 of 37
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