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The Opamp thread
Apr 9, 2010 at 12:09 PM Post #2,491 of 7,383
Quote:

Originally Posted by murrays /img/forum/go_quote.gif
Not really a "drop in": the AD797 is a single and the LM4562 is a dual.


You beat me to it.
icon10.gif
 
Apr 9, 2010 at 6:02 PM Post #2,493 of 7,383
So I am looking at the DIP adapters of my LT1028, where would I need to add what resistors to significantly lower gain of my NG98? It's simply too loud with all of my cans...
 
Apr 9, 2010 at 7:58 PM Post #2,494 of 7,383
Quote:

Originally Posted by buz /img/forum/go_quote.gif
So I am looking at the DIP adapters of my LT1028, where would I need to add what resistors to significantly lower gain of my NG98? It's simply too loud with all of my cans...


That's what I'd like to know as well.
 
Apr 9, 2010 at 9:20 PM Post #2,495 of 7,383
I got a new Sound Blaster X-FI , model number SB0670. It works with same drivers than SB0460 so no problems here even it is OEM card.
Modding was the same than with previous card, but this time I was very careful as I wanted to keep the high performance of this card intact but change the op amp to one that gives me most pleasure, AD8599. It isn't as transparent as AD8066/AD8620/AD8022 but it is the least fatiguing.

Here are some pics of the change:
289g207.jpg


http://i44.tinypic.com/346qp0g.jpg

http://i40.tinypic.com/263ahzs.jpg

http://i40.tinypic.com/oum639.jpg

And testing results:
http://i40.tinypic.com/k1evci.jpg
100 dB SNR
0.0017% THD
those are pure hifi to me!
It seems that AD8599 produces a little different harmonics than NJM4556.

Performance suffered a little, maybe from cold joints in bypassing the decoupling caps. There is no other mods yet.

If you say change AD8599 to something else, I might just do it, but not without good reasoning, the solder pads don't like desoldering! I think I need to get AD4898-2 !! that would be extremely transparent.

ps. Would I benefit from a high quality shielded cable
3.5 mm-> 2 RCA ? From x-fi to PPA V2
 
Apr 10, 2010 at 3:55 PM Post #2,497 of 7,383
Apr 10, 2010 at 3:56 PM Post #2,498 of 7,383
Apr 10, 2010 at 4:22 PM Post #2,499 of 7,383
Apr 10, 2010 at 4:33 PM Post #2,500 of 7,383
hehe, the performance between the AR and BR is negligible at best IMO, even the spec sheet is pretty much identical, plus I wouldnt trust buying BR on ebay anyway
 
Apr 10, 2010 at 7:19 PM Post #2,501 of 7,383
Quote:

Originally Posted by qusp /img/forum/go_quote.gif
hehe, the performance between the AR and BR is negligible at best IMO, even the spec sheet is pretty much identical, plus I wouldnt trust buying BR on ebay anyway


Yes, some same they hear a difference and some say they do not.

@Spacehead, if you did the soldering, it looks pretty good. I like asking other people about their SOIC soldering techniques. Can you give me a run down of how you go about it?
 
Apr 10, 2010 at 10:15 PM Post #2,502 of 7,383
Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif
@Spacehead, if you did the soldering, it looks pretty good. I like asking other people about their SOIC soldering techniques. Can you give me a run down of how you go about it?


Yes that is my work.

To remove the op amp:
I add solder to both sides so that legs get together. Then I alternate between sides heating with iron, I keep fast pace. At the same time I push it from the other side, when solder on both sides is hot enough the soic op amp slides away from the solder pads. When I notice it starts to move I lift it a bit too so that it clears any parts on the pcb.
Then I have a lot of solder on soic pads on PCB. I use solder wick to suck all the excess solder, I make the pads dry from solder. Then I use ethanol to clean the flux and dirt. Then pads are shiny and there is no impurities.
To add a new op amp:
I put some solder on new op amps legs. I might add some solder to soic pads on PCB but it is more difficult to get right amount there so I leave them dry usually.
There should be enough solder now on the op amps legs.
I put it down on soic pads, make sure it is properly aligned, I keep it still with tweezers. I touch legs and pad with iron, then the solder on op amp legs melts and forms a good joint between pad and leg. I need to press the op amp down sometimes a bit so that there won't be large gaps that would need to be filled.
Now it is very easy to solder rest of the legs and pads together. I check with multimeter that there is connection (0 resistance). If there is poor connection I add some solder directly to legs and pads, usually only 0.5 second apply is enough.


This all requires excellent eye sight and good steady hands, I am excited that I can do this. But there is always risk of failure. I have too large soldering iron tip for re-soldering very small SMD parts , 1.2 mm.

BTW. AD8599 hisses on my X-FI. I think I need to change it. Would the AD8620 be stable and good sounding? On X-FI op amps purpose is to convert differential to single ended and filtering.
 
Apr 11, 2010 at 12:46 AM Post #2,503 of 7,383
What was the original op amp on the X-Fi? Have you thoroughly cleaned the area around the SOIC? Might be a bad solder joint. AD8599 hasn't been a problem for me... other than I find it a bit too warm sounding.
 
Apr 11, 2010 at 2:15 AM Post #2,504 of 7,383
Quote:

Originally Posted by 12Bass /img/forum/go_quote.gif
What was the original op amp on the X-Fi? Have you thoroughly cleaned the area around the SOIC? Might be a bad solder joint. AD8599 hasn't been a problem for me... other than I find it a bit too warm sounding.


All my AD8599 seem to hiss a little. Original op amp was NJM4556. I have cleaned it very well IMO, but maybe the denatured ethanol leaves some residue which is conductive.
Joints should be good.

Now I already changed the op amp to AD8620 but it had that hissing too, I wonder what is going on. I hope to get that fixed without failing the card.
 
Apr 11, 2010 at 8:58 AM Post #2,505 of 7,383
Can anyone recommend a replacement for OPA2134 (hence, dual - browndogs won't fit my unit) that has excellent PSRR? My PSU is a wall wart (says regulated, but I doubt it), so trying to hunt down an opamp with the best PSRR.

Additionally, the headphone amp this is for uses a circuit which biases the output heavily into class A - any chips out there which would benefit from this?
 
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