BK201
Horns!
I've mentioned this a few times on the forum so here it is.
Inspired by the prevalent X-Fi mods at head-fi and others I adapted it to the Audigy 2 ZS
OK guess I should state this.
Perform all modifications at your own risk! I take no responsibility for broken cards and make no guarantee this information is correct!
now thats done...
First things first, replacing the stock opamps, they are terrible! I used National LM4562 dual opamps, there are four of them to make up all 8 channels (7.1 sound). They are labeled 1,2,3 and 4 in the diagram below.
http://img258.imageshack.us/img258/4936/audigy2zsmarkuplc1.jpg
Opamp 1 is for the front left and right channels, only this needs to be replaced for stereo operation.
Next order of business, coupling caps. Each opamp has four caps, circled in groups and labeled as C1, C2... in the diagram above. These block DC between the opamp and DAC. There are no coupling between the opamp and final output. I removed and shorted these.
With no coupling of course, lots of DC at the output. Heres where those lines labeled 1 through 8 come in. Each of the 8 channels has 2 transistors right at the output used for muting during computer startup/shutdown. We don't want any sticking transistors in our signal path! Out they come. They can be shorted like so...
But wait! What happened to coupling caps you say? This is a perfect place for them before the output! I soldered in a 4.7uF Jantzen Z-standard polypropylene cap to bridge each of the above labeled connections. So now we have 0mV DC offset! (as apposed to the ~30mV DC measured on a stock card)
Moving along to power, I replaced the main power filter cap (as labeled in diagram) with a panasonic FC 16V 2200uF. This is the main power filter for the card, some people claim it improved bass but I thinks thats BS. Its mostly for the digital side of things, more of a 'why not?' replace it kinda thing. I think it can help resolve popping and clicking issues some people have with the card.
I also replaced the caps labeled as C5 and C6 which I believe are the front stereo opamp and votage regulator power supply caps, respectively. I just used some high uF similar voltage caps I had leftover.
The opamp I have marked "in" on the diagram is responsible for the microphone input amplification. I don't use this so I left it as is.
Finished things off with a EMI shield made out of an anti-static bag.
This is as far as I've gone so far, It's been an ongoing project, adding a little at a time, tweaking, listening.
The caps are all of a really crappy brand, recapping the whole thing would be a good idea, as would replacing most components. Creative under engineered the thing pretty severely, lots of room for rebuilding some of the circuits. But the line has to be drawn somewhere.
I think I've reached the point of diminishing returns at this point, as for the sound... WOW, much better!
I could throw lots of adjectives at you but just take my word for it, simply better in ever aspect. 
Most difference came from opamp upgrade and coupling caps.
So far its the best digital source I've heard, which is a very short list and doesn't include anything remotely high end.
I'll leave you with some blury pics from my POS cheapo camera
Inspired by the prevalent X-Fi mods at head-fi and others I adapted it to the Audigy 2 ZS
OK guess I should state this.
Perform all modifications at your own risk! I take no responsibility for broken cards and make no guarantee this information is correct!
now thats done...
First things first, replacing the stock opamps, they are terrible! I used National LM4562 dual opamps, there are four of them to make up all 8 channels (7.1 sound). They are labeled 1,2,3 and 4 in the diagram below.
http://img258.imageshack.us/img258/4936/audigy2zsmarkuplc1.jpg
Opamp 1 is for the front left and right channels, only this needs to be replaced for stereo operation.
Next order of business, coupling caps. Each opamp has four caps, circled in groups and labeled as C1, C2... in the diagram above. These block DC between the opamp and DAC. There are no coupling between the opamp and final output. I removed and shorted these.
With no coupling of course, lots of DC at the output. Heres where those lines labeled 1 through 8 come in. Each of the 8 channels has 2 transistors right at the output used for muting during computer startup/shutdown. We don't want any sticking transistors in our signal path! Out they come. They can be shorted like so...
But wait! What happened to coupling caps you say? This is a perfect place for them before the output! I soldered in a 4.7uF Jantzen Z-standard polypropylene cap to bridge each of the above labeled connections. So now we have 0mV DC offset! (as apposed to the ~30mV DC measured on a stock card)
Moving along to power, I replaced the main power filter cap (as labeled in diagram) with a panasonic FC 16V 2200uF. This is the main power filter for the card, some people claim it improved bass but I thinks thats BS. Its mostly for the digital side of things, more of a 'why not?' replace it kinda thing. I think it can help resolve popping and clicking issues some people have with the card.
I also replaced the caps labeled as C5 and C6 which I believe are the front stereo opamp and votage regulator power supply caps, respectively. I just used some high uF similar voltage caps I had leftover.
The opamp I have marked "in" on the diagram is responsible for the microphone input amplification. I don't use this so I left it as is.
Finished things off with a EMI shield made out of an anti-static bag.
This is as far as I've gone so far, It's been an ongoing project, adding a little at a time, tweaking, listening.
The caps are all of a really crappy brand, recapping the whole thing would be a good idea, as would replacing most components. Creative under engineered the thing pretty severely, lots of room for rebuilding some of the circuits. But the line has to be drawn somewhere.
I think I've reached the point of diminishing returns at this point, as for the sound... WOW, much better!
I could throw lots of adjectives at you but just take my word for it, simply better in ever aspect. Most difference came from opamp upgrade and coupling caps.So far its the best digital source I've heard, which is a very short list and doesn't include anything remotely high end.
I'll leave you with some blury pics from my POS cheapo camera
Although I did work on some gear that did have DIPs surface-mounted too - nightmares, I tell ya. the pins had to be bent to about 30 degrees out and shortened to fit on the pads. Nasty stuff... 
I have some 420uf 16v I pulled off a pc board so im gonna use thos as cap replacements..
