[LawnGnome]

I have a SBlive, and I want to try to bypass the cards opamp, so I can go directly to my amp. Can anyone help me do this?

http://www.dearhoney.idv.tw/Museum/C...ve(CT4670).jpg
http://aryarya.net/wassyoi/pcimg/sblivect4670.jpg
http://www25.big.jp/~jam/audiocard/sblive/sbll.jpg

These are pictures to the card I own.

 

[balou]

Opamps have commonly 8 pins. You can see an 8-legged TDA1308 near the headphone out - this is the headphone driving chip (not exactly an opamp, but similar). A quick search with Google on "TDA1308" leads to it's datasheet (first match). On page 6 you can see a reference circuit - which brings bad news, it requires an output coupling cap. So your best choice is to add another completely independent output, or cut the traces of an existing plug and attach your own wires.
From the TDA1308, you should look where the traces are coming from (you can look up the where the input pins are in the datasheet). Then you can just connect directly from the chip preceding the TDA1308 to your new output jack. But beware, maybe there's a filter in there that's needed - you have to check yourself or submit a better picture
If the dac is also dc-coupled, you might need to add some dc blocking caps, but if you're feeding the signal to an amp, you deal with a high input impedance, which means you can use lower value caps, which in turn means high quality polypropylene instead of cheap electrolytics.

I tried to lay out my train of thoughts - I hope it'll serve as a general small tutorial how to bypass an opamp/headphone driver in a sound card

 

[LawnGnome]

This is the pdf for the dac that is used on the rear channel. I want to bypass any amplification on the rear channel.

 

[balou]

um... the TDA1308 is a "Class AB stereo headphone driver" compatible with the standard dual opamp pin out. According to some infos I found, the rear channel DAC is a UDA1330. Have you forgotten the link to the rear channel dac datasheet, or have you meant the TDA1308 by your "This is.."?

So... you want to bypass any amping on the rear channel? I just supposed you wanted to bypass it on the front channel. I'm sorry, but your reply is rather confusing.

 

[LawnGnome]

Quote:

Originally Posted by balou /img/forum/go_quote.gif um... the TDA1308 is a "Class AB stereo headphone driver" compatible with the standard dual opamp pin out. According to some infos I found, the rear channel DAC is a UDA1330. Have you forgotten the link to the rear channel dac datasheet, or have you meant the TDA1308 by your "This is.."? So... you want to bypass any amping on the rear channel? I just supposed you wanted to bypass it on the front channel. I'm sorry, but your reply is rather confusing.

Haha, I'm sorry. Should look closely at my posts when posting late at night.


The Live! uses a phillips DAC on the rear channel which has better performance than the DAC used on the front channel.

However, I think the performance of the DAC might be compromised by the boards amplification of the signal. So I want to bypass it.

I just want to try to eek every last bit of performance from this card, I'm used to volt modding video cards and motherboards, but audio is new to me.

Here is the link I forgot to add.

http://pdf1.alldatasheet.com/datashe...DA1330ATS.html