asus stxII with sparkos discrete opamps

I was just indicating that a slow slew rate may not reduce as much treble clarity as much when in I/V because it's responding to straight line square waveforms.

That being said, yes, a slow slew rate will ultimately result in poor treble. It's slowing down the waveforms so the midrange will get thicker and bass will get thicker/warmer. However, if you slow it down too much, it gets too warm and messy. There's no clarity or "separation of instruments".



I think you still have to have a minimum slew rate in audio.  However, you don't want a fast slew rate for I/V position.  The buffer/output stage can have a high slew rate, though.  I think the OPA827 is an excellent I/V op amp.  You could also try OPA2132 if you wanted to for I/V op amp.  They are relatively cheap at about $12 each from digikey (get the OPA2132P model).  The OPA2132 is the most popular op amp to be used for I/V position.  Even my Krell S1200U home theater processor uses opa2132 for I/V, but it has it's own fully discrete Class A output stages.

For output, if you wanted more clarity you could try Burson V6 Vivid.  Slew rate is around 40V/us.  (somewhere between 36 and 49).

However, your new OPA827 probably need to be burned in some.

Hi Johnny,

Based on our conversation, I have gone back to try different opamps for I/V in my reference modified DAC. The OPA827 appears to be the best in this position due to the slower slew rate when compared to my other reference op amps. However, when I use OPA827 in the output buffer, the sound actually slows down some. It’s not as clean/clear and doesn’t have as much attach or high frequency resolution. I found putting Burson V6 Vivid in the output buffer really helped in this case. The V6 Vivid is definitely better than OPA827 for output buffer. It is much cleaner and clearer. Midrange and high frequencies are faster and better represented. I don’t know how you are liking your current sound, but you might try getting a couple V6 Vivid for your output stage on the STX.

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Just a thought.

Hi. Thanks for the suggestion of the bursons. I will keep them very much in mind.
Do you know of any opamps with a very high gain. My soundcard is 7.1 and the bass output is a little on the low side so want to boost it without having to resort to eq, thought changing the opamp for the bass channel may help with this boosting.
Thanks.

The Xonar Essence STX is a 2-channel audio card, unless you have the model with the 6 channel extension card that has 6 RCA analog outputs.  Do you have this extension card?

That being said, the extension card really doesn't have good power supply capacitors.  Technically speaking, the "gain" of op amps is defined by the negative feedback circuit.  However, it is said that the Sparkos op amps have the most "perceived" gain.  They don't work well in your situation, however.   You could try using one of the OPA827 op amps for the sub channel I/V.  You could also try buying a OPA2132P from digikey.  They are $11.51 each.  Digikey part number is OPA2132P-ND.  They have a slower slew rate of 20V/us and may give a fuller waveform for bass.  I would suggest buying a few for the bass I/V and output buffer.