Looking at purchasing a Kinki Studio integrated, I think it uses 1 dual / 4 single op amps. My dac is fairly neutral so wd like to tailor the sound of amp for more warmth. Any suggestions for which op amps to try? TIA
To get more warmth, I reckon you'll need opamps which deliver lower noise in-circuit than those already in your integrated. Without knowing what those devices are, and also what the circuit impedances around them are, it'll be guesswork to suggest substitutions which improve on noise. One I'll guess at is OPA2210 for a low-noise dual.
If you are rolling opamps into an older design, it is paramount to AVOID OSCILLATION. Many new opamp designs are so fast that they are prone to oscillate when used in older layouts. I avoid this by always putting a 100nF X7R cap between the rails right at the opamp, and put 22pF COG caps across the feedback resistor path (pins 1/2, and 6/7 on a 8 pin IC). This will limit the bandwidth to ~ 200KHz (plenty for audio applications) and curb the tendency to oscillate. I also use gold-plated MillMax IC sockets for easy swapping for comparison.
Not generally recommended unless the opamp is unity gain stable. True enough, non-unity gain stable opamps are in the minority but still something to be aware of.
Never before heard such an unusual claim. Have you you reached this conclusion based on experimentation? What is the reasoning behind it?
With resistors it seems to be commonly accepted that the noisier parts do sound warmer.
"....put 22pF COG caps across the feedback resistor path (pins 1/2, and 6/7 on a 8 pin IC). This will limit the bandwidth to ~ 200KHz (plenty for audio applications) and curb the tendency to oscillate. "
"....Not generally recommended unless the opamp is unity gain stable. True enough, non-unity gain stable opamps are in the minority but still something to be aware of."
Please explain the reason for this. The only non-unity-stable opamp I am familiar with is the NE5534. In the datasheet they recommend that if you DO use this opamp in a unity-gain application that you put---yessiree---a 22pf cap in the feedback path.
"....Not generally recommended unless the opamp is unity gain stable. True enough, non-unity gain stable opamps are in the minority but still something to be aware of."
Please explain the reason for this. The only non-unity-stable opamp I am familiar with is the NE5534. In the datasheet they recommend that if you DO use this opamp in a unity-gain application that you put---yessiree---a 22pf cap in the feedback path.
NE5534 has a compensation cap between pin5 and pin8. This needs to be 22pF to make the device unity gain stable.
A few other non-unity gain stable opamps that might be encountered : LT1037, OPA637, LT1028, AD8067.
A few other non-unity gain stable opamps that might be encountered : LT1037, OPA637, LT1028, AD8067.
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Reading anything I can find on 2210 and 2228 plus the single channel versions
So I shortlisted these, Muses 01/02/03 and more expensive discrete offerings, Sparkos etc