ES9038PRO best I/V op amp

[bohrok2610]

So what. Still useless without the actual study.

 

[Markw4]

I believe Scott posted it exactly because he thought it was useful information.

 

[bohrok2610]

Probably useful to Scott as he has the original study but useless to those who don't have it.

 

[KSTR]

Yes, because ESS9038Pro output is not real "current output" but voltage output with 200 Ohm series resistor.

OK, the Norton vs. Thevenin equivalence

I think real series resistor is unlikely because how could one establish constant voltage across it to avoid distortion from its large voltage coefficient? Clamping the output voltage to a fixed voltage by an I/V would increase distortion rather than lowering it.

 

[KSTR]

That plot always puzzled me. The glitch pairs appear to be systematic in that they happen at some offset at either side of zero crossing and in the glitch direction, but why is there no glitch pair at 40ms?

 

[KSTR]

What I saw after the notch with my AP (top trace is without averaging), for the ES9038q2m of the Khadas Tone Board:

Doesn't look that much similar, notably I see no strong glitches, also indicated by the spectrum:

 

[altor]

I think real series resistor is unlikely

Maybe.

 

[Markw4]

@KSTR I could take a guess about the plot and why it differs from yours, but it would just be a guess.

At least we know Hyperstream modulators are very unusual based on their noise vs DC offset plots. Don't know if there might be some modulator difference between ES9018 and ES9038Q2M. It has also been observed that ESS dac distortion and noise can vary depending on clock frequency. Probably a different opamp in each case too.

 

[greierasul]

сan you insert a full schematic?

😃 I don't know russian laguage, is not my type. For a full schematic see the es9039pro datasheet.

 

[Baka]

Yep, OPA2156 looks quite similar but certainly not identical to OPA1656, key difference is dual (NMOS and PMOS) input stage, rail-to-rail input whereas the OPA1656 is NMOS only. The rest of the design might be exactly identical (2nd stage and output stage).

It still is an excellent OpAmp for Audio..

I am using OPA2156 as the first (preamp) stage in power amplifier section in my NAD M33. Excellent audio quality.