"The Crocodile"

[proid]

Finally found some free time to put those spectra from opa2156 distortion measurement into a document. There are mistakes for sure, so please open with caution

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This is the distortion of opa1656 alone with gain = +/-1 right?

 

[Shaq888]

OPA2156, but yes, one half of it by itself.

 

[proid]

OPA2156, but yes, one half of it by itself.

Oh, thanks for correcting me. So opamps these days are really good at driving heavy load. I thought that opa1622 is already the best but there are many other opamps have similar performance.

 

[00940]

@Shaq888: thanks a lot for those measurements

@proid: The advantage of the opa1622 for an headphones amp is that it is optimized to drive capacitive loads. The opa1656 isn't and the designer recommended to use an isolation resistor if used as a line or headphones driver.

 

[Shaq888]

No problems!

Yep, 1622 is quite a beast. Have done similar measurements for it in the past, it performed very well. Although the package can be a big turn off for some.

 

[Shaq888]

The massive parallel amp of D. Self was built with 5532's.

How they say, "for sh*ts and giggles"?

 

[DNi]

Reminds me of the boards in a PDP11/34 that our College got in the mid-seventies

 

[wolkegeist]

Hi Shaq, can I use OPA168 for output buffer and OPA1611 for input opamp?

 

[proid]

Hi Shaq888,
Can you help me check this: I follow your psu design, but using LM27313 instead and using power from 5V usb, it work quite well for light load, but with at higher load like 20ma i can hear it start to buzz and at 70ma, it's extremely loud. I upload some picture hope you take a look:
- first picture is the modified schematic, i just remove lc filter at output, and change some component value.
- second picture is the layout.
- third picture is the power supply noise floor without load, it's measured right at the output capacitor
- fourth picture is the power supply noise floor with 70ma load.