[sdiy] OPA604 anyone?

[René Schmitz]

Antti Huovilainen wrote:
> Actually you just might have...
> If you have say M-Audio Delta 1010, it has a THD of 0.0003%. Certainly 
> good enough to give an educated guess at least.

Well no, I don't.

> Feed -1dBFS sinewave throug a simple gain circuit (with the opamp to be 
> tested) and use resistor attenuator to bring the output gain back to 
> unity. Using FFT analysis (Adobe Audition for example can do this 
> easily), you can check both distortion and noise performance.

Eessentially this is what they have done at BB. If in a more contrieved 
and tricky way. There is a paragraph about the measurement technique in 
the datasheet.
Self appears to have used a more naive approach. Build 3.5x amplifier, 
and measure at the output, which means he will measure extra noise and 
the measurement aparatus is the limit, if I'm not totally off here.
But there is another thing which might account for these differences: 
The amplitude 3.5Vrms vs 7.75Vrms...

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159