"We need to move on and use distortion measurements that are perceptually meaningful."

[wynpalmer]

Do you find the Gm moves your designs in a different direction compared to using THD?

Yes. It emphasizes the need to have much lower higher order (for example, ninth) distortion products overall. This is not due solely to the non-linearity inherent in the input stages, but also the action of feedback and the presence of level and load dependent non-linearities in the output stages of the gain blocks, for example.

 

[192kbps]

I'm curious about what measurements the APx555 has and what the next generation AP will look like. The 555 seems to have been launched in 2014. Will a new generation be released in 2024?

 

[617]

Yes. It emphasizes the need to have much lower higher order (for example, ninth) distortion products overall. This is not due solely to the non-linearity inherent in the input stages, but also the action of feedback and the presence of level and load dependent non-linearities in the output stages of the gain blocks, for example.

Right and it appears that the reason for this is that despite low level, their distance from the fundamental makes them less prone to masking.

Does the high gain of a phono stage make minimizing these harmonics challenging?

 

[wynpalmer]

Right and it appears that the reason for this is that despite low level, their distance from the fundamental makes them less prone to masking.
View attachment 316370
Does the high gain of a phono stage make minimizing these harmonics challenging?

Yes, but careful design of the implementation of the pole-zero constellation, the use of very high and frequency independent levels of negative feedback, the use of highly linear caps and resistors and control of load impedances makes it doable, even for LOMC use.

 

[Ra1zel]

Frequency response is by far more sound determining than non-linear distortion.

I would like to add that frequency response consists not only of magnitude but also phase.

There is definitely not enough attention focused on the whole frequency response

 

[solderdude]

For speakers yes, for headphones not so much.
Frequency and phase both fall under linear distortion and an be corrected.

 

[NTK]

I would like to add that frequency response consists not only of magnitude but also phase.

There is definitely not enough attention focused on the whole frequency response

May be because Blauert and Laws found this out 40+ years ago?

Group delay distortions in electroacoustical systems

Group delay distortions in electroacoustical systems

www.academia.edu

 

[JSmith]

The 555 seems to have been launched in 2014

APx555B revision circa Dec 2018;

https://audioxpress.com/files/attachment/2707

JSmith