Get nipples.How can I get rid of ?

[catalin gramada]

Thanks Dave.

[J M Fahey]

To add to what Juan said -
The nipple on the grid is when the power tube is turned off so its plate voltage can't follow the input signal. The negative feedback loop tries to make the plate follow the input by driving the grid more negative. When you see the nipple on the grid that power tube is turned off so it is not contributing to the signal at the speaker.

More positive
Itīs trying to drive the power tube harder to supply current it no longer can, because it reached saturation.
I didnīt want to put the full explanation on my first answer because I wanted Catalin to notice he had already answered himself in post #12

As in:

Those nipple appears exactly in the moment when voltage peak into power grids is identical with dc bias voltage. NFB can be applied either in PI tail or into cathode of previous stage equally as it is not any supplementary pole in between. I just checked in both for the same amount with the same results.And is clear a nfb consequence as time without nfb the nipples are not present.

[Dave H]

More positive
Itīs trying to drive the power tube harder to supply current it no longer can, because it reached saturation.

Yes but the more prominent nipple is on the negative peak of the grid signal when the (other) tube is turned off. When the tube is driven to saturation the signal on its grid will be clamped at 0V by grid conduction so the nipple on the positive peak of the grid signal is less prominent.

[J M Fahey]

It may be clamped, less prominent, whatever, but the direction itīs moving is always positive.
Itīs trying (unsuccessfully) to drive power tube harder when it falters.
Itīs the essence of how NFB works.

[Dave H]

It may be clamped, less prominent, whatever, but the direction itīs moving is always positive.
Itīs trying (unsuccessfully) to drive power tube harder when it falters.
Itīs the essence of how NFB works.

OK I'll rephrase it

As the conducting tube approaches saturation NFB becomes ineffective so gain increases causing the grid of the conducting tube to be driven more positive and the grid of the non conducting tube to to be driven more negative.

The nipple occurs as the conducting tube saturates because that is when the NFB breaks down.

[catalin gramada]

Thank You gents. I put it everything in back with 220k leaks and 10k stoppers as didn't noticed any differences from a nipples point of view. Thanks.