Hmmm..what are these diodes doing in the power section?

[JubileeMan 2555]

I was looking over the Diaz Modded Vibroverb schematic and noticed something sorta strange. Here is an image of the regular ab763 schematic of the power section next to the diaz modded one. What do you think all that added mess is doing?

http://www.shelleygrund.com/images/powersection.jpg

[Old Tele man]

...they're "fly-back" diodes, used to clamp OT inductive-fly-back"-voltage that can occur (bad) across the primary windings.

[JubileeMan 2555]

...they're "fly-back" diodes, used to clamp OT inductive-fly-back"-voltage that can occur (bad) across the primary windings.

Is there anything sonic that happens? Or is this just a way to make the amp more rugged?

[John Phillips]

D2 and D3 are reverse flyback voltage spike protection diodes, as OTm said, which help protect the tubes.

D4 and D5 are protection diodes for the bias sensing resistors R72 and R73, to make sure they don't cook if a tube shorts. In normal running none of the diodes does anything, they're just there to prevent nasty things happening to other parts.

[JubileeMan 2555]

Thanks guys! Very cool...