Dual bias mod question

[joesatch]

Can someone tell me why they built two complete bias circuits in this layout instead of separating the grid leaks and feeding with separate pots from a single negative bias source? Nik does this with all his dual bias amps. Why?

[sluckey]

Builder's choice.

[joesatch]

So i'm good going this route?

[sluckey]

I like this...

[tubeswell]

I like this...

Or maybe this?

[Willabe]

I like this...

Or maybe this?

Why the 2 extra diodes? 

For isolation of the 2 -bias adjust circuits? 

[tubeswell]

I like this...

Or maybe this?

Why the 2 extra diodes? 

For isolation of the 2 -bias adjust circuits?

Yes I probably should have finished that more with another cap to ground at the 1k

[sluckey]

No need for isolation diodes. There is no interaction between the pots.

[astronomicum]

How about adding some resistors to protect in case of wiper failure (across terminals 1 and 2 on each of the pots). 680K perhaps.