IC stacking and bias

[Unlikekurt]

I've read some posts here and there about IC stacking (physically adding ICs in parallel) in circuits such as the Tube Screamer and RAT.
My question is if you stacked ICs would you have to change the Vref voltage divider resistors in order to accommodate for the increase current draw?  Or the Vref to Input resistors?  You would be doubling the bias current, no?

Also, on the same subject but a different theoretical approach.  Let's say you were to run two tube screamer circuits in series from the same power supply and a single Vref setup for both circuits.  In this scenario, again, you would be doubling the bias current.  BUT, as you aren't running the inputs in parallel as in question 1, you would still have 10K from Vref to each input.  In this scenario, again, would you adjust the Vref voltage divider resistor values in response to the increase current draw on the supply node?

[antonis]

IC's bias current is negligible so you'll haven't to double anything..

The only case which should be taken in mind is when you use extremelly small resistors for voltage divider, so the value of bias resistor + IC's input resistance would affect the actual voltage an the node of R1-R2..

If you use Vref for feeding(*)passive elements maybe you have to calculate the overall needed current supply..

*Connecting them to Vref DOESN'T necessary feed them - almost allways they use it as as convenient AC GND..

[ashcat_lt]

In most cases, that bias resistor also pretty much sets the input impedance.  Two of them in parallel would halve the in-Z.  Whether that's a problem depends in the circuit and your tastes.

Luckily, you shouldn't have to use two bias resistors.  Build one stage exactly like the schematic, and connect the +input of the other opamp to the first via straight wire.  Done.