discrete regulator supply

[regal]

I have a Borbely audio DAC board that includes a discrete regulator. The problem is its acceptable input voltage is an odd voltage with a relatively small range.
I am unable to find a transformer which has the correct voltage and regulation.

If I supply the discrete regulator with a LM317/LM337 will this negate the advantage of the discrete regulator? And would it make more sense to
Just bypass this on board discrete regulator going this route ?

[AndrewT]

Hi,
a pre-regulator is a good solution.
It lowers the noise being fed to the on board reg giving it an easier job and ensures that the on board stays within it's voltage limits.

[ppa]

Hi regal,

Hi AndrewT,



for using the 317/337 regolators is good adding big and small caps to the outs of these for bypassing, like 1000 uF + 47uF + 0,1 uF, so you are shure there are more advantage without using these regolators.
There are no problems for 317/337 to charge this caps when the power supply state go on, but protection diodes are indispensabile for discharge the caps when the power supply go off.
In the datasheet is shown the schematic with protection diodes.

scuse me for my bad english