I have built the JSR03 using the LM431 and P-A's recommended parts values, and it works fine, the board is very nice.
I am interested in trying the LM329, which presumably is a quieter reference. Looking at the schematic for the JSR03, it looks like the effective reference voltage using the LM431 is
Vref = 2.5V * (R4/(R5||R6) = 7.41V
using R4 = 10K, R5 = 5.6K and R6 =56K as shown in the schematic.
So if I replace the LM431 with the LM329 and remove R4-R6, the reference voltage will be now 6.95V and I will get a slightly different output voltage unless I replace R8 and R9.
Is this correct?
It also looks like if R6 is omitted when using the LM431, the effective reference voltage will then be 6.96V (from the formula above), almost the same as the LM329. Is there any reason not to build it this way, leaving out R6? Then you could get essentially the same output voltage using either LM431, with R4 and R5, or LM329 and omit R4-R6. Does R6 serve any other purpose?
Thanks for any replies!