LM338 Adjustable power supply circuit

It's a circuit of adjustable 10-A regulator , with the IC LM338. The first working mode 220V AC current reveled by T1 to 30VAC then rectified by four diodes D1,D2,D3,and D4 and become less than 30VDC. Not enough to be rectified voltage is filtered in the C1 and C2. And CT/ground  should not be used because the voltage needed on the circuit above is only plus and min, so the ground was stopped first. After the voltage is filtered and then go to two IC , for setting the voltage output is on Vr1, the output voltage of 0 to 30 Volt DC regulated.
LM338 regulator power supply
Part List :
R1 = 240R
R2 = 720R
R3 = 120R
Vr1 = 1K trim
D1-D4 = 1N4007
C1 = 6800uF/50V
C2 = 6800uF/50V
C3 = 0,1uF/50V
C4 = 1uF/50V
IC1,2 = LM338
T1 = Stepdown transformer 220V to 30V 10A