Tomo
DIY tube amps can be SHOCKING
- Joined
- Jun 22, 2001
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Hey,
Ok I am posting the calculation for ordinary LM317 regulated PSU.
Assumption: You have adequate post regulator stage.
Lets say 500mA draw
Lets have 4700uF preregulator stage.
2.4 X 500 / 4700 = 0.255V
I get 0.255 V ripple at the end of preregulator stage.
LM317 gives about -80dB rejection.
-80dB = 20 X Log10(V/Vo)
Vo = 0.255 V
V = 25.5 uV after regulation.
For my opamp based amps, current draw is probably 50mA ~ 100mA. Then,
2.4 X 100 / 4700 = 51 mV
2.4 X 50 / 4700 = 25.5 mV
I get 25.5~51 mV at the end of preregulator stage. Then the resulting ripple at the end of regulator stage is:
V = 2.55 uV ~ 5.1 uV
I think it is perfectly nice. However, note that LM317 is not particularly good at regulation at high frequency. I kill this with low pass filter, but if you use Jung's then you should get -80 dB at even at high frequency. (100kHz)
With -100dB which Jung's offer, For 50~100mA draw,
V = 0.25~0.5 uV
Which is even better. That is why I say Jung's full fledged regulator is better.
T
Ok I am posting the calculation for ordinary LM317 regulated PSU.
Assumption: You have adequate post regulator stage.
Lets say 500mA draw
Lets have 4700uF preregulator stage.
2.4 X 500 / 4700 = 0.255V
I get 0.255 V ripple at the end of preregulator stage.
LM317 gives about -80dB rejection.
-80dB = 20 X Log10(V/Vo)
Vo = 0.255 V
V = 25.5 uV after regulation.
For my opamp based amps, current draw is probably 50mA ~ 100mA. Then,
2.4 X 100 / 4700 = 51 mV
2.4 X 50 / 4700 = 25.5 mV
I get 25.5~51 mV at the end of preregulator stage. Then the resulting ripple at the end of regulator stage is:
V = 2.55 uV ~ 5.1 uV
I think it is perfectly nice. However, note that LM317 is not particularly good at regulation at high frequency. I kill this with low pass filter, but if you use Jung's then you should get -80 dB at even at high frequency. (100kHz)
With -100dB which Jung's offer, For 50~100mA draw,
V = 0.25~0.5 uV
Which is even better. That is why I say Jung's full fledged regulator is better.
T