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Hello Prasi, i need some help with the calculations. I am going to use the crc power supply with Saan’s PeeCeeBee 4hs. ( 2x40v 300w transformer for each channel). About R2/R’2 etc?
Please help
Thank you in advance
Please help
Thank you in advance
Hello Oracle,
I see that Shaan's PEECEEBEE V4H can deliver about 250W into 4 ohms.
This implies about 8 amps RMS current demand from the amplifier operating at full power.
With this, R2, the CRC resistor (if using a value of 0.1 to 0.15 ohms) needs to be atleast 10 watts rating. If you have no plans to operate the amp at full power all the time, you can use lower power rating for R2.
However, I would suggest you to use 3 nos. of R2 (5 W rating) with a value of 0.33-0.47 ohms piggy backed on top of each other. This would ensure peace of mind and won't result in heating of R2 very much.
Note that at full power(max current demand conditions) , using CRC will lead to a voltage drop of around 1.2V across R2.
Regards
Prasi
2200 ohms 3W.
In the BoM posted in post #811, the third sheet contains the calculation of power ratings for the selected resistor values. You can play around it, to see whats available/suitable to you.
regards
Prasi
Hi prasi,
i will received my CRC power supply PCB soon, i wondering how do you find the value of R2/R2' et R4/R4'? in the BoM you posted we have to enter the value, they are not calculated. Thanks
i will received my CRC power supply PCB soon, i wondering how do you find the value of R2/R2' et R4/R4'? in the BoM you posted we have to enter the value, they are not calculated. Thanks
Prasi, i am going to use 8 X RURG3060 with sk129-63 for each channel. About RS , CS , C2 and the C3,C4, C5, C6
Higher value of R2 will provide more ripple attenuation at the cost of lower headroom (lesser output voltage)and more dissipation in R2. you have to decide the value of R2.
R4 is a bleeder resistor that decides how fast the caps will get discharged after power off. Again you have to decide the value. here is a RC time constant calculator.
Resistor-Capacitor (RC) Time Constant Calculator | DigiKey Electronics
The calculation given in bom for all three resistors R2, R4, R-led help one to determine the power rating to be used.
Remember that this is a universal design. values you use will depend upon your supply voltage, current demand from amplifier and parts available in your parts bin.
regards
Prasi
For any transformer, you have to follow quasimodo procedure for calculation of RS, there is no standard values. In that case, no need to use C3-C6.
here is the quasimodo thread
Simple, no-math transformer snubber using Quasimodo test-jig
If its not possible, use C3-C6 values of 10n😉.
regards
Prasi
further to my post no. 833, here is a handy and visual excel calculator for selection of bleeder resistor by tt-electronics.
regards
prasi
regards
prasi
Hi Prasi,
I'm just trying to understand and I hope I do not bother you with that.
Why do you recommend using a value of 0.1 to 0.15 ohms for R2 in this example ?
Thanks
Hello Hicoco,
If you use higher values in a 250W power amp, the power dissipation and voltage drop across R2, will increase tremendously. Following text gives the example.
R2,ohm..... Power,W ..... Del V R2
0.1 ..... 6.1 ..... 0.8
0.15 ..... 9.1 ..... 1.2
0.22 ..... 13.3 ..... 1.7
0.33 ..... 20.0 ..... 2.6
0.47 ..... 28.4 ..... 3.7
If you use higher values in a 250W power amp, the power dissipation and voltage drop across R2, will increase tremendously. Following text gives the example.
R2,ohm..... Power,W ..... Del V R2
0.1 ..... 6.1 ..... 0.8
0.15 ..... 9.1 ..... 1.2
0.22 ..... 13.3 ..... 1.7
0.33 ..... 20.0 ..... 2.6
0.47 ..... 28.4 ..... 3.7
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