Hi Rafael,
Well done!!
This is pretty much a design right after the book..
For the parts:
The 40uF and 20uF PSU electrolytic capacitors should be 450V types.
The 2uF polyester output capacitor should be 160V
For the other small caps, use 250V types.
All the resistors could be standard ½W types, with the execption of those marked as 1, 2, 5, or 10 W.
Good luck with the project..
Jakob Erland
Gyraf Audio
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The caps after the rectifier should be 500VDC or better.
Last 20 microF can be 400VDC.
Anode and cathode resistors 1W,the 22K resistor on top 2W.
Any other resistor in series with the signal path 1/2 watt.
Voltage rating of the coupling caps 400VDC or higher.
Cheers,
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Frank
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About SS PSU:
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Hi Rafael,
Thanks for putting the schematics up. That is really good for the DIY spirit..
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R6 is for setting the voltage on the LM317 voltage regulator to exactly 48 V. Look at your phantomps.jpg schematic, this is the same circuit: a 10k trimmer could also be used here, as wattage is not that important..
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R11 is a bit more complicated. It drops the rectified DC heater voltage dovn to 6,3V. So the value is dependent on power consumption and transformer voltage.
IF the transformer actually gives (close to) 6,3Vac and only one channel is supplied, the math looks like this:
You're using DC heaters, so you rectify the heater voltage, which gives you a (x sqr2) higher DC voltage:
6.3Vac x 1.4142= 8.91VDC
This would quickly burn out the heaters in the tubes, so we have to reduce this voltage. We'll drop it over a resistor, which also acts as a ripple filter in conjunction with a 6800 uF capacitor.
Voltage to be dropped: 2.61V (8,91V - 6,3V)
The MB1 uses two tubes, a 12AX7 and a 12AU7 (providing we're talking PSU for one channel only!). Both these tubes each has a heater consumption of 300mA at 6,3V so connected in parallel the unit draws 600mA at 6,3V
So we need a drop of 2,61V at 600mA
Ohms Law (R=U/I) tells us that:
R11(Ohm)= 2,61/0,6
R11 = 4,35 Ohm.
Nearest larger value is 4.7 Ohm, which will be fine. We rather want a little lower voltage than a little too high, for tube life.
The Wattage for that resistor. Ohms Law again. 4R7 dropping 2.61V:
P(W)= UxU/R
P=2.61x2.61/4.7
P=6.81/4.7
P= 1.45W
Nearest larger value is 2W (but a larger one can be used):
In conclusion, R11 is 4.7 Ohm, 2W if one channel is driven. Redo the math yourself if you need powersupply for a dual preamp (using 4 tubes, heater current = 1,2A) ...
..good luck with the project..
and Merry X-mas..
Jakob Erland
Gyraf Audio
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