you asked for it, so here it is.
some values are left blank for you to calculate based on what you have.
nothing is critical, most values are just very common.
regarding caps observe voltage ratings and go higher if you can.
for 33.9VAC use min 50 Volt caps.
higher temp, 105 C instead of 85 C is preferred.
cap multiplier will give you a slow start avoiding speaker thumps.
regarding FETs, use what you have as long as it is powerful enough, min. requirement is IRF610 on a small heatsink, it has to sink some 6 volts at the required current.
the circuit is very flexible and can be adjusted to other uses accordingly.
everything can be assembled on a strip board.
one potential issue, and not only with this circuit, but with any circuit that employs transformers is the Primary AC voltage.
read dangerous.
take extra care and if not sure don't do it, ask for advice.
I use something similar, although SMPS fed instead of transformer to power my DIY Pearl I phono pre, from 48VDC down to 28VDC.
and all my other projects use the same Cx Mx circuit with minor changes.
works great all the time.
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Hi Stanislav,
I hope I do not ask for too much.
I have a similar scenario and do not know which values should I modify in your circuit.
Basically 37v transformer, 48v after rectifier - I would like to drop it to about 24v - similar values to yours. Would you be so kind and share with me your circuit or let me know how to modify your example one?
Thank you in advance,
xbitwise
Basically you work backwards.
if you need 24VDC to power your circuit add 4V for the drop in the CxMx.
that gets you to 28V at the CxMx input.
now, 48V - 28V = 20V
that's 20 Volts that need to be lost in the CRCR filter.
if one channel draws let's say 25mA and you power both channels with a single PSU then total current draw is 50mA (0.05A).
Still with me?
remember Ohm's Law:
I = V / R,
therefore R = V / I
R = 20V / 0.05A = 400 ohm
this is the total resistance needed to drop voltage from 48 to 28V.
important bit here is the power rating of the resistor(s):
P = V x I
or P = (V x V) / R
or P = (I x I) x R
both formulae will give you the same answer:
e.g. 20 x 20 / 400 = 1 Watt
or 0.05 x 0.05 x 400 = 1 W
that is the minimum wattage your resistor can be, very unsustainable
use 3 - 5 W resistors and sleep well.
be prepared to trim some values here and there and have fun.
Mr. Pass pcb boards have RCR filter and all adequate voltages for the plate and filaments.
Simply find SMPS power brick with 24V DC output ~ 1A and plug in with the B1Triode.
Mean Well or Triad brands is a good quality in separate plastic case. Greetings
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