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In Reply to: I'm in the same boat posted by Ray Moth on January 29, 2004 at 00:17:39:
470uF after just a 3 0Ohm resistor....hopefully someoene else will reply....otherwise do as I do..and just try it...Regards,
Bas
Follow Ups:
Bas, The choke is deliberately over-specified at 600mA. The mains tranny HT is nominal 359-0-350v, also rated at 600mA but the amplifier will not need all that juice: probably only 330mA or so. The 6.3v secondary windings can tolerate between them 20 amps but the load (including the 6D22S rectifiers) will only be 12 amps. So, I'm playing safe regarding power supply capacity.I agree with you that I could just try using a resistor instead of a choke and I probably will, but I don't want to wreck the 6D22S by using too high a capacitance so I thought I'd ask first. Actually, I'll probably split the power supply at that point; following the rectifier and 50uF smoothing capacitor, I'll use two 47 ohm resistors, each followed by 220uF smoothing capacitor, one feeding the left channel and the other feeding the right channel.
This is going to be a class A P-P amplifier (EL34s strapped as triodes, about 15W per channel), so power supply "stiffness" (low impedance) is not a prime concern. If it were, I'd probably be using SS rectifiers. Fatbottle is probably right about the noisiness of a resistor-smoothed PS so I should really the choke anyway; but, with the massive power tranny, two big (50W) OPTs and this heavy choke I can hardly lift the chassis. I don't want to do myself an injury! Besides, I'm hoping that any noise in the PS will be largely cancelled out by the fact that every stage in the amp will be balanced, because the design uses push-pull topology throughout.
Rgds,
Ray
Hello Ray,It has been my experience and honest opinion that any "cost cutting or weight curtting" you do in a triode amp's power supply, be it SE, P-P, A1, balanced or whatever, is DIRECTLY heard, with a negative effect, in the final overall performance.
There is no substitute for building the "very best supply you can", if you seek real sonic quality.
A high quality choke employed as the input filter is highly beneficial and should be used for several reasons, but primarily .........because it controls the current waveforms of the diode, versus its voltage waveforms.
Resistances (in place of inductance) in the early stages of a power supply, is IMHO and generally speaking, a far worse choice.
Of course you can elect to compromise your design, but it is helpful to know what is ideal and where you are compromising.
Its your listening experience .......and your choice to live with. But you will spend far more time listening to the final result, than lifting it !!
Jeff Medwin
Fair comment, that's the sort of advice I was seeking. Thanks! I've already planned and drilled the chassis assuming that I will be using the choke, so I'll bite the bullet. Just have to be careful lifting it.
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