power supply damping in psu d.

[Ianm2]

not much has been alluded to in this, but being a resistor, choke, and capacitor 'network', filter, etc., power supplies ring, oscillate, etc.

So I thought I would set the ball rolling,

using the diyhifi supply billie psu ( this amplifier is so good, its practically a textbook design, everything is pretty near perfect, although still room to change bits) for starters, here are the specs.:

mains tx is 415 volts, 80 ohms sec. resistance, use a 5u4 rectifier.

input resistor of 82 ohms.( you can't really alter this too much as it drops or raises voltage, but its good to play to see the effects, making it higher damps the ringing more, but you lose volts, it also delays the ramp up time before the psu 'fills up' with volts.

CLC: values, 100 uf, 80 ohm dcr choke, 8 henries, 100 uf cap.

so its a RC, LC filter with a current load of around 80 milliamps.

also notice something rather odd about this amp, in its prior incarnation, the series resistor, the mains tx secondary, the choke, and in fact the output transformer primary(thin wire, more resistance, less current, more volts than secondary), all have just about the same dc resistance, of around 80 ohms, design or accident??)

now upon startup, we get a bit of 'bounce'.

I wonder what would happen to the sound if we try to make an optimally damped power supply?

There are a few things we can tweak independantly and depandantly viz:

the series resistor ( transformer secondary is fixed)

more resistance gives more damping.

change the henries/dc R of the choke, remember this is largely fixed by the maker.

change the capacitors, better results are had with a lower input capacitor, and higher output one.

It seems as in some other designs on the web, failry good results are had with 20uf input, and 50-100uf output.

You can start 'gently' and reduce by say 20 uf each time, or simply 1/2 each time. It looks better with 50uf on the input at startup.

You want to tick the boxes to the left, either Volts in I-1 which is the current source, or volts in C2, both of which our output 300b valve will 'see' (ignoring the output tx)

I haven't the time to fiddle, but hopefully others will play a little and come up with some conclusions/answers.

Measuring resistances of chokes/trannies is easy, just a dc ohms measurement across the terminals...

Finally, anyone know how I drop in the extra rectifiers section, did it b4 but a different machine running, adn can't recall how I did it? help...

There is a schematic I have drawn, please scuse the triode as a rectifier, the prog. doens't have a diode!!

And I have managed to get an image of this on psu D, note the 'bounces' on the lhs, as of the improper damping.