Power supply inductors (what specs?)

[Bertie]

I'm just following Kristijans circuit for Aleph 5 power supply which has transformer, bridges, 2 x 47,000uF followed by 3.9mH followed by 2x 22,000uF

Are you saying the caps should be the other way round?

Why are air cores better than ferrite or iron?

[Salas]

Hi Bertie

Yes, the caps the other way around. Small keeps the voltage, coil feeds the big one in a relaxed charging angle.
Non gapped iron cores sound muddy.

Nick

[chris ma]

How do one handle the surge voltage in the CLC arrangement when power off the amp?
Thanks in advance,
Chris

[Salas]

Hi,

Some Rdc in the coil takes good care of the surge voltage as the magnetic field collapses.
Keep the final cap 2x to 3x the capacitance of the one before the inductance. Working voltage in a PSU cap is way lower than what it can handle in a ms. We normally find much higher than V+ rated caps in a Zen's suppply anyway. The market is full of 50,63,80V good caps as needed for class AB PP amps and the like.
I recommend to use a 20uf polyprop cap directly on the source mosfet V+ connection with a dedicated return cable to star earth.
Use 1/3 the thickness of PSU wire for V+ and speaker terminals than the one for PSU earth.
Star earth the amp and speaker on the edge of a 10cm long wire tapped off a -PSU caps star subjunction.

Regards

N.S.

[Bertie]

Do we know electricaly what differance the air / iron / ferrite cores have in a CLC supply application.

I don't doubt you that "iron cores sound muddy" but I was wondering the technical reasoning.

[eLarson]

Originally posted by Bertie
Do we know electricaly what differance the air / iron / ferrite cores have in a CLC supply application.

I don't doubt you that "iron cores sound muddy" but I was wondering the technical reasoning.

I've used really big inductors in a line amp's choke-input PSU (big ol' Hammond 1.5 H chokes) and there hasn't been any trouble at all, sonically speaking. Then again, there isn't a whole lot of current being drawn.

Perhaps in a power amplifier the current is high enough to saturate the core?

Erik

[roddyama]

The effects of core saturation in an inductor are the decrease in inductance (non-linear) and the generation of noise.

Here are 3 links that will tell the whole story from start to finish.
http://ece-www.colorado.edu/~pwrelec.../Ch13slide.pdf
http://www.fairchildsemi.com/an/AB/AB-12.pdf
http://www.cpes.vt.edu/cpespubs/proc...01pdf/6_06.pdf

Rodd Yamas***a

[Salas]

Hi,

Here is my proposed wiring scheme.

Nikos

[Bertie]

Originally posted by roddyama
The effects of core saturation in an inductor are the decrease in inductance (non-linear) and the generation of noise.


Rodd Yamas***a

But at this point in a power supply we're talking about basicaly DC with some AC noise element.

Are we really suggesting that there is so much AC in the form of noise that the core will saturate? Surely not?

Does the differance have something to do with the change of inductance with frequency? This changes dramaticaly but no one ever quotes the inductance at a particular frequency and anything from 2mH up is deemed to be acceptable.

All of this gives me the impression it's not that critical. Also to get an air core inductor of say, 3mH at 100 Hz with DC resistance below 0.5 ohm they end up like a coke can and I've never seen anything like that in any commercial product.

Does anyone know the innerds of the highly rated Musical Fidelity A3CR choke regulated power supply or is that a totaly different type of thing?

[Salas]

Hi,

Musical Fidelity pre amp is the same concept as ours. Filtration of ripple artefacts.
They use CLC PI's with EI core (box transformer type) coils in mono PSUs.
As for metal cores in general, the higher the frequency the easiest the saturation. When we filter 3A of current in a Zen Revisited for instance, we do so because we dont have pure DC in the first place. Ripple current is huge. And its full of HF garbage.
Therefore a non gapped core has its own aural signature.
Tube people know why they pay kBucks for a Tango or Tamura over a plain transformer. Their expensive proprietary cores sound vastly better.
To the contrary Rdc is ok. Check out the cheap speaker coils option as I mentioned in my earlier posts. They are small and effective.

Regards

Nikos