Advice about this choke

[mrevie]

Hi,

I recently discovered this choke for a relatively good price (The C210 model is only ~AUD8 - 2mH at 10A). However, I'm unsure about its suitability for use in a pi filtered power supply. Would it be suitable for use on both the positive and negative rails? Or should it be wired in series and use one per rail? Would wiring in series result in a 4mH total inductance or does the 2mH figure refer to both coils?

I've recently done some reading about common-mode chokes - is this a common mode choke?

Sorry about the newbish questions - I'm still relatively new to the amplifier contruction scene. I've built a few kits and spend my time endlessly reading and am now attempting to experiment with my own designs.

Thanks in advance!

Steve.

[pjp]

Using my amazing detective skillz, and a little help from google: Roxburgh EMC | Passives | EMC, RFI and Surge Protection | Inductor Through Hole | Inductors: Suppression |C210

To answer your questions: no, no, no, in series you get 4mH but not 10A maybe a few mA.
yes.

protip: In a common mode choke the magnetic fields of the two windings cancel each other out, giving you that awesome 10A rating. If you use the choke any other way, the core will saturate.

[mrevie]

Gah. That's a pain. Large inductors are so very, very expensive.

Thanks for the help pjp!

[mrevie]

Hmm. I'm really having difficulty sourcing inductors for power supplies. Does anyone have any suggestions?

[Captn Dave]

I'm a something of noob at this myself but I have a couple of observations. I'm sure someone will call me on it if I miss the point.

Are you sure you want to use an inductor? A pi filtered power supply can be made for less with large caps which are cheap in comparison to iron. Have you discovered Duncan Amps PSUII power supply design software? You can experiment with CRC power supplies and compare them to CRC types.

If you are using a tube rectifier, then there can be some advantage to using an inductor but it doesn't sound like you are so I'll pass on that discussion.

[woody]

Like Captin Dave said you might look at a CRC filter. Nelson Pass is using this type
filter in his Firstwatt amps. Or if you insist on playing with chokes you can use a regular
transformer as a choke I know it's not supposed to work but it does !

[mrevie]

Hmm. A CRC filter would be a much cheaper and easier option, I agree. However, from the reading i've been doing CLC filters are somewhat more desirable as they offer resistance/reactance purely to what you are trying to filter and next to none to DC - albeit they are more expensive.

I've used CRC filters in previous amps i've built - so I was looking to try something different. If not a CLC then a simple regulator.

[Captn Dave]

Originally Posted by mrevie

CLC filters are somewhat more desirable as they offer resistance/reactance purely to what you are trying to filter and next to none to DC

So, I think your point is that you end up with a higher B+ value with a choke than with a resistor for a given ripple value. This can be a good thing or a bad thing, depending on your target value and the transformer you are using. If you have 50 volts to burn, you can burn it across a resistor and save some iron.

As for something different, try building a virtual choke from a LR8N3-g 450 volt regulator and a TIP50. Use plenty of capacitance on the first cap and you will get very low ripple using a modest amount of capacitance on the second. If I could find a cheap PCB for this circuit, and I know they must be out there, I'd use it more often. (If anyone knows of one, please share it with me)