Newbie Question -- High Current Inductors

Design and use of Chokes for PS, anode and filament use.
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Skip Pack
Posts: 1
Joined: Thu Jan 05, 2006 3:35 pm

Newbie Question -- High Current Inductors

Post by Skip Pack »

I would very much appreciate several pointers:

1. Suggestions for the best documents for learning about inductors for the
non_engineering_enabled DIYer. I suspect we are looking for older
documents from instruction courses or the like. I would like to be better
informed to more fully appreciate discussions here and elswhere, and
move a little further in my ability to analyze schematics, etc.

2. Suggestions about where to find/buy low-voltage, high-current
inductors for experimenting in SS circuits. Chokes mostly, I suppose.
I would consider winding them myself, but I need study and instruction
to not be a hazard and to avoid wandering around totally clueless.

As an indication of my present level, I am comfortable building relaitively
simple amps and preams from schematics, and can puzzle out the simplest
of circuits.

Your suggestions are most welcome.

Skip
dave slagle
Posts: 2038
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
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Post by dave slagle »

Hey skip,
1. Suggestions for the best documents for learning about inductors for the non_engineering_enabled DIYer.
Not really, just get and real all that you can, the more ways you get the info presented, the more sense it starts to make.
2. Suggestions about where to find/buy low-voltage, high-current
inductors for experimenting in SS circuits. Chokes mostly, I suppose.
Well I am working on this idea. The paper design is quite easy, but being able to relate the paper design to reality is where things get subjective.
I would consider winding them myself
Trust me on this one... It is a slippery slope, this is how I stumbled into it and doing it as a money saving effort will never work. I do think that having a "custom choke" service where all of the "guts" could be assembled and the end user could tweek the design is a distinct possibility.

I could do the paper design and somehow get a box with all the needed stuff to assemble and then the end user could tweek the design in circuit and be responsible for the final "finishing" the beauty of this approach is existing cores and bobbins can be reconfigured to fit different needs. I am thinking a price structure based on core size and wire size. Stick with a square stack of EI's and offer a flat price for each core size and a price per turn for bobbins. The problem with winding your own is you essentially need 6 different core sizes and 30-40 different wire types to complete the range. Sure for $200 you could get a spool of #20 wire and 10 inches of EI-100 M-6 lams and wind 9 chokes for $22 each. But when you need a little more current handling it is another $60 for #19 wire, and $30 for some EI-125 lams... And it quickly spirals out of control. Trust me when I say this since I am the poster child for out of control :-)

I think it is possible with a little thought to provide the exact choke you need for the same price as off the shelf devices (ie a hammond) the rub will be you have to put in some time to finish the device to meet your needs. This may take a bit of education but in the end I think we all will win.

Can I have some more info on what you are looking for inductance and current wise?
Your suggestions are most welcome.
Feel free to ask questions and I'll try to answer. I do not have a traditional engineering background which gives me a unique perspective on the this topic since all of my info is empirically based. While I may not be 100% correct on all of my interpretations, at least they are honest and based on experience and the last thing I'll do is parrot some 50 year old text as proof of my design beliefs.

dave
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Post by Guest »

Can I have some more info on what you are looking for inductance and current wise?[
This particular thread was inspired by Nelson Pass's article in Audio
Express discussing a rudimentary jfet power amp. It's also available
on www.passdiy.com. He's using light bulbs as resistive loads, and will
probably follow it with an elaboration using a CCS. I'm just curious
how it would work with a choke load. It looks like you need to allow
for around 3 amps. The impedences are all low (though I don't understand
how you would calculate them) so a few henrys would probably work,
or usefully supplement a resistor upstream. None of the catalogs I have,
(Mouser, Digikey, and some audiophile websites) seem to go there, and I
understand that the resulting chokes would not be small or light.
Somebody probably makes this stuff, but I don't know where. In the diy
sense, I was thinking more of tearing apart a 200 VA isoaltion/stepdown
transformer, for example, and puting a maximal single winding at 18 ga,
and seeing what happens. A little refinement here would probably go a
long ways.

A second area would be chokes to use in the power supplies of amps
like the one I mentioned above, or gainclones, for that matter. I haven't
heard of a 2-5 amp choke input supply, but it might be good, particularly
in the case of an amp like the one above where every mv of ripple might
be audible.

Thanks for the reply, i hope to order a pair of your autoformers soon,
and will follow the threads here with interest.

Skip
dave slagle
Posts: 2038
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
Contact:

Post by dave slagle »

He's using light bulbs as resistive loads, and will
probably follow it with an elaboration using a CCS.
Lightbulbs have always interested me as a load. They are nonlinear so I would expect them to impart some sort of distortion to the sound (I accept that some distortions can be pleasing) For some time I was using some lightbulbs in place of some power resistors in an amp, and even though they were bypassed by a cap, they had a different flavor than the resistors they were substituted for.
I'm just curious how it would work with a choke load.
I would guess quite well.
It looks like you need to allow
for around 3 amps. The impedences are all low (though I don't understand
how you would calculate them) so a few henrys would probably work
I'm not sure either, I would guess they would b eburied in the spec sheet somewhere.
or usefully supplement a resistor upstream.
I don't see a resistor being useful in this situation, 10 ohms would net you 90W of dissipation and a 150mhy choke could do the same at 5W of dissipation. This would explain the lightbulbs, 100W of dissipation in a lightbulb is normal.

None of the catalogs I have,
(Mouser, Digikey, and some audiophile websites) seem to go there, and I
understand that the resulting chokes would not be small or light.
Check hammond, they have some chokes that might fit, but you really need a better idea of what your load really needs to be.
In the diy
sense, I was thinking more of tearing apart a 200 VA isoaltion/stepdown
transformer, for example, and puting a maximal single winding at 18 ga,
and seeing what happens. A little refinement here would probably go a
long ways.
You could also rework one of the hammonds. The empirical approach will get you a long way. If oyu had a core and a bobbin, simply fill it up with wire and place it in circuit. Then you can adjust the gap for the best low frequency response. Adding a little math into it (or using hanna's curves) should get you there a bit quicker. If you come up with a realistic inductance and current, I'll give you a starting point.
A second area would be chokes to use in the power supplies of amps
like the one I mentioned above, or gainclones, for that matter. I haven't
heard of a 2-5 amp choke input supply, but it might be good, particularly
in the case of an amp like the one above where every mv of ripple might
be audible.
Again agreed... It seems most people go straight for the active reg in a to-220 package.

dave
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