Type of Choke for CLC?

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I've been poking around for a while and can't seem to find a good answer to this, so I'm hoping someone here can provide some insight for me.

I'm building a "First Watt" type modular power supply for F4, M2, AJ, etc. The box will contain my power transformer, rectifiers, a few caps, and a choke on each rail. This will connect to a power jack in the back for the umbilical to the amp. Each amp will have a few more caps, forming a CLC power supply.

What type of inductor is preferred in this case? Air core? Iron core (sledgehammer), or P-core? There is a big difference in price and if there is not much difference in performance, I'd rather go for the cheaper ones.

Thanks!
 
Inductors

I've been poking around for a while and can't seem to find a good answer to this, so I'm hoping someone here can provide some insight for me.

I'm building a "First Watt" type modular power supply for F4, M2, AJ, etc. The box will contain my power transformer, rectifiers, a few caps, and a choke on each rail. This will connect to a power jack in the back for the umbilical to the amp. Each amp will have a few more caps, forming a CLC power supply.

What type of inductor is preferred in this case? Air core? Iron core (sledgehammer), or P-core? There is a big difference in price and if there is not much difference in performance, I'd rather go for the cheaper ones.

Thanks!

Hope that I'm not going to find myself swimming in shark infested waters but here goes...

Current in SE amplifiers will on average be Iq but will at any point in time be a value between zero and 2Iq - so 2Iq is the minimum current rating that you will need for your inductor. If you undersize the inductor and it has a core then the core will saturate (air core being the exception because it has no core to saturate and it's current capability is limited only by the gauge of the wire it is made from). If you have a bit of iron in your inductor then the inductance goes up (so you can make a smaller, cheaper inductor than an equivalent air core).

That's my understanding anyway....
 
Disabled Account
Joined 2002
Hello,
The French did use 200 or 150 my iron core chokes in some their high current class a designs.
If I would ever build one of these amps again I would use the high current rated filament chokes from Lundahl ll1694 or ll2733 depending on the current needed you can put the 2 coils in parallel. I think bbecause of higher my they would filter much better than the average air core coil.
Greetings, Eduard
 
Zen: Thanks for the input.

Eduard: The Lundhal's look nice, but they are a rather expensive option in this application.

Jason: Thanks for the link to the Amveco's on ebay - they look nice, but don't specify a Rdc and with an 8mH rating, I presume the Rdc is high.

I'll probably use these at Madisound (2.25mH, 15ga, 0.16Rdc) since I already need to place a Madisound order.
 
Disabled Account
Joined 2002
Hello,
But the Lundahl are the only ones designed for this option. I have been using them in a few of my gear. With ll2733 the 2 coils in parallel you will get 100 mH THEN you are making a filter.
2,2 mH you can probably measure the result but 100 mH you will say wow. Maybe you should wait a few weeks, I brought some ll2733 for a friend in Vietnam whom is going to use them in his Nelson Pass design.
It has been discussed before.
Sincere greetings from Eduard
 
But the Lundahl are the only ones designed for this option. It has been discussed before.

I'm always curious to know more. The Lundahl chokes sure do look nice, but come at a heavy price penalty. I presume these are the only ones designed for this purpose because they are filament chokes. Also, do you have a link to prior discussion on this topic - I've been poking around both here and the web in general and most of what I have found is for tube amps and Class-D power supplies. Neither of which fit Class-A solid state amps very well...
 
What type of inductor is preferred in this case? Air core? Iron core (sledgehammer), or P-core? There is a big difference in price and if there is not much difference in performance, I'd rather go for the cheaper ones.

If lowest cost is the object then I go for powdered iron toroids and wind them myself. The reason for that shape is being toroidal there's precious little flux leaking out. Powdered iron has a very smooth saturation characteristic, no sudden jumps in effective inductance so its graceful in overload. One disadvantage is that its hard to get high values (by which I mean anything over a few hundred uH) on these, so I don't use just one, rather a CLCLCLC approach.

Slightly more expensive is Sendust - they have a higher mu meaning more inductance is possible in the same size.

Top of the range would be permalloy toroids.

Another option to get much higher inductance in a relatively small volume would be gapped ferrite cores - buy PQ cores and gap them yourself with some layers of transformer tape between the two halves. Ferrite doesn't have the smooth overload characteristic of powdered iron though so correct design becomes more critical and the calculations to work out the number of turns and the gap size are fairly involved.
 
Disabled Account
Joined 2002
Hello,
I am using a tablet to write this message and bad WiFi in hotel so a bit difficult to find out exactly where they are.
But there are some threads in the solid state and in the Pass design ""group"" on this website.
I posted a lot there because people keep using the air coils and I keep telling them to use the LL2733 or the LL1694 but so far without success. Yes I brought them for a Vietnamese friend that I will meet again in 2 weeks but he has been busy with other amps. I told him to arrange a test set up before I arrive because I wanna know what he thinks.
I know Hammond also makes some chokes that can take some current and do have some my but I like the way the Lundahl are constructed, I never had any problems with them being noisy ( even when used with choke input and more than 1A) or interference with circuits near by.
Just buy a pair once and they will serve you all your life.
Just use LL2733 to search in both groups and postings will pop up I guess.
Sincere greetings from Eduard
 
Disabled Account
Joined 2002
Hello,
But with true choke input you will need a transformer with higher output voltage.i had an Hiraga with CLC power supply and my friend still using his Hiraga for over 25 years with similar power supply. A few weeks ago a famous technician told us to try it with a choke input using a so called swinging choke but that one has to made to measure. So would be more expensive than the ll2733
Sincere greetings from Eduard
 
Disabled Account
Joined 2002
Hello,
Recommended current for ll2733 is 3,4 A when used in parallel and it will saturate at 5,4 A but that is with 60 volts rms. One website in Germany writes that if 60 volts is lower which will be . Current can be considerable higher so I am sure 4A will be ok in a CLC power supply.
Sincere greetings from Eduard
 
Official Court Jester
Joined 2003
Paid Member
Hello,
Recommended current for ll2733 is 3,4 A when used in parallel and it will saturate at 5,4 A but that is with 60 volts rms. One website in Germany writes that if 60 volts is lower which will be . Current can be considerable higher so I am sure 4A will be ok in a CLC power supply.
Sincere greetings from Eduard

LL2733 is not dimensioned to cover current range of thirstier FW amps , where you need to deliver 2A + 2A for Iq ......... or certainly on the verge or more than 1A7 , which is max. recommended current through sole coil of LL

-that for case of having common PSU for both channels ;

paying for 4 pcs , having a pair LL2733 per channel ........ would be insane ........ taking in account how much other possibilities are there , many not worse , only better

so ,conclusion what you are doing , or - already did more than few times :

-advertising
-misleading
-not covering all necessary technical angles
 
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