K&K Audio / Lundahl Transformers

Welcome! Need support, you got it. Or share youe ideas and experiences.

Return to K&K Audio / Lundahl Transformers


Message Sort: Post Order or Asylum Reverse Threaded

How to connect LL2733 for choke input

46.67.224.5

Posted on November 6, 2016 at 13:02:57
vbenonisen
Audiophile

Posts: 103
Joined: November 20, 2010
I've read the paper on the Lunddahl LL2733 chokes where 3 different connections are suggested. One of them are called "serial connection for improved common mode rejection". The example shows a CLC setup, but is it possible to get the same "improved common" mode rejection in a choke input PSU - and if so - how do I connect it?

 

Hide full thread outline!
    ...
RE: How to connect LL2733 for choke input, posted on November 6, 2016 at 15:42:09
KevinC
Manufacturer

Posts: 2911
Location: NC
Joined: April 19, 2001
It is possible. Looking at the bottom diagram on the data sheet, "remove" the capacitor that follows the rectifier to give you a choke input diagram. Connect the audio circuit ground to the - terminal of the capacitor following the choke and the high voltage supply + to the + terminal of that same capacitor.

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: How to connect LL2733 for choke input, posted on November 6, 2016 at 16:38:44
vbenonisen
Audiophile

Posts: 103
Joined: November 20, 2010
Great! Thank you.

 

RE: How to connect LL2733 for choke input, posted on November 7, 2016 at 08:03:22
JKT
Audiophile

Posts: 471
Location: Midwest
Joined: November 26, 2002
You might still consider using a small value film cap after the rectifiers. There will be a short window in every AC cycle where the rectifiers are not conducting. As the magnetic field in the choke collapses it will generate a high voltage spike. A small cap before the choke will help mitigate that issue.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln

 

RE: How to connect LL2733 for choke input, posted on November 7, 2016 at 14:17:52
vbenonisen
Audiophile

Posts: 103
Joined: November 20, 2010
Ok, Thank you. Good to know. Tried to model it with PSU Designer II, but it didn't work out. How small should it be?

 

RE: How to connect LL2733 for choke input, posted on November 9, 2016 at 15:20:30
JKT
Audiophile

Posts: 471
Location: Midwest
Joined: November 26, 2002
My guess is you'd be looking at 0.2-1.0uF. It will increase the output voltage somewhat and also increase the output impedance of the PS by a small amount. Be sure to use a cap that is rated for high ripple current. Some of my projects that are designs of Kevin's use a Gentech 1.0uF cap that he favors and the big mono-blocks with a 600V B+ use 850V rated GE 0.68uF caps. Morgan Jones 4th ed. has a graph that illustrates the change in voltage and output impedance with different cap values.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln

 

Page processed in 0.020 seconds.