Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

---

[ Follow Ups ] Thread: [ Display  All  Email ] [ Tweakers' Asylum ]

---

[ Alert Moderator ] [ Edit ] [ Delete ]

---

Re: Practical Choke filters for power supply (Solid State)

Posted by Elso Kwak on June 10, 2001 at 05:13:27

In Reply to: how much can solid state amps be improved by using CLC filtering? posted by freddyi on June 9, 2001 at 22:30:09:

Hi Freddy,
My interest for choke filters in the power supply was arosen by the big claims by Mark Levinson and Tom Colangelo for the choke input in the Cello's power supply. In the book Transistor Circuit Techniques by G.J.Ritchie (Chapman & Hall) I found the circuit for a choke input filter i.e. a choke between the rectifier and the filter cap. For a supply of 20V and 0.5 A you end up with a minimum value for the choke of 40 mH (that is 40 milliHenry). Considering the current that is going through the choke it is a rather unpractical value.
So I experimented somewhat and decided to do a simple lowpass filter as used in a loudspeaker crossover. I placed the choke between the first supply cap and a second additional cap of the same value. I used a choke of 22mH and the caps are 4700 mufarad. For a dual supply say +/- 15 V you need four caps and two chokes. The nice thing is the ripple voltage is reduced by a factor 10. The choke I used is from Intertechnik Germany;. part#1340984 has a DCresistance of 4.26 Ohm and is about 6 $. The voltage drop is not too large. It is not a air coil but a 'Corobar' coil probably iron dust.
Later I found out Nelson Pass uses the same Pi-type filter in his power amps, with a 2.2 mH choke. I used the 2.5 mH choke from my Klipschorns crossover in the Ampzilla power amp.(Laminated iron core)
With the Ampzilla a heard a significant improvement in sound.{The Ampzilla does not use any active supply regulation}. With the preamp I did not hear a improvement in sound but I retained the choke because the hum is much lower with MC-phono. I do not use preregulation in my preamp as I found the Jung regulators sounded better that way. There is also a thread of me on powersupply's some time ago; could find it right now.
If you insist on using AIR coils you end up with boat anchors indeed, if you want a reasonable low DC resistance!
I hope my post clarifies the matter.
ELSO

• http://www.intertechnik.de

This post is made possible by the generous support of people like you and our sponsors:

VH Audio

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---