Lundahl Power Supply Chokes
Introduction All Lundahl products are based on their double coil (symmetrical) C-Core technology. Also the chokes. This means you have always two coils available. These you can wire in three ways:
NOTE: for For small power supplies with very low hum requirements, such as in pre-amps, you can use plate chokes like LL1667/25 as power supply chokes, they are qualified for this use as well. In the table (below) you see some of the plate chokes listed. You will get extremely high inductance that way. This allow you to work with less big capacitors, and in that way reduce capacitor charge peaks which are responsible for hum radiation. The relatively high DC resistance will however give not much voltage drop, since you work are low current. Even the DC resistance is good, since it is an additional stabilizer element, and also it is helpfully at start up when capacitors are still empty. Then again with higher current versions such as 50mA and more, you will see the DC resistance gets lower. All together the below table shows a very harmonic family of products.
In the double coil configuration, one coil is in the positive lead to the second capacitor, and one on the ground lead to the second capacitor. This will give lowest field radiation coming from the choke. Such good results can not be achieved with lower cost E-Core chokes, and the Lundahl double coil chokes are a major step into the direction of a really hum-free amplifier. The data sheets gives a good diagram of how to connect a double coil choke, using it's full features and get best noise rejection from it. (check for instance here, all at the bottom of the last page). Of course, it is still possible to use them as a single coil also. Overview of types
SOME DESIGN RULES FOR A HUM-FREE TUBE RECTIFIER CIRCUIT
Standard circuit diagram, with well defined earth point. In this circuit diagram the primary Capacitor is C1, the secondary Capacitor is C2.
Standard circuit diagram, with improved Common Mode rejection. In this circuit diagram the primary Capacitor is C1, the secondary Capacitor is C2.
Emission Labs Application Note about improved CMR Coil connection - CLICK HERE With High Voltage power supplies, the best results are always coming from a large choke. This has many times more effect than using large capacitors.
a) The CHOKE b) The SECONDARY Capacitor c) there is no c;) Subcribe or unsubscribe our Mailing List Copyright © JAC Music. All Rights Reserved. (Last updated: 02-Jan-2012 14:05 ) |
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