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Here is the manufacturers’ data on the Panasonic ELF-18D860C choke that Jeff is using in his modified Eico HF-81. See page 2.A few comments. It’s hard to tell, but I would guess the core material to be ferrite, not steel. So it’s likely that the inductance of the coil is not 22 mH at 120 Hz. Even if it were, the impedance of a 22 mH coil at 120 Hz is only 6.28*120*.022 = 16.6 Ohms. Not much.
Notice the ‘Impedance Characteristics’ plot (see page 2 of the attached pdf document) – the impedance peaks at about 200 Khz. This makes sense, given that the coil is designed for use with switching supplies, which typically switch in the 100 – 200 KHz region. Also notice that this choke is intended to be used in the AC lines, NOT after the rectifier (see ‘Circuit Example’). This may imply that the coil will saturate with a few hundred mA of DC current passing through it.
So, this coil will most effective at attenuating 'noise' in the 20 Khz - 2 Mhz region.
Jeff –
How are you connecting the 4 leads of the choke?
Follow Ups:
Dave,I just used one section, one half of the unit. It measures 37 mHY with a digital meter, whatever that means. I'll look to see if I have an extra at that value Dave. Give me 48 hours.
Jeff
jeff,just for kicks, try both sections in series and see what happens.
dave
two things.what exactly do you expect the inductance of this device to be at 120hz and why?
Why does the 120hz behavior even matter. It has never been stated that the alleged benefits from its use has anything to do with ripple frequency.
dave
Well, in theory, 16 Ohms impedance ( Z = 2*pi*f*l). Although when you think about, it better have a really low impedance at 60 HZ because in the intended use, it is placed in series with the line voltage. You wouldn't want it to look like 16 Ohms!I brought the subect up soley to point out that this choke clearly does not have a significant effect at the ripple frequency, so that the observed audio benefits must be due to the high frequency characteristics of the choke. It really isn't transforming a CRC filter into a LCRC filter, at least not in the traditional sense.
small value chokes used on the incoming AC line will reduce high order harmonics created from switch mode supplies/diode conduction spikes.I didn't bother to look at the data sheet. I just happen to be involved/concerned with reduction of odd order harmonics in power distribution systems.
Russ
That's what they are designed to do. However, when used as a filter choke in a DC supply, I really don't know what they will do.
to the 60hz line voltage this device (when wired as intended) should have near zero inductance.To be honest, i have no idea how Jeff is using this device, up until recently i was expecting it to be a traditional steel cored DC-carrying choke. Now that I know it is a common mode device (4 terminal), there are several possible ways to hook it up and it will behave differently depending how you do it.
Jeff.... how exactly did you wire this particular device? If you have an extra I'll gladly measure it to see how it behaves in circuit with your chosen hookup.
dave
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