I followed this article from EmissionLabs and tried using recommended option 5 (scroll to the very bottom of the page) in a PP amp with Lundahl LL1673. I ended up with a significant buzz that showed up only when I connected inputs of both channels directly or through a preamp. The buzz disappeared completely after I connected both coils in a serial connection as per option 4 in this article.
I keep researching this subject and just came across another article. It's in Russian but you can translate it with Google. I would greatly appreciate any experience/opinions on these two options from this article:
The article claims that its possible to use a a choke in applications with significantly higher current than the choke was designed for due to connecting coils "end-to-end".
I keep researching this subject and just came across another article. It's in Russian but you can translate it with Google. I would greatly appreciate any experience/opinions on these two options from this article:
An externally hosted image should be here but it was not working when we last tested it.
The article claims that its possible to use a a choke in applications with significantly higher current than the choke was designed for due to connecting coils "end-to-end".
An externally hosted image should be here but it was not working when we last tested it.
The cause of hum is clearly in the part of the circuit you didn't show.
About the 2 russian schematics: both are bad. The chokes here can not work as chokes but as lossy transformers, first coil transforms ripple current to the second so they can not show their high impedance. Only resistances and leakage inductance remains. The first is even worse since DC current can make core saturating while in the second one DC excitation is cancelled.
About the 2 russian schematics: both are bad. The chokes here can not work as chokes but as lossy transformers, first coil transforms ripple current to the second so they can not show their high impedance. Only resistances and leakage inductance remains. The first is even worse since DC current can make core saturating while in the second one DC excitation is cancelled.
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IIRC the notes said ripple dropped on the first half of the winding won't be seen on the second half as it is driven from the shunting capacitor and most of the alternating flux will remain. Yet on the other hand the windings are mutually coupled. Does this hold water?
well, this common-mode connection is recommended by Lundahl,
so it should work...
The inductance is the same as in the normal series connection.
i have a LL1673 in my EL83-SE-Amp in this common-mode
connection and it works perfectly, no hum whatsoever.
and the measured ripple voltages match the calculations in PSUDII
...but be sure you have no ground connection before the choke,
cause the potential before and after the choke is not the same.
so it should work...
The inductance is the same as in the normal series connection.
i have a LL1673 in my EL83-SE-Amp in this common-mode
connection and it works perfectly, no hum whatsoever.
and the measured ripple voltages match the calculations in PSUDII
...but be sure you have no ground connection before the choke,
cause the potential before and after the choke is not the same.
That is not the classic common-mode connection, but a re-ordered series connection. It may give a small reduction in common-mode noise due to leakage inductance, so is slightly better than the normal series connection. It is quite different from the auto-transformer connection mentioned in post 1. Can we decide what this thread is about?M_Balou said:
...eh, sorry, my fault, i thought this thread is about that the OPhas a hum-problem with his amp and is asking for help...
... but of course it´s much more fun to discuss some
obscure russian schematics....
and you´re right, the LL1673 is not a common-mode-choke
(...whats "Erbsenzähler" in english ??...)
...i´m out....
My intention was to discuss the best way to utilize double coil choke, like LL1673, not the hum problem. The schematics in the article look very interesting but it's not clear to me if they are reasonable at all. So I was hoping that someone had experience with this.
I think chokes in PSU are used for suppressing the ripple and as a current source.
- The second schematics should probably suppress the ripples very efficiently as the alternating current created by flux in the second coil goes against the remaining ripple current after the cap. I am bad at math and theory, it seems that there should be a combination of L and C tuned for a certain frequency?
- However, this schematic will probably not work as a current source as the DC flux is canceled by the second coil and no energy is stored.
I think chokes in PSU are used for suppressing the ripple and as a current source.
- The second schematics should probably suppress the ripples very efficiently as the alternating current created by flux in the second coil goes against the remaining ripple current after the cap. I am bad at math and theory, it seems that there should be a combination of L and C tuned for a certain frequency?
- However, this schematic will probably not work as a current source as the DC flux is canceled by the second coil and no energy is stored.
As always when I write long the post is lost...
Summary: tuning second capacitor and first coil to resonance can shunt all current on input at a single freq. But at higher harmonic freq the rejection will be much weaker then with normal connection, so I wouldnt say it's better. Harmonic content of ripple is rather high.
Summary: tuning second capacitor and first coil to resonance can shunt all current on input at a single freq. But at higher harmonic freq the rejection will be much weaker then with normal connection, so I wouldnt say it's better. Harmonic content of ripple is rather high.
Don't take too much notice of that EmissionLabs page linked from post 1. They seem to give extra stars for poorer grounding, for a start! They appear not to understand the difference between a common-mode choke, and the separated series choke connection. It could be that page is the source of the confusion we see on this forum from time to time.
I have used a dual bobbin core type inductor, windings in series on each leg of an AC heater supply as a combined ballast, soft start, mains harmonic filter and HF common mode filter. I would probably do the same with a balanced DC supply if I didn't already have a pair.
If it were me I'd look at the standard configurations and see if they look useful, split or not.
I don't know that tuning for the ripple fundamental would always be the best use of the choke, or indeed necessary. Will it work for you in a choke input supply?
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