Hi,
as the PSU voltage comes down and the current goes up, then LC supplies (choke input) become uneconomic.
The very big and heavy and most expensive in the range of Musical Fidelity used to use LC (they called it choke regulated) PSU.
Keep in mind that the DCvoltage from the transformer becomes 0.9*Vac instead of 1.4*Vac.
BUT the voltage holds very steady and hum free with small changes in current, until the operating current drops below the regulating current then voltage rises from 0.9 to 1.4 times and ClassAB can end up with 50% overvoltage if designed incorrectly.
as the PSU voltage comes down and the current goes up, then LC supplies (choke input) become uneconomic.
The very big and heavy and most expensive in the range of Musical Fidelity used to use LC (they called it choke regulated) PSU.
Keep in mind that the DCvoltage from the transformer becomes 0.9*Vac instead of 1.4*Vac.
BUT the voltage holds very steady and hum free with small changes in current, until the operating current drops below the regulating current then voltage rises from 0.9 to 1.4 times and ClassAB can end up with 50% overvoltage if designed incorrectly.
As currents go up (or rather, impedances go down), you may need less inductance, so - you could take a fair sized power transformer core and wind relatively few turns of somewhat heavy gauge wire on the bobbin, before stacking the laminations for DC.
Probably one of the easier winding excercises available.
Probably one of the easier winding excercises available.
I wasn't thinking of using it for power amps. mainly for preamps as preamp transformer at higher VA (higher voltage but needing to maintain the same current requirement) is not a lot more expensive.
it is probably uneconomical for power amps. but it seems it would work with the F4 (the amp i'm planning to build) as the manual says it's Class A. I guess it's easy enough to check prices from the local supplier
it is probably uneconomical for power amps. but it seems it would work with the F4 (the amp i'm planning to build) as the manual says it's Class A. I guess it's easy enough to check prices from the local supplier
Hard to tell since the LC only stood for a week or so and then change it to CLC couse rail voltage was to low. the LC was impressive and I would have left it that way. At that time I remember saying next amp I'll do its LC from the start. Now it's time to do the F4 that way.
Both settings do an exceptional regulation and give a sound free of grunge to a point of saying something strange is going on.
Both settings do an exceptional regulation and give a sound free of grunge to a point of saying something strange is going on.
Have a look at this research report by John Atkins:
DC filament supply test
Although this is about heater supplies for tubes, the results are applicable to power supplies for class A solid state amplifiers. Using an LC input filter greatly reduces the charging current in the bridge rectifier.
DC filament supply test
Although this is about heater supplies for tubes, the results are applicable to power supplies for class A solid state amplifiers. Using an LC input filter greatly reduces the charging current in the bridge rectifier.
Using a CLC filter in the power supply should cut down harmonics frm the power supply. Theoretically speaking the L with say R=0.15 ohms and 1mH inductance should drop upper harmonic trash by 20 db or more.
Now can this be an iron ( lamination) core or ferrite core ? Not a closed magnetic loop , just a slug in the core. Since the slug is an open magnetic circuit with a 'very' large airgap , it should be OK at dc (?). Will there be any non linearities at various load currents ?
Cheers.
Now can this be an iron ( lamination) core or ferrite core ? Not a closed magnetic loop , just a slug in the core. Since the slug is an open magnetic circuit with a 'very' large airgap , it should be OK at dc (?). Will there be any non linearities at various load currents ?
Cheers.
Ach! You have touched a raw nerve with me: I've been trying to get a choke-loaded PSU working for some time.
My experience is solid-state diodes cannot perform well with a choke-loaded PSU. The P-N junction collapse as the AC waveform crosses the zero axis creates noise. The faster the diode, the worse the noise is. I've seen my HEXFRED diodes produce nanosecond spikes that are almost impossible to snub.
What happens is the transformer current is somewhat continuous (because of the inductor), and the diodes need to switch when the AC waveform crosses zero. The diode that was conducting abruptly shuts down, and the charge contained in the PN junction is injected into the PSU, plus a little bit of "back current" as the diode is shutting down. This shows up as a very fast spike. The nanosecond pulse is easily transmitted through the choke, and appears on the filtered PSU rails. I haven't found an effective snubber yet. (I am assuming it goes through the choke via the winding capacitance).
Tube rectifiers easily get around this problem: there is no back current when a tube diode stops conducting. Current through a tube can only go one way. There is no junction collapse. This is one of the reasons why tube buffs swear that a tube PSU always sounds better than a diode PSU, and rightly so.
So I'm still stuck with the Zen PSU, even after many years. I want the power factor and low peak currents that a choke-regulated PSU gives me, but I can't fix the diode ringing problem. If you find a fix, let me know.
Here are some previous posts on this subject:
Post about diode ringing
Choke-Loaded PSU Post
My experience is solid-state diodes cannot perform well with a choke-loaded PSU. The P-N junction collapse as the AC waveform crosses the zero axis creates noise. The faster the diode, the worse the noise is. I've seen my HEXFRED diodes produce nanosecond spikes that are almost impossible to snub.
What happens is the transformer current is somewhat continuous (because of the inductor), and the diodes need to switch when the AC waveform crosses zero. The diode that was conducting abruptly shuts down, and the charge contained in the PN junction is injected into the PSU, plus a little bit of "back current" as the diode is shutting down. This shows up as a very fast spike. The nanosecond pulse is easily transmitted through the choke, and appears on the filtered PSU rails. I haven't found an effective snubber yet. (I am assuming it goes through the choke via the winding capacitance).
Tube rectifiers easily get around this problem: there is no back current when a tube diode stops conducting. Current through a tube can only go one way. There is no junction collapse. This is one of the reasons why tube buffs swear that a tube PSU always sounds better than a diode PSU, and rightly so.
So I'm still stuck with the Zen PSU, even after many years. I want the power factor and low peak currents that a choke-regulated PSU gives me, but I can't fix the diode ringing problem. If you find a fix, let me know.
Here are some previous posts on this subject:
Post about diode ringing
Choke-Loaded PSU Post
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