I've seen a number of single-ended designs in old solid state circuit textbooks which employ an inductor as a current source for the output rather than a resistor or active current source.
1. Would anyone be willing to offer an explanation for this approach? Is the idea to present a low impedance at audio frequencies? How would one calculate the appropriate inductor value?
2. As many of the inductor values I've seen in these old circuits are large, would it be possible to use a smaller inductor in series with a lightbuld ala ZenLite?
3. Is the larger inductor in ZenLite (power supply) used because the lightbulb itself is intrinsically noisy or because it presents a low impedance to the power supply.
Your advice is most appreciated. As I've been unable to divine the ansers from the old texts.
Thanks
Mike
1. Would anyone be willing to offer an explanation for this approach? Is the idea to present a low impedance at audio frequencies? How would one calculate the appropriate inductor value?
2. As many of the inductor values I've seen in these old circuits are large, would it be possible to use a smaller inductor in series with a lightbuld ala ZenLite?
3. Is the larger inductor in ZenLite (power supply) used because the lightbulb itself is intrinsically noisy or because it presents a low impedance to the power supply.
Your advice is most appreciated. As I've been unable to divine the ansers from the old texts.
Thanks
Mike
No, we want a high impedance at audio frequencies.
Inductors work great. I have built a Zen with a 1 Henry
air core coil (...alright, a spool of magnet wire) and it had
about 40% efficiency and good low distortion. Of course it
has very low resistance, and so the Zen's original bias
network cannot be used to set the DC current.
As seen in ZV1, light bulbs work pretty well too, but at much
lesser efficiency.
Inductors work great. I have built a Zen with a 1 Henry
air core coil (...alright, a spool of magnet wire) and it had
about 40% efficiency and good low distortion. Of course it
has very low resistance, and so the Zen's original bias
network cannot be used to set the DC current.
As seen in ZV1, light bulbs work pretty well too, but at much
lesser efficiency.
Jocko Homo said:
I had always thought that Lamps run better & longer with DC. Here in Detroit We have Tommy Edison's original Light(Running on DC) still running. There were even quite a few "Add-On" diode sets for consumer lamps a few years back. I also thought that much of the power used in the telecom industry was still AC.
Anyone know about this??
Tall Shadow
Paul:
No, they're audio circuits. I've seen them in very simple demonstration circuits in old transistor books. I guess the idea didn't have much appeal because of the size of the inductor required since, from a cost and weight standpoint, a 1 Henry inductor doesn't offer much over a transformer-coupled output.
Of course, this is of little consequence to us fanatics!
Mike
No, they're audio circuits. I've seen them in very simple demonstration circuits in old transistor books. I guess the idea didn't have much appeal because of the size of the inductor required since, from a cost and weight standpoint, a 1 Henry inductor doesn't offer much over a transformer-coupled output.
Of course, this is of little consequence to us fanatics!
Mike
70% nom voltage = 100 times longer life
LJUSSTYRKA= strenght of light
ARBETSSPÄNNING= work voltage
MÄRKSPÄNNING= mark voltage (nominal)
STRÖM= current
the picture is from www.elfa.com pages with facts
It is on how the lifespan in ordinary lightbulbs correlates to working voltage
LIVSTID= lifespanNelson Pass said:
LJUSSTYRKA= strenght of light
ARBETSSPÄNNING= work voltage
MÄRKSPÄNNING= mark voltage (nominal)
STRÖM= current
the picture is from www.elfa.com pages with facts
It is on how the lifespan in ordinary lightbulbs correlates to working voltage
Light bulbs......
Continuous DC causes a phenomenon called DC notching which eats away at the filament. With AC, the current flow is constantly reversing. If I had my old Collins Radio "Prefered Standard Parts Manual", I could cut & paste that section. But I don't.......
Yes, cutting way back on the current helps.
Those silly "buttons" are half-wave rectifiers (yes, just a diode!) that only serves to eat up light bulbs and generate lots of asymetry on your AC mains. Makes your toroid transformers sing a song all by themselves!
A better way to save light bulbs is to install some form of surge limiter, as the most common failure mode is turn-on transients.
The telephone system runs on -48 V DC.
Jocko
Continuous DC causes a phenomenon called DC notching which eats away at the filament. With AC, the current flow is constantly reversing. If I had my old Collins Radio "Prefered Standard Parts Manual", I could cut & paste that section. But I don't.......
Yes, cutting way back on the current helps.
Those silly "buttons" are half-wave rectifiers (yes, just a diode!) that only serves to eat up light bulbs and generate lots of asymetry on your AC mains. Makes your toroid transformers sing a song all by themselves!
A better way to save light bulbs is to install some form of surge limiter, as the most common failure mode is turn-on transients.
The telephone system runs on -48 V DC.
Jocko
Yay chokes!
For those who hadn't seen it, my still-progressing Class A amp uses chokes in the source follower output stages.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=6338
For those who hadn't seen it, my still-progressing Class A amp uses chokes in the source follower output stages.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=6338
a case for Pjotr
with the data you have provided, we can find out milliHenry of coil
there are at least a couple different formulas,
but I have forgotten them
maybe Pjotr
with his mathematical skill can help us
I do not really know, if there is such a benefit of using such a large airwounded inductor, that it justifies for the size of it.
A powdered iron toroidcore or a ferrite core with a gap
is much smaller.
Maybe someone of these could be used,
resulting in a satisfactory filtering of the supply line.
with the data you have provided, we can find out milliHenry of coil
there are at least a couple different formulas,
but I have forgotten them
maybe Pjotr
with his mathematical skill can help us
I do not really know, if there is such a benefit of using such a large airwounded inductor, that it justifies for the size of it.
A powdered iron toroidcore or a ferrite core with a gap
is much smaller.
Maybe someone of these could be used,
resulting in a satisfactory filtering of the supply line.
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