Inductors, Lightbulbs As Current Sources - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th November 2002, 04:53 PM   #1
diyAudio Member
 
Join Date: May 2001
Blog Entries: 5
Default Inductors, Lightbulbs As Current Sources

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
  Reply With Quote
Old 6th November 2002, 05:39 PM   #2
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
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.
  Reply With Quote
Old 8th November 2002, 02:51 PM   #3
diyAudio Member
 
Join Date: May 2001
Blog Entries: 5
Thanks Mr. Pass

I like the spool of magnet wire idea.
  Reply With Quote
Old 8th November 2002, 03:19 PM   #4
Banned
 
Join Date: Apr 2002
Location: Germany, Clausthal
what is magnet wire?
  Reply With Quote
Old 8th November 2002, 03:33 PM   #5
Banned
 
Join Date: Feb 2002
Location: As far from the NOSsers as possible
Light bulbs are used in the telephone industry as current limiting devices. But they do not like contiuous DC being passed through them. Unless you like replacing them frequently.

Jocko
  Reply With Quote
Old 8th November 2002, 04:34 PM   #6
diyAudio Member
 
Join Date: Oct 2002
Location: Royal Oak, MI.
Quote:
Originally posted by Jocko Homo
Light bulbs are used in the telephone industry as current limiting devices. But they do not like contiuous DC being passed through them. Unless you like replacing them frequently.

Jocko
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
  Reply With Quote
Old 8th November 2002, 06:11 PM   #7
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally posted by Jocko Homo
But they do not like contiuous DC being passed through them.
I haven't had any problems, but then I have run them
very much below their ratings.
  Reply With Quote
Old 8th November 2002, 06:23 PM   #8
paulb is offline paulb  Canada
diyAudio Member
 
Join Date: Jun 2001
Location: Calgary
Default Re: Inductors, Lightbulbs As Current Sources

Quote:
Originally posted by mrothacher
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.
Could the designs be referring to RF circuits?
  Reply With Quote
Old 8th November 2002, 06:43 PM   #9
diyAudio Member
 
Join Date: May 2001
Blog Entries: 5
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
  Reply With Quote
Old 8th November 2002, 07:03 PM   #10
halojoy is offline halojoy  Sweden
On Hiatus
 
Join Date: Nov 2002
Default 70% nom voltage = 100 times longer life

Quote:
Originally posted by Nelson Pass
I haven't had any problems, but then I have run them
very much below their ratings.
LIVSTID= lifespan
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
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pass Son of Zen w/current sources (etc.) GRollins Pass Labs 89 18th September 2012 02:45 PM
Current Sources vinay Pass Labs 1 19th March 2005 04:23 AM
Op Amp based current sources Kevinbd Solid State 1 3rd October 2004 07:18 AM
Aleph P current sources? stefan Pass Labs 12 20th August 2002 08:01 AM
Current sources (not sinks) dlharmon Pass Labs 1 6th February 2002 10:36 PM


New To Site? Need Help?

All times are GMT. The time now is 02:46 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2