Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

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 3rd April 2012, 07:02 AM   #1
fret is offline fret  Australia
diyAudio Member
 
Join Date: Jan 2012
Location: Sydney
Default Looking for an inductor: 50mH @ 3A?

So far it's been hard to find. Element14 has a 2.3A inductor at that rating but I need 3A. The circuit I'm looking at building is this one.

Anyone know where I can get some at a reasonable price?
  Reply With Quote
Old 3rd April 2012, 08:30 PM   #2
diyAudio Member
 
dchisholm's Avatar
 
Join Date: Mar 2011
Location: St Louis, Mo
That circuit is a generic test jig that emulates no particular speaker cabinet, so the actual inductance value isn't critical. (Although it should be measured and documented, so it could be repeated.) Anything from 40 mH to 60 mH, perhaps wider, will probably be acceptable.

Some ideas to consider:
  • Combine several inductors in series/parallel arrangements. If you can find, say, 27 mH with a 3 amp (or higher) current rating, put two of them in series. If you can find 100 mH with a 1.5 amp (or higher) current rating, connect two in parallel. If you can find 50 mH with 1.5 amp rating, put two in series (to make 100 mH with 1.5 A rating), then put two of those pairs in parallel to make 50 mH at 3 amps.
  • (When connecting inductors in series or parallel, pay attention to layout so their fields don't interact with each other to any appreciable degree.)
  • Think about creating your own inductor. I might start by looking at the large toroids offered by Amidon or Fair-Rite Products. Their catalogs and web pages contain the design information you need.
  • This thing doesn't need to behave like an inductor much above 100 Hz or so. Power supply filter chokes built with E-I laminations should be quite adequate. For example, the Hammond model 193T is 50 mH rated for 2 amps. The Hammond 195R10 is 50 mH rated for 10 amps; a pair of 195P5's in series gives you 60 mH at 5 amps.
  • I'd consider rewinding a filter choke salvaged from an old power supply, battery charger, or vacuum tube amp. Look for a choke weighing around 5 pounds (2.2 kg) or more. Strip off the old windings. Do a test winding of 10 or 20 turns; measure the resulting inductance; and use that to determine the number of turns you need. (Inductance is proportional to the square of the turns count.)
  • Commercial C-cores are also available in small quantities for winding your own chokes. (Use the "Search" on this forum to find vendors.) I know the manufacturers give design information for using them as transformers, but I don't know if the they supply design information for choke applications.
  • As a last resort, I'd wind an inductor on a salvaged power or vacuum tube output transformer core. Probably have to gap the center leg with a hacksaw, and hope there's enough varnish to keep the pieces from falling apart. Wind a test coil and procede as described above.
Dale
  Reply With Quote
Old 3rd April 2012, 09:30 PM   #3
fret is offline fret  Australia
diyAudio Member
 
Join Date: Jan 2012
Location: Sydney
Hey great ideas!

I did find this guy:
25.5mH 4A

So 2 of those in series should do the trick. Price seems ok too. All the rest of the parts are available at element14 as well.
  Reply With Quote
Old 3rd April 2012, 11:33 PM   #4
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
You should be able to use lower current inductors,if you plan on using this at lower power levels.
  Reply With Quote
Old 4th April 2012, 12:18 AM   #5
sreten is online now sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

Why not simply use a real speaker in a real box ?

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 4th April 2012, 12:44 AM   #6
fret is offline fret  Australia
diyAudio Member
 
Join Date: Jan 2012
Location: Sydney
Quote:
Originally Posted by sreten View Post
Why not simply use a real speaker in a real box?
FYI Whats not in the circuit shown is the part that taps off the signal to be processed and output via an XLR. Basically a high resistance voltage divider going into a ACD and then a DSP chip running a IR convolution of some sort. Probably a speaker/mic IR like those from Redwires.

- Sometimes the volume is an issue (kids asleep in the same house, small clubs with low stage level).
- Repeatability with mic positioning is not the greatest. In all my years of mic'ing up a tube amp, it always sounds different.

Now maybe it would be nice to have say a single 12" guitar speaker/cab inline with this load/processor for stage monitoring, and the XLR output for the PA. I will look into that once I've got more of this up and running.
  Reply With Quote
Old 4th April 2012, 02:19 AM   #7
jamesdb is offline jamesdb  United States
diyAudio Member
 
Join Date: Jun 2007
Signal Transformers has a choke CH-4 that is 70mH 4A, or CH-6 is 40mH 6A.
Not cheap, though.
  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
Copper coil inductor vs. round core inductor tomchaoda Pass Labs 7 21st September 2011 04:42 AM
10uH 3A inductor for class-D amp yakideo Parts 4 10th May 2011 08:33 PM
+/- 28V 3A supply andRookie Power Supplies 29 7th May 2010 10:16 PM
air core inductor vs. iron core inductor WBS Planars & Exotics 5 7th May 2007 11:02 PM
1mh variable 3A or higher Inductor LeakSt20 Parts 2 1st August 2005 10:38 AM


New To Site? Need Help?

All times are GMT. The time now is 06:57 PM.


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