How do autoformer impedance matching controls work - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 11th March 2005, 06:41 AM   #1
dan4 is offline dan4  United States
diyAudio Member
 
Join Date: Mar 2005
Location: WI
Default How do autoformer impedance matching controls work

I am in desperate need to understand how an autoformer based volume control works. Ideally, I would like to get my hands on a schematic. I helped a friend install four volume controls (installed in parallel using the x4 setting to present a combined 8ohm load). I am however perplexed how these controls work and need to understand to resolve a problem.

Any help is greatly appreciated. Thanks.
  Reply With Quote
Old 11th March 2005, 07:21 AM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
the autotransformer will do both impedance matching and volume control. Which do you need?
For a volume control the autoT can provide either gain or attenuation or a range of both.
Consider an autoT with 5 wires; start, 25%, 50%, 75% and finish.
Connect the input to start and finish then the output can be connected to any pair but with no gain available.
eg. output s/25% gives -12db. s/50% gives -6db, s/75% gives -2.5db, s/f gives 0db. The formula is 20 * log(volt gain). If volt gain is less than 1 then the log will be negative. If you need to specify the transformer tappings then the reverse formula can be applied using the 10^x key on your calculator.
If you connect the input to s/50% then you can get gain (2 tappings) and attenuation.
For impedance conversion use the (volt gain ^2) * impedance to give the new impedance.
Maybe that is what you want, I hope I'm not trying to teach you have to suck eggs, Sorry if I have.
__________________
regards Andrew T.
  Reply With Quote
Old 11th March 2005, 10:47 AM   #3
moamps is offline moamps  Croatia
diyAudio Member
 
Join Date: Oct 2002
Location: Croatia
http://www.rane.com/note136.html

my little calculation:
Attached Images
File Type: jpg autotr.jpg (48.5 KB, 217 views)
  Reply With Quote
Old 12th March 2005, 07:51 AM   #4
dan4 is offline dan4  United States
diyAudio Member
 
Join Date: Mar 2005
Location: WI
Thank you. The wiring diagram provided is what I was looking to obtain. Much appreciated!!!
  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
Impedance matching Triod lover Tubes / Valves 2 12th January 2007 09:59 AM
impedance matching to a pro amp... MyNameIsJake Solid State 2 4th June 2006 05:32 PM
Need help understanding transformer impedance ratios and impedance matching percy Tubes / Valves 5 28th February 2005 08:35 PM
impedance matching fragman56 Tubes / Valves 17 20th March 2003 02:38 PM
Impedance Matching bryce66 Solid State 6 9th November 2001 09:02 AM


New To Site? Need Help?

All times are GMT. The time now is 02:51 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