opinions - transformer cores for ribbons - diyAudio
Go Back   Home > Forums > Loudspeakers > Planars & Exotics

Planars & Exotics ESL's, planars, and alternative technologies

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 18th August 2011, 12:43 PM   #1
diyAudio Member
 
Join Date: May 2002
Location: oz
Default opinions - transformer cores for ribbons

Hi All

I'm looking for suitable cores to build some impedence matching trannies for some ribbon speaker (down to approx 500Hz I hope.)

Can anybody offer an educated opinion on these ?

Push pull single end Audio output transformer core kit1 | eBay

I'm also looking for AMCC alternatives with a reasonable price into Australia (postage seems to be a killer -what a silly place to put a country..)
AMCC = amorphous C-core as per RAAL

Also also , Has anybody had any decent success using toroidal powr transformers as audio transformers? (say 240v step down to 9v)

Many thanks in advance

George
__________________
george a
  Reply With Quote
Old 18th August 2011, 05:20 PM   #2
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Yes,We have had Great Sucsess using the modern day toroidal power transformers for audio.
Mostly lately in step-up,I had started to embark in a step down design but other projects are in the way at the moment.

Using the standard 240V primary winding will allow you to get down to 15Hz at 60v.
You shoudn't have any problems there.

Just remember that if you are driving a ribbon that the secondary turns must have a very low DC resistance,less than that of the ribbon this can be difficult but not imposible.
Do not confuse this with Impedence ratio.

And, The secondary winding must cover the entire surface area of the toroid completely to keep the losses from leakage inductance on the low side of things.

All of the same rules apply in step down as in step up used for esl's.
Your High Frequency response will be determined by the leakage inductance and any stray capacitance + any other load capactitances.
In this case as you are not driving an esl (pure capacitance) driver,the transformer resonance should be rather high.

I Have tested a few different ones that I have around and tested to be good and flat up to as much as 200khz and as far as 1Mhz (the limit of my audio generator) with peaks due to the self resonance of the transformer itself in the 300Khz to 900Khz range.
This has been documented in another thread.

I had taken one of my transformers that has two 120v windings and and had connected it it to an amplifier and a fullrange speaker at a 1:1 ratio just to see if I could hear any major differences through it.

There was only one that was annoying.

It was at the extreme low end that had a slight distortion and was expected probably due to core saturation other than that it was transparent to me as far as what I heard from the mid bass (100Hz) on up,this is a simple test that you can try yourself as well.

The bass wasn't severly bad or anything but I could tell it was there and this could probably be rememdied if I had a much larger core and more primary turns as this is what determines the lowest frequecy of operation of a transformer.

My cores are in the 200 watt range maybe a little more as it varies abit depending on how the manufacture rates them.
Mine are 1.75"H X 4"D with the stock windings.


I hope this helps you and gives you some idea's.

jer
  Reply With Quote
Old 19th August 2011, 09:30 AM   #3
diyAudio Member
 
Join Date: May 2002
Location: oz
Hi Jer

Many thanks for the great trouble you've gone to in your response.
I will investigate the toroidal transformer option as part my my ribbon re-build

- currently in pieces due to accident when i was carrying 1 of the 2 30' ribbons across the room , a bit to close to the other ribbon assembly- the neo magnets caught sight of each other with a resulting mess - i"m glad my fingers weren't in the way!.
so a total rebuild is required.
However - you make an interesting comment re having the secondary winding cover all of the toroid core , all the discussions i have seen and photos only have very few windings - 3 -or so on the secondary , with no chance of giving much cover at all to the core - .....or do we use foil.....?

Thanks
George
__________________
george a
  Reply With Quote
Old 19th August 2011, 01:53 PM   #4
diyAudio Member
 
bolserst's Avatar
 
Join Date: Jun 2005
Location: Fort Worth, Texas
Quote:
Originally Posted by george a View Post
- you make an interesting comment re having the secondary winding cover all of the toroid core , all the discussions i have seen and photos only have very few windings - 3 -or so on the secondary , with no chance of giving much cover at all to the core - .....or do we use foil.....?
Yes, foils helps with complete coverage.
If you need a secondary with very few turns, try using several foil secondaries of the same number of turns spaced around the toroid and then hooked in parallel. This will lower the DC resistance of the secondary as well as the leakage inductance.
  Reply With Quote
Old 22nd August 2011, 03:59 PM   #5
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally Posted by bolserst View Post
...
If you need a secondary with very few turns, try using several foil secondaries of the same number of turns spaced around the toroid and then hooked in parallel. This will lower the DC resistance of the secondary as well as the leakage inductance.
Yes, i had good results making a secondary this way ....

my "paralleled secondaries" had a single turn, so not even insulation
was necessary. But that depends on primary/secondary turn ratio and
primary inductance to be achieved for lower cutoff.
__________________
Oliver, RFZ believer (?)
www.dipol-audio.de
  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
Swapping transformer cores thoriated Tubes / Valves 13 10th May 2010 02:20 PM
Output transformer cores Mario Pankov Tubes / Valves 12 21st November 2009 01:21 AM
Output transformer cores Mario Pankov Tubes / Valves 1 19th November 2009 02:24 PM
Russian Transformer cores Jaime Tubes / Valves 4 5th November 2007 10:39 PM
Transformer wiring with different cores rtarbell Power Supplies 3 20th January 2006 07:46 AM


New To Site? Need Help?

All times are GMT. The time now is 08:54 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