
Home  Forums  Rules  Articles  The diyAudio Store  Gallery  Blogs  Register  Donations  FAQ  Calendar  Search  Today's Posts  Mark Forums Read  Search 
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 

Thread Tools  Search this Thread 
2nd June 2012, 05:38 PM  #1 
diyAudio Member
Join Date: Mar 2002

power xfmr specs vs audio xfmr specs
I do not want to explore why or why not power supply toroids
will work as audio output transformers. I would like to know how to translate power supply toroid specifications into audio transformer specifications. For instance how would one convert these specs: http://www.toroid.com/standard_trans...701.062_M4.pdf Into this context: VTP156711100  Firefly Push Pull Output Transformer 22.5k to 8 ohms 1.5 watts And viceversa
__________________
http://www.youtube.com/watch?v=xZmfCYr8mwA Last edited by hitsware; 2nd June 2012 at 05:40 PM. 
3rd June 2012, 02:23 AM  #2 
diyAudio Member
Join Date: Mar 2002

bump
__________________
http://www.youtube.com/watch?v=xZmfCYr8mwA 
3rd June 2012, 03:03 AM  #3 
expert in tautology
diyAudio Member

determine the turns ratio of the power transformer.
then look up the formula that relates turns ratio to impedance ratio. that will get you in the ball park. it will NOT tell you if you have sufficient primary inductance or if you have enough turns in the primary to handle the current, nor will it tell you if you will have any voltage breakdown issues... and tells you nothing about DC imbalance nor leakage inductance and capacitance issues...
__________________
__bear http://www.bearlabs.com  Btw, I don't actually know anything, FYI  [...2SJ74 Toshiba bogus asian parts  beware! ] 
3rd June 2012, 04:54 AM  #4 
diyAudio Member
Join Date: Feb 2003
Location: ..

pri magnetizing current should be on most pwr xmfr datasheets  can calc Lm
valid only for specified line V, freq VT product  pwr xfmr core often working into saturation  2x increase in VT can give 10x increase in Im conversely if you can operate at lower V (VT really) the reduction in Im is similarly disproportionate pwr xfmr cores are not gapped, don't tolerate DC bias current  use pushpull only Last edited by jcx; 3rd June 2012 at 05:00 AM. 
3rd June 2012, 09:48 AM  #5 
diyAudio Member
Join Date: Mar 2002

> determine the turns ratio of the power transformer.
> then look up the formula that relates turns ratio to impedance ratio. O.K ...... If I have the ratio, then how do I determine the impedance ?
__________________
http://www.youtube.com/watch?v=xZmfCYr8mwA 
3rd June 2012, 09:52 AM  #6 
diyAudio Member
Join Date: Mar 2002

> pri magnetizing current
Would that be 'rated primary current' ?
__________________
http://www.youtube.com/watch?v=xZmfCYr8mwA 
3rd June 2012, 11:53 AM  #7  
diyAudio Member
Join Date: Mar 2012
Location: Bradford

Quote:
There is insufficient information in the power transformer datasheet. The turns ratio is, near enough, the unloaded voltage ratio, but you only have the loaded ratio. To calculate one from the other you need the regulation, which isn't given. It could be approximated from winding resistance, but that's not given either. Some power transformers have more infomative datasheets. If you knew the turns ratio, it's really not hard to find out how to calculate the impedance ratio. The rated primary current, at a known voltage, provides for a rough estimate of maximum power before meltdown. I trust you know how to calculate power, given a current and a voltage. 

3rd June 2012, 02:31 PM  #8 
diyAudio Member
Join Date: Jan 2009

Forget this nasty little toroid a substitue for the VVT Firefly transformer.
What you want to know is the impedance ratio is the square of the turns ratio. There is the text 'Uo=8.1V RMS' in the spec, this may well be the unloaded secondary voltage. This makes the regulation about 25%. The temp rise of 63 degrees C seems high as well. Assuming you connect the secondaries in parallel and 234V in gives 8V out then the turns ratio is 29.25 and impedance ratio is 855.5 An 8 Ohms speaker load will give Raa = 6.84K which is way too low. 
3rd June 2012, 03:09 PM  #9 
expert in tautology
diyAudio Member

low power output transformers are cheap. plentiful, buy one??
__bear
__________________
__bear http://www.bearlabs.com  Btw, I don't actually know anything, FYI  [...2SJ74 Toshiba bogus asian parts  beware! ] 
3rd June 2012, 03:18 PM  #10  
diyAudio Member
Join Date: Mar 2002

Quote:
((234/unloaded out)^2)*8 ~ primary Z ? I'm not trying to replace the 1 example with the other, just to find a method of calculation ........... Thanks
__________________
http://www.youtube.com/watch?v=xZmfCYr8mwA 

Thread Tools  Search this Thread 


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Chicago power XFMR question.  mltube  Tubes / Valves  7  16th December 2011 09:06 PM 
Looking for specs on this Beyer Xfmr  Goldstache  Tubes / Valves  2  12th December 2011 11:00 PM 
What audio output xfmr for a 6BM8 pp amp?  bichela  Tubes / Valves  55  18th March 2011 03:02 AM 
Power XFMR Choice  sherpa  Tubelab  3  18th October 2010 09:05 AM 
Harman Kardon TA5000X power XFMR  dharper8  Tubes / Valves  1  21st November 2009 03:26 AM 
New To Site?  Need Help? 