Power transformer as Parafeed output? - Page 5 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 August 2007, 05:46 AM   #41
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Quote:
Originally posted by soundbrigade
What about those 100V line distribution transformers. What can be done with them. Can they be used in as parafeed transformers or similar applications?
do you have them on hand? what are the taps available? is that autotransformer type?

we can determine ratios if can give us the data on those 100 volt line transformers.
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 6th August 2007, 10:47 AM   #42
diyAudio Member
 
soundbrigade's Avatar
 
Join Date: Feb 2006
Location: Vaenersborg, Sweden
Send a message via MSN to soundbrigade
Darn, have no data. Have no LC-meter, have no ...
They have separate pri/sec-windings. Measuring DC-resistans give nothing.
They are marked: 100V 8ohm, and have 5 sec taps 0, 10W, 2.5W, 1,25W.
__________________
/Magnus
  Reply With Quote
Old 6th August 2007, 10:56 AM   #43
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Quote:
Originally posted by soundbrigade
Darn, have no data. Have no LC-meter, have no ...
They have separate pri/sec-windings. Measuring DC-resistans give nothing.
They are marked: 100V 8ohm, and have 5 sec taps 0, 10W, 2.5W, 1,25W.
Why bother when a toroid will have better performance ? Those 70/100V transformers don't usually have enough inductance to give any sort of decent bass . In fact why parafeed at all ? A toroid can be used SE if there is a tertiary winding to offset the core DC , then the parafeed cap and anode load choke (or CCS) are redundant . Below is a schematic of a recent amp which used a 30VA 230:9+9 toroid where one of the secondaries is used to (nearly) 100% offset the anode current . -3dB points at 15Hz and 47khz with a 280mH choke (not 30mH as in the schematic) . Finding suitable offset chokes is the main problem , although if there is enough compliance I'm sure a CCS could be used

Click the image to open in full size.

cheers

316A
  Reply With Quote
Old 6th August 2007, 11:02 AM   #44
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Quote:
Originally posted by Shoog
So your conclusion is that smaller (to a point) would be better.

Shoog
Smaller units have higher turns per volt and hence more inductance . 30VA came out slightly better than a 50VA unit in my case . The smaller 15VA toroids , which also had potted cores measured worse .

cheers

316a
  Reply With Quote
Old 6th August 2007, 11:24 AM   #45
diyAudio Member
 
Join Date: May 2007
Quote:
Originally posted by soundbrigade
Darn, have no data. Have no LC-meter, have no ...
They have separate pri/sec-windings. Measuring DC-resistans give nothing.
They are marked: 100V 8ohm, and have 5 sec taps 0, 10W, 2.5W, 1,25W.
Hi Magnus,

100V line, 10W, 8ohm is around 1 kohm primary (winding ratio ca 11:1).
It is about time you make something out of those 12B4s, maybe by parallelling a few and parafeed them into the line formers!
See you again at "hifi-forum"!
  Reply With Quote
Old 6th August 2007, 12:56 PM   #46
diyAudio Member
 
soundbrigade's Avatar
 
Join Date: Feb 2006
Location: Vaenersborg, Sweden
Send a message via MSN to soundbrigade
Thanks Lars. See you!
__________________
/Magnus
  Reply With Quote
Old 6th August 2007, 12:59 PM   #47
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Quote:
They are marked: 100V 8ohm, and have 5 sec taps 0, 10W, 2.5W, 1,25W.
okey, so at tap 1.25W and 8ohms, we have a transformer good for 3.5k to 8ohms....
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 6th August 2007, 01:17 PM   #48
diyAudio Member
 
soundbrigade's Avatar
 
Join Date: Feb 2006
Location: Vaenersborg, Sweden
Send a message via MSN to soundbrigade
I may consider use the transformers for a headphone amp I need no power at all ... hardly.
__________________
/Magnus
  Reply With Quote
Old 6th August 2007, 01:20 PM   #49
diyAudio Member
 
Join Date: May 2007
Quote:
Originally posted by Tony


okey, so at tap 1.25W and 8ohms, we have a transformer good for 3.5k to 8ohms....
Nope,
In my calculations the winding-ratio is 31,6:1 which corresponds to 8k:8ohm impedance-ratio.
  Reply With Quote
Old 6th August 2007, 01:21 PM   #50
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
yes i believe so, the primary will never see 100volts so response should be okey...
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  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
Output transformer current and power ratings boywonder Tubes / Valves 3 29th April 2009 09:00 PM
2A3 SE parafeed with PP-transformer revintage Tubes / Valves 66 28th October 2008 09:47 AM
Transformer VA versus output power VA nigelwright7557 Solid State 8 18th May 2008 02:57 PM
Parafeed output croccodillo Tubes / Valves 0 17th January 2007 02:51 PM
High Power - Output transformer h_andree Chip Amps 8 2nd March 2004 05:45 PM


New To Site? Need Help?

All times are GMT. The time now is 07:56 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