valve/tube output transformer construction - 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 2nd March 2012, 11:01 PM   #1
jdef is offline jdef  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
Location: UK SW
Default valve/tube output transformer construction

Hi,

I am thinking of winding a pair of output transformers for an EL34 PP based circuit. I have looked at the Williamson transformer design details and also gone through the Radio Designers Handbook (ed4) and roughly worked out turns ratio, core size etc., but I am interested in knowing more before constructing a coil winding machine to help with the process. Firstly, the Williamson amplifier uses two bobbins with one put on the other way to make the windings symmetrical yet I see few commercial amplifiers employing this method; so is it necessary and if so what sonic advantages does it give ?

Also, the RDH refers to electrostatic shielding between sectionalised primaries and secondaries. Is this between every boundary between the primary and secondary windings, and what form does it take, a brass shim; or would an aluminium one do ? What's the purpose of these, is it to reduce the effect of winding capacitances, and again, are they used in commercial transformers ?

Any information or insight would be very much appreciated.

Yours,

Jolyon
  Reply With Quote
Old 2nd March 2012, 11:09 PM   #2
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
lots of threads here on the topic, please seek out posts by BudP, cerrem, YvesM and smoking-amps......
__________________
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 2nd March 2012, 11:37 PM   #3
diyAudio Member
 
aardvarkash10's Avatar
 
Join Date: Mar 2007
Location: Auckland, NZ
spend a few hours on Patrick Turner's site too - near-impenetrable theory stuff, but worth it
__________________
"Folks, you can't prove truthiness with information. You prove truthiness with more truthiness. In a process known as truthinessiness." - Stephen Colbert, The Colbert Report
  Reply With Quote
Old 2nd March 2012, 11:41 PM   #4
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
yes, Patrick Turner is a good read indeed......
__________________
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 3rd March 2012, 12:00 AM   #5
jdef is offline jdef  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
Location: UK SW
Thanks everyone, just been looking. Very valuable stuff there. I'll need some time to take it in !

Yrs,

J.
  Reply With Quote
Old 3rd March 2012, 02:39 AM   #6
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
J.

Williamson style topology requires O/P "iron" of the VERY best quality. Otherwise, the phase shifts in the circuitry will eat you alive. I suggest you consider Mullard style circuitry, as it is less problematic in the stability dept.
__________________
Eli D.
  Reply With Quote
Old 3rd March 2012, 01:18 PM   #7
jdef is offline jdef  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
Location: UK SW
Hi Eli,

I was going to use the Lowther LL26 circuit as the basis for my amplifier and am planning on using c cores for the op transformers. I just mentioned the Williamson cct as it came with reasonable detail on transformer construction. However, no mention is made of electrostatic shielding in the Williamson op tx.

Yrs,

Jolly
  Reply With Quote
Old 3rd March 2012, 01:46 PM   #8
diyAudio Member
 
Join Date: Aug 2008
Audio transformers have NO electrostatic shields !
  Reply With Quote
Old 3rd March 2012, 02:31 PM   #9
Yvesm is offline Yvesm  France
diyAudio Member
 
Yvesm's Avatar
 
Join Date: Jul 2004
Location: Ardeche
Quote:
Originally Posted by jdef View Post
Hi,
. . .
Firstly, the Williamson amplifier uses two bobbins with one put on the other way to make the windings symmetrical yet I see few commercial amplifiers employing this method; so is it necessary and if so what sonic advantages does it give ?
Using two bobbins is not necessarly used to make windings symmetric but it's a mean to reduce the end to end capacitance of a winding.
RDH4 uses the term of "vertical sectionizing". Browse for that, but this not the only way.
End to end capacitance of windings are responsible for peaks of resonance at high frequencies and should be avoided at less than, say, 50Khz, that is 2 or 3 octaves above the usual 20Khz limit in order to do not produce excessive in band phase shift.
Quote:
Also, the RDH refers to electrostatic shielding between sectionalised primaries and secondaries. Is this between every boundary between the primary and secondary windings, and what form does it take, a brass shim; or would an aluminium one do ? What's the purpose of these, is it to reduce the effect of winding capacitances, and again, are they used in commercial transformers ?
In output transformers, impedance ratio is usually large enough to allow looking at the secondaries as being at (or near) the ground potential for the primaries.
Browse RDH4's chapter 5 again, and again and again . . .

Yves.
  Reply With Quote
Old 3rd March 2012, 04:41 PM   #10
jdef is offline jdef  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
Location: UK SW
Thank you all; it's great to be able to discuss this with people who know and are willing to share their knowledge.

Yrs,

Jolyon.
  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
Laszlo's Valve Output Stage with Lundahl transformer oshifis Digital Source 21 4th October 2010 12:12 PM
Quick valve construction question eeka chu Tubes / Valves 25 28th February 2006 09:20 PM
Output Tube biasing for Toroidal Output Transformer gingertube Tubes / Valves 7 17th April 2005 04:40 PM
toroid Transformer as output Transformer for tube preamp? tone Tubes / Valves 15 2nd February 2003 04:36 AM


New To Site? Need Help?

All times are GMT. The time now is 05:08 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