Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Joining two NCT transformers
Joining two NCT transformers
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
Old 22nd February 2007, 09:33 PM   #1
Sasquatch is offline Sasquatch  United States
diyAudio Member
Join Date: Aug 2004
Location: Alabama
Default Joining two NCT transformers

I have two identical non center tapped 1:2 power transfomers left over from a couple of cheap monoblocks I once owned.

I am wondering if I can make a 1:2 center tapped transformer as follows:

1) Wire the primaries in series and attach 110 AC to both ends. 2) Wire the secondaries in series and use the middle point as the center tap.

Also if I need twice the voltage, can I just use each as a half wave rectifier, one for the positive and the other for the negative? In other words, wire the secondaries in series but connect each primary to line voltage separately.

  Reply With Quote
Old 22nd February 2007, 10:02 PM   #2
zigzagflux is offline zigzagflux  United States
diyAudio Member
zigzagflux's Avatar
Join Date: Oct 2006
Location: Charlotte, NC
Your first method will result in a 120VCT transformer, with 60V on each secondary winding. You also are limited to using the transformers at 50% of their rating, as you are wiring 120V primaries in series.

Your second method is better, wiring the primaries in parallel and feeding them with 120V. You would then end up with 240VCT output at full transformer capacity.

Be careful to check your instantaneous polarities on the secondary: it's either right or wrong. If you get 0V output from outside leg to outside leg, swap the polarity of one of the secondaries.
  Reply With Quote
Old 23rd February 2007, 12:14 AM   #3
Tom Bavis is offline Tom Bavis
diyAudio Member
Tom Bavis's Avatar
Join Date: Jun 2002
Location: Macedon NY
All true, but one more thing to consider - if you are using half-wave rectifiers on each secondary, the current will be limited to a small fraction of the AC rating, since the DC flux will saturate the core. You COULD use separate full-wave bridge rectifiers (sand is cheap!) but DON'T connect the secondaries together anywhere - connect the DC outputs, - to +.

You also would not want to use the two transformers together center-tapped) with a 2-diode full-wave rectifier (half-bridge). Each transformer would have net DC current, the DC fluxes can't cancel when they are in different cores.

In essence, avoid half-wave rectifiers.
  Reply With Quote
Old 23rd February 2007, 01:53 AM   #4
Sasquatch is offline Sasquatch  United States
diyAudio Member
Join Date: Aug 2004
Location: Alabama
Then another question. I do have a proper full wave rectifier out of an old console. Trouble is I don't remember what was in the amp I pulled it out of. How can I determine its wattage capacity? Is there a general rule of thumb regarding weight versus power or some easy way to test when it overtaxes?

With the other two, it sounds like a better strategy could be to use one as a bridge rectifier using two tube half wave rectifiers (I want to use tubes) for the HT and the other could be the filament transformer. Unfortunately, this would mean extra filament current for an extra rectifier tube.
  Reply With Quote


Joining two NCT transformersHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Joining the Tubelab SE club PaulyT Tubelab 236 2nd October 2009 12:16 AM
Joining audio-tape turntable belts. Aleksunder Analogue Source 5 28th November 2007 10:14 PM
entry level do-it-yourselfer joining.. jz23 Introductions 2 7th April 2007 03:32 PM
Relapse audio freak joining. jbop Introductions 2 4th April 2007 11:39 AM
Joining the T-amp community ackcheng Class D 7 19th March 2006 02:43 AM

New To Site? Need Help?

All times are GMT. The time now is 01:27 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio